A method for optimizing performance of TMDs plasmonic phototransistors by laser impact

Abstract

The application discloses a method for optimizing the performance of a TMDs plasmonic phototransistor by laser impact. The method comprises the following steps: providing a composite nanostructure layer, wherein the composite nanostructure layer comprises a two-layer metal nanoparticle layer and a TMDs layer arranged between the two-layer metal nanoparticle layer; treating the composite nanostructure layer by using pulse laser impact; forming a metal electrode on the composite nanostructure layer subjected to the laser impact to obtain a phototransistor, and testing the performance of the phototransistor. In the technical scheme, the method for optimizing the performance of the TMDs plasmonic phototransistor by laser impact can make the TMDs and the metal nanoparticles undergo cooperative deformation, reduce the gap between the nanoparticles, further improve the local field enhancement effect of the "gap mode" LSPR, and cause the strain of the TMDs to increase, the band gap to decrease, the light absorption range to expand, and finally the performance of the phototransistor to be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser nanoscale processing of semiconductor transistors, and particularly relates to a method for optimizing performance of a TMDs plasmonic phototransistor by laser impact. BACKGROUND

[0002] For a TMDs phototransistor, the low light absorption rate of the material itself has always been a key problem that hinders the improvement of device performance. How to improve the light responsivity of the device while reducing the response time of the device is a great challenge. In the past, people have used multi-layer structures, single multi-layer heterojunction structures, introduced photonic crystals or surface plasmon resonance to enhance the light absorption capacity of single-layer TMDs and improve device performance. The localized surface plasmon resonance (LSPR) generated by metal nanostructures can provide many advantages, such as controllable manufacturing, device reliability and wavelength adjustability. Previous studies have focused on adjusting the LSPR behavior by adjusting the optical constants, geometry and arrangement of nanostructures of the material, for example, nanoparticles with sharp tips exhibit resonance in a wider wavelength range and have better local field enhancement effect at sharp edges. In addition, for metal nanoparticle dimers formed by high-density distribution, a "gap mode" localized surface plasmon resonance is generated, and according to the plasmonic hybridization theory, the size of the gap will play a decisive role in the size of the generated local electric field.

[0003] For TMDs, good mechanical properties allow elastic strain, usually reaching about ten percent before breaking. It has been reported that placing exfoliated 1L-TMDs on a well-designed corrugated surface has been proven to increase the field-effect mobility of electronic devices by one to two orders of magnitude, and the strain can change the conformation (length, angle and strength) of atomic bonds and the interaction between electron orbitals, which greatly enriches the future application potential of TMDs under strain engineering. However, for large-scale application and actual industrialization, 1L-TMDs synthesized by chemical vapor deposition (CVD) and subsequent transfer are essentially accompanied by many wrinkles, which relax the elastic strain and disturb the morphological design. SUMMARY

[0004] Therefore, the present application provides a method for optimizing performance of a TMDs plasmonic phototransistor by laser impact, which enhances LSPR, increases the strain of TMDs, changes its optical and electrical behavior, thereby widening the spectral response range of the TMDs phototransistor, improving light responsivity and reducing response time.

[0005] <Creation process>

[0006] In the face of the problem that the performance improvement means of TMDs phototransistors in the related art is limited, the inventors have unexpectedly found through systematic experimental research that the stress caused by laser impact can realize the synergistic deformation of metal nanoparticles and TMDs, on the basis of changing the shape of the metal nanoparticles, affecting the relative position distribution of the particles, reducing the gap of the plasmonic dimers, and making the LSPR of the "gap mode" produce greater local field enhancement effect. At the same time, the specific surface area of the TMDs in contact with the particles is increased, and the wrinkle phenomenon caused by strain relaxation is reduced, so that the TMDs produce greater strain.

[0007] Based on the above-mentioned creative findings, through systematic experimental tests, it is found that the method of the present application can make the TMD plasmonic phototransistor have an order of magnitude improvement in terms of light detection range, light responsivity, and light response time. This has a promoting effect on the practical application of TMD plasmonic phototransistors, especially in image sensors, ultrathin photodetectors, or visible light communication receivers. Thus, the present invention is created.

[0008] The present application provides a method for optimizing the performance of TMD plasmonic phototransistors by laser impact, comprising the following steps:

[0009] A composite nanostructure layer is provided, which includes two layers of metal nanoparticle layers and a TMD layer stacked between the two layers of metal nanoparticle layers.

[0010] The composite nanostructure layer is treated using pulsed laser impact.

[0011] A metal electrode is formed on the composite nanostructure layer subjected to laser impact to obtain a phototransistor, and the performance of the phototransistor is tested.

[0012] Suitably but not limitingly, the TMD layer is stacked between the metal nanoparticle layers by wet transfer or dry transfer.

[0013] Suitably but not limitingly, the material of the metal nanoparticle layer is at least one of silver (Ag), aluminum (Al), and gold (Au).

[0014] Suitably but not limitingly, the particle size of the nanoparticles in the metal nanoparticle layer is 20-80 nm.

[0015] Suitably but not limitingly, the reagent for wet transfer is at least one of PMMA and PS.

[0016] Suitably but not limitingly, the dry transfer is mechanical peeling.

[0017] Suitably but not limitingly, the wavelength of the pulsed laser is 1064 nm, the pulse width is 1-10 ns, the frequency is 1-10 Hz, and the laser fluence is 10-20 kJ / cm2. 2 The irradiation time is 1 s.

[0018] Suitably but not limitingly, the metal electrode is deposited by at least one of magnetron sputtering, thermal evaporation, atomic layer deposition, and electron beam evaporation.

[0019] Suitably but not limitingly, the metal electrode material is at least one of Pt, Ti, Au, Cr, Pd, and Ag.

[0020] The present application has the following beneficial effects:

[0021] The elastic strain engineering generated by the laser shock processing of the present method can cause the metal nanoparticles and the TMDs to undergo cooperative deformation, which, while ensuring the optimization of the "interstitial mode" LSPR, causes the optical and electronic behaviors of the TMDs to change, thereby optimizing the performance of the optoelectronic transistor. The method is simple, controllable, efficient, and stable, and is suitable for large-area industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0022] The technical solutions and other beneficial effects of the present application will become apparent from the following detailed description of specific embodiments of the present application, with reference to the accompanying drawings.

[0023] Figure 1 Fig. 1 is a device structure schematic diagram of a single-layer MoS2 after laser shock, for an embodiment of the present application;

[0024] Figure 2 Fig. 2 is a schematic diagram of the deformation process of metal nanoparticles subjected to laser shock, for an embodiment of the present application, obtained by molecular dynamics simulation; Figs. I, II, III, and IV are atomic snapshot diagrams at 0 ps, 15 ps, 35 ps, and 50 ps, respectively;

[0025] Figure 3 Fig. 3 is a steady-state photoluminescence spectrum (PL) for an embodiment of the present application;

[0026] Figure 4 Fig. 4 is an x-z view of the electromagnetic field distribution of metal nanoparticles before and after laser shock, for an embodiment of the present application, obtained by finite-difference time-domain (FDTD) calculation; Figs. (a)-(d) are the electromagnetic field distributions at different particle positions before shock, and Figs. (e)-(f) are the electromagnetic field distributions at different particle positions after shock;

[0027] Figs. 5(a)-(d) are optical response schematic diagrams under 650 nm and 720 nm illumination, for an embodiment of the present application;

[0028] Fig. 6(a)-(f) are schematic diagrams of the light response of the embodiment of the present application under 405 nm and 532 nm light irradiation;

[0029] Fig. 7(a)-(c) are light response diagrams of a single cycle of the embodiment of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0031] In the description of the present application, it should be understood that the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0032] In the description of the present application, it should be noted that, unless otherwise specifically defined and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection or can communicate with each other; it can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to the same reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides various specific examples of processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0034] The structure is as follows Figure 1As shown, the device prepared by the method of the present application has a conductive silicon substrate as the back gate of the transistor, and a 300 nm-thick SiO2layer is coated thereon. Due to the large strain generated by laser impact and the underlying Ag nanoparticles, MoS2bends. Above MoS2, there are also Ag nanoparticles, and two Au electrodes are used as the source and drain electrodes, respectively, with a channel width of 30 microns. The specific preparation includes the following processes:

[0035] R1) Purchase a clean Si / SiO2substrate ready for cleaning; obtain a single layer of MoS2using chemical vapor deposition technology; obtain an array of Au electrodes with a channel length of 30 microns using laser lithography technology;

[0036] R2) Form a thin and thin Ag film on the thin film by vacuum magnetron sputtering technology, and anneal at 150°C for 30 min to obtain a layer of randomly distributed Ag nanoparticles with a diameter of about 40 nm;

[0037] R3) Spin a layer of polystyrene (PS) on the previously prepared MoS2, use wet transfer technology to transfer MoS2to the sample prepared in step R2, and go through annealing and toluene cleaning to make MoS2stick to the substrate and remove impurities;

[0038] R4) Continue the method used in step R2 to form a new layer of Ag nanoparticles on MoS2;

[0039] R5) Use pulsed laser impact to process the sample obtained in step R4, with a pulse laser wavelength of 1064 nm, a pulse width of 9 ns, a frequency of 1 Hz, a laser flux of 12 kJ / cm 2 , and an irradiation time of 1 s.

[0040] R6) Use wet transfer technology to mount the gold electrodes prepared in step R1 on the sample obtained in step R5, and anneal at 200°C to make the electrodes stick to the sample.

[0041] Among them, the examples not treated by steps R2, R4 and R5 are named 1L-MoS2, the examples not treated by step R5 are named Ag-MoS2, and the examples treated by the above steps are named LS_Ag-MoS2.

[0042] To verify the effectiveness of laser impact on the shape change of metal nanoparticles, we performed molecular dynamics simulation. From Figure 2It can be seen that, with the change of time, under the stress effect of laser shock, whether the upper and lower particles are stacked vertically or the upper and lower particles are stacked obliquely, the Ag nanoparticles are finally flattened into spheroids with relatively sharp corners, the particle size is increased, and the nanogap between the particles is also reduced. MoS2 has good ductility, and during the laser shock process, it also bends downward as the silver particles deform, resulting in greater tensile strain. Therefore, laser shock has a stress effect on both Ag nanoparticles and MoS2, and the synergistic deformation is reasonable, and the regulation of the final device performance is profitable.

[0043] To illustrate the effect of tensile strain on MoS2 material, we tested the steady-state PL of MoS2 of the three embodiments. As can be seen from the results of Figure 3, after applying tensile strain to MoS2, the light emission peak is red-shifted, the band gap is reduced, and the light absorption range is widened.

[0044] To further verify the change of the above strain on the local field enhancement effect of LSPR, we used FDTD simulation and calculation to construct several relative position distributions of ideal models. Since the Ag nanoparticles are prepared by rapid annealing in air, there is a thin Ag2O shell on the surface, and for this core-shell structured metal nanoparticle, the generated LSPR is mostly located near the edge of the particle. Comparing Figure 4 a and Figure 4 d, it can be seen that the flat particles have stronger electric field at the sharp corners. As shown in Figure 4 b and Figure 4 e, Figure 4 c and Figure 4 f, for the dimer, the enhancement factor |E / E0| of the "gap mode" LSPR generated is much higher than that of a single particle, and the change in shape brings a shorter nanogap, not only between the two core-shell structured Ag nanoparticles, but also a higher intensity "hot spot" appears, and it is also conducive to the generated LSPR better acting on TMDs. The above results fully prove that the regulation of laser shock on LSPR can achieve better field enhancement effect, which is beneficial to the photoelectric performance of LS_AgMoS2.

[0045] Then we tested the photoresponse of the three embodiments and compared the photoresponse of the three embodiments under different light intensities of 650 nm light. As shown in Figure 5a- c, the photocurrents of both 1L-MoS2 and Ag-MoS2 are almost the same and do not change with the light intensity. However, the photocurrent of LS_AgMoS2 increases with the light intensity and is much larger than that of the other two. This result also shows that the stress induced by laser shock makes the Ag nanoparticles become oblate spheroids, the plasmonic resonance is enhanced and red-shifted, and the phototransistor has more obvious recognition ability for long-wave light. In addition, under 720 nm light, both 1L-MoS2 and Ag-MoS2 do not generate obvious photocurrent, while LS_AgMoS2 still has obvious photocurrent and light response characteristics, as shown in Figure 5d The above results show that the method proposed in the present application can effectively widen the light response range of TMDs plasmonic phototransistors, which also provides a positive method for future infrared band detection expansion, and even has application significance for smart home and human motion detection.

[0046] Finally, the above-mentioned embodiments are supplemented by testing the device photoelectric response under 532 nm and 405 nm light irradiation at different light intensities. It can be seen that the photocurrent of the device with LSPR is much larger than that of pure MoS2, which is consistent with the results under 650 nm light. Through the present application, we can obtain a TMDs photoresponsive transistor with a highest light response of 572 A / W, while the 1L-MoS2 without the present application treatment is only 10.7 A / W, which is more than 50 times higher.

[0047] In addition, we magnify the single period of the light response of the three devices and compare the light response time. As shown in FIG. 7, compared with the longer OFF-ON and ON-OFF response time of 1L-MoS2, the response time of Ag-MoS2 and LS_AgMoS2 is obviously improved, and even in the LS_AgMoS2 embodiment, the OFF-ON response time is only 0.02 s, and the ON-OFF response time is as fast as 0.08 s. According to our knowledge, compared with the same low-K medium single-layer MoS2 phototransistor device, the response time of the phototransistor device obtained by the method of the present application is the best.

[0048] The above-mentioned is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for optimizing the performance of TMDs plasmonic phototransistors using laser shock, characterized in that, Includes the following steps: A composite nanostructure layer is provided, the composite nanostructure layer comprising a two-layer metal nanoparticle layer and a TMDs layer stacked between the two-layer metal nanoparticle layer; the TMDs layer is a MoS2 layer. The composite nanostructure layer is treated with pulsed laser shock. The stress caused by the laser shock is used to achieve synergistic deformation of metal nanoparticles and TMDs. By changing the shape of the metal nanoparticles, the relative position distribution of the particles is affected, and the gap of the plasmonic dimers is reduced. The gap of the plasmonic dimers is the thickness of a single MoS2 layer, which makes the gap mode LSPR produce a greater local field enhancement effect. Metal electrodes are formed on a composite nanostructure layer subjected to laser shock to obtain a phototransistor, and the performance of the phototransistor is tested.

2. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The TMDs layers are stacked between the metal nanoparticle layers by wet transfer or dry transfer.

3. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The material of the metal nanoparticle layer is at least one of silver (Ag), aluminum (Al), and gold (Au).

4. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The nanoparticles in the metal nanoparticle layer have a particle size of 20-80 nm.

5. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 2, characterized in that, The reagent used for wet transfer is at least one of PMMA and PS.

6. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 2, characterized in that, The dry transfer method is mechanical stripping.

7. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The pulsed laser has a wavelength of 1064 nm, a pulse width of 1-10 ns, a frequency of 1-10 Hz, and a laser flux of 10-20 kJ / cm². 2 The irradiation time is 1 second.

8. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The metal electrode is deposited by at least one of magnetron sputtering, thermal evaporation, atomic layer deposition, and electron beam evaporation.

9. The method for optimizing the performance of TMDs plasmonic phototransistors using laser shock according to claim 1, characterized in that, The metal electrode material is at least one of Pt, Ti, Au, Cr, Pd, and Ag.

Images