Preparation method of photoelectric detector with light modulation negative differential resistance phenomenon
A dry transfer method for stacking MoS2, h-BN, and WS2 layers on a SiO2/Si substrate with gold electrodes creates a photodetector with light-modulated negative differential resistance, addressing the complexity and cost issues of existing devices, enabling efficient integration and adjustable performance in optoelectronics.
Patent Information
- Application Number
- CN202411322157.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-23
- Publication Date
- 2024-12-20
AI Technical Summary
Existing electrically controlled negative differential resistance devices are complex and energy-intensive, hindering their practical application in large-scale integrated circuits, necessitating the development of an optically controlled photodetector with a simple preparation process and low cost for integration in optoelectronic devices.
A method involving a dry transfer process to stack MoS2, h-BN, and WS2 layers on a SiO2/Si substrate with gold electrodes, forming a unipolar barrier photodetector that exhibits light-modulated negative differential resistance.
The method enables a simple, cost-effective photodetector with light-adjustable negative differential resistance, suitable for high-frequency oscillators, and facilitates easy integration into optoelectronic devices.
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Figure CN119170711A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of preparing two-dimensional material electronic devices by dry transfer method, and specifically relates to a preparation method of a photoelectric detector with light-modulated negative differential resistance phenomenon. Background Art
[0002] The gradual miniaturization of electronic devices has driven the development of various technologies towards higher performance and higher efficiency, but in order to achieve greater progress and innovative solutions, it is necessary to turn from traditional methods to transformative material systems and integrated technologies. Negative differential resistance is one of the hottest topics in solid-state electronic devices. The negative differential resistance phenomenon indicates that the drain current decreases with the increase of drain voltage in a specific voltage region, showing an "N"-shaped current-voltage (IV) characteristic curve, thereby having a folded current-voltage with multiple voltage thresholds. Based on this unique characteristic, negative differential resistance devices have broad application prospects in optoelectronics. In recent years, the electrically controlled negative differential resistance phenomenon reported has been applied in various electronic devices such as radio frequency oscillators, multipliers, and multi-valued logic. However, electrically controlled devices often lead to complex hardware structures and increased energy consumption, which to a certain extent hinders practical applications, especially in large-scale integrated circuits. Therefore, there is an urgent need to design an optical control device. Optical control devices have very wide applications in optoelectronics, such as photodetectors, high-resolution optocouplers, photo-memristors, etc. Optically controlled negative differential resistance devices play an important role in the development of microelectronic devices. They can provide additional control terminals, broaden the integration and application range of negative differential resistance devices. Therefore, it is necessary to invent a photodetector with optically modulated negative differential resistance function that has a simple preparation process, low cost, and is easy to integrate. It is expected to be applied to optoelectronic oscillators, optical matrix multipliers, and multi-valued logic optical electronic operators. Summary of the invention
[0003] The purpose of the present invention is to provide a method for preparing a photodetector with a light-modulated negative differential resistance phenomenon, in view of the blank of the existing light-modulated negative differential resistance device. The method adopts a dry transfer method to transfer MoS2, h-BN and WS2 prepared by mechanical exfoliation to a SiO2 / Si substrate, and then affix a gold electrode to make a unipolar barrier photodetector. The method has a simple preparation process, low cost, and is easy to vertically integrate. It can realize the light-modulated negative differential resistance function. After the circuit is connected to the inductor, the negative differential resistance phenomenon is used in a high-frequency oscillator.
[0004] The purpose of the present invention is achieved through the following technical solutions.
[0005] A method for preparing a photoelectric detector with light-modulated negative differential resistance phenomenon comprises the following steps:
[0006] Step 1. First, the highly p-type doped 300nm SiO2 / Si substrate is cleaned with oxygen plasma for 5 minutes, and two-dimensional MoS2, h-BN and WS2 materials are prepared on the cleaned substrate surface by mechanical stripping.
[0007] Step 2, preparing a polypropylene carbonate / polydimethylsiloxane film, injecting a small amount of polypropylene carbonate solvent onto the top of the polydimethylsiloxane located at the center of the slide glass, and then obtaining a polypropylene carbonate film on the polydimethylsiloxane by spin coating.
[0008] Step 3, stacking MoS2 / h-BN / WS2 heterostructures using polypropylene carbonate / polydimethylsiloxane assisted dry transfer method. Using polypropylene carbonate / polydimethylsiloxane film, the h-BN layer is transferred from the SiO2 / Si substrate to the target SiO2 / Si substrate surface including another selected WS2 layer. That is, the polypropylene carbonate / polydimethylsiloxane film is first contacted with the h-BN area on the SiO2 / Si substrate. After heating, the adhesion between polypropylene carbonate and h-BN will be greater than the adhesion between h-BN and SiO2 / Si substrate, so that h-BN is attached to the polypropylene carbonate / polydimethylsiloxane film. Subsequently, the prepared polydimethylsiloxane / polypropylene carbonate / h-BN was contacted with WS2 on the SiO2 / Si substrate, the temperature was increased to separate the polydimethylsiloxane from the polypropylene carbonate film, and then the polypropylene carbonate was dissolved in acetone, leaving the h-BN on WS2 to form an h-BN / WS2 heterojunction.
[0009] In step 4, the method described in step 3 is the same as that described in step 3. The MoS2 layer is transferred through the polypropylene carbonate / polydimethylsiloxane film and stacked on the previously transferred h-BN / WS2 heterojunction to obtain a MoS2 / h-BN / WS2 heterojunction, and the heterojunction is annealed in a high vacuum environment to remove surface residues.
[0010] Step 5: Prepare electrodes to make MoS2 / h-BN / WS2 heterojunction photodetectors. First, a gold flake is prepared on a Si / SiO2 substrate by thermal evaporation. Then, a probe is used to pick up the gold flake and attach it to the sample using van der Waals forces as an electrode to prepare a MoS2 / h-BN / WS2 heterojunction photodetector.
[0011] In step 1, the thickness of the h-BN is less than 10 nm.
[0012] In step 2, the amount of polypropylene carbonate is 0.05 ml.
[0013] In step 3, the temperature of picking up h-BN with polypropylene carbonate is 34° C.
[0014] In step 3, the heating temperature of the polypropylene carbonate to pick up h-BN and transfer it to WS2 is 130°C.
[0015] In step 4, the annealing temperature is 300° C. and the time is 1 h.
[0016] In step 5, the thickness of the prepared gold flake is 100 nm.
[0017] Advantages and beneficial effects of the present invention:
[0018] The present invention uses a dry transfer method to prepare a unipolar barrier photodetector under the condition of using SiO2 / Si as a substrate. The advantages are simple preparation process, low cost and easy integration. The device exhibits a negative differential resistance phenomenon under light conditions, which is light-excited and adjustable. After the circuit is connected to an inductor, the negative differential resistance phenomenon is used in a high-frequency oscillator. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a schematic structural diagram of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention.
[0020] Figure 2 This is an optical microscopic image of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention.
[0021] Figure 3 Morphological characterization of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention. a, AFM image, b, height distribution diagram corresponding to MoS2, h-BN and WS2 in Figure a.
[0022] Figure 4 Raman spectra of single MoS2, WS2 and MoS2 / h-BN / WS2 heterojunction regions of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention under 488nm laser irradiation.
[0023] Figure 5 Photoluminescence (PL) spectra of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention under 488nm laser irradiation, single MoS2, WS2 and MoS2 / h-BN / WS2 heterojunction regions.
[0024] Figure 6Negative differential resistance phenomenon of MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention. a, I under 488nm laser irradiation with laser irradiation power varying from 0.107μW to 40.05μW ds -V ds b, I under 488nm laser irradiation with laser irradiation power varying from 100.5μW to 1.021mW ds -V ds Curve c, I under 488nm laser irradiation with laser irradiation power varying from 5.323mW to 48.66mW ds -V ds curve.
[0025] Figure 7 The negative differential resistance characteristics of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention under 488nm laser irradiation. a, the peak voltage (V peak ). b, The peak-to-valley current ratio (PVCR) of the device changes with laser power. c, The peak current density (J peak ).
[0026] Figure 8 The RF oscillator of the MoS2 / h-BN / WS2 nBn unipolar barrier photodetector prepared in Example 1 of the present invention. a, The MoS2 / h-BN / WS2 nBn unipolar barrier photodetector is connected to an inductor (L) for LC oscillation. b, The relationship between the resonant frequency of the oscillator and the inductance of the LC circuit. The red line is a model that fits the data. The inset in the upper left corner shows the equivalent circuit diagram of the negative differential resistance oscillator, and the inset in the lower right corner shows the time domain LC oscillation of the circuit with the integrated inductor L=1mH under a DC voltage of 0.3V. DETAILED DESCRIPTION
[0027] The present invention adopts a dry transfer method to vertically stack mechanically exfoliated MoS2, h-BN and WS2 on a SiO2 / Si substrate to prepare a unipolar barrier photodetector. The preferred embodiment of the present invention is further described below in conjunction with the accompanying drawings and specific examples.
[0028] The morphology of the material was analyzed using an optical microscope (OM, Olympus, BX51). Raman spectra were measured using a micro-Raman spectrometer (Witec, Alpha 300R) equipped with a 488nm laser. The thickness of the interface was measured using an atomic mechanical microscope (BrukerDimension Icon). Under 488nm laser irradiation, the optoelectronic properties of the device were measured using a source meter (Keithley 2450), and the time-domain LC oscillation of the device was measured using a semiconductor parameter analyzer (Agilent 4155C).
[0029] Example 1
[0030] A method for preparing a photoelectric detector with light-modulated negative differential resistance phenomenon comprises the following steps:
[0031] Step 1. First, the highly p-type doped 300nm SiO2 / Si substrate is cleaned with oxygen plasma for 5 minutes, and two-dimensional MoS2, h-BN and WS2 materials are prepared on the cleaned substrate surface by mechanical stripping.
[0032] Step 2, prepare the poly(propylene carbonate) / polydimethylsiloxane) film by injecting a small amount of poly(propylene carbonate) solvent into the top of the polydimethylsiloxane located at the center of the slide glass, and then obtain the poly(propylene carbonate) film on the polydimethylsiloxane by spin coating.
[0033] Step 3, stacking MoS2 / h-BN / WS2 heterostructures using polypropylene carbonate / polydimethylsiloxane assisted dry transfer method. Using polypropylene carbonate / polydimethylsiloxane film, the h-BN layer is transferred from the SiO2 / Si substrate to the target SiO2 / Si substrate surface including another selected WS2 layer. That is, the polypropylene carbonate / polydimethylsiloxane film is first contacted with the h-BN area on the SiO2 / Si substrate. After heating, the adhesion between polypropylene carbonate and h-BN will be greater than the adhesion between h-BN and SiO2 / Si substrate, so that h-BN is attached to the polypropylene carbonate / polydimethylsiloxane film. Subsequently, the prepared polydimethylsiloxane / polypropylene carbonate / h-BN was brought into contact with WS2 on a SiO2 / Si substrate, the temperature was raised to separate the polydimethylsiloxane from the polypropylene carbonate film, and then the polypropylene carbonate was dissolved in acetone, leaving the h-BN on the target WS2 to form an h-BN / WS2 heterojunction.
[0034] In step 4, the method described in step 3 is the same as that described in step 3. The MoS2 layer is transferred through the polypropylene carbonate / polydimethylsiloxane film and stacked on the previously transferred h-BN / WS2 heterojunction to obtain a MoS2 / h-BN / WS2 heterojunction, and the heterojunction is annealed in a high vacuum environment to remove surface residues.
[0035] Step 5: Prepare electrodes to make MoS2 / h-BN / WS2 heterojunction photodetectors. First, a gold flake is prepared on a Si / SiO2 substrate by thermal evaporation. Then, a probe is used to pick up the gold flake and attach it to the sample using van der Waals forces as an electrode to prepare a MoS2 / h-BN / WS2 heterojunction photodetector.
[0036] The schematic diagram of the sample structure obtained in Example 1 of the present invention is as follows Figure 1 As shown. By dry transfer technology, mechanically exfoliated MoS2, h-BN and WS2 were vertically stacked on an oxygen plasma cleaned Si / SiO2 substrate and affixed with gold electrodes, and a MoS2 / h-BN / WS2 nBn-type unipolar barrier photodetector was successfully prepared. The detector consists of MoS2 as a visible wavelength n-type photon absorption layer, h-BN as a barrier layer, WS2 as a contact layer, and gold electrodes as source and drain. The corresponding optical image of the device is shown in Figure 2 As shown, the surface morphology and thickness of the heterostructure were further analyzed using atomic force microscopy (AFM), as shown in Figure 3 a. The average thicknesses of MoS2, h-BN and WS2 are 36, 7 and 45 nm, respectively. Figure 3 b. Under room temperature excitation of 488 nm laser, the Raman and photoluminescence (PL) spectra of the MoS2 / h-BN / WS2 van der Waals heterostructure were characterized in the overlapping region of the prepared device, and the Raman and PL spectra of MoS2 and WS2 were characterized in the non-overlapping region, as shown in Figure 4 , Figure 5 As shown, the Raman characteristic peak of MoS2 was observed at 384 cm -1 and 411.8cm -1 , corresponding to the in-plane vibration E 1 2g Mode and out-of-plane vibration A 1g mode, the in-plane vibration E of WS2 1 2g Mode and out-of-plane vibration A 1g The Raman characteristic peak of the mode is located at 351.8 cm -1 and 421.4cm -1 , Figure 4 The inset shows the Raman spectra of h-BN and h-BN in heterojunction. The Raman characteristic peak is located at 1365.5 cm -1 At, corresponding to the in-plane vibration E2g The individual peaks of the pattern are consistent with the overlapping area, indicating that the transferred material is of high quality. The PL peaks of MoS2 and WS2 are located at 1.82eV and 1.93eV, respectively. The PL signal of a single material is effectively quenched in the heterojunction, which is attributed to the charge transfer at the heterojunction interface. This quenching phenomenon proves the charge separation at the heterojunction, and also means that ultrafast photoexcited carrier transport will occur, which has a promoting effect on the optoelectronic performance of the device.
[0037] The unipolar barrier photodetector prepared in Example 1 was subjected to photoelectric testing. The photoelectric characteristics of the device were measured using a Keithley 2450 source meter under 488nm laser irradiation. Under light-added conditions, the device exhibited a negative differential resistance phenomenon. The negative differential resistance phenomenon under light regulation will change regularly with the increase of laser power, and can be divided into three stages of change. First, the peak current increases with the increase of laser power, such as Figure 6 As shown in a, secondly, the peak current decreases with the increase of laser power, as shown in Figure 6 As shown in b, the inset is an enlarged view of the negative differential resistance area. Finally, as the laser power continues to increase, the negative differential resistance phenomenon disappears, as shown in Figure 6 c. Our device does not observe negative differential resistance under dark current, but produces negative differential resistance under light, which shows that light can be used as a control terminal for the negative differential resistance phenomenon, and the negative differential resistance phenomenon is caused by electron tunneling. Under dark conditions, due to the high barrier layer of h-BN, electrons on the source side cannot pass through the barrier layer, and no tunneling current is generated, so no negative differential resistance phenomenon is observed. Figure 6 In stage a, electrons gain energy under illumination and generate photogenerated electrons. The electrons gain energy and can pass through the h-BN barrier. When the illumination increases, more and more electrons pass through the barrier layer, so the peak current increases with the increase of voltage. Figure 6 In stage b, as the light intensity continues to increase, the electrons gradually gain more energy. Some of them gain enough energy to cross the potential barrier layer, and a small part of them flows into the drain through tunneling. Therefore, the peak current gradually decreases with the increase of voltage, while the total current gradually increases. Figure 6 In stage c, when the light intensity is large enough, the electrons gain enough energy to cross the h-BN barrier layer, and no tunneling process occurs, so the negative differential resistance phenomenon disappears. In the entire test range, the peak-to-valley voltage increases with the increase of laser power, such as Figure 7 This is because the carrier density distribution is mainly controlled by light. For larger laser powers, more electrons accumulate at the interface and further change the channel resistance, so a higher V is required. ds to activate the negative differential resistance effect. PVCR and J peakAll of them change regularly with the increase of laser power, that is, they increase first and then decrease. Figure 7 As shown in b and c, a PVCR value of 4.7 was obtained at a laser power of 5.341 μW, and a PVCR value of 25.2 mA / cm was obtained at a laser power of 40.05 μW. 2 J peak Light has a selective controllable effect on the negative differential resistance characteristics of the device. When the device works under low laser power, the electrons do not obtain enough energy, and the existence of the barrier layer is not conducive to the collection of photogenerated electrons by the drain, which leads to an increase in the channel electron density. Therefore, PVCR and J peak After increasing the laser power, the electrons gain enough energy to cross the barrier layer, the channel electron density gradually decreases, and the negative differential resistance phenomenon gradually disappears. Therefore, PVCR and J peak Gradually decrease.
[0038] The device application that exploits the negative differential resistance behavior in MoS2 / h-BN / WS2 unipolar barrier photodetectors is the LC oscillator, which is realized by applying a constant DC voltage in the negative differential resistance region. Its schematic diagram is shown in Figure 1 along with the inductor (L) symbol. Figure 8 a. Figure 8 b shows the relationship between the resonant frequency of the oscillator and the inductance of the LC circuit. Figure 8 The inset in the upper left corner of b shows the equivalent circuit diagram of the negative differential resistance oscillator, and the inset in the lower right corner shows the time domain LC oscillation of the circuit when the integrated inductor L = 1mH is applied with a 0.3V DC voltage. Stable sinusoidal oscillation is achieved in the negative differential resistance region, and the oscillation frequency can be adjusted by changing the parameters of the external circuit. The operation of the LC oscillator based on negative differential resistance can be understood as follows. Once excited, the LC circuit produces damped oscillations that decay rapidly to zero. This is mainly caused by the internal dissipation resistance R of the resonator and other losses. When the device operates in the negative differential resistance region, its negative resistance offsets the internal loss resistance, thereby supporting continuous and stable oscillations at the resonant frequency of the LC circuit.
[0039] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.
Claims
1. A method for preparing a photodetector having a light-modulated negative differential resistance phenomenon, characterized in that: The nBn type unipolar barrier photodetector has the phenomenon of negative differential resistance modulated by light; The method comprises the following steps: Step 1: First, a highly p-type doped 300nm SiO2 / Si substrate is cleaned with oxygen plasma for 5 minutes, and two-dimensional MoS2, h-BN and WS2 materials are prepared on the cleaned substrate surface by mechanical stripping; Step 2, preparing a polypropylene carbonate / polydimethylsiloxane film, injecting a small amount of polypropylene carbonate solvent into the top of the polydimethylsiloxane located at the center of the glass slide, and then obtaining a polypropylene carbonate film on the polydimethylsiloxane by spin coating; Step 3, using polypropylene carbonate / polydimethylsiloxane assisted dry transfer method to stack MoS2 / h-BN / WS2 heterostructure, using polypropylene carbonate / polydimethylsiloxane film, the h-BN layer is transferred from the SiO2 / Si substrate to the target SiO2 / Si substrate surface including another selected WS2 layer, that is, firstly the polypropylene carbonate / polydimethylsiloxane film is brought into contact with the h-BN region on the SiO2 / Si substrate, and after heating, the polypropylene carbonate and h-BN The adhesion between them will be greater than the adhesion between h-BN and SiO2 / Si substrate, so that h-BN is attached to the polypropylene carbonate / polydimethylsiloxane film. Subsequently, the prepared polydimethylsiloxane / polypropylene carbonate / h-BN is brought into contact with WS2 on the SiO2 / Si substrate, the temperature is raised to separate the polydimethylsiloxane from the polypropylene carbonate film, and then the polypropylene carbonate is dissolved in acetone, leaving the h-BN on the peeled WS2 to form an h-BN / WS2 heterojunction. Step 4, the method described in step 3, the MoS2 layer is transferred through the polypropylene carbonate / polydimethylsiloxane film and stacked on the previously transferred h-BN / WS2 heterojunction to obtain the MoS2 / h-BN / WS2 heterojunction, and the heterojunction is annealed in a high vacuum environment to remove the residue on the surface; Step 5, prepare electrodes and make MoS2 / h-BN / WS2 heterojunction photodetector. First, prepare a gold flake on a Si / SiO2 substrate by thermal evaporation. Then, use a probe to pick up the gold flake and use van der Waals force to attach it to the sample as an electrode to prepare a MoS2 / h-BN / WS2 heterojunction photodetector.
2. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In the step 1, the thickness of the h-BN is less than 10 nm.
3. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In step 2, the amount of polypropylene carbonate is 0.05 ml.
4. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In the step 3, the temperature of picking up h-BN with polypropylene carbonate is 34°C.
5. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In step 3, the heating temperature of picking up h-BN with polypropylene carbonate and transferring it to WS2 is 130°C.
6. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In step 4, the annealing temperature is 300° C. and the time is 1 hour.
7. The method for preparing a photodetector having a light-modulated negative differential resistance phenomenon according to claim 1, characterized in that: In step 5, the prepared gold flake has a thickness of 100 nm and is attached to the sample using a probe as an electrode to form a van der Waals contact.