System for exciton-trion conversion and light emission

Abstract

The present invention relates to an exciton-trion conversion and light emission control system, and may include a composite structure of a two-dimensional semiconductor material and a plasmonic nanostructure, a laser irradiation device for irradiating a laser, a plasmonic probe for generating thermionic electrons by the laser irradiation device and injecting them into the composite structure, and a position adjustment unit for adjusting the position of the plasmonic probe.

Description

Technology Field

[0001] The present invention relates to an exciton-trion conversion and light emission control system, and more specifically, to a system capable of controlling the amount of exciton radiation emission by thermionic injection using a gold probe. Background Technology

[0002] Generally, a technology that combines plasmonic nanostructures with two-dimensional semiconductor materials to control exciton formation and emission characteristics is widely used as a method to improve and control the electrical and optical properties of two-dimensional semiconductors.

[0003] In particular, using plasmonic waveguide structures such as nanowires allows for spatial control of excitons, which has high potential for application in the development of optical integrated devices.

[0004] In this case, the coupling between excitons generated in a two-dimensional semiconductor and surface plasmons generated in a plasmonic structure is mainly utilized, and generally, the coupling strength between excitons and surface plasmons is proportional to the light intensity measured in the plasmonic structure.

[0005] Therefore, by designing plasmonic nanostructures to understand the surface plasmon distribution in space and combining them with two-dimensional semiconductors, it is possible to apply high-density optical integrated devices and high-efficiency optoelectronic devices.

[0006] As related prior art, there is the applicant of the present invention’s registered patent No. 10-2589324 (registered on October 10, 2023, optical signal recording method and medium).

[0007] In order to effectively combine and utilize exciton quasiparticles and surface plasmons generated in two-dimensional semiconductor and plasmonic composite structures, a structure suitable for each purpose is required.

[0008] Since it is difficult to change the properties of fixed composite structures, it is necessary to fabricate new structures to modify electrical and optical properties.

[0009] This reduces the versatility of the manufactured structure, resulting in many limitations on its application.

[0010] To address this, a technology has been developed to fabricate a device structure on a substrate and induce a change in properties according to the substrate strain, but the problem still exists that the deformation occurs throughout the entire structure and the deformation may be irreversible. The problem to be solved

[0012] The problem that the present invention aims to solve, taking into account the above-mentioned problems, is to provide a system capable of controlling the characteristics of a two-dimensional semiconductor and a plasmonic composite structure by providing various control variables. means of solving the problem

[0014] The system of the present invention for solving the above technical problems may include a composite structure of a two-dimensional semiconductor material and a plasmonic nanostructure, a laser irradiation device for irradiating a laser, a plasmonic probe that generates thermionic electrons by the laser irradiation device and injects them into the composite structure, and a position adjustment unit for adjusting the position of the plasmonic probe.

[0015] In an embodiment of the present invention, the two-dimensional semiconductor material is a molybdenum diselenide monolayer, the plasmonic nanostructure is a metal nanowire, and the composite structure may be composed of a molybdenum diselenide monolayer transferred onto the metal nanowire formed on the upper surface of a substrate.

[0016] In an embodiment of the present invention, the plasmonic probe generates energy through localized surface plasmon resonance by the laser, and hot electrons may be emitted during the decay process of the energy.

[0017] In an embodiment of the present invention, the plasmonic probe may be a metal probe.

[0018] In an embodiment of the present invention, the plasmonic probe is adjusted by the positioning unit within a range of 1 to 10 nm with respect to the composite structure, thereby controlling the thermionic electrons injected into the composite structure.

[0019] In an embodiment of the present invention, the composite structure, the two-dimensional semiconductor material and the plasmonic nanostructure have charges distributed spatially differently, so that neutral excitons and negative trions can be converted and light emitted.

[0020] In an embodiment of the present invention, the neutral exciton of the two-dimensional semiconductor material can be changed into a negative trion by the thermionic electron injected from the plasmonic probe, thereby controlling the light emission.

[0021] In an embodiment of the present invention, the conversion of excitons into trions by electrostatic interaction can be controlled according to the charge distribution of each of the plasmonic probe and the plasmonic nanostructure. Effects of the invention

[0023] The exciton-trion conversion and light emission control system of the present invention provides a composite structure in which molybdenum diselenide, a two-dimensional semiconductor, and gold nanowires, a plasmonic nanostructure, are joined. When a laser is excited, charges distributed in space are induced by plasmons generated from the gold nanowires, and the induced charges induce electrostatic doping of the molybdenum diselenide, a two-dimensional semiconductor, thereby having the effect of being able to control the conversion ratio of neutral excitons and negative trions among exciton quasiparticles in various ways.

[0024] In addition, the present invention utilizes a probe controlled with nanometer-level precision to adjust the distance and position to the composite structure, thereby providing various control variables. This allows for application not only to photovoltaic devices but also to solar cells, display semiconductors, and the like, thus enhancing versatility. Brief explanation of the drawing

[0025] FIG. 1 is a block diagram of the exciton-trion conversion and light emission control system of the present invention. Figure 2 is a manufacturing process flowchart of a composite structure applied to the present invention. Figure 3 shows the result of measuring the optical signal of the composite structure with a confocal microscope and displaying it as a hyperspectral image. Figure 4 is the simulation result for theoretical analysis. FIG. 5 is a schematic diagram of controlling exciton quasiparticles generated in a composite structure (10) with a gold probe (Au tip). Figure 6 is a graph of experimental results to confirm the thermionic emission effect of a gold probe (Au tip). Figure 7 is an example of a measurement using a probe-enhanced nanomicroscope with a composite structure. Specific details for implementing the invention

[0026] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of the embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. In the attached drawings, components are depicted enlarged from their actual size for convenience of explanation, and the proportions of each component may be exaggerated or reduced.

[0027] Terms such as 'first' and 'second' may be used to describe various components, but said components should not be limited by said terms. These terms may be used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, 'first component' may be named 'second component,' and similarly, 'second component' may be named 'first component.' Furthermore, singular expressions include plural expressions unless the context clearly indicates otherwise. Unless otherwise defined, terms used in the embodiments of the present invention may be interpreted in the sense commonly known to those skilled in the art.

[0029] FIG. 1 is a block diagram of the exciton-trion conversion and light emission control system of the present invention.

[0030] Referring to FIG. 1, the present invention may include a composite structure (10) of a two-dimensional semiconductor material and a plasmonic nanostructure, a laser irradiation device (20) for irradiating a laser, a plasmonic probe (30) for generating thermionic electrons by the laser irradiation device (20) and injecting them into the composite structure (10), and a position adjustment unit (40) for adjusting the position of the plasmonic probe (30).

[0031] Hereinafter, the configuration and operation of an exciton-trion conversion and light emission control system according to a preferred embodiment of the present invention configured as described above will be explained in more detail.

[0032] FIG. 2 is a flowchart of the manufacturing process of a composite structure (10) applied to the present invention.

[0033] Referring to FIG. 2, the composite structure (10) applied to the present invention is composed of a composite structure of a two-dimensional semiconductor material and a plasmonic nanostructure.

[0034] The above two-dimensional semiconductor material uses molybdenum diselenide (MoSe2), and the plasmonic nanostructure can use gold nanowires.

[0035] First, a single layer of molybdenum diselenide (MoSe2), which is a two-dimensional semiconductor material layer grown on a substrate, is prepared, and poly(methyl methacrylate), PMMA, is coated on top of the molybdenum diselenide by spin coating at 2000 RPM for 60 seconds.

[0036] After that, the PMMA / MoSe2 film on the substrate is immersed in a diluted hydrofluoric acid (dHF) solution to separate the substrate.

[0037] Next, the PMMA / MoSe2 film is washed with distilled water and then transferred to a new substrate on which gold nanowires (AuNWs) are formed.

[0038] In this case, the new substrate can be a dielectric substrate, and an SiO2 substrate can be used.

[0039] Afterwards, the transferred sample is immersed in acetone for at least 10 minutes to remove PMMA.

[0040] Finally, wash off the acetone residue with isopropyl alcohol.

[0041] Although a composite structure of molybdenum diselenide and gold nanowires can be fabricated through such a process, the present invention is not limited to this manufacturing method.

[0042] For convenience of explanation, the molybdenum diselenide and gold nanowire composite structure can be described as a composite structure (10).

[0043] Figure 3 shows the result of measuring the optical signal of the composite structure fabricated above with a confocal microscope and displaying it as a hyperspectral image.

[0044] Figure 3a shows the result of imaging the scattering signal of surface plasmon polaritons (SPPs) generated in gold nanowires within a composite structure, through which the spatial distribution of plasmons can be determined.

[0045] Figure 3b shows the result of a super-resolved image of the trion (X-) photoluminescence (PL) signal generated in molybdenum diselenide within the composite structure, and it can be seen that it is different from the SPP distribution in Figure 3a.

[0046] Figure 3c is an image showing the exciton (X0) to trion ratio occurring in molybdenum diselenide, and it is confirmed that X0 / X- decreases in the opposite direction at the two locations showing maximum values ​​in Figure 2b.

[0047] Finally, Figure 3d is a graph comparing the line profiles indicated by white dashed lines in the images of Figures 3a and 3b. As can be seen in Figure 3d, an X-distribution different from the SPP, which has four peak points, is observed. It can be confirmed that the locations of the three minimums between the four peak points in the SPP line profile are identical to the locations showing two maximums and one minimum in the X-line profile.

[0048] Figure 4 is a simulation result for theoretically analyzing the result of Figure 3.

[0049] Figure 4a defines the simulation calculation conditions for theoretically analyzing the results of Figure 3, and the length of the gold nanowire, the wavelength of the excitation light, and the polarization direction can be set identically to the experimental conditions of Figure 3.

[0050] The length of the gold nanowire was set to 2.2 μm.

[0051] The simulation results are shown in Fig. 4b.

[0052] The simulation results confirmed that there are four maximum values ​​on the nanowire surface, consistent with the experimental results, and it is predicted that the reason for these results is the charge distribution as shown in Fig. 4c.

[0053] The charge distribution above is the charge distribution of the gold nanowire in the line profile described earlier.

[0054] In Fig. 4d, the four maximums of the SPP are equal to the electric field (Ex), and in Fig. 4e, the three maximums of the trion (two maximums and one minimum) are equal to the three minimums between the four maximums predicted in the simulation.

[0055] Through the results of Figures 3 and 4, it was confirmed that plasmons generated in a plasmonic structure induce charges distributed in space, and that these charges influence the formation of exciton-trions in a two-dimensional semiconductor.

[0056] Next, a plasmonic probe (30) is used as a method to control the generation and radiative emission of exciton-trions. The plasmonic probe (30) may use a gold probe (Au tip), and the description of the invention describes a gold probe. However, the invention may use a metal probe that performs the same function in addition to a gold probe.

[0057] FIG. 5 is a schematic diagram of controlling exciton quasiparticles generated in a composite structure (10) with a gold probe (Au tip).

[0058] Referring to FIG. 5, exciton quasiparticles generated in the MoSe2 / AuNW composite structure can be controlled by a gold probe (Au tip) which is a plasmonic probe (30).

[0059] Through the process of Fig. 4, the electrical and optical properties of the composite structure on the substrate are understood, and

[0060] A gold probe (Au tip), whose position is controlled by a position adjustment unit (40), is brought into the composite structure.

[0061] The position adjustment unit (40) can use an atomic force microscope (AFM).

[0062] At this time, when a laser is excited on a gold probe (Au tip), localized surface plasmon resonance occurs in the gold probe, and hot electrons are generated during the decay process of the energy generated at this time.

[0063] To do this, a laser irradiation device (20) that irradiates a laser is used.

[0064] These thermionic electrons can be transferred / injected into adjacent materials within 10 nanometers of the gold probe.

[0065] At this time, the amount of injected thermionic electrons varies depending on the distance between the gold probe (Au tip) and the composite gold nanowire (AuNW).

[0066] In other words, the closer the gold probe (Au tip) is to the gold nanowire (AuNW), the more thermionic electrons are injected.

[0067] Therefore, exciton radiation emission can be enhanced by controlling the position of the gold probe (Au tip), and the generation and radiation emission of excitons and trions occurring in the molybdenum diselenide monolayer of the composite structure can be controlled.

[0068] As such, the present invention can provide various control variables depending on the position adjustment of the gold probe (Au tip) and can be applied to various systems that are actively controlled at the nanoscale (1–10 nm). In other words, versatility can be improved.

[0069] Figure 6 is a graph of experimental results to confirm the thermionic emission effect of a gold probe (Au tip).

[0070] Figure 6a is a simulation result showing the magnitude of the electric field (Ez) generated between a gold nanowire (AuNW) and a gold probe (Au tip).

[0071] As described above, the area on the surface of the gold nanowire (AuNW) where the electric field is strongest is where the gold probe (Au tip) is located, and it can be confirmed that the gold probe-gold nanowire cavity exhibits high enhancement.

[0072] Figure 6b is the spectroscopic spectrum before and after a gold probe approaches a monolayer sample of molybdenum diselenide without nanowires.

[0073] Before the gold probe approaches (FF), most of the photoluminescent signal consists of excitons (X0).

[0074] When the gold probe approaches the sample and the distance between the gold probe and the sample becomes less than 10 nanometers, it can be confirmed that not only is the overall photoluminescence signal increased due to the enhancement effect of the probe, but the number of trions (X-) also increases significantly due to the thermionic injection effect by the gold probe.

[0075] When comparing the two signals measured when the gold probe was at a distance of 3 nanometers and 8 nanometers from the sample, it was observed that when the probe was closer (3 nm), the excitons in the photoluminescence signal decreased and the trions increased further.

[0076] This means that the thermionic injection effect of the gold probe increases as the distance increases, and is significantly affected by nanometer-level distance control.

[0077] Figure 7 is an example of a measurement using a probe-enhanced nanomicroscope with the composite structure of Figures 3 and 4.

[0078] Figure 7a is a super-resolved image of the exciton photoluminescence wavelength range obtained using a probe-enhanced nanomicroscope, showing the enhanced light intensity compared to when there is no gold probe.

[0079] It is confirmed that the enhancement is greater at a total of three locations: both ends and the center of the gold nanowire.

[0080] Figure 7b is an image showing the photoluminescence probe enhancement rate of the trion in the same way as Figure 7a, and also shows the charge distribution of the gold nanowire at different positions.

[0081] Comparing Figure 7a and 7b, it was confirmed that the enhancement rate for both excitons and trions was highest at the positively charged position (+), while conversely, the enhancement rate for both excitons and trions was relatively low at the negatively charged position (-).

[0082] For a more detailed comparison, the spectroscopic signals before and after the gold probe approach at each location with positive and negative charges were analyzed, and it was confirmed that at the location with negative charge (i), the exciton increased significantly when the gold probe approached, but the trion decreased conversely.

[0083] In the case of the positively charged position (ii), it was confirmed that both excitons and trions increased significantly when the gold probe approached.

[0084] These results confirm that when the gold probe is negatively charged by thermionic electrons, electrostatic attraction or repulsion occurs depending on the surface charge of a nearby nanowire; consequently, a stronger thermionic injection effect is observed when attraction occurs between the two charges, while the thermionic injection effect is weakened when repulsion occurs.

[0085] The present invention shows that a two-dimensional semiconductor and plasmonic nanowire composite structure can induce charge distribution in space, and by combining a plasmonic probe, the thermionic injection effect in a probe-nanowire cavity structure and the exciton-trion conversion by electrostatic interaction according to the charges of the probe and the nanowire, respectively, can be actively controlled.

[0087] Although embodiments according to the present invention have been described above, they are merely illustrative and those skilled in the art will understand that various modifications and equivalent embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the following claims. Explanation of the symbols

[0089] 10: Composite structure 20: Laser irradiation device 30: Plasmonic probe 40: Position adjustment unit

Claims

Claim 1 An exciton-trion conversion and light emission control system comprising: a composite structure of a two-dimensional semiconductor material and a plasmonic nanostructure; a laser irradiation device for irradiating a laser; a plasmonic probe that generates thermionic electrons by the laser irradiation device and injects them into the composite structure; and a position adjustment unit for adjusting the position of the plasmonic probe, wherein the composite structure comprises a two-dimensional semiconductor material and a plasmonic nanostructure having spatially different charge distributions to convert neutral excitons and negative trions and emit light, and the neutral excitons of the two-dimensional semiconductor material are converted into negative trions by thermionic electrons injected from the plasmonic probe to control light emission, wherein the conversion of excitons into trions by electrostatic interaction is controlled according to the charge distribution of each of the plasmonic probe and the plasmonic nanostructure. Claim 2 An exciton-trion conversion and light emission control system according to claim 1, wherein the two-dimensional semiconductor material is a molybdenum diselenide monolayer, the plasmonic nanostructure is a metal nanowire, and the composite structure is composed of a molybdenum diselenide monolayer transferred onto the metal nanowire formed on the upper surface of a substrate. Claim 3 An exciton-trion conversion and light emission control system according to claim 1 or 2, wherein the plasmonic probe generates energy through localized surface plasmon resonance by the laser, and emits hot electrons during the decay process of said energy. Claim 4 An exciton-trion conversion and light emission control system according to claim 3, characterized in that the plasmonic probe is a metal probe. Claim 5 An exciton-trion conversion and light emission control system according to claim 3, wherein the plasmonic probe is adjusted by the positioning unit within a range of 1 to 10 nm with respect to the composite structure to control the thermionic electrons injected into the composite structure. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete

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