A method for preparing a copper-zinc tin nitride Schottky junction

Abstract

The present invention discloses a copper-zinc-tin nitride Schottky junction and a preparation method thereof, wherein the method comprises the following steps: in a flowing nitrogen and argon atmosphere, depositing a zinc-tin alloy target with a Zn:Sn ratio of 5:1 on a substrate by radio frequency sputtering, thereby obtaining a zinc-tin nitride thin film. In a flowing argon atmosphere, the zinc-tin nitride thin film is annealed at 300 to 400°C, thereby obtaining an annealed zinc-tin nitride thin film. In a flowing argon atmosphere, depositing a copper target on the annealed zinc-tin nitride thin film by direct current sputtering, thereby obtaining a copper-zinc-tin nitride Schottky junction. The present invention solves the problem that the copper-zinc-tin nitride Schottky junction prepared by the existing method has poor rectification effect and no photovoltaic effect.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor thin film materials, and in particular to a method for preparing a copper-zinc tin nitride Schottky junction. Background Art

[0002] As an emerging ternary semiconductor material, zinc tin nitride (ZnSnN2) thin film is considered an ideal absorber layer for next-generation solar cells due to its abundant resources, non-toxicity, low cost, high absorption coefficient and adjustable energy band (1.0-2.0eV). However, despite the excellent performance of zinc tin nitride thin film, its research is not as in-depth as other Zn-IV-N2 materials. This is mainly due to its intrinsic defect Sn occupying the position of Zn (Sn Zn ) and the donor formation energy generated is extremely low, and the carrier concentration is simplified, which will weaken its key semiconductor properties. In addition, carrier mobility is another important factor affecting the photoelectric conversion efficiency of solar cells, but the mobility of zinc tin nitride thin films is generally low. At the same time, copper is a metal with excellent electrical conductivity, low price and abundant resource reserves. It is very valuable to form a Schottky junction between copper and zinc tin nitride to study the photovoltaic effect. However, it is difficult to combine the two, and no photovoltaic effect has been found so far, and the rectification effect of the Schottky junction is poor. Moreover, there are currently no reports on copper-zinc tin nitride Schottky junctions and solar cells thereof.

[0003] Therefore, there is an urgent need for a simple and effective method to prepare a copper-zinc tin nitride Schottky junction with good rectification effect and photovoltaic effect, so as to enhance its application value in photovoltaics. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for preparing a copper-zinc-tin nitride Schottky junction with good rectification effect and photovoltaic effect, aiming to solve the problem that the copper-zinc-tin nitride Schottky junction prepared by the existing method has poor rectification effect and cannot produce photovoltaic effect.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing a copper-zinc tin nitride Schottky junction, comprising the steps of:

[0007] In nitrogen and argon atmosphere, a zinc-tin alloy target is deposited on a substrate by radio frequency sputtering to obtain a zinc-tin nitride thin film.

[0008] The zinc tin nitride film is annealed in an argon atmosphere to obtain an annealed zinc tin nitride film.

[0009] In an argon atmosphere, metallic copper is deposited on the annealed zinc tin nitride film by DC sputtering to obtain a copper-zinc tin nitride Schottky junction.

[0010] The method for preparing the copper-zinc tin nitride Schottky junction comprises the following steps:

[0011] First, fix the zinc-tin alloy target on the RF target position, evacuate the sputtering system, and then continuously introduce nitrogen and argon while keeping the gas pressure stable. Then, zinc and tin are simultaneously deposited on silicon wafers or glass substrates or ITO glass by RF sputtering to obtain zinc-tin nitride thin films.

[0012] First, place the zinc tin nitride film into the sputtering system, evacuate the vacuum chamber, and then continuously introduce argon gas while keeping the gas pressure stable. Heat the vacuum chamber to a specified temperature and keep the temperature constant for a period of time to obtain the annealed zinc tin nitride film.

[0013] First, the annealed zinc tin nitride film is placed in the sputtering system, the copper metal target is fixed on the DC target position, the vacuum chamber is evacuated, and then argon gas is continuously introduced and the gas pressure is kept stable. Then, copper is deposited on the annealed zinc tin nitride film by DC sputtering to obtain a copper-zinc tin nitride Schottky junction.

[0014] In the method for preparing the zinc tin nitride thin film, the nitrogen is 99.999% high-purity nitrogen, and the argon is 99.995% high-purity argon.

[0015] In the method for preparing the zinc tin nitride thin film, the flow rate of the nitrogen gas is 5 sccm, and the flow rate of the argon gas is 8 sccm.

[0016] The method for preparing the zinc tin nitride thin film, wherein the radio frequency sputtering power is 30W.

[0017] The method for preparing the zinc tin nitride thin film, wherein the gas pressure of the radio frequency sputtering is 3Pa.

[0018] In the method for preparing the zinc tin nitride thin film, the substrate needs to be cleaned in advance.

[0019] In the method for preparing the zinc tin nitride thin film, the substrate needs to be cleaned in advance with acetone, alcohol and deionized water.

[0020] In the method for preparing the zinc tin nitride thin film, the substrate needs to be heated to 50-150° C. before thin film deposition.

[0021] In the annealing method of the zinc tin nitride film, the argon gas is 99.995% high-purity argon gas.

[0022] In the annealing method for the zinc tin nitride film, the flow rate of the argon gas is 30 sccm.

[0023] The annealing method of the zinc tin nitride film, wherein the gas pressure during the annealing is 1 Pa.

[0024] In the annealing method of the zinc tin nitride film, the zinc tin nitride film needs to be heated to 300-400° C. before annealing.

[0025] In the method for preparing the copper-zinc tin nitride Schottky junction, the argon gas is 99.995% high-purity argon gas.

[0026] In the method for preparing the copper-zinc tin nitride Schottky junction, the flow rate of the argon gas is 30 sccm.

[0027] The method for preparing the copper-zinc tin nitride Schottky junction, wherein the gas pressure of the DC sputtering is 2Pa.

[0028] A copper-zinc tin nitride Schottky junction is characterized by being prepared by the method described above.

[0029] Beneficial effects: The present invention solves the problem of poor rectification effect by depositing an alloy target on a substrate by radio frequency sputtering in a flowing nitrogen and argon atmosphere, and then annealing and forming a Schottky junction with copper, thereby discovering that a photovoltaic effect occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 X-ray diffraction pattern of the sample prepared in the present invention;

[0031] Figure 2 X-ray electron energy scattering spectrum of the sample prepared by the present invention;

[0032] Figure 3 This is the dark state IV test diagram of the sample prepared by the present invention.

[0033] Figure 4 This is a test diagram of the illumination state IV of the sample prepared in the present invention. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a copper-zinc tin nitride Schottky junction. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0035] The method for preparing a copper-zinc tin nitride Schottky junction of the present invention comprises the steps of:

[0036] In a flowing nitrogen and argon atmosphere, a zinc-tin alloy target is deposited on a substrate by radio frequency sputtering to obtain a zinc-tin nitride film.

[0037] Unlike the conventional method of preparing zinc-tin nitride thin films by co-sputtering metallic zinc by radio frequency sputtering and metallic tin by direct current sputtering, the present invention uses flowing nitrogen as the reaction gas and flowing argon as the bombarding particles to perform radio frequency sputtering on a zinc-tin alloy target and deposit the target on the substrate, thereby preparing a zinc-tin nitride thin film with a low carrier concentration.

[0038] In the method for preparing the zinc tin nitride thin film of the present invention, the zinc tin alloy target is first fixed on the radio frequency target position, and then the entire sputtering system is evacuated to a vacuum degree of 4.5×10 -4 Pa to ensure that there is no impurity gas such as oxygen, and then continuously introduce nitrogen and argon and keep the pressure stable, that is, while introducing nitrogen and argon, they are discharged at a certain rate to ensure that the entire magnetron sputtering system is maintained at a certain pressure environment, and then zinc and tin are simultaneously deposited on silicon wafers or glass substrates by radio frequency sputtering to obtain zinc tin nitride thin films.

[0039] Preferably, the substrate is pre-cleaned, for example, by sequentially cleaning with acetone, alcohol, and deionized water under an ultrasonic environment to remove oil, impurities, and the like from the substrate surface to facilitate thin film deposition. The substrate is then dried for later use. The substrate can be single crystal silicon, indium tin oxide (ITO) glass, or inexpensive silicon wafers or glass such as Si(100) or K9 glass, all of which can be used to prepare zinc tin nitride thin films in the present invention.

[0040] Preferably, in the present invention, before thin film deposition, the substrate is preheated and maintained at 50-150° C., because impurities are likely to appear if the temperature is too high, and the thin film is likely to become amorphous if the temperature is too low.

[0041] Before depositing the thin film, the alloy target can be pre-sputtered for a period of time (e.g., 5 minutes) to remove oxides and impurities on the target surface to prevent these oxides or impurities from being deposited on the substrate, which ultimately leads to contamination or even failure of the zinc tin nitride film.

[0042] The zinc-tin alloy target is a zinc-tin alloy target with a ratio of Zn:Sn=5:1. The power of radio frequency sputtering on the zinc-tin alloy target is 30W, so that the target is deposited on the substrate to form a zinc-tin nitride film.

[0043] In the method for preparing the zinc tin nitride film, the nitrogen is 99.999% high-purity nitrogen and the argon is 99.995% high-purity argon, so as to avoid the interference of impurity gases on the sputtering reaction as much as possible, thereby improving the quality of the zinc tin nitride film.

[0044] Preferably, the flow rate of the nitrogen gas is 5 sccm, and the flow rate of the argon gas is 8 sccm. The zinc tin nitride film prepared under the above flow rates of flowing nitrogen and argon has a low carrier concentration and high mobility, and is of particularly good quality.

[0045] In a flowing argon atmosphere, at a constant temperature and pressure, the zinc tin nitride film is placed in a sputtering system for a period of time to obtain an annealed zinc tin nitride film.

[0046] Different from the conventional high vacuum annealing method, the present invention uses argon gas at a certain flow rate to maintain a stable gas pressure, thereby producing an annealed zinc tin nitride film with low carrier concentration and good crystallinity.

[0047] In the annealing method of the zinc tin nitride film of the present invention, the zinc tin nitride film is first placed in a sputtering system, and then the entire sputtering system is evacuated to a vacuum degree of 4.5×10 -4 Pa to ensure that there is no impurity gas such as oxygen, while controlling the temperature to remain constant, and then continuously introducing argon and keeping the pressure stable, that is, while introducing argon, it is discharged at a certain rate to ensure that the entire vacuum chamber is maintained at a certain pressure environment, and then maintained for a period of time to obtain the annealed zinc tin nitride film.

[0048] Preferably, the zinc tin nitride film needs to be prepared in advance, for example, the zinc tin nitride film used for this annealing is the zinc tin nitride film prepared above. Zinc tin nitride films prepared under other conditions can also be used to prepare the annealed zinc tin nitride film in the present invention.

[0049] Preferably, in the present invention, before the thin film annealing is performed, the substrate is preheated and maintained at 300-400° C., and the thin film is annealed at a constant temperature of 300-400° C.

[0050] In the annealing method of the zinc tin nitride film, the argon gas is 99.995% high-purity argon gas to minimize interference of impurity gases with annealing, thereby improving the quality of the annealed zinc tin nitride film. At the same time, the gas pressure of the entire system is ensured to be stable at 1 Pa. Even if the annealing pressure is 1 Pa, under this pressure intensity, the film can have better crystallinity, better film density, lower carrier concentration and better carrier mobility.

[0051] Preferably, the flow rate of the argon gas is 30 sccm. The zinc tin nitride film annealed under the flowing argon gas with the above flow rate has a low carrier concentration and a high mobility, and is of particularly good quality.

[0052] In a flowing argon atmosphere and at a fixed pressure, a copper target is deposited on an annealed zinc tin nitride film by a DC sputtering method to obtain a copper-zinc tin nitride Schottky junction.

[0053] In the present invention, argon gas with a certain flow rate is used to maintain a stable gas pressure and is used as bombarding particles to perform DC sputtering on a copper target, thereby preparing a copper-zinc tin nitride Schottky junction with good rectification effect and photovoltaic effect.

[0054] In the method for preparing the copper-zinc tin nitride Schottky junction of the present invention, the copper target is first fixed on the DC target position, and then the entire sputtering system is evacuated to a vacuum degree of 4.5×10 -4 Pa to ensure that there is no impurity gas such as oxygen, and then continuously introduce argon and keep the pressure stable, that is, while introducing argon, it is discharged at a certain rate to ensure that the entire vacuum chamber is maintained at a certain pressure environment. Then, copper is deposited on the annealed zinc tin nitride film by DC sputtering to obtain a copper-zinc tin nitride Schottky junction.

[0055] Preferably, the annealed zinc tin nitride film needs to be prepared in advance. For example, the zinc tin nitride film used for this annealing is the annealed zinc tin nitride film prepared above. Annealed zinc tin nitride films prepared under other conditions can also be used to prepare copper-zinc tin nitride Schottky junctions in the present invention.

[0056] In the method for preparing the copper-zinc-tin nitride Schottky junction, the argon gas is 99.995% high-purity argon gas to minimize interference of impurity gases with annealing, thereby improving the quality of the copper-zinc-tin nitride Schottky junction. At the same time, the gas pressure of the entire system is ensured to be stable at 2 Pa. Even at a sputtering pressure of 2 Pa, the copper electrode can be better bonded to the zinc-tin nitride film, while the copper thickness is relatively uniform.

[0057] Preferably, the flow rate of the argon gas is 30 sccm. The zinc tin nitride film annealed under the flowing argon gas with the above flow rate has a low carrier concentration and a high mobility, and is of particularly good quality.

[0058] The present invention also provides a copper-zinc tin nitride Schottky junction, which is prepared by the method described above.

[0059] The present invention is described in detail below by way of examples.

[0060] Example 1

[0061] Si(100) and K9 glass were used as substrates, and the substrates were ultrasonically cleaned with acetone, alcohol and deionized water in sequence. A zinc target with a Zn:Sn ratio of 5:1 was fixed on the RF target position. The background vacuum of the sputtering system was then evacuated to 4.5×10 -4Pa, high-purity nitrogen at a flow rate of 5sccm and high-purity argon at a flow rate of 8sccm were introduced. The target was pre-sputtered for 5 minutes to remove oxides and impurities on the target surface. The substrate was then heated to 100°C. The zinc-tin alloy target was then radio-frequency sputtered at a sputtering power of 30W at a working pressure of 3Pa for 60 minutes to obtain a zinc-tin nitride film. After the sputtering coating was completed, the sputtering source and the gas inlet valve were turned off. After the substrate temperature dropped to room temperature, the vacuum pump, power supply, and other switches were turned off in sequence, and the sample was removed.

[0062] The samples were tested by X-ray diffraction (XRD), and the results were as follows: Figure 1 As shown, from Figure 1 It can be seen that under the preparation conditions adopted in the present invention, the prepared film is in a microcrystalline state.

[0063] The samples were tested by EDS, and the results were as follows: Figure 2 As shown, from Figure 2 It can be seen that the film is not disturbed by other gas elements and its main elements are zinc, tin and nitrogen.

[0064] Place the sample in the sputtering system and then pump the background vacuum of the sputtering system to 4.5×10 -4 Pa, high-purity argon gas at a flow rate of 30 sccm was introduced, and the substrate was then heated to 350°C. The temperature was then maintained at a working pressure of 1 Pa for 60 minutes to obtain an annealed zinc tin nitride film. After the zinc tin nitride annealing was completed, the gas inlet valve was closed, and the substrate temperature was allowed to cool to room temperature. The vacuum pump, power supply, and other switches were then turned off in sequence, and the sample was removed.

[0065] The annealed sample was placed in the sputtering system; a copper target with a purity of 99.999% was fixed on the DC target position; and the background vacuum of the sputtering system was evacuated to 4.5×10 -4 Pa, high-purity argon gas at a flow rate of 30 sccm was introduced, and the target was pre-sputtered for 5 minutes to remove oxides and impurities on the target surface. Then, the copper target was RF sputtered at a working pressure of 2 Pa and a sputtering power of 10 W for 20 minutes to obtain a copper-zinc tin nitride Schottky junction. After the sputtering coating was completed, the sputtering source and the gas inlet valve were turned off. After the substrate temperature dropped to room temperature, the vacuum pump, power supply, and other switches were turned off in sequence, and the sample was removed.

[0066] The samples were tested in dark state and light state. Figure 3 and Figure 4 As shown. Figure 3 It can be seen that the rectification effect of copper-zinc tin nitride Schottky junction is better. Figure 4 Show its photovoltaic effect.

[0067] From the above implementation, it can be seen that the zinc tin nitride film obtained by sputtering at 100°C, annealing it at 350°C and combining it with copper to form a Schottky junction can effectively improve the problem of poor rectification effect and produce a photovoltaic effect.

[0068] In summary, the present invention provides a copper-zinc-tin nitride Schottky junction and its preparation method. In a flowing nitrogen and argon atmosphere, a zinc-tin alloy target with a ratio of Zn:Sn = 5:1 is deposited on a substrate using radio frequency sputtering, thereby producing a zinc-tin nitride thin film with low carrier concentration and high mobility. After annealing, the copper target is then sputtered onto the zinc-tin nitride film using direct current sputtering to form a Schottky junction. This solves the problem of poor rectification and lack of photovoltaic effect associated with copper-zinc-tin nitride Schottky junctions.

[0069] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a copper-zinc tin nitride Schottky junction, characterized in that: Including steps: In a flowing nitrogen and argon atmosphere, a zinc-tin alloy target with a ratio of Zn:Sn=5:1 is deposited on a substrate by radio frequency sputtering to obtain a zinc-tin nitride film; in a flowing argon atmosphere, the zinc-tin nitride film is annealed at a certain temperature; in a flowing argon atmosphere, a copper target is deposited on the zinc-tin nitride film by direct current sputtering to obtain a copper-zinc-tin nitride Schottky junction.

2. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: Including steps: First, fix the alloy target with Zn:Sn=5:1 on the RF target position, evacuate the sputtering system, and then continuously introduce nitrogen and argon while keeping the gas pressure stable. Then, zinc and tin are simultaneously deposited on a silicon wafer or glass substrate by RF sputtering to obtain a zinc-tin nitride film. Place the zinc-tin nitride film in the sputtering system, evacuate the sputtering system, and then continuously introduce argon while keeping the gas pressure stable. Then, copper is deposited on the zinc-tin nitride film by DC sputtering to obtain a copper-zinc-tin nitride Schottky junction.

3. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 2, wherein: The nitrogen is 99.999% high-purity nitrogen, and the argon is 99.995% high-purity argon.

4. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 3, wherein: The flow rate of the nitrogen gas is 5 sccm, the flow rate of the argon gas for preparing the zinc tin nitride film is 8 sccm, the flow rate of the argon gas for annealing the zinc tin nitride film is 30 sccm, and the flow rate of the argon gas for preparing the copper-zinc tin nitride Schottky junction is 30 sccm.

5. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: The radio frequency sputtering power is 30W, and the direct current sputtering power is 10W.

6. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: The gas pressure for preparing the zinc tin nitride film is 3Pa, the gas pressure for annealing the zinc tin nitride film is 1Pa, and the gas pressure for preparing the copper-zinc tin nitride Schottky junction is 2Pa.

7. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: The substrate needs to be cleaned in advance.

8. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: The substrate needs to be cleaned with acetone, alcohol and deionized water in advance.

9. The method for preparing a copper-zinc tin nitride Schottky junction according to claim 1, wherein: The substrate needs to be heated to 50-150° C. before the zinc tin nitride film is deposited, and the zinc tin nitride film needs to be heated to 300-400° C. before annealing.

10. A copper-zinc-tin nitride Schottky junction, characterized in that: The method is prepared by any one of claims 1 to 9.

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