Heterogeneous periodic structure film with large negative capacitance and low hysteresis and preparation method thereof

Abstract

The negative capacitance effect transistor is regarded as one of ideal choices for continuing the Moore's law, and the subthreshold swing and hysteresis as low as possible and the high reliability during working condition temperature change are the fundamental premise for the negative capacitance effect to be applied to actual transistor devices. According to a traditional strategy of improving polarization intensity in one aspect, hysteresis is inevitably increased while the sub-threshold swing is reduced, and the operation stability of a device is seriously influenced. According to the invention, CaTiO3 and PbTiO3 with different periodic thicknesses are stacked to form a heterogeneous periodic structure film, and polarization self-shielding based on heterogeneous periodic interface controllable lattice distortion and an interface effect are utilized to synergistically optimize the strength and state stability of a negative capacitance effect, so that the film has large negative capacitance, low hysteresis and good working thermal stability, and can be applied to the field of microwave devices. And low hysteresis and low subthreshold swing are expected to be realized in a negative capacitance transistor, and the material has good application value in the field of microelectronic devices.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic devices, and particularly to a heteroperiodic structure thin film with large negative capacitance and low hysteresis and a preparation method thereof. Background Art

[0002] Traditional configuration transistors are faced with the power consumption bottleneck restricted by the Boltzmann electron distribution. Negative capacitance field-effect transistors can revolutionarily reduce the subthreshold swing (SS) to below 60 mV / decade and have attracted much attention since they were proposed. The key problems that need to be solved for the negative capacitance effect in practical device applications are: as low a subthreshold swing and hysteresis as possible; and secondly, the working reliability when the temperature changes. Traditionally, the polarization intensity is unilaterally increased to enhance the negative capacitance effect to reduce the subthreshold swing, but this will increase the energy consumption in the polarization flipping process and inevitably lead to an increase in hysteresis. This hysteresis effect will cause serious circuit reliability problems. For example, the threshold voltage shift in digital logic circuits will reduce the noise margin and cause logic misjudgment. Therefore, simply pursuing a low subthreshold swing while ignoring hysteresis control will lead to the deterioration of the comprehensive performance of the device.

[0003] Therefore, how to achieve the coordinated optimization of the negative capacitance effect intensity and hysteresis is the key challenge for negative capacitance effect transistors in practical applications and has become an important issue of concern to researchers in this field. Summary of the Invention

[0004] The present invention selects CaTiO3 (Ca ions have a small atomic radius) as one of the materials in the heteroperiodic structure, stacks CaTiO3 and PbTiO3 with a certain thickness ratio in a specific period ratio to form a heteroperiodic structure thin film with controllable interfacial lattice distortion, modulates the polarization shielding mechanism, and obtains a CaTiO3 / PbTiO3 heteroperiodic structure thin film with coordinated optimization of the capacitance enhancement value and hysteresis. Through a pulsed laser technique with a controllable spot area, the controllable preparation of the interfacial lattice distortion of the CaTiO3 / PbTiO3 heteroperiodic structure thin film is realized with appropriate parameters, and the potential application of a negative capacitance effect transistor based on the CaTiO3 / PbTiO3 heteroperiodic structure thin film is provided.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A heteroperiodic structure thin film with large negative capacitance and low hysteresis, characterized in that it includes a substrate; a conductive perovskite buffer layer formed on the substrate; and a negative capacitance functional layer formed on the conductive perovskite buffer layer;

[0007] Wherein, the negative capacitance functional layer is formed by self-assembling and periodically stacking two materials, PbTiO3 and CaTiO3, in a specific thickness ratio to construct a heteroperiodic structure with controllable interfacial lattice distortion.

[0008] Optionally, the interfacial lattice distortion in the negative capacitance functional layer includes ferroelectric lattice distortion and interfacial oxygen octahedron distortion, the polarization vector rotation angle is -90 to 90°, and the rotation angle of the interfacial oxygen octahedron is -10 to 10°.

[0009] Optionally, the periodic thickness ratio of the PbTiO3 layer to the CaTiO3 layer in the negative capacitance functional layer is 0.5 to 2, the cycle period of the negative capacitance functional layer is 12 to 30 times, and the total thickness of the negative capacitance functional layer is 50 to 200 nm.

[0010] Optionally, the substrate is any one of SrTiO3, DyScO3, and TbScO3, and the crystal plane orientation is any one of (001), (111), or (110).

[0011] Optionally, the conductive perovskite buffer layer is an SrRuO3 thin film grown on the substrate, the crystal plane orientation is any one of (001), (111), or (110), the thickness is 5 to 20 nm, and the morphological structure fluctuation is 100 to 1000 pm.

[0012] The second object of the present invention is to claim the preparation method of the above-mentioned heterogeneous periodic structure thin film with large negative capacitance and low hysteresis, including the following steps:

[0013] (1) Sequentially perform ultrasonic cleaning with anhydrous ethanol and stepwise thermal desorption composite treatment on the surface of the single crystal substrate;

[0014] (2) Epitaxially grow an SrRuO3 conductive perovskite buffer layer on the substrate;

[0015] (3) On the SrRuO3 conductive perovskite buffer layer, alternately deposit PbTiO3 and CaTiO3 in a self-assembled periodic stacking mode to form a negative capacitance functional layer, that is, obtain a CaTiO3 / PbTiO3 heterogeneous periodic structure thin film with large negative capacitance and low hysteresis.

[0016] Optionally, in step (1), the stepwise thermal desorption treatment of the substrate, in step (2), the deposition of the conductive perovskite buffer layer, and in step (3), the deposition of the negative capacitance functional layer are all carried out by pulsed laser deposition.

[0017] Optionally, for the stepwise thermal desorption treatment of the substrate in step (1): the base vacuum degree is 1×10 -10 ~1×10 -5 Pa, two-stage thermal desorption (desorbing the physical adsorption layer at 300°C to 500°C, decomposing the chemical adsorbate at 650°C - 850°C).

[0018] Optionally, in step (2), the conductive perovskite buffer layer is deposited by pulsed laser deposition technology with a controllable spot area. Under the conditions of a background vacuum of 1×10 -10 ~1×10 -5 Pa and a deposition temperature of 650 - 700 °C, the rectangular laser spot area is dynamically adjusted to 0.1 - 0.5 cm 2 through an optical zoom system, and the energy gradient attenuation rate from the center to the edge of the spot is 1 - 15%. Combining a laser energy of 450 - 530 mJ and a mass flow meter to dynamically adjust the oxygen partial pressure to 50 - 100 mTorr, precise control of the interfacial lattice distortion is achieved.

[0019] Optionally, in step (3), the negative capacitance functional layer is deposited by pulsed laser deposition technology with a controllable spot area. Under the conditions of a background vacuum of 1×10 -10 ~1×10 -5 Pa and a deposition temperature of 580 - 650 °C, the rectangular laser spot area is dynamically adjusted to 0.1 - 0.3 cm 2 through an optical zoom system, and the energy gradient attenuation rate from the center to the edge of the spot is 1 - 10%. Combining a laser energy of 400 - 500 mJ and a mass flow meter to dynamically adjust the oxygen partial pressure to 180 - 250 mTorr, precise control of the interfacial lattice distortion is achieved.

[0020] In addition, the third object of the present invention is to claim the above-mentioned hetero-periodic structure thin film with large negative capacitance and low hysteresis, or the hetero-periodic structure thin film with large negative capacitance and low hysteresis prepared by the above method, which is expected to achieve a low subthreshold swing and low hysteresis in field effect transistors, thus having an important application prospect in microelectronics fields such as low-power logic devices.

[0021] Advantages of the present invention:

[0022] 1. Traditional negative capacitance effect regulation only focuses on the change in the intensity of polarization in the vertical direction, and regulates the negative capacitance and hysteresis characteristics through a single way of the capacitance value ratio between the ferroelectric layer and the dielectric layer, resulting in the inability to optimize the two synergistically. Based on the understanding that the negative capacitance effect originates from the depolarization effect (polarization shielding mechanism) in polarization reversal, the present invention selects to regulate the polarization shielding mechanism and the negative capacitance effect by finely changing the interfacial lattice distortion. Specifically, the present invention drives the polarization and oxygen octahedra near the interface in the CaTiO3 / PbTiO3 hetero-periodic structure to rotate at a specific angle by using Ca ions with a smaller atomic radius, thereby finely changing the interfacial electronic structure and providing more freely migratable charges. Using a new physical mechanism, the present invention overcomes the capacitance matching rule limitation of traditional negative capacitance effect regulation, can shield and stabilize a larger spontaneous polarization value, and finally realizes the synergistic optimization of the capacitance enhancement value and hysteresis;

[0023] 2. The selected CaTiO3 material in the present invention can not only make the lattice distortion at the interface controllable, but also, due to the high thermal conductivity of CaTiO3, the thermal stability of the negative capacitance effect of the CaTiO3 / PbTiO3 heteroperiodic structure thin film is significantly improved compared with traditional heteroperiodic structure materials, enhancing the working thermal stability of the negative capacitance transistor device;

[0024] 3. Traditional pulsed laser deposition technology only focuses on the linear adjustment of laser energy and lacks consideration of the influence of the laser spot shape on lattice growth dynamics. The uneven attenuation from the center to the periphery of the laser spot results in an energy adjustment accuracy of only the millijoule level for the laser deposition plume, ultimately causing uncontrollable lattice distortion in the atomic layer-by-layer epitaxy. To achieve the controllable preparation of the lattice distortion at the interface of the CaTiO3 / PbTiO3 heteroperiodic structure thin film, based on the idea of fine control of laser energy and deposition plume, by comprehensively considering the influence of the laser shape and laser energy distribution on the deposition plume caused by target ablation, the controllable and efficient preparation of the CaTiO3 / PbTiO3 heteroperiodic structure thin film with a narrow process range, its ferroelectric lattice distortion, and oxygen octahedron distortion is realized with ultra-high-precision energy plume control, and finally a CaTiO3 / PbTiO3 heteroperiodic structure thin film with large negative capacitance and low hysteresis is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0026] Figure 1 It is a schematic diagram of the structure of the CaTiO3 / PbTiO3 heteroperiodic structure thin film provided by the present invention and a TEM image of the CaTiO3 / PbTiO3 heteroperiodic structure thin film prepared in Example 2.

[0027] Figure 2 It is a STEM image and a polarization vector diagram of the CaTiO3 / PbTiO3 heteroperiodic structure thin film prepared in Example 2 of the present invention.

[0028] Figure 3 It is the capacitance-voltage curves of the CaTiO3 / PbTiO3 heteroperiodic structure thin films and the single-layer CaTiO3 thin films prepared in Examples 1-4 of the present invention.

[0029] Figure 4 It is the charge-voltage curve of the CaTiO3 / PbTiO3 heteroperiodic structure thin film prepared in Example 1 of the present invention.

[0030] Figure 5 The dielectric constant / dielectric loss - temperature curve of the CaTiO3 / PbTiO3 hetero - periodic structure thin film prepared in Example 1 of the present invention. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention and the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1

[0033] In this embodiment, an SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 , and a crystal plane orientation of (001) is selected.

[0034] Using pulsed laser deposition technology, step - type thermal desorption treatment of the substrate: the base vacuum is 1×10 -7 Pa, two - stage thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemical adsorbate at 700 °C).

[0035] Using pulsed laser deposition technology, deposit a conductive perovskite buffer layer SrRuO3 on the SrTiO3 substrate. The operating conditions are: the base vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, the rectangular laser spot area is 0.3 cm 2 , the energy gradient attenuation rate from the center to the edge of the spot is 7%, and the deposition time is 5 min, obtaining an SrRuO3 layer with a thickness of about 10 nm.

[0036] Using pulsed laser deposition technology, periodically stack PbTiO3 and CaTiO3 alternately on the SrRuO3 conductive perovskite buffer layer. The operating conditions are: the base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.2 cm 2 , the energy gradient attenuation rate from the center to the edge of the spot is 5%, the deposition time for each layer is 3 min, and the cycle period is 12 times, obtaining a CaTiO3 / PbTiO3 hetero - periodic structure thin film with a periodic thickness of about 18 u.c.

[0037] Example 2

[0038] In this embodiment, an SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 and a crystal plane orientation of (001) is selected.

[0039] Using pulsed laser deposition technology, stepwise thermal desorption treatment of the substrate: The base vacuum is 1×10 -7 Pa, two-stage thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemisorbed substances at 700 °C).

[0040] Using pulsed laser deposition technology, deposit a conductive perovskite buffer layer SrRuO3 on the SrTiO3 substrate. The operating conditions are as follows: The base vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, the rectangular laser spot area is 0.3 cm 2 ², the energy gradient decay rate from the center to the edge of the spot is 7%, and the deposition time is 5 min to obtain an SrRuO3 layer with a thickness of about 10 nm.

[0041] Using pulsed laser deposition technology, periodically stack PbTiO3 and CaTiO3 alternately on the SrRuO3 conductive perovskite buffer layer. The operating conditions are as follows: The base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.2 cm 2 ², the energy gradient decay rate from the center to the edge of the spot is 5%, the deposition time for each layer is 1.5 min, and the cycle period is 15 times to obtain a CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of about 9 u.c.

[0042] Example 3

[0043] In this embodiment, an SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 and a crystal plane orientation of (001) is selected.

[0044] Using pulsed laser deposition technology, stepwise thermal desorption treatment of the substrate: The base vacuum is 1×10 -7 Pa, two-stage thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemisorbed substances at 700 °C).

[0045] Using pulsed laser deposition technology, deposit a conductive perovskite buffer layer SrRuO3 on the SrTiO3 substrate. The operating conditions are as follows: The base vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, the rectangular laser spot area is 0.3 cm 2, the energy gradient attenuation rate from the center to the edge of the light spot is 7%, and the deposition time is 5 min, obtaining an SrRuO3 layer with a thickness of about 10 nm.

[0046] Using pulsed laser deposition technology, PbTiO3 and CaTiO3 are periodically and alternately stacked on the SrRuO3 conductive perovskite buffer layer. The operating conditions are as follows: the background vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, and the area of the rectangular laser spot is 0.2 cm 2 , the energy gradient attenuation rate from the center to the edge of the light spot is 5%, the deposition time for each layer is 1 min, and the cycle period is 20 times, obtaining a CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of about 6 u.c.

[0047] Example 4

[0048] In this example, an SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 , and a crystal plane orientation of (001) is selected.

[0049] Using pulsed laser deposition technology, stepwise thermal desorption treatment of the substrate: the background vacuum is 1×10 -7 Pa, two-stage thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemical adsorbate at 700 °C).

[0050] Using pulsed laser deposition technology, deposit the conductive perovskite buffer layer SrRuO3 on the SrTiO3 substrate. The operating conditions are as follows: the background vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, and the area of the rectangular laser spot is 0.3 cm 2 , the energy gradient attenuation rate from the center to the edge of the light spot is 7%, and the deposition time is 5 min, obtaining an SrRuO3 layer with a thickness of about 10 nm.

[0051] Using pulsed laser deposition technology, PbTiO3 and CaTiO3 are periodically and alternately stacked on the SrRuO3 conductive perovskite buffer layer. The operating conditions are as follows: the background vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, and the area of the rectangular laser spot is 0.2 cm 2 , the energy gradient attenuation rate from the center to the edge of the light spot is 5%, the deposition time for each layer is 0.5 min, and the cycle period is 30 times, obtaining a CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of about 3 u.c.

[0052] The above Examples 1-4 were tested and analyzed.

[0053] Figure 1 are the structural schematic diagram of the CaTiO3 / PbTiO3 hetero-periodic structure thin film and the TEM image of the CaTiO3 / PbTiO3 hetero-periodic structure thin film prepared in Example 2. The results show the high-quality epitaxial growth of the CaTiO3 / PbTiO3 hetero-periodic structure thin film.

[0054] Figure 2 are the STEM image and the polarization vector diagram of the CaTiO3 / PbTiO3 hetero-periodic structure thin film prepared in Example 2. The results show that the tilt angle of the interfacial oxygen octahedron reaches 7°, and the rotation angle of the polarization vector is -90 to 90°, presenting a sinusoidal waveform polarization.

[0055] Figure 3 are the capacitance-voltage curves of the CaTiO3 / PbTiO3 hetero-periodic structure thin films with different periodic thicknesses and the single-layer CaTiO3 thin film prepared in Examples 1-4. The results show that the capacitance values of the CaTiO3 / PbTiO3 hetero-periodic structure thin films with periodic thicknesses of 3, 6, 9, and 18 u.c. are enhanced by 1.8, 2, 2.3, and 2.1 times respectively compared with the capacitance value of the single-layer CTO thin film.

[0056] Figure 4 is the charge-voltage curve of the CaTiO3 / PbTiO3 hetero-periodic structure thin film prepared in Example 1. The results show that the Q-V curves during the polarization switching and back switching of the CaTiO3 / PbTiO3 hetero-periodic structure thin film basically coincide, indicating that the CaTiO3 / PbTiO3 hetero-periodic structure thin film has a small hysteresis at this periodic thickness.

[0057] The above results show that by using the pulsed laser deposition technology with a controllable spot area, the interfacial lattice distortion of the CaTiO3 / PbTiO3 hetero-periodic structure thin film is regulated, thereby improving the interfacial screening mechanism, synergistically optimizing the negative capacitance effect intensity and state stability, and obtaining a large capacitance enhancement value and a low hysteresis.

[0058] Figure 5 is the dielectric constant / dielectric loss-temperature curve of the CaTiO3 / PbTiO3 hetero-periodic structure thin film prepared in Example 1. The results show that the change in the dielectric constant of the CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of 18 u.c. with temperature is small (2.6%), indicating its good thermal stability for operation.

[0059] In summary, it is shown that the CaTiO3 / PbTiO3 hetero-periodic structure thin film has large negative capacitance, low hysteresis, and good thermal stability during operation, and is expected to achieve low sub-threshold swing and low hysteresis in negative capacitance field effect transistors.

[0060] Example 5

[0061] In this example, an SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 , and a crystal plane orientation of (001) was selected.

[0062] Using pulsed laser deposition technology, stepwise thermal desorption treatment of the substrate: the base vacuum was 1×10 -7 Pa, two-step thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemisorbed substances at 700 °C).

[0063] Using pulsed laser deposition technology, deposit a conductive perovskite buffer layer SrRuO3 on the SrTiO3 substrate. The operating conditions are as follows: the base vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, the rectangular laser spot area is 0.3 cm 2 , the energy gradient attenuation rate from the center to the edge of the spot is 7%, and the deposition time is 5 min to obtain an SrRuO3 layer with a thickness of about 10 nm.

[0064] Using pulsed laser deposition technology, alternately stack PbTiO3 and CaTiO3 periodically on the SrRuO3 conductive perovskite buffer layer. The operating conditions are as follows: when depositing the PbTiO3 thin film, the base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.2 cm 2 , the energy gradient attenuation rate from the center to the edge of the spot is 5%; when depositing the CaTiO3 thin film, the base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.25 cm 2 , the energy gradient attenuation rate from the center to the edge of the spot is 6%; the deposition time for each layer is 3 min, and the cycle period is 12 times to obtain a CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of about 18 u.c.

[0065] According to the test method in Example 1, the results show that the effect of Example 2 is roughly the same as that of Example 1.

[0066] Example 6

[0067] In this embodiment, a SrTiO3 substrate with a thickness of 0.5 mm, a size of 25 mm 2 and a crystal plane orientation of (001) is selected.

[0068] Using pulsed laser deposition technology, the substrate is subjected to stepped thermal desorption treatment: the base vacuum is 1×10 -7 Pa, and two-stage thermal desorption (desorbing the physical adsorption layer at 400 °C and decomposing the chemisorbed substances at 700 °C).

[0069] Using pulsed laser deposition technology, a conductive perovskite buffer layer SrRuO3 is deposited on the SrTiO3 substrate. The operating conditions are as follows: the base vacuum is 1×10 -7 Pa, the deposition temperature is 690 °C, the oxygen partial pressure is 80 mTorr, the laser energy is 500 mJ, the rectangular laser spot area is 0.3 cm 2 , the energy gradient decay rate from the center to the edge of the spot is 7%, and the deposition time is 5 min, resulting in a SrRuO3 layer with a thickness of about 10 nm.

[0070] Using pulsed laser deposition technology, PbTiO3 and CaTiO3 are periodically and alternately stacked on the SrRuO3 conductive perovskite buffer layer. The operating conditions are as follows: when depositing the PbTiO3 thin film, the base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the deposition oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.25 cm 2 , the energy gradient decay rate from the center to the edge of the spot is 6%; when depositing the CaTiO3 thin film, the base vacuum is 1×10 -7 Pa, the deposition temperature is 600 °C, the oxygen partial pressure is 200 mTorr, the laser energy is 450 mJ, the rectangular laser spot area is 0.2 cm 2 , the energy gradient decay rate from the center to the edge of the spot is 5%; the deposition time for each layer is 3 min, and the cycle period is 12 times, resulting in a CaTiO3 / PbTiO3 hetero-periodic structure thin film with a periodic thickness of about 18 u.c.

[0071] According to the test method in Example 1, the results show that the effect of Example 6 is roughly similar to that of Example 1.

[0072] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heterogeneous periodic structure thin film with large negative capacitance and low hysteresis, characterized in that, It includes a substrate; a conductive perovskite buffer layer formed on the substrate; and a negative capacitance functional layer for controlling interfacial lattice distortion formed on the conductive perovskite buffer layer. Among them, the negative capacitance functional layer is formed by self-assembled periodic stacking of two materials, PbTiO3 and CaTiO3, in a specific thickness ratio to construct a hetero-periodic structure with controllable interfacial lattice distortion.

2. The hetero-periodic structure thin film with large negative capacitance and low hysteresis according to claim 1, wherein The interfacial lattice distortion in the negative capacitance functional layer includes ferroelectric lattice distortion and interfacial oxygen octahedron distortion. The polarization vector rotation angle is -90 to 90°, and the rotation angle of the interfacial oxygen octahedron is -10 to 10°.

3. A heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 1, characterized in that The periodic thickness ratio of the PbTiO3 layer to the CaTiO3 layer in the negative capacitance functional layer is 0.5 to 2. The cycle period of the negative capacitance functional layer is 12 to 30 times, and the total thickness of the negative capacitance functional layer is 50 to 200 nm.

4. A heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 1, characterized in that, The substrate is any one of SrTiO3, DyScO3, and TbScO3, and the crystal plane orientation is any one of (001), (111), or (110).

5. A heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 1, characterized in that, The conductive perovskite buffer layer is a SrRuO3 thin film grown on the substrate. The crystal plane orientation is any one of (001), (111), or (110), the thickness is 5 to 20 nm, and the morphological structure fluctuation is 100 to 1000 pm.

6. The preparation method of a heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 1, characterized in that, It includes the following steps: (1) Sequentially perform ultrasonic cleaning with anhydrous ethanol and stepwise thermal desorption composite treatment on the surface of the single crystal substrate. (2) Epitaxially grow a SrRuO3 conductive perovskite buffer layer on the substrate. (3) On the SrRuO3 conductive perovskite buffer layer, alternately deposit PbTiO3 and CaTiO3 in a self-assembled periodic stacking mode to form a negative capacitance functional layer, that is, a CaTiO3 / PbTiO3 hetero-periodic structure thin film with large negative capacitance and low hysteresis is obtained.

7. The preparation method of a heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 6, characterized in that, In step (1), the stepwise thermal desorption treatment of the substrate, in step (2), the deposition of the conductive perovskite buffer layer, and in step (3), the deposition of the negative capacitance functional layer are all carried out by pulsed laser deposition.

8. The preparation method of a heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 6, characterized in that, The stepwise thermal desorption treatment conditions of the substrate in step (1): the background vacuum degree is 1×10 -10 ~1×10 -5 Pa, two-stage thermal desorption (desorbing the physically adsorbed layer at 300°C to 500°C, decomposing the chemically adsorbed substances at 650°C to 850°C).

9. The preparation method of a heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 6, characterized in that, In step (2), the conductive perovskite buffer layer is deposited by pulsed laser deposition technology with a controllable spot area. Under the conditions of a background vacuum of 1×10 -10 ~1×10 -5 Pa and a deposition temperature of 650 - 700 °C, the rectangular laser spot area is dynamically adjusted to 0.1 - 0.5 cm 2 , and the energy gradient decay rate from the center to the edge of the spot is 1 - 15%. Combining a laser energy of 450 - 530 mJ and a mass flow meter to dynamically adjust the oxygen partial pressure to 50 - 100 mTorr, precise control of the interfacial lattice distortion is achieved.

10. The preparation method of a heterogeneous periodic structure thin film with large negative capacitance and low hysteresis according to claim 6, characterized in that, In step (3), the negative capacitance functional layer is deposited by pulsed laser deposition technology with a controllable spot area. Under the conditions of a background vacuum of 1×10 -10 ~1×10 -5 Pa and a deposition temperature of 580 - 650 °C, the rectangular laser spot area is dynamically adjusted to 0.1 - 0.3 cm 2 through an optical zoom system, and the energy gradient attenuation rate from the center to the edge of the spot is 1 - 10%. Combining a laser energy of 400 - 500 mJ and a mass flow meter to dynamically adjust the oxygen partial pressure to 180 - 250 mTorr, precise control of the interfacial lattice distortion is achieved.

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