CN101429643A - Low temperature production method of transparent conductive oxide film - Google Patents

Abstract

The invention provides a low-temperature preparation method for a transparent conductive oxide film. After using a pulse laser method to prepare a seed layer, the pulse laser method or the magnetron sputtering method is used to subsequently prepare a niobium-doped titanium oxide transparent conductive film material. The crystal layer is titanium oxide single crystal with anatase crystal structure. The pulse laser deposition controls the thickness between 0.5 and several unit cell c-axis lengths; the pulse laser method or magnetron sputtering is used on the substrate material with the seed layer. The method continues to grow to prepare titanium oxide-based thin film materials. The preparation process is less dependent on the preparation process and growth conditions. The preparation process is flexible and selective. The visible light transmittance of the obtained titanium oxide-based transparent conductive film is better than 90%. The room temperature resistivity is less than 8×10 ^-4 ohm.cm; realizing the low-temperature growth and preparation of transparent conductive oxide films that can replace ITO.

Description

Low-temperature Preparation Method of Transparent Conductive Oxide Thin Film

technical field

The invention relates to a low-temperature preparation method of a transparent conductive oxide film, belonging to the technical field of photoelectric information materials.

Background technique

Transparent conductive oxide (Transparent Conducting Oxide: TCO) film refers to the high light transmittance (>80%) and low resistivity (<1×10-3Ω cm) of visible light (wavelength λ=380-780nm). A class of oxide thin film materials. TCO thin films are currently widely used in solar cells, screen displays, photodetectors, window coatings, low-wavelength lasers, high-density storage, optical fiber communications, and other fields. The current research and application of TCO thin films mainly focus on tin-doped indium oxide (Indium Tin Oxide: ITO) thin films. Because ITO film has the characteristics of high transmittance in the visible light region, strong infrared light reflection, low resistivity, strong adhesion to glass, good wear resistance and chemical stability, it has formed a huge market in the above application fields. scale. And with the development of science and technology and the continuous improvement of people's living standards, the wide application of high-resolution and large-size flat-panel displays and solar cells, the market demand for TCO thin films is increasing. The demand for TCO thin film materials used in solar cells will also increase day by day. In recent years, with the high price of indium element and the impending depletion of indium element resources, people are actively researching and developing new TCO thin film materials based on the strategic level of environmentally friendly and resource-rich elements.

The design and development of the new TCO thin film revolves around how to make the organic unity of light transmission and conductivity better. In principle, the two can be realized by adjusting the bandgap structure, carrier concentration, mobility and work function of the material. The unity of contradictions. In 2005, Furubayashi et al. found that the niobium-doped anatase phase TiO ₂ thin film material has excellent electrical conductivity and visible light transmittance, and the single crystal thin film epitaxially grown on the oxide single crystal substrate, its various The physical properties are comparable to those of ITO materials [Appl.Phys.Lett., Vol.86, pp.252101, 2005]. The TiO ₂ parent material is non-toxic, tasteless and abundant, and has a wide range of applications in photocatalysis and dilute magnetic semiconductors. At the same time, the new _TiO2- based TCO thin film material has obvious advantages in chemical stability compared with the ZnO-based TCO thin film material that has been studied more at present. However, how to grow new _TiO2- based TCO thin film materials on cheap and more practical glass and flexible substrates is a crucial step in practical application research and product development. At present, foreign research in this area has just started, and there are many influencing factors, such as the microscopic morphology and phase structure of the film, and the influence of oxygen vacancies on the carrier mobility and optical parameters, etc. The experimental work is still in the process of exploration. Phase [Appl. Phys. Lett., Vol.90, pp.212106, 2007]. On the other hand, compared with TCO films deposited on hard material substrates, TCO thin films prepared on flexible substrates have the advantages of light weight, flexibility, unbreakability, and easy large-area production, and can be applied to flexible substrates. Bottom solar cells and flexible nano-optoelectronic devices and other fields. And with the miniaturization and portability of electronic devices, the research on growing TCO thin films on flexible substrates has attracted widespread attention, and it is expected to become an updated product of TCO thin films on hard substrates. In the process of growing TCO thin films on flexible substrates, it is usually necessary to choose a higher substrate growth temperature or subsequent atmosphere heat treatment to ensure the crystallization quality of TCO thin films. However, flexible substrates are not resistant to high temperatures, which is not conducive to the growth of TCO thin film materials with excellent optoelectronic properties. In the preparation process, it adds difficulties to the growth process of TCO thin films and poses new challenges.

Therefore, the development of low-temperature growth technology for TCO thin films is of great value and significance for improving the preparation conditions of thin films and expanding the application of TCO thin films in fields such as flexible substrate solar cells.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a low-temperature preparation method of a transparent conductive oxide film.

The purpose of the present invention is achieved through the following technical solutions:

The low-temperature preparation method of the transparent conductive oxide thin film, after preparing the seed layer by the pulse laser method, and then respectively using the pulse laser method or the magnetron sputtering method to subsequently prepare the niobium-doped titanium oxide transparent conductive thin film material, the specific steps are:

①Growth of the seed layer: first clean the single crystal oxide substrate material, blow it dry, and immediately put it into a vacuum chamber. The absolute pressure of the back of the reaction chamber before deposition is lower than 1×10 ^-5 Torr; TiO ₂ sheet is used as the target material, and O ₂ with a purity higher than 99.99% is used as the deposition atmosphere. The seed layer film is prepared by pulsed laser deposition. During the preparation process, the control: the substrate temperature is 400-573K, and the absolute pressure of the background is lower than 5×10 ^-4 Torr, laser energy density 5~8J/cm ² , frequency 3~8Hz, deposition O ₂ partial pressure 1×10 ^-2 ～1×10 ^-5 Torr, vertical distance between target and substrate 40mm-50mm; after the deposition process, cool down to room temperature with the furnace, cut off the oxygen, and take it out; real-time monitoring of in-situ high-energy reflection electron diffraction shows that the seed layer structure is an anatase titanium oxide single crystal, and the out-of-plane It is c-axis orientation, and the film thickness of the seed layer is between 0.5 and several unit cell c-axis lengths;

② Subsequent growth: Continue to grow and prepare titanium oxide-based transparent conductive film on the substrate material with seed layer prepared above by pulse laser method or magnetron sputtering method, and the substrate temperature is controlled in the low temperature section below 473K , the target composition is Nb ₂ O ₅ —TiO ₂ , and the atomic percentage of niobium in TiO ₂ is 2-8%; among them,

Using the pulsed laser method: the deposition temperature is from room temperature to 473K, the pulse frequency is 1-5Hz, the laser energy density is 2-8J/cm ² , the deposition O ₂ partial pressure is 1×10 ^-2 to 1×10 ^-5 Torr, and the target The vertical distance from the substrate is 40mm to 60mm, and the film deposition thickness is less than 300nm;

Using magnetron sputtering method: Ar gas and O ₂ gas are fully mixed and then introduced into the reaction chamber through the catheter, the flow ratio of Ar gas and O ₂ gas is controlled between 4 and 8, and the substrate temperature is heated to 400 ~ 473K After the temperature interval, the sputtering gas is introduced into the reaction chamber to the deposition chamber. After the overall pressure reaches 1-10Pa, the sputtering film is started. The sputtering power is controlled at 40-100W, and the vertical distance between the target and the substrate is 50-100mm. The thickness of the film is controlled below 300 nanometers;

After the deposition by the pulse laser method or the magnetron sputtering method is completed, after cooling to room temperature with the furnace, the gas source is cut off and taken out to obtain a titanium oxide-based transparent conductive film.

Furthermore, in the low-temperature preparation method of the above-mentioned transparent conductive oxide thin film, the single crystal oxide substrate material is SrTiO ₃ , or LaAlO ₃ , or SrLaAlO ₄ , or (LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 .

Furthermore, in the low-temperature preparation method of the above transparent conductive oxide film, the single crystal oxide substrate material is first cleaned with acetone, then cleaned with ethanol, and finally cleaned with deionized water ultrasonically, and blown with a nitrogen gun after cleaning. Dry.

Still further, in the low-temperature preparation method of the transparent conductive oxide film, the visible light transmittance of the obtained titanium oxide-based transparent conductive film is better than 90%, and the room temperature resistivity is less than 8×10-4 Ohm.cm.

The outstanding substantive features and remarkable progress of the technical solution of the present invention are mainly reflected in:

The invention adopts a seed crystal layer with a c-axis length of 0.5 to several unit cells to induce low-temperature growth, and obtains a titanium oxide-based film material with good transparent conductivity. The seed layer is titanium oxide single crystal of anatase crystal type, which is prepared by pulsed laser deposition method, and the thickness is controlled at 0.5 to several unit cell c-axis lengths; The laser method or magnetron sputtering method continues to grow and prepare titanium oxide-based thin film materials. This preparation process is less dependent on the preparation process and growth conditions. The preparation process is flexible and selective. The obtained titanium oxide-based transparent conductive film is visible light The transmittance is better than 90%, and the resistivity at room temperature is less than 8×10 ^-4 ohm.cm. The invention realizes the low-temperature growth and preparation of the transparent conductive oxide thin film for replacing ITO, and greatly expands the application range of such materials.

Description of drawings

Below in conjunction with accompanying drawing, technical solution of the present invention will be further described:

Figure 1: In-situ high-energy reflection electron diffraction real-time monitoring pattern during the growth of the seed layer;

Figure 2a: Titanium oxide-based thin film material prepared by continuing to grow on a single crystal oxide substrate material (LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 with a seed layer by pulsed laser method;

Fig. 2b: Titanium oxide-based thin film material prepared by continuing to grow on a single crystal oxide substrate material (LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 with a seed layer by magnetron sputtering.

Detailed ways

The invention provides a low-temperature preparation method of a transparent conductive oxide thin film for replacing ITO. A seed layer with a length of 0.5 to several c-axis of a unit cell is used to induce low-temperature growth to obtain a titanium oxide-based thin film material with good transparent conductivity.

The technical solution of the present invention will be further described below through specific examples.

Example 1:

First, the single crystal oxide substrate material (SrTiO ₃ ) was cleaned with acetone, then with ethanol, and finally with deionized water for ultrasonic cleaning. After cleaning, it was dried with a nitrogen gun and immediately placed in a vacuum chamber. The bottom absolute pressure is lower than 1×10 ^-5 Torr; the sintered ceramic TiO ₂ sheet is used as the target material, and the O ₂ with a purity better than 99.99% is used as the deposition atmosphere, and the pulse laser deposition method is used to prepare the seed layer film, and the control: the substrate The temperature is 400-450K, the absolute pressure of the background is lower than 5×10 ^-4 Torr, the laser energy density is 5J/cm ² , the frequency is 5Hz, the partial pressure of O ₂ deposited is 1×10 ^-3 Torr, the target and the substrate The vertical spacing is 40mm; after the deposition process is completed, cool down to room temperature with the furnace, cut off the oxygen, and take it out. The thickness of the seed layer film is controlled at 0.5 to several unit cell c-axis lengths;

On the substrate material with the seed layer, the pulsed laser method is used to continue to grow the titanium oxide-based transparent conductive film. The substrate temperature is controlled at a low temperature below 473K, and the target material composition is Nb ₂ O ₅ —TiO ₂ , niobium The atomic percentage of TiO ₂ is 2%; the deposition temperature is from room temperature to 473K, the pulse frequency is 5Hz, the laser energy density is 8J/cm ² , and the deposition O ₂ partial pressure is 1×10 ^-3 Torr, the target and the substrate The vertical spacing is 60 mm, and the film deposition thickness is controlled below 300 nanometers; after the pulse laser deposition is completed, all are cooled to room temperature with the furnace, the gas source is cut off, and the titanium oxide-based transparent conductive film is obtained. The visible light transmittance of the thin film is better than 95%, and the resistivity at room temperature is 6.45×10-4Ohm.cm.

Example 2:

The single crystal oxide substrate material (LaAlO ₃ ) was first cleaned with acetone, then ethanol, and finally ultrasonically cleaned with deionized water. After cleaning, it was blown dry with a nitrogen gun, and immediately placed in a vacuum chamber. The bottom absolute pressure is lower than 1×10 ^-5 Torr; the sintered ceramic TiO ₂ sheet is used as the target material, and the O ₂ with a purity better than 99.99% is used as the deposition atmosphere, and the pulse laser deposition method is used to prepare the seed layer film, and the control: the substrate The temperature is 450-500K, the absolute pressure of the background is lower than 5×10 ^-4 Torr, the laser energy density is 6J/cm ² , the frequency is 8Hz, the partial pressure of deposited O ₂ is 1×10 ^-2 Torr, the target and the substrate The vertical spacing is 50 mm; after the deposition process is completed, cool down to room temperature with the furnace, cut off the oxygen, and take it out. The thickness of the seed layer film is controlled at 0.5 to several unit cell c-axis lengths;

On the substrate material with the seed layer, the pulsed laser method is used to continue to grow and prepare the titanium oxide-based transparent conductive film. The substrate temperature is controlled at a low temperature below 473K, and the target material composition is Nb ₂ O ₅ —TiO ₂ . The atomic percentage of niobium in TiO ₂ is 4%; the deposition temperature is from room temperature to 473K, the pulse frequency is 1Hz, the laser energy density is 2J/cm ² , the deposition O ₂ partial pressure is 1×10 ^-2 Torr, the target and substrate The bottom vertical distance is 40 mm, and the film deposition thickness is controlled below 300 nanometers; after the pulse laser deposition is completed, it is cooled to room temperature with the furnace, the gas source is cut off, and the titanium oxide-based transparent conductive film is obtained. The visible light transmittance of the thin film is better than 93%, and the resistivity at room temperature is 7.15×10-4Ohm.cm.

Example 3:

The single crystal oxide substrate material (SrLaAlO ₄ ) was first cleaned with acetone, then ethanol, and finally ultrasonically cleaned with deionized water. After cleaning, it was dried with a nitrogen gun and immediately placed in a vacuum chamber. The bottom absolute pressure is lower than 1×10 ^-5 Torr; the sintered ceramic TiO ₂ sheet is used as the target material, and the O ₂ with a purity better than 99.99% is used as the deposition atmosphere, and the pulse laser deposition method is used to prepare the seed layer film, and the control: the substrate The temperature is 420-480K, the absolute pressure of the background is lower than 5×10 ^-4 Torr, the laser energy density is 7J/cm ² , the frequency is 3Hz, the partial pressure of O ₂ deposited is 1×10 ^-4 Torr, the target and the substrate The vertical spacing is 45 mm; after the deposition process is completed, cool down to room temperature with the furnace, cut off the oxygen, and take it out. The thickness of the seed layer film is controlled at 0.5 to several unit cell c-axis lengths;

On the substrate material with the seed layer, the magnetron sputtering method is used to continue to grow the titanium oxide-based transparent conductive film. The substrate temperature is controlled at a low temperature below 473K, and the target material composition is Nb ₂ O ₅ —TiO ₂ , niobium in TiO ₂ atomic percentage accounts for 6%; Ar gas and O ₂ gas are introduced into the reaction chamber by the conduit after being fully mixed, and the flow ratio of Ar gas and O ₂ gas is controlled at 4 (Ar gas is 24sccm, O ₂ is 6 sccm), after the substrate temperature is heated to the temperature range of 400-473K, the sputtering gas is introduced into the reaction chamber to the deposition chamber, and after the overall pressure reaches 1-10Pa, the sputtering film formation starts, the sputtering power is controlled at 100W, and the target The vertical distance between the material and the substrate is 50 mm, and the thickness of the film is controlled below 300 nanometers; after the magnetron sputtering method is deposited, it is cooled to room temperature with the furnace, the gas source is cut off, and the titanium oxide-based transparent conductive film is obtained. The visible light transmittance of the thin film is better than 90%, and the resistivity at room temperature is 7.46×10-4Ohm.cm.

Example 4:

First, the single crystal oxide substrate material ((LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 ) was cleaned with acetone, then with ethanol, and finally with deionized water for ultrasonic cleaning. After cleaning, dry it with a nitrogen gun and put it away immediately. Into a vacuum chamber, the absolute pressure of the back of the reaction chamber before deposition is lower than 1×10 ^-5 Torr; sintered ceramic TiO ₂ sheets are used as the target material, and O ₂ with a purity better than 99.99% is used as the deposition atmosphere, and the pulsed laser deposition method is used Prepare the seed layer thin film, control: the substrate temperature is 500-573K, the absolute pressure of the background is lower than 5×10 ^-4 Torr, the laser energy density is 8J/cm ² , the frequency is 3Hz, and the deposition O ₂ partial pressure is 1× 10 ^-5 Torr, the vertical distance between the target and the substrate is 50mm; after the deposition process is completed, cool down to room temperature with the furnace, cut off the oxygen, and take it out. The thickness of the seed layer film is controlled at 0.5 to several unit cell c-axis lengths;

On the substrate material with the seed layer, the magnetron sputtering method is used to continue to grow the titanium oxide-based transparent conductive film. The substrate temperature is controlled at a low temperature below 473K, and the target material composition is Nb ₂ O ₅ —TiO ₂ , niobium in TiO ₂ atomic percentage accounts for 8%; Ar gas and O ₂ gas are introduced into the reaction chamber by the conduit after being fully mixed, and the flow ratio of Ar gas and O ₂ gas is controlled at 8 (Ar gas is 24sccm, O ₂ is 3sccm), after the substrate temperature is heated to the temperature range of 400-473K, the sputtering gas is introduced into the reaction chamber to the deposition chamber, and after the overall pressure reaches 1-10Pa, the sputtering film formation starts, the sputtering power is controlled at 40W, the target The vertical distance between the material and the substrate is 100 mm, and the thickness of the film is controlled below 300 nanometers; after the magnetron sputtering method is deposited, it is cooled to room temperature with the furnace, the gas source is cut off, and the titanium oxide-based transparent conductive film is obtained. The visible light transmittance of the thin film is better than 90%, and the resistivity at room temperature is 7.69×10-4Ohm.cm.

Figure 1 shows the in-situ high-energy _reflection electron diffraction real _- time monitoring _{pattern of} the growth process of the seed layer _; Titanium oxide-based thin film material prepared by pulsed laser method; Figure 2b schematically shows the use of magnetron sputtering on a single crystal oxide substrate material (LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 with a seed layer Titanium oxide-based thin film material prepared by continuous growth by radiation method.

In summary, the present invention uses a seed layer with a length of 0.5 to several unit cell c-axis to induce low-temperature growth, and obtain a titanium oxide-based film material with good transparent conductivity. The seed layer is a titanium oxide single crystal of anatase crystal type, which is first prepared by pulsed laser deposition, and the thickness is controlled at 0.5 to several c-axis lengths of the unit cell; then, on the substrate material with the seed layer, use The pulsed laser method or magnetron sputtering method continues to grow and prepare titanium oxide-based thin film materials. This preparation process is less dependent on the preparation process and growth conditions. The preparation process is flexible and selective. The obtained titanium oxide-based transparent conductive film The visible light transmittance is better than 90%, and the resistivity at room temperature is less than 8×10-4ohm.cm. The invention realizes the low-temperature growth and preparation of the transparent conductive oxide thin film for replacing ITO, and greatly expands the application range of such materials.

It should be understood that: the above description is not intended to limit the present invention, and additions, transformations, replacements, etc. within the scope of the concept of the present invention should also belong to the protection scope of the present invention.

Claims (4)

1. A low-temperature preparation method for a transparent conductive oxide film, characterized in that it specifically includes the following steps—— ①Growth of the seed layer: first clean the single crystal oxide substrate material, blow it dry, and immediately put it into a vacuum chamber. The absolute pressure of the back of the reaction chamber before deposition is lower than 1×10 ^-5 Torr; TiO ₂ sheet is used as the target material, and O ₂ with a purity higher than 99.99% is used as the deposition atmosphere. The seed layer film is prepared by pulsed laser deposition. During the preparation process, the control: the substrate temperature is 400-573K, and the absolute pressure of the background is lower than 5×10 ^-4 Torr, laser energy density 5~8J/cm ² , frequency 3~8Hz, deposition O ₂ partial pressure 1×10 ^-2 ～1×10 ^-5 Torr, vertical distance between target and substrate 40mm to 50mm; after the deposition process, cool to room temperature with the furnace, cut off the oxygen, take it out, and the thickness of the seed layer film is 0.5 to several unit cell c-axis lengths; ② Subsequent growth: Continue to grow and prepare titanium oxide-based transparent conductive film on the substrate material with seed layer prepared above by pulse laser method or magnetron sputtering method, and the substrate temperature is controlled in the low temperature section below 473K , the target composition is Nb ₂ O ₅ —TiO ₂ , and the atomic percentage of niobium in TiO ₂ is 2-8%; among them, Using the pulsed laser method: the deposition temperature is from room temperature to 473K, the pulse frequency is 1-5Hz, the laser energy density is 2-8J/cm ² , the deposition O ₂ partial pressure is 1×10 ^-2 to 1×10 ^-5 Torr, and the target The vertical distance from the substrate is 40mm to 60mm, and the film deposition thickness is less than 300nm; Using magnetron sputtering method: Ar gas and O ₂ gas are fully mixed and then introduced into the reaction chamber through the catheter, the flow ratio of Ar gas and O ₂ gas is controlled between 4 and 8, and the substrate temperature is heated to 400 ~ 473K After the temperature interval, the sputtering gas is introduced into the reaction chamber to the deposition chamber. After the overall pressure reaches 1-10Pa, the sputtering film is started. The sputtering power is controlled at 40-100W, and the vertical distance between the target and the substrate is 50-100mm. The thickness of the film is controlled below 300 nanometers; After the deposition by the pulse laser method or the magnetron sputtering method is completed, after cooling to room temperature with the furnace, the gas source is cut off and taken out to obtain a titanium oxide-based transparent conductive film. 2. The low-temperature preparation method of transparent conductive oxide film according to claim 1, characterized in that: the single crystal oxide substrate material is SrTiO ₃ , or LaAlO ₃ , or SrLaAlO ₄ , or (LaAlO ₃ ) _0.3 (Sr ₂ AlTaO ₆ ) _0.7 . 3. The low-temperature preparation method of transparent conductive oxide film according to claim 1 or 2, characterized in that: the single crystal oxide substrate material is first cleaned with acetone, then with ethanol, and finally with deionized water Ultrasonic cleaning, blow dry with nitrogen gun after cleaning. 4. The low-temperature preparation method of transparent conductive oxide film according to claim 1, characterized in that: the visible light transmittance of the obtained titanium oxide-based transparent conductive film is better than 90%, and the room temperature resistivity is less than 8×10-4Ohm .cm.

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