Terahertz ferroelectric resonator

Abstract

To provide an improved method for coupling an oscillation in a terahertz spectral range of electrons in an electrical circuit or of a terahertz electromagnetic wave with a resonator.SOLUTION: A heterostructure of a device comprises an alternating stacking sequence of dielectric layers of a plurality of dielectric layers and ferroelectric layers of a plurality of ferroelectric layers. Each ferroelectric layer of the plurality of ferroelectric layers comprises a plurality of ferroelectric polarization domains each forming a polarization pattern. The polarization pattern is adapted to perform, with a resonance frequency in a terahertz frequency range, an oscillation related to an oscillation of a total or local polarization. The method comprises functionally coupling, by the device, the oscillation of the polarization pattern and an oscillation of electrons in an electrical circuit or of a terahertz electromagnetic wave. The device further comprises at least one intermediate electrode arranged between an intermediate top layer and an intermediate bottom layer, where the intermediate top layer is one of the ferroelectric layer and the dielectric layer of the plurality of dielectric layers, and where the intermediate bottom layer is the other.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present disclosure relates to electrical resonator circuits, and more particularly to electrical resonators in integrated circuits. [Background technology]

[0002] The semiconductor industry is driven by its goal of miniaturizing integrated electronic circuits and increasing their switching frequency and speed. Conventional silicon-based integrated circuits may at some point reach fundamental limits on switching frequency, determined by device capacitance and inductivity and energy losses during signal transmission. Higher speed circuits and alternative transmission path concepts are desirable. Signal transmission via electromagnetic waves, rather than electronic transmission, has been proposed. The evolution from today's gigahertz electronics to future terahertz electronics may enable electronic signal processing and electromagnetic signal transmission at similar frequencies using the same or similar integrated electronic elements. Therefore, integrated elements that couple terahertz circuits to electromagnetic fields are desirable.

[0003] Terahertz electromagnetic signal transmission, and particularly reception, may also be useful in existing applications such as medical imaging and security screening, or for long-distance signal transmission, for example in the aerospace industry and space or satellite data communications.

[0004] Existing terahertz integrated electronic devices, such as resonators required for transmitting and receiving signals, include split-ring and split-disk resonators. The dimensions of these structures are determined by the terahertz wavelength and are much larger than the typical critical dimensions of silicon-based integrated circuits. Improvements are desirable to enable miniaturization and co-integration of terahertz oscillators and resonators with miniaturized integrated circuits. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Luk'yanchuk et al., Physical Review B 98,024107(2018) Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned technical problems, there is a need for improved methods for coupling electrons in electrical circuits or vibrations in the terahertz spectral range of terahertz electromagnetic waves to resonators, especially resonators that can be integrated into miniaturized integrated circuits. [Means for solving the problem]

[0007] This object is achieved by a method according to independent claim 1. Independent claim 11 provides a device having a heterostructure adapted for application as a resonator. Independent claim 14 provides a method for manufacturing a device having a heterostructure suitable for application as a resonator. The dependent claims relate to preferred embodiments.

[0008] In a first aspect, the present disclosure relates to a method for utilizing a device having a heterostructure as a resonator for electrons in an electric circuit or terahertz electromagnetic waves. The heterostructure comprises at least one dielectric layer and at least one ferroelectric layer. The at least one ferroelectric layer includes a plurality of ferroelectric polarization domains forming a polarization pattern. The polarization pattern is adapted to oscillate at a resonant frequency within the terahertz frequency range. The method includes functionally coupling oscillations of the polarization pattern with oscillations of the electrons in the electric circuit or terahertz electromagnetic waves through the device.

[0009] Devices having heterostructures comprising at least one dielectric layer and at least one ferroelectric layer can be integrated into compact integrated circuits, which can offer advantages over existing terahertz resonators, such as split-ring and split-disk resonators. In particular, the lateral dimensions of the devices can be reduced to, for example, the critical dimensions of today's semiconductor devices. Furthermore, the at least one ferroelectric layer and / or the at least one dielectric layer can be deposited using well-developed techniques in layer deposition technology. Advantageously, for the sake of miniaturization, elements that introduce significant inductance can be omitted within the devices.

[0010] Advantageously, the at least one ferroelectric layer and the at least one dielectric layer can be formed from an insulating material that exhibits little response to vibrations, such as electromagnetic waves, at frequencies much lower or much higher than the resonant frequency, or at the frequencies of oscillations of polarization patterns, electrons in electrical circuits, or terahertz electromagnetic waves, which can suppress undesirable responses and noise that might otherwise result from responses to vibrations, such as electromagnetic waves, at much higher or lower frequencies.

[0011] In the context of the present disclosure, a heterostructure may include a sandwich-like or stacked heterostructure, a multilayer structure, and / or a superlattice.

[0012] The resonant frequency can be selected from a plurality of resonant frequencies of the heterostructure and / or polarization pattern. In particular, the resonant frequency can correspond to a dominant resonant frequency of the plurality of resonant frequencies of the heterostructure and / or polarization pattern.

[0013] Furthermore, the insulating material of the at least one ferroelectric layer and / or the at least one dielectric layer can reduce the risk of undesired electrical shorts throughout the device. Advantageously, the polarization pattern of the device has a resonant frequency in the terahertz spectral range that can be tailored to the requirements of a particular application, for example, by selecting an appropriate thickness of the at least one ferroelectric layer or the at least one dielectric layer, or by selecting an appropriate material composition of the at least one ferroelectric layer and the at least one dielectric layer. The resonant frequency can advantageously be used for resonant coupling between the oscillations of the polarization pattern and the oscillations of electrons in an electrical circuit or terahertz electromagnetic waves. Resonant coupling provides a particularly efficient coupling.

[0014] In the context of the present disclosure, the terahertz frequency range may include frequencies of at least 0.05 THz, in particular at least 0.1 THz or at least 0.2 THz.

[0015] In the context of the present disclosure, the terahertz frequency range may include frequencies up to 20 THz, in particular up to 10 THz or up to 3 THz.

[0016] The oscillation of the polarization pattern can have an oscillation frequency in the second terahertz frequency range.

[0017] The oscillations of the electrons in the electrical circuit or the terahertz electromagnetic waves can have a coupling frequency within the second terahertz frequency range.

[0018] The second terahertz frequency range may include frequencies of at least 0.05 THz, in particular at least 0.1 THz or at least 0.2 THz.

[0019] The second terahertz frequency range may include frequencies up to 20 THz, in particular up to 10 THz or up to 3 THz.

[0020] Oscillations of the polarization pattern and / or the electrical circuit or terahertz electromagnetic waves having an oscillation or coupling frequency that is not too far from the resonant frequency of the polarization pattern may advantageously allow efficient coupling between the oscillations of the polarization pattern and the electrical circuit or terahertz electromagnetic waves.

[0021] The oscillation of the polarization pattern can have an oscillation frequency, and the oscillation of the electrons in the electrical circuit or the terahertz electromagnetic waves can have a coupling frequency, which can match the oscillation frequency.

[0022] According to one embodiment of the present disclosure, the vibration frequency matches the resonant frequency.

[0023] The resulting resonant coupling can allow particularly efficient coupling between the oscillations of the polarization pattern and the oscillations of electrons in an electrical circuit or terahertz electromagnetic waves.

[0024] According to one embodiment, the coupling frequency matches the resonant frequency.

[0025] The resulting resonant coupling can allow particularly efficient coupling between the oscillations of the polarization pattern and the oscillations of electrons in an electrical circuit or terahertz electromagnetic waves.

[0026] The matching frequencies may deviate from each other by a factor of up to 2, in particular by a factor of up to 1.5, or even by a factor of up to 1.1.

[0027] According to one embodiment, the heterostructure may comprise a plurality of ferroelectric layers, which may comprise at least three ferroelectric layers, in particular at least five, ten, twenty or fifty ferroelectric layers.

[0028] In particular, the at least one ferroelectric layer may be at least one ferroelectric layer of the plurality of ferroelectric layers, the at least one ferroelectric layer may be or may include the thickest ferroelectric layer of the plurality of ferroelectric layers or the thinnest ferroelectric layer of the plurality of ferroelectric layers.

[0029] Each ferroelectric layer of the plurality of ferroelectric layers can include a plurality of ferroelectric polarization domains that form a polarization pattern.

[0030] According to one embodiment, each of the plurality of ferroelectric layers may have the same maximum ferroelectric layer thickness, in particular, each of the plurality of ferroelectric layers may have the same ferroelectric layer thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to the at least one ferroelectric layer.

[0031] Alternatively or additionally, the heterostructure may comprise a plurality of dielectric layers, which may include at least three dielectric layers, in particular at least five, ten, twenty or fifty dielectric layers.

[0032] In particular, the at least one dielectric layer may be at least one dielectric layer of the plurality of dielectric layers, and may be or include the thickest dielectric layer of the plurality of dielectric layers or the thinnest dielectric layer of the plurality of dielectric layers.

[0033] According to one embodiment, each of the plurality of dielectric layers may have the same maximum dielectric thickness, in particular, each of the plurality of dielectric layers may have the same dielectric thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to the at least one dielectric layer.

[0034] The heterostructure may include an alternating stacked sequence of dielectric layers of a plurality of dielectric layers and ferroelectric layers of a plurality of ferroelectric layers.

[0035] Alternatively or additionally, the heterostructure may comprise a stacking sequence having at least two subsequent ferroelectric layers of a plurality of ferroelectric layers or at least two subsequent dielectric layers of a plurality of dielectric layers.

[0036] Alternatively or additionally, the heterostructure may include a stacking sequence having at least one additional layer between a first one of the plurality of ferroelectric layers or plurality of dielectric layers and a second one of the plurality of ferroelectric layers or plurality of dielectric layers.

[0037] Multiple ferroelectric layers and / or multiple dielectric layers can increase the coupling volume and therefore the strength of the coupling between the oscillation of the polarization pattern and the oscillation of the electric circuit or terahertz electromagnetic wave.

[0038] According to one embodiment, the method further includes utilizing the device as a component of a receiver or transmitter for terahertz electromagnetic waves.

[0039] Utilizing the device as a receiver or transmitter component advantageously utilizes the coupling between the oscillations of the polarization pattern and the coupling of electrons in an electrical circuit, which may be particularly useful for device applications related to inter- and / or intra-chip signal transmission and / or processing, 6G WiFi communications, and / or satellite communications.

[0040] According to one embodiment, the heterostructure is operatively coupled to a diode or a transistor. In particular, the device may be a component of a receiver, the diode or the transistor acting as a rectifier.

[0041] Because devices with heterostructures can be integrated with small semiconductor elements such as transistors and / or diodes, these well-established semiconductor elements can be advantageously used to implement driver and / or readout circuits for the resonators.

[0042] According to one embodiment, the device is a first component of a common integrated circuit, and the diode or transistor is a second component of the common integrated circuit. For example, the first component of the common integrated circuit and the second component of the common integrated circuit may be disposed on a common substrate. For example, the common substrate may be a semiconductor substrate or a dielectric substrate. In particular, the semiconductor or dielectric substrate may be a semiconductor or dielectric wafer.

[0043] According to one embodiment, the first component of the common integrated circuit and the second component of the common integrated circuit are disposed in direct physical contact with each other.

[0044] At least one layer of the device and at least one portion of the second component of the common integrated circuit may be composed of the same material, and the same material composition of the layer of the device and the portion of the second component of the common integrated circuit may be the result of a common deposition step.

[0045] The device may be operatively coupled to an additional antenna, which in particular may be a split ring resonator or a split disk resonator.

[0046] According to one embodiment, the method further comprises applying the device as a component of an RC circuit. In particular, the device may be used as a capacitor in an RC circuit.

[0047] The implementation of the device as an RC circuit provides a resonator that has the potential for being very miniaturized and integrated, in particular, the implementation as an RC circuit makes it possible to omit significant inductances that tend to require large lateral areas in the layout of integrated circuits.

[0048] The RC circuit may comprise a resistor in parallel or in series with the heterostructure. According to one embodiment, the device is a first component of a common integrated circuit and the resistor is a second component of the common integrated circuit.

[0049] The device and resistor may advantageously be formed as components of a common integrated circuit.

[0050] The common integrated circuit, the first component of the common integrated circuit, and the second component of the common integrated circuit may be characterized by features corresponding to those described in the context of the diode or transistor forming the second component of the common integrated circuit.

[0051] The device may be used as a component of a low-pass filter, a high-pass filter, or a band-pass filter.

[0052] In particular, an RC circuit comprising the device as a component may be used as a component of a low-pass filter, a high-pass filter, or a band-pass filter.

[0053] A low-pass filter, a high-pass filter, or a band-pass filter can have a cut-off frequency within a cut-off frequency range.

[0054] The bandpass filter may have a second cutoff frequency within the cutoff frequency range.

[0055] The cut-off frequency range may include frequencies of at least 0.1 THz, in particular at least 1 THz or at least 0.2 THz.

[0056] The cut-off frequency range may include frequencies up to 1.00 THz, in particular up to 10 THz.

[0057] The low-pass, high-pass or band-pass filter may be an electronic low-pass, high-pass or band-pass filter.

[0058] The device may be used as a clock component.

[0059] The device advantageously provides a resonant frequency in the terahertz frequency range, slightly above the frequency range used by current electronic devices, and can therefore make it possible to implement clocks that operate at higher frequencies, and therefore with greater precision, than those currently used in semiconductor devices.

[0060] Utilizing the device as a component of a clock may involve determining a maximum or minimum value of a parameter that characterizes the oscillation of the polarization pattern.

[0061] Utilizing the device as a component of a clock can include counting a plurality of maximum or minimum values, each maximum or minimum value being a maximum or minimum value of a parameter associated with oscillation of the polarization pattern.

[0062] The parameter relating to the oscillation of the polarization pattern may be a measure of the overall polarization of the polarization pattern, or may be a measure of the change in the overall polarization of the polarization pattern.

[0063] The parameter relating to the oscillation of the polarization pattern may be a measure of the local polarization of the polarization pattern or may be a measure of the change in the local polarization of the polarization pattern.

[0064] The device may further include a second heterostructure comprising at least one second dielectric layer and at least one second ferroelectric layer. The second ferroelectric layer may include a second plurality of ferroelectric polarization domains forming a second polarization pattern, the second polarization pattern being adapted to perform a second oscillation having a second resonant frequency within the terahertz frequency range. Applying the device may further include utilizing the heterostructure as a component of a transmitter adapted to generate transient terahertz electromagnetic waves and utilizing the second heterostructure as a component of a receiver adapted to receive the transient terahertz electromagnetic waves. This may be particularly useful for device applications related to intra-chip signal transmission and / or processing.

[0065] The second heterostructure may comprise a second plurality of ferroelectric layers, which may comprise at least three ferroelectric layers, in particular at least five, ten, twenty or fifty ferroelectric layers.

[0066] According to one embodiment, the at least one second ferroelectric layer may be at least one ferroelectric layer of the second plurality of ferroelectric layers, and may be or include the thickest ferroelectric layer of the second plurality of ferroelectric layers or the thinnest ferroelectric layer of the second plurality of ferroelectric layers.

[0067] In particular, each layer of the second plurality of ferroelectric layers can have the same second maximum ferroelectric layer thickness, for example, along a line intersecting the second heterostructure, in particular along a line intersecting the second heterostructure along a direction perpendicular to the second ferroelectric layer.

[0068] Alternatively or additionally, the second heterostructure may comprise a second plurality of dielectric layers, which may include at least three ferroelectric layers, in particular at least five, ten, twenty or fifty dielectric layers.

[0069] According to one embodiment, the at least one second dielectric layer may be one dielectric layer of the second plurality of dielectric layers, and may be or include the thickest dielectric layer of the second plurality of dielectric layers or the thinnest dielectric layer of the second plurality of dielectric layers.

[0070] In particular, each layer of the second plurality of dielectric layers can have the same second maximum dielectric layer thickness, for example along a line intersecting the second heterostructure, in particular along a line intersecting the second heterostructure along a direction perpendicular to the at least one second dielectric layer.

[0071] According to one embodiment, the heterostructure is a first component of a common integrated circuit and the second heterostructure is a second component of the common integrated circuit.

[0072] The common integrated circuit, the first component of the common integrated circuit, and the second component of the common integrated circuit may be characterized by features corresponding to those described in the context of the diode or transistor forming the second component of the common integrated circuit.

[0073] The method may further include guiding the transient terahertz electromagnetic waves using a waveguide structure.

[0074] The method may further comprise guiding the transient terahertz electromagnetic wave using a metallic channel, in particular a metallic channel that functions as a plasmonic interconnect channel.

[0075] The waveguide structures and / or plasmonic interconnect channels may be particularly useful in device applications related to intra-chip signal transmission and / or processing.

[0076] The method may further include using the device as a component of a terahertz optical device for manipulating terahertz electromagnetic waves and controlling at least one terahertz optical parameter.

[0077] For example, the terahertz optical device may be a mirror that reflects terahertz electromagnetic waves, and the terahertz optical parameter may be reflectivity.

[0078] For example, the terahertz optical device may be an attenuator that transmits a portion of the terahertz electromagnetic radiation, and the terahertz optical parameter may be attenuation.

[0079] For example, the terahertz optical device may be a beam splitter for reflecting one portion of the terahertz electromagnetic wave and transmitting another portion of the terahertz electromagnetic wave, where the terahertz optical parameter may be reflectivity and the second terahertz optical parameter may be transmittance.

[0080] For example, the terahertz optical device may be a phase adjuster for changing the phase of the terahertz electromagnetic wave, and the terahertz optical parameter may be a phase shift.

[0081] For example, the terahertz optical device may be a terahertz optical low-pass filter, a terahertz optical high-pass filter, or a terahertz optical band-pass filter for terahertz electromagnetic waves, and the terahertz optical parameter may be a cutoff frequency.

[0082] Advantageously, techniques for the design of layered dielectric optics can be used to tailor terahertz optical devices to suit the requirements of a particular application, for example as mirrors, beam splitters, attenuators, phase adjusters, dichroic mirrors, (terahertz) optical high-pass filters, (terahertz) optical low-pass filters, (terahertz) band-pass filters, or (terahertz) optical notch filters.

[0083] For example, the terahertz optical device may be a guiding structure for terahertz electromagnetic waves, and the terahertz optical parameter may be a direction of the terahertz electromagnetic waves. In particular, the terahertz optical device may include a terahertz optical metamaterial for guiding the terahertz electromagnetic waves within the heterostructure.

[0084] The thickness of the at least one ferroelectric layer can be tailored to control the terahertz optical parameters.

[0085] The method may further include applying an electrostatic field to the heterostructure to control the terahertz optical parameters.

[0086] The method may further include triggering oscillations of electrons in the electrical circuit to control the terahertz optical parameter.

[0087] The method may further include applying a mechanical stress to the heterostructure to control the terahertz optical parameters.

[0088] The heterostructure may be a first component of a common integrated circuit, and the additional terahertz optical device or the additional terahertz optoelectronic device may be a second component of the common integrated circuit.

[0089] The common integrated circuit, the first component of the common integrated circuit, and the second component of the common integrated circuit may be characterized by features corresponding to those described in the context of a diode or a transistor as the second component of the common integrated circuit.

[0090] The method may further include utilizing the device as a component of a terahertz electromagnetic wave receiver or transmitter in addition to using the device as a component of a terahertz optical device for manipulating terahertz electromagnetic waves and controlling at least one terahertz optical parameter.

[0091] In a second aspect, the present disclosure relates to a device having a heterostructure adapted to be applied as a resonator for electrons in an electric circuit or terahertz electromagnetic waves. The heterostructure comprises at least one dielectric layer and at least one ferroelectric layer. The ferroelectric layer includes a plurality of ferroelectric polarization domains forming a polarization pattern. The polarization pattern is adapted to oscillate at a resonant frequency within the terahertz frequency range. The device is adapted to couple the oscillation of the polarization pattern with oscillations at a coupling frequency of the electrons in the electric circuit or terahertz electromagnetic waves. The oscillation of the polarization pattern has an oscillation frequency within a second terahertz frequency range.

[0092] A device having a heterostructure can be advantageously applied in a method comprising at least some of the above-mentioned features.

[0093] The terahertz frequency range and / or the second terahertz frequency range may be defined as in the context of the first aspect of the present disclosure.

[0094] The heterostructure may comprise a plurality of ferroelectric layers, which may comprise at least three ferroelectric layers, in particular at least five, ten, twenty or fifty ferroelectric layers.

[0095] According to one embodiment, the at least one ferroelectric layer may be at least one ferroelectric layer of the plurality of ferroelectric layers, and may be or include the thickest ferroelectric layer of the plurality of ferroelectric layers or the thinnest ferroelectric layer of the plurality of ferroelectric layers.

[0096] In particular, each of the plurality of ferroelectric layers can have the same maximum ferroelectric layer thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to the at least one ferroelectric layer.

[0097] Alternatively or additionally, the heterostructure may comprise a plurality of dielectric layers, which may include at least three dielectric layers, in particular at least five, ten, twenty or fifty dielectric layers.

[0098] According to one embodiment, the at least one dielectric layer may be at least one dielectric layer of the plurality of dielectric layers, and may be or include the thickest dielectric layer of the plurality of dielectric layers or the thinnest dielectric layer of the plurality of dielectric layers.

[0099] In particular, each of the plurality of dielectric layers can have the same maximum dielectric thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to the at least one dielectric layer.

[0100] The heterostructure may have a height of at least 5 nm, in particular at least 100 nm, in particular at least 500 nm, in particular at least 1 μm.

[0101] Heterostructures up to 25 mm 2 , especially up to 500 μm 2 , especially up to 100 μm 2 , or up to 10 μm 2 , or up to 25nm 2 can cover a lateral area of

[0102] The polarization pattern may have a spatial periodicity along the lateral direction of the at least one ferroelectric layer, in particular the polarization pattern may be a periodic polarization pattern.

[0103] According to one embodiment, the thickness of the at least one ferroelectric layer does not exceed 100 nm, in particular 70 nm, 40 nm, 30 nm or 5 nm.

[0104] In general, some or all of the ferroelectric layers of the plurality of ferroelectric layers may have the same thickness, although in other embodiments the thicknesses of some or all of the ferroelectric layers of the plurality of ferroelectric layers may differ.

[0105] In embodiments having multiple ferroelectric layers, the thickness of some or any of the ferroelectric layers included in the multiple ferroelectric layers may not exceed 100 nm, particularly 70 nm, 40 nm, 30 nm or 5 nm.

[0106] At least one ferroelectric layer may comprise lead titanate, barium titanate, zirconium oxide, or hafnium oxide. In embodiments having multiple ferroelectric layers, a first ferroelectric layer of the multiple ferroelectric layers and a second ferroelectric layer of the multiple ferroelectric layers may be composed of the same material or different materials.

[0107] According to one embodiment, the thickness of at least one dielectric layer included in the plurality of dielectric layers does not exceed 100 nm, in particular 70 nm, 40 nm, 30 nm or 5 nm.

[0108] In general, some or all of the dielectric layers of the plurality of dielectric layers may have the same thickness, although in other embodiments the thicknesses of some or all of the dielectric layers of the plurality of dielectric layers may differ.

[0109] In embodiments having multiple dielectric layers, the thickness of some or any of the dielectric layers included in the multiple dielectric layers may not exceed 100 nm, particularly 70 nm, 40 nm, 30 nm or 5 nm.

[0110] At least one dielectric layer may comprise an insulating material, such as strontium titanate. In embodiments having multiple dielectric layers, a first dielectric layer of the multiple dielectric layers and a second dielectric layer of the multiple dielectric layers may be composed of the same material or different materials.

[0111] The device may further comprise a bottom electrode disposed below the heterostructure.

[0112] In particular, in embodiments having multiple dielectric layers and / or multiple ferroelectric layers, the bottom electrode may be disposed below the multiple dielectric layers and / or below the multiple ferroelectric layers.

[0113] The device may further comprise a top electrode disposed above the heterostructure. In particular, in embodiments having multiple dielectric layers and / or multiple ferroelectric layers, the top electrode may be disposed above the multiple dielectric layers and / or above the multiple ferroelectric layers.

[0114] The device may further comprise at least one intermediate electrode disposed between the intermediate top layer and the intermediate bottom layer.

[0115] In embodiments having a heterostructure with one dielectric layer and one ferroelectric layer, the intermediate top layer may be a ferroelectric layer or a dielectric layer, and the intermediate bottom layer may be a dielectric layer or a ferroelectric layer, respectively.

[0116] In embodiments having multiple dielectric layers, the intermediate bottom layer may be a dielectric layer from the multiple dielectric layers and / or the intermediate top layer may be a dielectric layer from the multiple dielectric layers.

[0117] In embodiments having multiple ferroelectric layers, the intermediate bottom layer may be a ferroelectric layer from the multiple ferroelectric layers and / or the intermediate top layer may be a ferroelectric layer from the multiple ferroelectric layers.

[0118] The structure and material composition of the intermediate electrode may generally correspond to the structure and material composition of the bottom and top electrodes described above.

[0119] Intermediate electrodes placed within the heterostructure may enable more versatile applications of the resonator.

[0120] Each of the bottom electrode, top electrode, and bottom electrode can be adapted to be connected to an external drive circuit or to ground.

[0121] The heterostructure may be disposed above a substrate.

[0122] The substrate can be structured to facilitate the formation of the device. Advantageously, additional elements can be formed on the same device to implement complex integrated circuits. Furthermore, the device can be selected to facilitate the formation of at least one layer of the device, for example, via the wetting properties of the substrate or via epitaxial growth of at least one layer of the device on the substrate.

[0123] The substrate may be a semiconductor substrate or a dielectric substrate.

[0124] Semiconductor or dielectric substrates are well developed and affordable and the formation of layers on semiconductor or dielectric substrates is highly developed in the context of layer deposition techniques.

[0125] The substrate can include a single-crystal portion having lateral dimensions at least as large as lateral dimensions of the heterostructure. In particular, the substrate can be adapted to promote epitaxial growth of at least one dielectric layer or at least one ferroelectric layer.

[0126] The crystalline portion of the substrate can facilitate epitaxial growth of at least one layer of the device, which tends to minimize the density of defects within the layer.

[0127] The device may be a mechanically flexible device.

[0128] In particular, the device may be a stand-alone device.

[0129] The apparatus may further comprise an additional integrated element, the heterostructure being a first component of a common integrated circuit and the additional integrated element being a second component of the common integrated circuit.

[0130] The common integrated circuit, the first component of the common integrated circuit, and the second component of the common integrated circuit may be characterized by features corresponding to those described in the context of the method with a diode or a transistor as the second component of the common integrated circuit.

[0131] For example, the additional integrated element may be a resistor, which may be placed in series or in parallel with the heterostructure.

[0132] For example, the additional integrated element may be a diode or a transistor, which may be operatively coupled to the heterostructure.

[0133] For example, the additional integrated element may be an additional terahertz optical device or an additional terahertz optoelectronic device.

[0134] For example, the additional integrated element may be an additional antenna coupled to the heterostructure.

[0135] In particular, the additional antenna may be a split ring resonator or a split disk resonator.

[0136] The apparatus may further comprise a plurality of integrated elements, each integrated element of the plurality of integrated elements being a component of a common integrated circuit.

[0137] The device may further include a second heterostructure adapted to be used as a second resonator for the electrons of the second electric circuit or the second terahertz electromagnetic wave. The second heterostructure may include at least one dielectric layer and at least one second ferroelectric layer. The at least one second ferroelectric layer may include a second plurality of ferroelectric polarization domains forming a second polarization pattern. The second polarization pattern may be adapted to perform a second oscillation at a second resonant frequency within the terahertz frequency range. The device may be adapted to couple the second oscillation of the second polarization pattern with a third oscillation at a second coupling frequency of the electrons of the second electric circuit or the second terahertz electromagnetic wave. The second oscillation of the second polarization pattern may have a second oscillation frequency within the second terahertz frequency range.

[0138] In some embodiments, the design and characteristics of the second heterostructure may correspond to those of the heterostructures described above in terms of layout, number and location of the ferroelectric and dielectric layers, layer thicknesses and material compositions, etc.

[0139] The second heterostructure may comprise a second plurality of ferroelectric layers, which may comprise at least three ferroelectric layers, in particular at least five, ten, twenty or fifty ferroelectric layers.

[0140] In particular, the at least one second ferroelectric layer may be at least one ferroelectric layer of the second plurality of ferroelectric layers, and may be or include the thickest ferroelectric layer of the second plurality of ferroelectric layers or the thinnest ferroelectric layer of the second plurality of ferroelectric layers.

[0141] According to one embodiment, each layer of the second plurality of ferroelectric layers may have the same second maximum ferroelectric layer thickness, in particular, each layer of the second plurality of ferroelectric layers may have the same second ferroelectric layer thickness, for example along a line intersecting the second heterostructure, in particular along a line intersecting the second heterostructure along a direction perpendicular to the at least one second ferroelectric layer.

[0142] Alternatively or additionally, the second heterostructure may comprise a second plurality of dielectric layers, which may include at least three ferroelectric layers, in particular at least five, ten, twenty or fifty dielectric layers.

[0143] In particular, the at least one second dielectric layer may be at least one dielectric layer of the second plurality of dielectric layers, and may be or include the thickest dielectric layer of the second plurality of dielectric layers or the thinnest dielectric layer of the second plurality of dielectric layers.

[0144] According to one embodiment, each layer of the second plurality of dielectric layers can have the same second maximum dielectric layer thickness, in particular, each layer of the second plurality of dielectric layers can have the same second dielectric layer thickness, for example along a line intersecting the second heterostructure, in particular along a line intersecting the second heterostructure along a direction perpendicular to the at least one second dielectric layer.

[0145] The second resonant frequency may be selected from a second plurality of resonant frequencies of the second heterostructure and / or the second polarization pattern.

[0146] In particular, the second resonant frequency may correspond to a dominant resonant frequency of a second plurality of resonant frequencies of the second heterostructure and / or the second polarization pattern.

[0147] The second resonant frequency may match the resonant frequency.

[0148] The matching frequencies may deviate from each other by a factor of up to 2, in particular by a factor of up to 1.5, or even by a factor of up to 1.1.

[0149] The second terahertz electromagnetic wave and the terahertz electromagnetic wave may be the same, and the device may be adapted to couple the oscillation of the polarization pattern with the second oscillation of the second polarization pattern using the terahertz electromagnetic wave.

[0150] In a third aspect, the present disclosure relates to a method for fabricating a device having a heterostructure suitable for use as a resonator for electrons in an electric circuit or for terahertz electromagnetic waves. The method includes depositing at least one ferroelectric layer and at least one dielectric layer, wherein the ferroelectric layer thickness of the at least one ferroelectric layer does not exceed a predetermined maximum thickness such that the at least one ferroelectric layer includes a plurality of ferroelectric polarization domains that form a polarization pattern adapted to oscillate at a resonant frequency. The method further includes adjusting the predetermined maximum thickness to a resonant frequency within the terahertz frequency range.

[0151] The method may further comprise depositing a plurality of ferroelectric layers, for example, depositing a plurality of ferroelectric layers may comprise depositing at least three ferroelectric layers, in particular at least five, ten, twenty, or fifty ferroelectric layers.

[0152] In particular, the at least one ferroelectric layer may be included in the plurality of ferroelectric layers, and the at least one ferroelectric layer may be deposited such that it is or may include the thickest ferroelectric layer of the plurality of ferroelectric layers or the thinnest ferroelectric layer of the plurality of ferroelectric layers.

[0153] According to one embodiment, each layer of the plurality of ferroelectric layers may be deposited with the same ferroelectric layer thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to at least one ferroelectric layer.

[0154] Alternatively or additionally, the method may include depositing a plurality of dielectric layers, for example, depositing a plurality of dielectric layers may include depositing at least three dielectric layers, particularly at least five, ten, twenty, or fifty dielectric layers.

[0155] In particular, the plurality of dielectric layers may include at least one dielectric layer that may be deposited to be or include the thickest dielectric layer of the plurality of dielectric layers or the thinnest dielectric layer of the plurality of dielectric layers.

[0156] According to one embodiment, each layer of the plurality of dielectric layers may be deposited with the same dielectric layer thickness, for example along a line intersecting the heterostructure, in particular along a line intersecting the heterostructure along a direction perpendicular to at least one of the dielectric layers.

[0157] The predetermined maximum thickness may include the maximum thickness of at least one ferroelectric layer along a lateral direction of the heterostructure.

[0158] In embodiments having top and bottom electrodes, the predetermined maximum thickness may include the maximum thickness of at least one ferroelectric layer in the volume between the top and bottom electrodes.

[0159] In embodiments having multiple ferroelectric layers, the predetermined maximum thickness may be the thickness of the thickest ferroelectric layer of the multiple ferroelectric layers along a line that intersects the heterostructure, and in particular along a line that is perpendicular to the multiple ferroelectric layers.

[0160] In embodiments having top and bottom electrodes and multiple ferroelectric layers, the predetermined maximum thickness may include the thickness of the thickest ferroelectric layer of the multiple ferroelectric layers along a line connecting the bottom and top electrodes, particularly a line perpendicular to the bottom and top electrodes.

[0161] Alternatively or additionally, the method may include adjusting the ratio between the thickness of the ferroelectric layer and the dielectric constant of the at least one ferroelectric layer.

[0162] The terahertz frequency range may include frequencies of at least 0.05 THz, in particular at least 0.1 THz or at least 0.2 THz.

[0163] The terahertz frequency range may include frequencies up to 20 THz, in particular up to 10 THz or up to 3 THz.

[0164] According to one embodiment, adjusting the predetermined maximum thickness may comprise selecting the predetermined maximum thickness according to a material constant of a material comprised in the at least one ferroelectric layer, in particular the material constant of a material comprised in the at least one ferroelectric layer may be a dielectric constant of a material comprised in the at least one ferroelectric layer.

[0165] Adjusting the predetermined maximum thickness can include selecting the predetermined maximum thickness according to a lateral area of ​​the at least one ferroelectric layer.

[0166] Adjusting the predetermined maximum thickness may include selecting the predetermined maximum thickness according to the dielectric constant of the material included in the at least one dielectric layer.

[0167] Adjusting the predetermined maximum thickness can include selecting the predetermined maximum thickness according to a thickness of the at least one dielectric layer.

[0168] In embodiments having multiple dielectric layers and / or multiple ferroelectric layers, adjusting the predetermined maximum thickness may include selecting the predetermined maximum thickness according to the number of dielectric layers and / or the number of ferroelectric layers.

[0169] Adjusting the predetermined maximum thickness can include selecting the predetermined maximum thickness according to an average size of the ferroelectric polarization domains.

[0170] Adjusting the predetermined maximum thickness can include selecting the predetermined maximum thickness according to the size distribution of the ferroelectric polarization domains. [Brief explanation of the drawings]

[0171] [Figure 1a] FIG. 1 illustrates a terahertz ferroelectric resonator (TFR) according to one embodiment of the present disclosure, having thicknesses hd of individual dielectric layers, thicknesses hf of individual ferroelectric layers, overall thickness H of the heterostructure, and area S of the top surface. [Figure 1b] FIG. 1 illustrates an electronic graphic symbol for a terahertz ferroelectric resonator (TFR). [Figure 2a] FIG. 1 illustrates a terahertz ferroelectric resonator (TFR) heterostructure with a periodic stripe polarization pattern according to an embodiment of the present disclosure. [Figure 2b] FIG. 10 illustrates a terahertz ferroelectric resonator (TFR) heterostructure with a cylindrical or bubble-like periodic polarization pattern according to another embodiment of the present disclosure. [Figure 3]FIG. 1 illustrates a typical frequency dependence of the real and imaginary parts of the permittivity Re ε and Im ε of a terahertz ferroelectric resonator (TFR) heterostructure having an individual ferroelectric layer thickness hf of 25 nm, according to an embodiment of the present disclosure. [Figure 4] FIG. 2 illustrates a typical frequency dependence of the resonant frequency of a terahertz ferroelectric resonator (TFR) heterostructure according to an embodiment of the present disclosure. [Figure 5] FIG. 10 illustrates typical frequency dependence of impedance amplitude of a terahertz ferroelectric resonator (TFR) for different thicknesses h1, h2, and h3 according to three embodiments of the present disclosure, where h1 corresponds to hf=hd=10 nm, h2 corresponds to hf=hd=15 nm, and h3 corresponds to hf=hd=20 nm. [Figure 6] FIG. 1 illustrates a system for satellite communications comprising a terahertz ferroelectric resonator (TFR) according to an embodiment of the present disclosure. [Figure 7] FIG. 1 illustrates a system for 6G wireless communication comprising a terahertz ferroelectric resonator (TFR) according to one embodiment of the present disclosure. [Figure 8] FIG. 1 illustrates an integrated circuit comprising a terahertz ferroelectric resonator (TFR) according to an embodiment of the present disclosure. [Figure 9a] FIG. 1 illustrates an integrated circuit comprising a terahertz ferroelectric resonator (TFR) and a load resistor integrated in series according to an embodiment of the present disclosure. [Figure 9b] FIG. 9b is a circuit diagram of the integrated circuit of FIG. 9a. [Figure 9c] FIG. 10 illustrates an integrated circuit comprising a terahertz ferroelectric resonator (TFR) and a load resistor integrated in parallel according to yet another embodiment of the present disclosure. [Figure 9d] FIG. 9c is a circuit diagram of the integrated circuit of FIG. [Figure 10] FIG. 10 illustrates two communicating terahertz ferroelectric resonators (TFRs) according to yet another embodiment of the present disclosure. [Figure 11a]FIG. 10 is a circuit diagram of an integrated circuit for high-pass and low-pass frequency filtering based on terahertz ferroelectric resonators (TFRs) according to yet another embodiment of the present disclosure. [Figure 11b] 11a shows typical frequency-dependent output characteristics of the integrated circuit high-pass filter of FIG. 11a for different load resistances with a terahertz ferroelectric resonator (TFR) with hf=10 nm, hd=5 nm, H=1 μm, and S=100 μm2. [Figure 11c] 11a shows typical frequency-dependent output characteristics of the integrated circuit low-pass filter of FIG. 11a for different load resistances with a terahertz ferroelectric resonator (TFR) with hf=10 nm, hd=5 nm, H=1 μm, and S=100 μm2. [Figure 12] FIG. 1 illustrates a terahertz optical device according to an embodiment of the present disclosure. [Figure 13a] FIG. 1 illustrates the frequency dependent refractive index of a terahertz optical device with hf=hd=25 nm in terms of its real part Re n and its imaginary part Im n according to an embodiment of the present disclosure. [Figure 13b] FIG. 10 illustrates the terahertz frequency dependent optical reflection coefficient R0 at normal incidence for a terahertz optical device with hf=hd=25 nm according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0172] The present disclosure relates to devices having heterostructures with multiple ferroelectric layers that can provide a strong frequency dependence of the dielectric permittivity in the terahertz (THz) frequency range.

[0173] Terahertz frequencies are not uniquely defined and, in the context of the present disclosure, may be understood to begin at frequencies of 0.05 THz, particularly 0.1 THz or 0.2 THz. Correspondingly, the terahertz frequency range may include frequencies up to 20 THz, particularly up to 10 THz or up to 3 THz. According to one possible definition, the THz spectral range may correspond to wavelengths in the range of 1 mm to 0.1 mm. The terahertz electromagnetic spectrum may generally be understood to lie between microwaves and far infrared rays.

[0174] In the following, a device with a heterostructure according to claim 1 will be described using the example of a terahertz ferroelectric resonator (TFR).

[0175] FIG. 1a illustrates an example of a TFR 100. A typical TFR 100 comprises a heterostructure, which may be a sandwich-like heterostructure, a multilayer structure, or a superlattice. The heterostructure may be deposited, for example, on a dielectric or semiconductor substrate 102. The TFR 100 includes an alternating series of layers, including multiple dielectric layers 104 and multiple ferroelectric layers 106. While the example TFR 100 of FIG. 1a includes six dielectric layers 104 and five ferroelectric layers 106, other embodiments of the TFR 100 may include a different number of layers, such as one ferroelectric layer and one dielectric layer, or any other number of ferroelectric and / or dielectric layers, depending on the application.

[0176] The heterostructure of the TFR 100 can be realized, for example, as an epitaxially grown superlattice in which one, some, or all of the dielectric layers 104 are composed mostly of SrTiO3 perovskite oxide and one, some, or all of the ferroelectric layers 106 are composed mostly of PbTiO3 perovskite oxide. Alternatively, the ferroelectric layers 106 may include other oxides with a perovskite structure, such as barium titanate or lead zirconate titanate, or non-perovskite oxides, such as zirconium oxide or hafnium oxide, particularly doped hafnium oxide. Other material compositions, including, for example, halides, are also possible.

[0177] Typical thickness h of the individual layers of the dielectric layer 104 d and a typical thickness h of the ferroelectric layer 106 f can be in the range of a few nm to tens of nm. The number of dielectric layers 104 and ferroelectric layers 106 can vary from a few to tens to hundreds or even more. In this example, the total thickness H of the dielectric layers 104 and ferroelectric layers 106, and the lateral area of ​​the device, which can be related to the area S of the top surface of the device, are determined to be less than the characteristic terahertz wavelength λ / √ε in the heterostructure to avoid parasitic inductances. ≒ 10 μm (3 THz in vacuum) for the wavelength of electromagnetic waves with a terahertz frequency ≒ 100 and λ ≒ 100μm).

[0178] The ferroelectric material possesses ferroelectric polarization domains 108, 110 with uniaxial anisotropy of polarization, which may be naturally occurring or strain-induced and / or tailored by strain engineering. To this end, an epitaxial relationship between the dielectric layers 104 within the ferroelectric layer 106 may be useful, but is not required. Additionally, a dielectric relationship between the dielectric layers 104 or ferroelectric layer 106 and the substrate 102 may be useful, but is not required.

[0179] According to the example shown in Figure 1a, the polarization of the ferroelectric polarization domains 108, 110 is oriented along the z-axis defined along the surface normal of the layers of the heterostructure, although other orientations of polarization are possible.

[0180] The ferroelectric layer 106 of the heterostructure of FIG. 1a is insulating, and the heterostructure is insulating. The heterostructure is confined between a bottom electrode 112 and a top electrode 114. The bottom electrode 112 and the top electrode 114 can each have a thickness in the range of 1 to 10 nm and comprise a metal or semiconductor material. The combination of the bottom electrode 112, the top electrode 114, and the heterostructure with the dielectric layer 104 and the ferroelectric layer 106 can be considered an effective capacitor. The TFR 100 can be fabricated, for example, by sequentially and / or alternately depositing the dielectric layer 104 and the ferroelectric layer 106 on the substrate 102. In this case, the bottom electrode 112 is deposited on the substrate 102 before the deposition of the heterostructure. As a result, at least a portion of the bottom electrode 112 is disposed between the substrate 102 and the heterostructure of the TFR 100. The top electrode 114 can be fabricated above the heterostructure in an additional deposition process after the deposition of the heterostructure. A bottom contact 116 may be attached to the bottom electrode 112 and a top contact 118 may be attached to the top electrode 114 for making electrical connection to an external circuit.

[0181] FIG. 1b shows an electronic graphic symbol 130 of the TFR 100.

[0182] A feature of the alternating combination of dielectric layers 104 and ferroelectric layers 106 is that the polarization of each ferroelectric layer 106 terminates at the corresponding dielectric-ferroelectric interface, generating an interface depolarization charge. The interface depolarization charge is positive at the beginning of the polarization termination, corresponding to the dielectric-ferroelectric interface of each ferroelectric layer 106 in the heterostructure, and negative at the end, corresponding to the opposite dielectric-ferroelectric interface of the same individual ferroelectric layer 106 in the heterostructure. The interface depolarization charge induces a depolarization field. The depolarization field induced by the interface depolarization charge is energetically expensive. This results in the formation of ferroelectric polarization domains that form a polarization pattern. The polarization pattern can be spatially periodic along one or both transverse directions of the film.

[0183] 2a and 2b show examples of periodic polarization patterns for heterostructures 200 and 210. The heterostructure 200 in FIG. 2a has a stripe-shaped periodic polarization pattern. The heterostructure 210 in FIG. 2b has a cylindrical or bubble-shaped periodic polarization pattern. For example, if the ferroelectric layer 106 is composed of PbTiO3, the periodic polarization pattern in FIG. 2a can have a periodicity of 5 to 20 nm for the ferroelectric polarization domains 108 and 110. The periodic polarization pattern and the resulting reduction in depolarization charge in the ferroelectric polarization domains 108 and 110 can substantially reduce the electrostatic energy associated with the depolarization charge.

[0184] The polarization pattern, such as the periodic polarization pattern of the heterostructures 200, 210 in Figures 2a and 2b, can undergo oscillation. Coupling of the oscillation of the polarization pattern with a sub-THz-THz signal constitutes an important aspect of the present disclosure. Here, the sub-THz-THz signal can have a frequency within the terahertz frequency range. The terahertz frequency range of the sub-THz-THz signal can correspond to the terahertz frequency range of the resonant frequency to facilitate resonant coupling, or can be a broader frequency range in the case of non-resonant coupling. The sub-THz-THz signal can be or be related to the oscillation of electrons in an electrical circuit or the oscillation of terahertz electromagnetic waves.

[0185] At the structural level, the oscillation of the ferroelectric polarization domains 108, 110 or the oscillation of the polarization pattern, respectively, can be associated with a dynamic oscillation mode of the periodic polarization pattern having a resonant frequency. In particular, the oscillation of the ferroelectric polarization domains 108, 110 or the oscillation of the polarization pattern, respectively, can be associated with an oscillation of the global polarization or an oscillation of the local polarization. The oscillation of the polarization pattern can be coupled to a sub-THz to THz signal.

[0186] The present disclosure may advantageously, but not necessarily, utilize resonant coupling to achieve strong and efficient coupling between the oscillations of the polarization pattern and the sub-THz-to-THz signal. Resonant coupling occurs when the frequency of the sub-THz-to-THz signal matches the resonant frequency. In this context, match may refer to a match within a factor of 2, particularly within a factor of 1.5 or 1.1.

[0187] In situations where the sub-THz to THz signal is a terahertz electromagnetic wave with a wavelength of 0.1 to 1 mm, the terahertz wavelength may exceed the thickness of the device, in which case the action of the terahertz electromagnetic wave can be thought of as one of a uniform time-dependent electric field acting on the TFR 100, which can be thought of as an effective capacitor device. The response of the TFR 100 can therefore be expressed as an effective dynamic frequency-dependent impedance Z TFR For a heterostructure formed by N pairs of ferroelectric layers 106 and N pairs of dielectric layers 104, the effective dynamic frequency dependent impedance Z TFR can be written as follows:

[0188]

number

[0189] In the formula, h d is the thickness of one of the dielectric layers 104, and ε d is the dielectric constant of one of the dielectric layers 104, and h f is the thickness of one of the ferroelectric layers 106, and ε f is the dielectric constant of one of the ferroelectric layers 106, ε is the dielectric permittivity of vacuum, and S is the lateral area of ​​the heterostructure. ε in the frequency range of sub-THz to THz signals fThe frequency dependence of is related to the oscillation of the polarization pattern and the corresponding resonance, and therefore can be controlled by controlling the resonance, e.g., by controlling the resonant frequency and the dynamic oscillation mode, and / or by selecting a particular dynamic oscillation mode, e.g., a dominant resonant frequency and / or a dominant resonant mode having a dominant resonant frequency.

[0190] As an example, ε f We present the effect of resonances corresponding to specific dynamic vibration modes associated with the alternating contraction-expansion vibration of the domain chain with respect to ε. In this example, f =ε f (ω) can be expressed by the following equation derived in Luk'yanchuk et al., Physical Review B 98,024107(2018):

[0191]

number

[0192] where Γ is the damping coefficient and is related to energy dissipation. For example, the energy dissipation can be due to domain wall vibration. The non-uniformity coefficient g ~ 0.4-0.9 accounts for the non-uniformity of the electric field distribution near the interface between one of the dielectric layers 104 and one of the ferroelectric layers 106.

[0193] 3 shows a typical permittivity 300 as a function of frequency v(THz), where v(THz)=ω / 2π, according to one embodiment of the present disclosure. The permittivity has a complex value, and in FIG. 3 the real part of the permittivity 300, Re ε, and the imaginary part of the permittivity 300, Im ε, are shown separately. Resonant Frequency

number

[0194] FIG. 4 shows the resonant frequency of an embodiment of the present disclosure having a ferroelectric layer 106 made of PbTiO3 and a dielectric layer 104 made of SrTiO3.

number

[0195] Figure 5 shows the impedance amplitude |Z TFR Graph 500 shows the dependence of impedance amplitude |Z for three different thicknesses of the ferroelectric layer. TFR | is given, and h1 is h f =h d = 10 nm, and h2 corresponds to h f =h d = 15 nm, and h3 corresponds to h f =h d = 20 nm. Impedance amplitude |Z TFR| has a maximum at a frequency similar to or identical to the resonant frequency ν. The frequency dependence of the impedance amplitude of the heterostructure is similar to that of well-known electronic components, such as parallel LC resonant circuits. Therefore, the heterostructure and TFR100 device can be utilized in electronic devices, such as signal receivers, transmitters, or processing devices, operating in the frequency range of sub-THz to THz signals, and the integration and application of the heterostructure and TFR100 device can advantageously utilize highly developed concepts for the integration and application of well-known electronic components, such as LC resonant circuits.

[0196] According to the present disclosure, the thickness h of the ferroelectric layer f can be advantageously selected to adjust the resonant frequency ν and hence the frequency dependence of the impedance amplitude, in particular the frequency at which the impedance amplitude has a maximum. Again, the materials of the ferroelectric layer 106 and the dielectric layer 104 can be advantageously selected and / or electrostatic fields and / or mechanical stresses can be applied to the heterostructure to adjust the resonant frequency ω.

[0197] 6 and 7 illustrate exemplary applications in which a signal receiver, transmitter, or processing device using TFR 100 and operating in the frequency range of sub-THz to THz signals may be particularly beneficial.

[0198] For example, as shown in FIG. 6 , a device utilizing the TFR 100 as a component of a terahertz electromagnetic wave transmitter and / or receiver can find application in satellite communications. Terahertz electromagnetic waves 602 can be exchanged between a first satellite 604 and a second satellite 606, each equipped with a transmitter and / or receiver based on the TFR 100. The space between the satellites is transparent in the terahertz spectral range to allow the propagation of the terahertz electromagnetic waves 602. The TFR 100, and particularly integrated circuits incorporating the TFR 100, can provide an energy-efficient means of communication for the first satellite 604 and the second satellite 606 in environments where energy efficiency is particularly important. The TFR 100 also provides a lightweight means of communication, thereby reducing the cost of launching the first satellite 604 and the second satellite 606 into space. Importantly, the resonant coupling between the terahertz electromagnetic waves 602 and the TFR 100 provides a frequency-selective means of communication, suppressing noise from radiation at frequencies different from the resonant frequency of the TFR 100. This advantage can be particularly important in the space environment, where radiation of various frequencies can be abundant.

[0199] Furthermore, as shown in FIG. 7, devices utilizing the TFR 100 as a transmitter and / or receiver component of terahertz electromagnetic waves can form the basis for 6G WiFi communications in this frequency range. The TFR 100 can be highly integrated with other electrical components in the integrated electrical circuitry of a communications hub or end-user device 704, thus providing cost-effective communications technology for consumer products. In particular, the same or similar TFR 100 within a single device can be used for coupling to electromagnetic waves 702 on the one hand and for electronic signal processing within the integrated circuit on the other. Both the communications hub and the end-user device 704 may each comprise an integrated circuit having one or more TFRs 100.

[0200] The TFR100 device according to the present disclosure is advantageously compatible with existing, miniaturized, and highly developed semiconductor technology and integration into integrated circuits. Due to its small lateral area, the TFR100 can be co-integrated with semiconductor elements such as diodes or transistors.

[0201] FIG. 8 illustrates an integrated circuit 800 having a TFR100 and a semiconductor device 802 according to one embodiment of the present disclosure. Portions of the TFR100 device can be processed, e.g., deposited or structured, in a single process step along with portions of the semiconductor device 802. For example, layers of the TFR100, such as the dielectric layer 104, the ferroelectric layer 106, or the bottom electrode 112 and / or the top electrode 114 of the TFR100 device, can be deposited along with similar layers of the semiconductor device 802 in a single deposition step. Also, layers of the TFR100 device can be etched along with layers of the semiconductor device in a single etching step. Also, layers of the TFR100 device can be masked along with layers of the semiconductor device in a single masking step. Driver circuits for driving a transmitter for terahertz electromagnetic waves or readout circuits for reading out a receiver for terahertz electromagnetic waves can be implemented using semiconductor devices 802, such as diodes or transistors. For example, the heterostructure of the TFR 100 can be coupled to a diode or a transistor 802, particularly to the gate of a transistor, to implement a rectifier that converts the sub-THz to THz signal of the terahertz electromagnetic wave from an oscillation to a polar signal.

[0202] The frequency-dependent characteristics of the TFR100 device, particularly the frequency dependence of the TFR100's impedance amplitude, can be advantageously optimized for a particular device application. In addition, the frequency-dependent impedance of a circuit including the TFR100 device, such as an RC circuit, can be optimized by integrating additional electrical components, such as a load resistor, into the circuit. The load resistor may be implemented as a load resistor 900 integrated in series with the TFR100 device, as shown in FIG. 9a, or as a load resistor 920 integrated in parallel with the TFR, as shown in FIG. 9c.

[0203] 9b and 9d show the electronic graphic symbol 130 of the TFR 100, a corresponding circuit diagram 910, 930 with a resistor 912 in series and a resistor 932 in parallel.

[0204] Implementing a circuit according to the circuit diagram 910 of FIG. 9b can be achieved by forming an extended top electrode 114 or an extended bottom electrode 112 integrated with an additional resistive portion 902 composed of one or several metal or semiconductor layers whose thickness and material composition can be selected to optimize the resistance according to the requirements of the application in a particular device.

[0205] 9d can be achieved by integrating the parallel load as a shunt-like structure using a metal or semiconductor shunt 922 connecting the top electrode 114 and the bottom electrode 112. The metal or semiconductor shunt 922 may be disposed between the top electrode 114 and the bottom electrode 112, or at least a portion of the metal or semiconductor shunt 922 may be disposed outside the volume between the top electrode 114 and the bottom electrode 112.

[0206] 10 shows another example of an integrated circuit 1000 including two TFRs 100. Due to their small size, the TFRs 100 can be co-integrated into various integrated circuits. Further examples of integrated circuits that can include and / or be based on the TFRs 100 include terahertz antennas, transmitters, and receivers, which may also be referred to as sensors of terahertz radiation. In particular, a device in an integrated circuit including a TFR 100 can be applied as a receiver for detecting sub-THz to THz signals emitted from another device in the integrated circuit.

[0207] Alternatively or additionally, an integrated circuit device including the TFR 100 may be applied as a transmitter for generating sub-THz signals to be detected by another device in the integrated circuit. Advantageously, a TFR 100-based transmitter and a TFR 100-based receiver may be located on the same integrated circuit for transmitting, directing, and / or manipulating sub-THz signals. FIG. 10 shows an example of a corresponding integrated circuit 1000. In this example, the semiconductor devices 802 may correspond to, for example, processors or memory devices. The TFR 100 may be used to establish communication between the semiconductor devices 802 via terahertz electromagnetic waves 1002. The terahertz electromagnetic waves 1002 may be electromagnetic waves that propagate freely in vacuum, gas, dielectrics, or other forms of matter, or may be guided by a waveguide structure or supported by a metallic channel, particularly a plasmonic channel. In this embodiment, the TFR 100 functions as a component of an integrated electrical circuit, such as a transmitter, receiver, or transceiver, but may also function as a terahertz optical device, as described in more detail below.

[0208] 11a shows a circuit diagram 1100 corresponding to one embodiment of a frequency filter having a TFR 100. A circuit according to the circuit diagram 1100 may be utilized as a low-pass filter, a high-pass filter, or a band-pass filter. A high-pass filter applies an input voltage U across both the TFRs 100, 130 and a resistor 912 in series, as shown in FIG. in The TFR 100 and 130 can be implemented by placing TFR (ω). The series resistor 912 has an essentially frequency independent resistance R. The high pass filter converts the high voltage across the series resistor 912 into an output voltage U out,high This can be completed by using the output voltage U out,high can be written using the following equation:

[0209]

number

[0210] FIG. 11b illustrates the output voltage U of the high-pass filter according to one embodiment of the present disclosure. out,high 1110 frequency dependence.

[0211] The low-pass filter is out,low is obtained from TFR 130. Figure 11c shows the frequency dependent output voltage U of the low pass filter, given by out,low Shows 1120.

[0212]

number

[0213] By utilizing the coupling of the TFR100 to terahertz electromagnetic radiation, the TFR100 can also be utilized in a terahertz optical device to guide the terahertz electromagnetic radiation and / or manipulate its properties, such as its amplitude, phase, direction, or (in the case of pulsed terahertz electromagnetic radiation) pulse shape. Advantageously, due to the layered structure of the TFR100 heterostructure, highly developed techniques for the design of layered dielectric optics can be used to tailor the TFR100 to meet the requirements of a particular application, for example, as a mirror, beam splitter, attenuator, phase adjuster, dichroic mirror, (terahertz) optical high-pass filter, (terahertz) optical low-pass filter, (terahertz) band-pass filter, or (terahertz) optical notch filter. Advantageously, the use of a device having the TFR100 as a terahertz optical device can be combined with the use of the same device as an electronic resonator, for example, as a receiver. In particular, a portion of the terahertz electromagnetic radiation absorbed by the TFR 100 can be used for sensing, while another portion of the terahertz electromagnetic radiation can be guided, reflected, or transmitted by the same TFR 100 functioning as a terahertz optical device.

[0214] 12 illustrates an example of a terahertz optical device 1200 having a TFR 100 for manipulating terahertz electromagnetic waves, according to one embodiment of the present disclosure. The terahertz optical device 1200 can reflect a portion of an incident terahertz electromagnetic wave 1202 to generate a reflected terahertz electromagnetic wave 1204. The device can also transmit a portion of the incident terahertz electromagnetic wave 1202 to generate a transmitted terahertz electromagnetic wave 1206. Additionally, the terahertz optical device 1200 can absorb a portion of the incident terahertz electromagnetic wave 1202. The terahertz optical device 1200 can use the portion of the incident terahertz electromagnetic wave 1202 absorbed by the device for electronic signal processing, e.g., to sense the incident terahertz electromagnetic wave 1202.

[0215] 13a and 13b show the optical properties as a function of frequency v (THz) of a heterostructure according to one embodiment of the present disclosure. FIG. 13a shows the complex refractive index n=√ε1300. Because the complex refractive index 1300 is a complex quantity, the real part of the complex refractive index 1300, Re n, and the imaginary part of the complex refractive index 1300, Im n, are given separately. FIG. 13b shows the corresponding terahertz optical reflection coefficient R for normal incidence. The terahertz optical reflection coefficient R can be related to the complex refractive index n=√ε1300 as follows:

[0216]

number

[0217] The properties of the layers of the TFR 100 heterostructure, such as the dielectric layer 104, the ferroelectric layer 106, the bottom electrode 112, and the top electrode 114, can be tailored using well-developed techniques for designing layered dielectric optics. In particular, the properties of the heterostructure layers can be tailored to achieve a desired amplitude, phase, or direction of the reflected terahertz electromagnetic wave 1204 and / or the transmitted terahertz electromagnetic wave 1206. For example, the thickness and material composition of the heterostructure layers can be tailored. Alternatively or additionally, electrostatic fields and / or mechanical stresses can be constantly or dynamically applied to the heterostructure (e.g., for terahertz optical switching) to adjust the resonant frequency ω. Terahertz optical devices including the TFR 100 can be advantageously applied, for example, in wireless terahertz communication technologies or for on-chip wireless signal transmission and processing. In some of these applications, it may be useful to tailor the thickness of the heterostructure to exceed or match the emission wavelength. This can complicate the deposition of the bottom electrode 112 or top electrode 114. Advantageously, in applications where the terahertz optical device 1200 is not used for electronic signal processing, deposition of the top electrode 112 and / or bottom electrode 114 can be omitted.

[0218] The description of the embodiments and drawings only serves to illustrate the present disclosure and its associated advantages and should not be construed as meaning any limitation, the scope of which should be determined from the appended claims.

Claims

1. A method for utilizing a device (100) having a heterostructure (200, 210) as a resonator for electrons or terahertz electromagnetic waves (602, 702, 1002, 1202) in an electrical circuit (800, 900, 920, 1000), comprising: The heterostructure (200, 210) comprises a plurality of dielectric layers (104) and a plurality of ferroelectric layers (106), and an alternating stacking sequence of dielectric layers (104) of the plurality of dielectric layers (104) and ferroelectric layers (106) of the plurality of ferroelectric layers (106), each of the plurality of ferroelectric layers (106) includes a plurality of ferroelectric polarization domains (108, 110) each forming a polarization pattern; the polarization pattern is adapted to perform oscillations associated with global or local polarization oscillations at a resonant frequency in the terahertz frequency range; The method comprises: operatively coupling the oscillation of the polarization pattern with the oscillation of the electrons or the terahertz electromagnetic waves of the electrical circuit by the device; The device (100) further comprises at least one intermediate electrode disposed between an intermediate top layer, which is one of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106), and an intermediate bottom layer, which is the other of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106); The device (100) comprises a bottom electrode (112) disposed below the heterostructure (200, 210), and / or The method further comprises a top electrode (114) disposed above the heterostructure (200, 210).

2. The method of claim 1 , further comprising applying an electrostatic field to the heterostructure (200, 210) to control a resonant frequency within the terahertz frequency range.

3. The device (100) further comprises additional integrated elements (802, 902, 922); said heterostructure (200, 210) being a first component of a common integrated circuit (800, 900, 920, 1000); 3. The method of claim 1, wherein the additional integrated element (802, 902, 922) is a second component of the common integrated circuit (800, 900, 920, 1000).

4. The method of claim 3, wherein the additional integrated element (802) is a diode or a transistor.

5. the additional integrated element (802) is part of a small semiconductor element; 5. The method according to claim 3 or 4, wherein the miniature semiconductor device is configured as a driver and / or readout circuit for the resonator.

6. The method of claim 1 or 2, wherein the device (100) further comprises a metal or semiconductor shunt (922) connecting the top electrode (114) and the bottom electrode (112).

7. The method of claim 1 or 4, further comprising utilizing the device (100) as a component of a receiver or transmitter for the terahertz electromagnetic waves (602, 702, 1002, 1202).

8. The device (100) further comprises a second heterostructure (200, 210) comprising at least one second dielectric layer (104) and at least one second ferroelectric layer (106), the at least one second ferroelectric layer (106) including a second plurality of ferroelectric polarization domains (108, 110) forming a second polarization pattern, the second polarization pattern having a second resonant frequency within the terahertz frequency range and adapted to perform a second oscillation associated with the oscillation of the polarization; Applying the device (100) Utilizing the heterostructure (200, 210) as a component of a transmitter adapted to generate transient terahertz electromagnetic waves (602, 702, 1002); The method of claim 1 or 7, further comprising: utilizing the second heterostructure (200, 210) as a component of a receiver for receiving the transient terahertz electromagnetic wave (602, 702, 1002, 1202).

9. 10. The method of claim 8, further comprising guiding the transient terahertz electromagnetic wave (602, 702, 1002) using a metallic channel that functions as a plasmonic interconnect channel.

10. 3. The method of claim 1 or 2, further comprising using the device (100) as a component of a terahertz optical device (100) that is a mirror, a beam splitter, an attenuator, a phase adjuster, a dichroic mirror, a terahertz optical high-pass filter, a terahertz optical low-pass filter, a terahertz band-pass filter, or a terahertz optical notch filter to manipulate the terahertz electromagnetic wave (602, 702, 1002, 1202) and control at least one terahertz optical parameter.

11. A device (100) having a heterostructure (200, 210) adapted to be applied as a resonator for electrons or terahertz electromagnetic waves (602, 702, 1002, 1202) in an electric circuit (800, 900, 920, 1000), comprising: The heterostructure (200, 210) comprises a plurality of dielectric layers (104) and a plurality of ferroelectric layers (106), and an alternating stacking sequence of dielectric layers (104) of the plurality of dielectric layers (104) and ferroelectric layers (106) of the plurality of ferroelectric layers (106), each of the plurality of ferroelectric layers (106) includes a plurality of ferroelectric polarization domains (108, 110) each forming a polarization pattern; the polarization pattern is adapted to perform oscillations associated with global or local polarization oscillations at a resonant frequency in the terahertz frequency range; The device (100) comprises: adapted to couple oscillations of the polarization pattern with oscillations at a coupling frequency of the electrons or the terahertz electromagnetic waves of the electric circuit (800, 900, 920, 1000), wherein the oscillations of the polarization pattern have an oscillation frequency within the terahertz frequency range; The device (100) further comprises at least one intermediate electrode disposed between an intermediate top layer, which is one of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106), and an intermediate bottom layer, which is the other of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106); The device (100) comprises a bottom electrode (112) disposed below the heterostructure (200, 210), and / or The device (100) further comprises a top electrode (114) disposed above the heterostructure (200, 210).

12. The device (100) of claim 11, wherein the heterostructure (200, 210) is disposed above a substrate (102).

13. A method for manufacturing a device (100) having a heterostructure (200, 210), the device (100) having the heterostructure (200, 210) being suitable for application as a resonator for electrons or terahertz electromagnetic waves (602, 702, 1002, 1202) in an electric circuit (800, 900, 920, 1000), the method comprising: depositing the plurality of ferroelectric layers (106) of the heterostructure (200, 210) and the plurality of dielectric layers (104) of the heterostructure (200, 210) in a stacked sequence of alternating dielectric layers (104) of the plurality of dielectric layers (104) and ferroelectric layers (106) of the plurality of ferroelectric layers; The thickness (h) of the ferroelectric layer (106) of the plurality of ferroelectric layers (106) ｆ ) does not exceed a predetermined maximum thickness, resulting in depositing the plurality of ferroelectric layers (106), each of the ferroelectric layers (106) including a plurality of ferroelectric polarization domains (108, 110), each of the ferroelectric layers (106) forming a polarization pattern adapted to oscillate in relation to an oscillation of a global or local polarization at a resonant frequency; and adjusting the predetermined maximum thickness to a resonant frequency in the terahertz frequency range; The device (100) further comprises at least one intermediate electrode disposed between an intermediate top layer, which is one of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106), and an intermediate bottom layer, which is the other of the dielectric layer (104) of the plurality of dielectric layers (104) or the ferroelectric layer (106) of the plurality of ferroelectric layers (106); The device (100) comprises a bottom electrode (112) disposed below the heterostructure (200, 210), and / or The method further comprises a top electrode (114) disposed above the heterostructure (200, 210).

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