Visible-near infrared wide spectrum semiconductor transparent electrode and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor films, and relates to a visible-near infrared wide spectrum semiconductor transparent electrode and a preparation method thereof. The visible-near-infrared wide-spectrum semiconductor transparent electrode comprises a substrate and an indium tin oxide film formed on the substrate, the indium tin oxide film comprises In, O and Sn, and the film structure is a glass state indium tin oxide embedded In2O3 and SnO2 crystal particle network. The prepared indium tin oxide thin film is of a special structure that glassy state indium tin oxide is inlaid with an In2O3 and SnO2 crystal particle network, the scattering absorption of the thin film to near-infrared incident light is greatly reduced through the glassy state structure, and the average transmittance gt of the thin film in the visible to near-infrared band (380 nm to 2500 nm) is made to be gt; the In2O3 and SnO2 crystal particle network structure endows the material with good conductive characteristics, and the low resistivity of the material is lower than (lt: 10 <-3 > omega.cm).

Description

A visible-near-infrared broadband semiconductor transparent electrode and its preparation method Technical Field

[0001] This invention relates to the application of transparent electrodes, belonging to the field of semiconductor thin film technology, and specifically to a visible-near-infrared broadband semiconductor transparent electrode and its preparation method. Background Technology

[0002] With the development of science and technology, optoelectronic devices (including photovoltaic devices, optoelectronic displays, optoelectronic sensors, and optical communication equipment) have become indispensable elements in people's lives. Transparent electrodes are a crucial structure in optoelectronic devices; their conductivity and transmittance to the target wavelength directly affect the photoelectric conversion efficiency and response band of the device. Indium tin oxide (ITO) thin films possess excellent optoelectronic properties, exhibiting over 90% transmittance in the visible light band (380-780nm) and a sheet resistance close to 10Ω / □, demonstrating good compatibility with traditional semiconductor devices. They are currently the most widely used transparent electrode material in optoelectronic devices. In the past decade, significant progress has been made in the development of emerging optoelectronic materials such as organic materials, quantum dot materials, two-dimensional materials, and perovskite materials. The characteristics and application requirements of these emerging optoelectronic materials determine the development direction of the next generation of optoelectronic devices: integration, flexibility, low cost, multifunctionality, high performance, and broad spectrum. The continuous upgrading of optoelectronic devices has also placed new demands on the next generation of transparent electrodes. For example, optoelectronic devices such as organic solar cells, quantum dot detectors, low-light detectors, and multi-band laser communication equipment all require transparent electrodes to have a wide spectrum of transmission characteristics from visible to near-infrared. Although ITO electrodes have excellent transmittance in the visible light band, their transmittance in the infrared band drops sharply due to scattering and reflection. Existing ITO electrodes are not suitable as transparent electrodes for next-generation photovoltaic, communication, and detection devices that require a wide spectrum response.

[0003] Materials such as metal mesh films, graphene, metal nanowire films, polymer (PEDOT:PSS), and carbon nanotube films all possess broad-spectrum transmission characteristics. In recent years, there has been an increasing trend in the literature reporting on the application of these transparent electrode materials in broad-spectrum optoelectronic devices. However, metal mesh films suffer from poor stability and complex fabrication processes; graphene and carbon nanotube films are expensive and have high resistivity; silver nanowire films are easily oxidized and lack large-area uniform film formation methods; and PEDOT:PSS is unstable, not heat-resistant, and easily deteriorates under ultraviolet radiation. Furthermore, all of these transparent electrode materials have compatibility issues with the semiconductor industry. Therefore, their application is mainly concentrated in small-scale basic research. Until significant breakthroughs are achieved in material properties and manufacturing processes, these broad-spectrum transparent electrode materials cannot be applied at the industrial level. ITO films and their fabrication processes have been proven to be highly compatible with the semiconductor industry. Expanding the near-infrared transmittance of ITO films based on existing technology is an effective means to obtain conductive films with broad-spectrum transmission characteristics. Existing research has confirmed that adding a buffer layer, reducing the thickness of the ITO film, changing the ratio of In2O3 to SnO2, and applying antireflection structures can effectively improve the near-infrared transmittance of ITO films, thereby achieving broad-spectrum transmission characteristics. However, these processes increase the number of steps, reduce film stability, and increase costs, which is not conducive to large-scale promotion. More efficient and direct processing technologies are needed to obtain conductive films with broad visible-near-infrared transmission properties. Summary of the Invention

[0004] (I) Purpose of the Invention The purpose of this invention is to provide a broadband semiconductor transparent electrode and its preparation method, which relates to the preparation process of indium tin oxide thin film. The indium tin oxide thin film prepared by this method has a special structure of glassy indium tin oxide embedded with In2O3 and SnO2 crystalline particle network. The thin film has the characteristics of high visible to near infrared transmittance, low resistivity, simple preparation process, low cost, and semiconductor process compatibility.

[0005] (II) Technical Solution Based on the urgent need for broadband transparent electrodes in next-generation photovoltaic, communication, and detection devices, and the technical bottlenecks in the large-scale application of broadband transparent electrode materials, this invention proposes a broadband semiconductor transparent electrode and its preparation method. By adjusting the sputtering voltage, substrate temperature, target In2O3 / SnO2 ratio, and growth chamber vacuum degree in the magnetron sputtering process, the deposition rate, grain size, surface particle size, In / Sn / O composition ratio, and micro-ordered structure of the ITO thin film are controlled. This successfully prepares an ITO thin film with a glassy embedded In2O3 and SnO2 crystalline particle network. The glassy structure reduces the scattering of In2O3 and SnO2 grains in the near-infrared region, giving the film good near-infrared transmittance. The In2O3 and SnO2 crystalline particle network structure allows for the formation of a conductive network within the film, giving it good conductivity. The ITO thin film prepared by this invention has an average transmittance exceeding 80% in the visible to near-infrared (380-2500nm) range and a resistivity below 1×10⁻⁶. -3 With a strength of Ω·cm, it can meet the needs of next-generation photovoltaic, communication, and detection devices for broadband transparent electrodes, and has excellent development potential.

[0006] This invention uses an In2O3·SnO2 alloy target as the sputtering material and employs DC magnetron sputtering to maintain a high background vacuum (<5×10⁻⁶). -6 In a pure argon (Ar) atmosphere, a glassy indium tin oxide (ITO) thin film is deposited on a substrate. During the deposition process, the substrate temperature, sputtering power, and voltage are controlled to keep the deposition rate below 5 nm / min. A low vacuum, a low substrate temperature, and an appropriate deposition rate are maintained to prevent the ITO film from overheating and directly undergoing annealing and crystallization. The ITO film contains In, O, and Sn elements, and its structure is a unique glassy ITO film with an embedded network of In₂O₃ and SnO₂ crystalline particles.

[0007] The broadband semiconductor transparent electrode of the present invention includes a substrate and an indium tin oxide thin film formed thereon.

[0008] The substrate includes one of the following: glass, quartz, sapphire, silicon, silicon carbide, gallium arsenide, indium phosphide, polyimide (PI), and polyethylene terephthalate (PET).

[0009] The indium tin oxide film contains three elements: In, O, and Sn. The film thickness is 50nm~150nm. The film structure is a glassy indium tin oxide embedded with a network of In2O3 and SnO2 crystalline particles. The glassy indium tin oxide can significantly improve the near-infrared transmittance of the film, and the embedded In2O3 and SnO2 crystalline particle network can ensure the good conductivity of the film.

[0010] In the indium tin oxide thin film, the molar content of In2O3 is 85%-95% and the molar content of SnO2 is 5%-15%, which is consistent with the alloy target used for sputtering.

[0011] Among them, the film thickness of 50nm exhibits good visible light transmittance characteristics; the film thickness of 150nm exhibits good electrical conductivity characteristics.

[0012] The method for preparing a broadband semiconductor transparent electrode of the present invention includes the following steps: S1: preparing and cleaning the substrate; S2: transferring the cleaned substrate from the pretreatment chamber to the growth chamber; S3: adjusting the substrate temperature and pre-sputtering the target material; S4: opening the baffle and sputtering and depositing an indium tin oxide thin film under a pure Ar atmosphere; S5: waiting for the sample to cool and taking out the sample.

[0013] In steps S2 and S3, the background vacuum in the growth chamber is below 5 × 10⁻⁶. -6 During sputtering, the vacuum chamber pressure is between 0.1 Pa and 0.2 Pa. Before preparing indium tin oxide (ITO) thin films, it is necessary to maintain an extremely low vacuum in the growth chamber to avoid the influence of residual water, oxygen, and other impurities on the film and to improve the film growth quality.

[0014] In steps S3 and S4, the sputtering source is an In2O3·SnO2 alloy target with an In2O3 molar content of 85%~95%, a SnO2 molar content of 5%~15%, and an In, Sn, and O element purity of 99.999%.

[0015] In step S4, pure Ar is used as the sputtering gas, and no other gases are introduced during the film growth process. The indium tin oxide (ITO) film is prepared by DC magnetron sputtering. During the film deposition process, process parameters such as sputtering power, substrate temperature, and vacuum level are strictly controlled to prevent the deposited ITO film from being crystallized by high-temperature annealing, and to prevent the ITO film from exhibiting a completely glassy state.

[0016] When preparing indium tin oxide thin films using magnetron sputtering, the sputtering power must be strictly controlled between 20W and 40W to avoid excessive sputtering energy, which would lead to excessive energy of sputtered particles and heat accumulation on the substrate, causing the film to anneal and crystallize as a whole. At the same time, it is also necessary to avoid sputtering energy that is too low, which would cause the film to be in a completely glassy state.

[0017] When preparing indium tin oxide thin films using magnetron sputtering, the substrate temperature should be controlled between 80℃ and 250℃ to avoid excessively high temperatures that could cause overall annealing and crystallization of the film, while also avoiding excessively low substrate temperatures that could cause the film to exhibit a completely glassy state.

[0018] When preparing indium tin oxide thin films using magnetron sputtering, the Ar gas flow rate is 5 sccm to 30 sccm, and the vacuum degree of the growth chamber is controlled between 0.1 Pa and 2.0 Pa during sputtering.

[0019] When preparing indium tin oxide thin films using magnetron sputtering, the deposition rate is controlled below 5 nm / min, and the root mean square roughness of the final deposited film surface is less than 5 nm.

[0020] The preparation process used in this invention has a temperature below 250°C, and is compatible with some organic substrates such as polyimide (PI) and polyethylene terephthalate (PET).

[0021] (III) Beneficial Effects The visible-near infrared broadband semiconductor transparent electrode and its preparation method provided by the above technical solution have the following beneficial effects: 1. The indium tin oxide thin film prepared by the present invention has a smooth surface with a root mean square roughness of less than 5 nm. The film is dense and of excellent quality, and the overall process flow is compatible with the semiconductor device preparation process.

[0022] 2. The indium tin oxide thin film prepared by this invention has a special structure of glassy indium tin oxide embedded with In2O3 and SnO2 crystalline particle networks. The glassy structure significantly reduces the scattering and absorption of near-infrared incident light, resulting in an average transmittance >80% in the visible to near-infrared band (380nm to 2500nm). The In2O3 and SnO2 crystalline particle network structure endows it with good electrical conductivity, and its low resistivity is less than (<10). -3 Ω·cm).

[0023] 3. The process temperature for preparing indium tin oxide thin films according to the present invention is below 250°C, which is compatible with organic materials and flexible substrates, and is suitable for the process system of high-performance organic optoelectronic devices that are interconnected and integrated with CMOS circuits.

[0024] 4. The indium tin oxide thin film prepared by this invention has an average transmittance of >80% in the visible to near-infrared band (380nm to 2500nm). In contrast, the commercially available ITO thin film has an average transmittance of <50% in the corresponding band. The indium tin oxide thin film prepared by this invention has great application potential in broadband photovoltaic, communication and detection devices. Attached Figure Description

[0025] Figure 1 is a schematic diagram of the overall process for preparing indium tin oxide thin films according to the present invention. Figure 2 is the XRD pattern of the thin film sample prepared in Example 1. Figure 3 is the visible-near-infrared transmission spectrum of the thin film samples prepared in Examples 1-3. Figure 4 is the AFM morphology of the thin film sample prepared in Example 2. Figure 5 is the SEM cross-sectional view of the thin film sample prepared in Example 3. To make the objectives, content, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0026] Example 1: As shown in Figure 1, the cleaned quartz substrate was picked up with clean tweezers, dried with nitrogen gas, and then fixed onto a substrate holder. The substrate holder was then transferred from the pretreatment chamber to the growth chamber, where the vacuum level was 1.0 × 10⁻⁶. -2 Pa-3.0×10 -2 Pa, the background vacuum level of the growth chamber is 3.5 × 10⁻⁶ Pa. -6 Pa. After adjusting the substrate temperature to 80℃ and maintaining it at that temperature for 30 minutes, start the sputtering power supply and preheat for 10 minutes. Turn on the substrate rotation power supply, open the argon valve, and control the argon flow rate to 5 sccm. After the gas pressure stabilizes, pre-sputter at a pure Ar working pressure of 1.0 Pa and a sputtering power of 30 W for 5 minutes to remove the surface impurity layer.

[0027] After the sputtering voltage stabilizes, the baffle of the substrate holder is opened, and the sputtering argon gas pressure is reduced to 0.1 Pa. An indium tin oxide film with a thickness of 80 nm is deposited on the quartz substrate at a deposition rate of 2.8 nm / min. After sputtering, the substrate is allowed to cool naturally to below 60°C. The substrate holder is then transferred from the growth chamber back to the pretreatment chamber. The pretreatment chamber is filled with nitrogen gas. After the pressure in the pretreatment chamber rises to standard atmospheric pressure, the sample is taken out and recorded as ITO-80.

[0028] The XRD pattern of the sample was analyzed using an X-ray diffraction analyzer, as shown in Figure 2. The visible-near-infrared transmission spectrum and sheet resistance of the ITO-80 sample were measured using a spectrometer and a four-probe sheet resistance meter, respectively, to analyze the photoelectric properties of the sample, as shown in Figure 3. The XRD, spectral, and sheet resistance test results confirmed that the ITO-80 sample prepared in Example 1 has a microcrystalline structure of In2O3 and SnO2, with an average transmittance of 86% and a sheet resistance of 90 Ω / □ in the 380 nm to 2500 nm wavelength range.

[0029] Example 2: The cleaned quartz substrate was picked up with clean tweezers, dried with nitrogen gas, and then fixed onto a substrate holder. The substrate holder was then transferred from the pretreatment chamber to the growth chamber, where the vacuum level was 1.0 × 10⁻⁶. -2 Pa-3.0×10 -2 Pa, the background vacuum level of the growth chamber is 3.5 × 10⁻⁶ Pa. -6Pa. After adjusting the substrate temperature to 150℃ and maintaining it at that temperature for 30 minutes, start the sputtering power supply and preheat for 10 minutes. Turn on the substrate rotation power supply, open the argon valve, and control the argon flow rate to 20 sccm. After the gas pressure stabilizes, pre-sputter at a pure Ar working pressure of 2.0 Pa and a sputtering power of 40 W for 5 minutes to remove the surface impurity layer.

[0030] After the sputtering voltage stabilizes, the baffle of the substrate holder is opened, and the sputtering argon gas pressure is reduced to 0.3 Pa. An indium tin oxide film with a thickness of 150 nm is deposited on the quartz substrate at a deposition rate of 4.3 nm / min. After sputtering, the substrate is allowed to cool naturally to below 60°C. The substrate holder is then transferred from the growth chamber back to the pretreatment chamber. The pretreatment chamber is filled with nitrogen gas. After the pressure in the pretreatment chamber rises to standard atmospheric pressure, the sample is taken out and recorded as ITO-150.

[0031] The visible-near-infrared transmission spectrum and sheet resistance of the ITO-150 sample were measured using a spectrometer and a four-probe sheet resistance meter, respectively, to analyze the photoelectric properties of the sample, as shown in Figure 3. The surface morphology of the ITO-150 sample was analyzed using atomic force microscopy (AFM), as shown in Figure 4. The spectral, sheet resistance, and AFM surface morphology results confirmed that the ITO-150 sample prepared in Example 2 had an average transmittance of 83% in the 380 nm to 2500 nm wavelength range, a sheet resistance of 50 Ω / □, and a root mean square roughness of 4.68 nm.

[0032] Example 3: The cleaned quartz substrate was picked up with clean tweezers, dried with nitrogen gas, and then fixed onto the substrate holder. The substrate holder was then transferred to the growth chamber via the pretreatment chamber, which had a vacuum degree of 1.0 × 10⁻⁶. -2 Pa-3.0×10 -2 Pa, the background vacuum level of the growth chamber is 3.5 × 10⁻⁶ Pa. -6 Pa. After adjusting the substrate temperature to 150℃ and maintaining it at that temperature for 30 minutes, start the sputtering power supply and preheat for 10 minutes. Turn on the substrate rotation power supply, open the argon valve, and control the argon flow rate to 15 sccm. After the gas pressure stabilizes, pre-sputter at a pure Ar working pressure of 1.0 Pa and a sputtering power of 20 W for 5 minutes to remove the surface impurity layer.

[0033] After the sputtering voltage stabilizes, the baffle of the substrate holder is opened, and the sputtering argon gas pressure is reduced to 0.2 Pa. An indium tin oxide film with a thickness of 100 nm is deposited on the quartz substrate at a deposition rate of 2.0 nm / min. After sputtering, the substrate is allowed to cool naturally to below 60°C. The substrate holder is then transferred from the growth chamber back to the pretreatment chamber. The pretreatment chamber is filled with nitrogen gas. After the pressure in the pretreatment chamber rises to standard atmospheric pressure, the sample is taken out and recorded as ITO-100.

[0034] The visible-near-infrared transmission spectrum and sheet resistance of sample ITO-100 were measured using a spectrometer and a four-probe sheet resistance meter, respectively, to analyze the photoelectric properties of the sample, as shown in Figure 5. The spectral and sheet resistance test results confirmed that the sample ITO-GL prepared in Example 3 had an average transmittance of 85% and a sheet resistance of 75 Ω / □ in the 380 nm to 2500 nm wavelength range.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A visible-near-infrared broadband semiconductor transparent electrode, characterized in that, include: It includes a substrate and an indium tin oxide film formed thereon. The indium tin oxide film contains three elements: In, O, and Sn. The film structure is a glassy indium tin oxide embedded with a network of In2O3 and SnO2 crystalline particles.

2. The visible-near-infrared broadband semiconductor transparent electrode as described in claim 1, characterized in that, The substrate is one of glass, quartz, sapphire, silicon, silicon carbide, gallium arsenide, indium phosphide, polyimide, or polyethylene terephthalate.

3. The visible-near-infrared broadband semiconductor transparent electrode as described in claim 2, characterized in that, The thickness of the indium tin oxide film is 50nm~150nm.

4. The visible-near-infrared broadband semiconductor transparent electrode as described in claim 3, characterized in that, In the indium tin oxide thin film, the molar content of In2O3 is 85%-95% and the molar content of SnO2 is 5%-15%, which is consistent with the alloy target used for sputtering.

5. A method for preparing a visible-near-infrared broadband semiconductor transparent electrode according to claim 4, characterized in that, Includes the following steps: S1: Prepare and clean the substrate; S2: Transfer the cleaned substrate from the pretreatment chamber to the growth chamber; S3: Adjust the substrate temperature and pre-sputter the target material; S4: Open the baffle and sputter to deposit an indium tin oxide thin film under a pure Ar atmosphere; S5: Wait for the sample to cool and then remove the sample.

6. The method for fabricating a visible-near-infrared broadband semiconductor transparent electrode as described in claim 5, characterized in that, In step S2, the background vacuum in the growth chamber is below 5 × 10⁻⁶. -6 Pa.

7. The method for fabricating a visible-near-infrared broadband semiconductor transparent electrode as described in claim 6, characterized in that, In steps S3 and S4, the sputtering source is an In2O3·SnO2 alloy target with an In2O3 molar content of 85%~95%, a SnO2 molar content of 5%~15%, and an In, Sn, and O element purity of 99.999%.

8. The method for fabricating a visible-near-infrared broadband semiconductor transparent electrode as described in claim 7, characterized in that, In step S4, pure Ar is used as the sputtering gas, and no other gas is introduced during the film growth process; the indium tin oxide film is formed by DC magnetron sputtering.

9. The method for fabricating a visible-near-infrared broadband semiconductor transparent electrode as described in claim 8, characterized in that, In step S4, the sputtering power is controlled between 20W and 40W.

10. The method for fabricating a visible-near-infrared broadband semiconductor transparent electrode as described in claim 9, characterized in that, In steps S3 and S4, the substrate temperature is controlled between 80℃ and 250℃; in step S4, the Ar gas flow rate is 5 sccm to 30 sccm, and the vacuum degree of the growth chamber is controlled between 0.1 Pa and 2.0 Pa during sputtering.

Images