Method for preparing PdTe2 quantum dots locally embedded in SiO2 / Si on SiO2 / Si

Abstract

The invention provides a method for preparing PdTe2 quantum dots locally embedded in SiO2 / Si on SiO2 / Si, which comprises the following steps: (a) firstly, ultrasonically cleaning a SiO2 / Si substrate in acetone, absolute ethyl alcohol and deionized water in sequence, and then spin-drying the cleaned substrate by using a spin coater for later use; (b) sputtering a layer of Pd film on the SiO2 / Si substrate by adopting a high-vacuum magnetron sputtering film deposition system; and (c) putting the Pd / SiO2 / Si precursor after sputtering of the Pd film and Te powder into a double-temperature-zone tubular furnace together to prepare the PdTe2 quantum dots on SiO2 / Si. The sizes and forms of the quantum dots are influenced by the diffusion rate and the reaction temperature of Te steam to a certain extent, and small quantum dots can be formed at a low temperature, so that the PdTe2 quantum dots are prepared at a low temperature, and the light absorption intensity and the light absorption range of the PdTe2 quantum dots are improved. Compared with other PdTe2 film preparation methods, the method has the advantages that preparation of the PdTe2 quantum dots is proposed for the first time, and compared with a traditional two-dimensional material, the quantum dots have the advantage that light absorption of the visible-near infrared band is greatly improved.

Description

Technical Field

[0001] The invention belongs to the process of preparing thin films by heat-assisted conversion method, and in particular provides a tellurization method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si. Background Art

[0002] In recent years, a class of two-dimensional (2D) topological semimetal materials has become a promising material system due to their unique physical and optoelectronic properties at the nanoscale. The van der Waals forces between the layers of two-dimensional materials allow the materials to be stacked and the gapless electronic structure can detect light wavelengths in an ultra-wide band. Based on the above characteristics, two-dimensional topological semimetals have become ideal candidates for infrared photodetection. Among the wide range of two-dimensional (2D) topological semimetal materials, two-dimensional PdTe2 has attracted increasing attention due to its tunable narrow band gap, high carrier mobility and excellent air stability. These advantages make two-dimensional topological semimetals an ideal candidate for infrared photodetection. For example, Zhang et al. proposed a silicon island-type ZnO@PdTe2 composite material as a heterojunction photodetector with high sensitivity in a wide band from the solar blind zone (254 nm) to the short infrared (1.55 μm). The device has an ultrafast response (1.58 / 1.34 μs) and a detectivity of up to 1.56 × 10 13 Jones, sensitivity up to 10 7 cm 2 / W. Due to its good electrical and thermal conductivity, PdTe2 has great potential in the fields of optical sensing, multispectral imaging and optical communications. Traditional PdTe2 films have weak light absorption intensity and short light absorption wavelength range. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention provides a method for preparing tellurization of PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si. The thickness of the bottom of the PdTe2 quantum dots embedded in the SiO2 / Si substrate is 25nm. By controlling the growth temperature, reaction time, and carrier gas flow rate, Pd / SiO2 / Si / precursor and Te powder are placed in a double-temperature zone tubular furnace for growth, and finally a large area of ​​uniform PdTe2 quantum dots are generated.

[0004] The advantage of PdTe2 quantum dots is that they can greatly improve the light absorption intensity, wavelength range and responsiveness, and have great application potential. Therefore, the present invention provides a method for preparing PdTe2 quantum dots partially embedded in SiO2 by a simple, convenient, and large-scale tellurization method.

[0005] The present invention provides a method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si. The method is characterized in that a Pd / SiO2 / Si precursor treated with a sputtered Pd film is placed in a dual-temperature zone tubular furnace together with Te powder for reaction to prepare PdTe2 quantum dots on SiO2 / Si. The technical features of the method are as follows: 1) The sputtering Pd film treatment process includes: sputtering a layer of Pd film on the cleaned and dried SiO2 / Si substrate using a high vacuum magnetron sputtering film deposition system; 2) The reaction conditions of the dual-temperature zone tubular furnace for converting Pd atoms into Pd quantum dots are as follows: 450-500°C in the Te powder zone, 350-400°C in the Pd / SiO2 / Si zone, 8°C / min heating rate in the upper zone, 10°C / min heating rate in the lower zone, 50-150 sccm argon flow rate, and 2-3 h insulation. 3) The dual-temperature zone tubular furnace used for the reaction has the following features: The specifications of the quartz tube of the double temperature zone tubular furnace are 1000mm in length, 50mm in outer diameter, 4mm in thickness, and 42mm in inner diameter. The double temperature zone tubular furnace is pumped by a vacuum pump with an air pressure of 0.1Pa. 4) The dual-temperature zone tubular furnace used for the reaction is also equipped with an exhaust gas recovery device, which has the following characteristics: 5) For tail gas recovery, 10% NaOH is mixed with deionized water in a ratio of 1:20 and then put into a 250ml, 24 / 29 gas washing bottle, which is connected to the gas outlet of the dual-temperature zone tubular furnace; 6) The working conditions of magnetron sputtering include: room temperature, power 40-60 W, gas pressure 0.5-1 Pa, vacuum degree 1×10 4 Pa.

[0006] 7) The working conditions of the magnetron sputtering conditions also include: using a Pd target material with a purity of 99.99%, a specification of φ50.8*0.1mm, and a sputtering time of 20-30 s; 8) The process of cleaning and drying the SiO2 / Si substrate includes: first, ultrasonically cleaning the SiO2 / Si substrate in acetone, anhydrous ethanol, and deionized water in sequence, and then spinning the cleaned substrate dry with a glue spreader for later use.

[0007] 9) The characteristics of the SiO2 / Si substrate include: oxide layer thickness of 200nm, total thickness of 525.2μm, and resistivity of 0.01-0.05Ω·m.

[0008] A PdTe2 quantum dot is prepared according to a method having the above technical characteristics 1) to 9).

[0009] To achieve the above object, the present invention adopts the following technical solution: The invention provides a method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si. The preparation method comprises: (a) firstly ultrasonically cleaning the SiO2 / Si substrate in acetone, anhydrous ethanol and deionized water in sequence, and then spinning the cleaned substrate with a glue spreader for standby use; (b) sputtering a layer of Pd film on the SiO2 / Si substrate by a high vacuum magnetron sputtering film deposition system; (c) placing a Pd / SiO2 / Si precursor after sputtering the Pd film and Te powder into a double-temperature zone tubular furnace together to prepare PdTe2 quantum dots on SiO2 / Si.

[0010] The SiO2 / Si substrate has an oxide layer thickness of 200 nm, a total thickness of 525.2 μm, and a resistivity of 0.01-0.05 Ω·m.

[0011] The magnetron sputtering conditions are: room temperature, power 40-60 W, gas pressure 0.5-1 Pa, vacuum degree 1×10 4 The specifications of Pa and Pd targets (99.99%) are φ50.8*0.1mm, the sputtering time is 20-30 s, and the expected thickness is about 5nm.

[0012] The specifications of the quartz tube of the dual-temperature zone tubular furnace are 1000 mm in length, 50 mm in outer diameter, 4 mm in thickness, and 42 mm in inner diameter. The dual-temperature zone tubular furnace is extracted by a vacuum pump, and the air pressure is 0.1 Pa. The tail gas is recovered by mixing NaOH (concentration of 10%) with deionized water at a ratio of 1:20 and then put into a gas washing bottle (250 ml, 24 / 29), and the gas washing bottle is connected to the gas outlet of the dual-temperature zone tubular furnace.

[0013] The dual-temperature zone tubular furnace can make Pd atoms become Pd quantum dots under the following reaction conditions: Te powder zone 450-500°C, Pd / SiO2 / Si zone 350-400°C, upper temperature zone heating rate 8°C / min, lower temperature zone heating rate 10°C / min, argon gas flow rate 50-150 sccm, insulation for 2-3 h, so that it fully reacts and can generate PdTe2 quantum dots. If the reaction temperature of the upper temperature zone is lower than 450°C and the reaction temperature of the lower temperature zone is lower than 330°C, tellurization cannot generate PdTe2 quantum dots.

[0014] In addition, during the tellurization process, as the temperature of the dual-temperature zone tubular furnace gradually increases, the surface energy of the Pd film is higher than that of SiO2, causing Pd atoms to aggregate in SiO2 / Si to form Pd quantum dots. In order to reduce the total free energy of the system, the Pd atoms in the small quantum dots tend to migrate to larger quantum dots. Larger quantum dots have relatively small surface areas and thus lower surface energy, so they can more stably adsorb or integrate these migrated Pd atoms, and eventually agglomerate into larger Pd quantum dots. Subsequently, Te vapor is transported to the lower temperature zone through Ar gas to react with Pd quantum dots, and finally generate PdTe2 quantum dots. The size and morphology of these quantum dots are affected to a certain extent by the diffusion rate of Te vapor and the reaction temperature. Lower temperatures will form smaller quantum dots, so the present invention prepares PdTe2 quantum dots at low temperatures to improve its light absorption intensity and its absorption range. The present invention is different from other methods for preparing PdTe2 thin films in that it is the first to propose the preparation of PdTe2 quantum dots. The advantage of quantum dots over traditional two-dimensional materials is that their light absorption in the visible-near infrared band is greatly improved.

[0015] What makes the present invention different from other methods of preparing PdTe2 thin films is that it is the first to propose the preparation of PdTe2 quantum dots. Compared with traditional two-dimensional materials, the light absorption of quantum dots in the visible-near infrared band is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the tubular furnace tellurization of the present invention.

[0017] Figure 2 This is a physical picture of PdTe2 quantum dots on SiO2 / Si of the present invention.

[0018] Figure 3 This is the XRD diagram of PdTe2 quantum dots of the present invention.

[0019] Figure 4 This is the Raman diagram of PdTe2 quantum dots of the present invention.

[0020] Figure 5 These are the SEM and EDS images of the PdTe2 quantum dots of the present invention.

[0021] Figure 6 TEM image of PdTe2 quantum dots on SiO2 / Si of the present invention and its element distribution map.

[0022] Figure 7 This is the AFM image of PdTe2 quantum dots on SiO2 / Si of the present invention.

[0023] Figure 8 This is the height profile of PdTe2 quantum dots on SiO2 / Si of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0026] First, the commercially available 4-inch SiO2 / Si wafer (oxide layer thickness 200nm, total thickness 525.2μm) was cut into standard 1cm×1cm using a wafer dicing machine. The cut sample was organically cleaned by placing the SiO2 / Si wafer in acetone, alcohol and deionized water (18.25 MΩ·cm) for 10 minutes of ultrasonic cleaning. After cleaning, the SiO2 / Si wafer was repeatedly rinsed with deionized water several times to remove the residual solution on the sample surface, and then a glue machine (3500 rpm) was used to spin for 30 seconds to dry the moisture on the sample surface.

[0027] The dried SiO2 / Si substrate was fixed on the sputtering tray and about 5nm Pd was sputtered using a high vacuum magnetron sputtering thin film deposition system. The Pd target material specifications were: purity 99.99% and size φ50.8*0.1mm. The specific operation method is as follows: First, the chamber was vacuumed and the vacuum degree was reduced to 1×10 -4 After the vacuum is below Pa, 50sccm Ar gas is introduced for 10 minutes. Then adjust the molecular pump valve to make the vacuum degree in the chamber reach 0.7-0.8Pa, maintain it for 5 minutes, and then set the process parameters. The pre-sputtering time is 120s and the power is 40W. Then the formal sputtering is carried out with a power of 40W, a sputtering time of 20s, and a sputtering thickness of about 5nm.

[0028] First, the sputtered Pd / SiO2 / Si sample is placed on a 4 cm×6 cm quartz plate, and then the sample is placed in the lower temperature zone of the dual-temperature zone tube furnace. Then, about 0.3 g of Te powder is weighed and placed on the quartz plate with a hole, and then the quartz plate is placed in the upper temperature zone of the tube furnace. The Te powder and the sample must be kept level. A mechanical pump is used to vacuum the chamber of the dual-temperature zone tube furnace for about 10 minutes. When the vacuum degree of the tube furnace is reduced to 0.1 Pa, about 1200 sccm of Ar gas is introduced to replace the residual gas in the dual-temperature zone tube furnace. This step is repeated three times to ensure that the content of impurity gas molecules inside the quartz tube reaches the lowest level. This process is called the gas washing process. After the gas washing is completed, set the upper temperature zone temperature (450 ℃-500 ℃), the lower temperature zone temperature (350 ℃-400 ℃), the Ar gas flow rate is 100 sccm, the upper temperature zone heating rate is 8 ℃ / min, the lower temperature zone heating rate is 10 ℃ / min, and the heat preservation is 2 hours to ensure that the reaction is complete. After the program is completed, wait for the temperature of the temperature zone to drop to room temperature before taking out the sample. The specifications of the quartz tube of the double temperature zone tubular furnace are 1000mm in length, 50mm in outer diameter, 4mm in thickness, and 42mm in inner diameter. The double temperature zone tubular furnace is extracted by a vacuum pump, and the vacuum degree in the quartz tube is 0.1Pa. The tail gas is recovered by mixing NaOH (concentration of 10%) with deionized water in a ratio of 1:20 and adding it to the gas washing bottle (250ml, 24 / 29), and the gas washing bottle is connected to the outlet of the double temperature zone tubular furnace. The PdTe2 quantum dot samples were then tested by X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM).

[0029] Figure 1 Schematic diagram of tubular furnace tellurization. The sputtered Pd / SiO2 / Si / precursor and Te powder are placed in a tubular furnace for tellurization. Te powder is placed in the upper temperature zone of the dual-temperature zone tubular furnace, and Pd / SiO2 / Si / precursor is placed in the lower temperature zone of the dual-temperature zone tubular furnace. After the dual-temperature zone temperature rise tellurization is completed and then cooled to room temperature, sampling is performed to obtain a PdTe2 quantum dot film.

[0030] Figure 2 This is a real picture of PdTe2 quantum dots. From the real picture, it can be observed that the surface of the sample is uniform.

[0031] Figure 3The XRD diagram of PdTe2 quantum dots. The prepared PdTe2 quantum dots were subjected to XRD analysis, and it can be clearly observed that there are obvious diffraction peaks at 17.481°, 31.041°, 35.081°, 53.651° and 74.021°, which correspond to the (001), (101), (002), (003) and (004) crystal planes of PdTe2, respectively, proving the generation of PdTe2 quantum dots. No additional Pd peaks were detected in the figure, indicating that the Pd precursor has been completely converted into PdTe2 quantum dots with higher purity.

[0032] Figure 4 This is the Raman diagram of PdTe2 quantum dots. It can be observed that the -1 The two peaks at g In-plane vibration mode and A 1g In the out-of-plane vibration mode, there is no Pd diffraction peak, indicating that the tellurization is complete.

[0033] Figure 5 The SEM and EDS images of PdTe2 quantum dots show that after tellurization, approximately 40nm-70nm PdTe2 quantum dots are generated, with a Pd:Te atomic ratio of approximately 2:1.

[0034] Figure 6 TEM image of PdTe2 quantum dots on SiO2 / Si and its element distribution map. Figure 7 It can be clearly observed that the size of PdTe2 quantum dots is about 50nm, and PdTe2 quantum dots are embedded in SiO2 / Si. It is speculated that the reason may be that as the tellurization temperature increases, Pd quantum dots and Te atoms diffuse into SiO2 / Si. The diffusion process is a temperature-dependent process. As the temperature increases, the activation energy of atomic diffusion decreases, the migration speed of atoms in the lattice accelerates, and because the surface energy of Pd and Te is higher than that of SiO2, Pd and Te atoms are more easily diffused into the SiO2 / Si substrate.

[0035] Figure 7 This is an AFM image of PdTe2 quantum dots on SiO2 / Si. As can be seen from the figure, PdTe2 presents a quantum dot state structure and is evenly distributed on the SiO2 surface.

[0036] Figure 8 This is the height profile of PdTe2 quantum dots on SiO2 / Si. Figure 8 It can be concluded that the thickness of the PdTe2 film is about 34.5nm.

[0037] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si, characterized in that: The Pd / SiO2 / Si precursor treated with a sputtered Pd film is placed together with Te powder in a double-temperature zone tubular furnace for reaction to prepare PdTe2 quantum dots on SiO2 / Si.

2. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 1, characterized in that: The sputtering Pd film treatment process includes: using a high vacuum magnetron sputtering film deposition system to sputter a layer of Pd film on a cleaned and dried SiO2 / Si substrate.

3. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 1, characterized in that: The reaction conditions of the dual-zone tubular furnace for converting Pd atoms into Pd quantum dots are as follows: Te powder zone 450-500°C, Pd / SiO2 / Si zone 350-400°C, upper temperature zone heating rate 8°C / min, lower temperature zone heating rate 10°C / min, argon flow rate 50-150 sccm, and insulation for 2-3 h.

4. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 1, characterized in that: The dual-zone tube furnace used for the reaction also has the following features: The specifications of the quartz tube of the double-temperature zone tubular furnace are as follows: length 1000mm, outer diameter 50mm, thickness 4mm, inner diameter 42mm; the double-temperature zone tubular furnace is evacuated by a vacuum pump, and the air pressure is 0.1Pa.

5. The method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 1, characterized in that: The dual-zone tube furnace used for the reaction is also equipped with an exhaust gas recovery device, which has the following features: For tail gas recovery, 10% NaOH is mixed with deionized water in a ratio of 1:20 and then put into a 250ml, 24 / 29 gas washing bottle, which is connected to the gas outlet of the dual-temperature zone tubular furnace.

6. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 2, characterized in that: The working conditions of magnetron sputtering include: room temperature, power 40-60 W, gas pressure 0.5-1 Pa, vacuum degree 1×10 4 Pa.

7. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 2, characterized in that: The working conditions of the magnetron sputtering conditions also include: using a Pd target material with a purity of 99.99%, a specification of φ50.8*0.1mm, and a sputtering time of 20-30 s.

8. The method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 2, characterized in that: The process of cleaning and drying the SiO2 / Si substrate includes: firstly, ultrasonically cleaning the SiO2 / Si substrate in acetone, anhydrous ethanol and deionized water in sequence, and then drying the cleaned substrate with a glue spreader for later use.

9. A method for preparing PdTe2 quantum dots partially embedded in SiO2 / Si on SiO2 / Si according to claim 2, characterized in that: The characteristics of SiO2 / Si substrate include: oxide layer thickness of 200nm, total thickness of 525.2μm, and resistivity of 0.01-0.05Ω·m.

10. A PdTe2 quantum dot, characterized in that: Prepared according to the method according to any one of claims 1 to 9.

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