KR101432682B1 - Manufacturing method for preparing ZnO thin films - Google Patents

Abstract

Disclosure of the Invention The present invention provides a zinc oxide thin film doped with boron or tantalum, which is excellent in electric and optical characteristics, by using the electrostatic spraying method, As well as a zinc oxide thin film having low resistance and high transmittance.

Description

[0001] The present invention relates to a method for preparing a zinc oxide thin film,

The present invention relates to a method of manufacturing a zinc oxide thin film, and more particularly, to a method of manufacturing a metal-doped zinc oxide thin film having high transmittance and low resistance.

Zinc oxide (ZnO) is an n-type semiconductor material with a band gap of about 3.4 eV and is used in various fields such as piezoelectric materials, solar cells, flat panel displays, gas sensors, transparent conductive oxides (TCO) (B) XD Wang, CJ Summers, ZL Wang, Nano Lett., 4 (2004), pp. (D) KC Park, DY Ma, KH Kim, K. Kim, and Y. Li, H. Zhang, TJ Marks, RPH Chang, Y. Yoshino, T. Makino, Y. Katayama, T. Hata, Vacuum 59 (2000) 538; (f) JB Lee, HJ Kim, SG Kim, CS Hwang, S.-H. Hong, YH Shin, NH Lee, Thin Solid Films 435 (2003) 179). This is because zinc oxide has excellent optical and electrical properties in connection with the band gap energy, low toxicity and abundance in nature. However, zinc oxide thin films, which are not doped with metal atoms due to the desorption / adsorption of oxygen, cause a change in the surface conductivity, resulting in formation of an unstable zinc oxide thin film. In this regard, it is possible to alleviate the problem by doping a specific atom, and the specific atom also plays a role of improving resistance and optical characteristics. A research has been conducted to prepare a zinc oxide thin film by doping indium (In), gallium (Ga), or aluminum (Al) as the specific atom (R. Wang, AW Sleight, D. Cleary, Chem. Mater. 8 (1996) 433; (b) A. Ambrosini, S. Malo, K. Poeppelmeier, Chem.

On the other hand, from the viewpoint of the transparent conductive film, zinc oxide has a possibility to replace indium tin oxide (ITO). Since ITO is expensive and rare in spite of its usefulness, research continues to replace it with cheap and harmless materials such as zinc oxide. A technique for manufacturing zinc oxide as a thin film for replacing ITO has been demanded and it has been reported that it can be generally manufactured by a chemical thin film growth method, a laser deposition method, a spray pyrolysis method, a sol-gel process, or the like. As a representative method, a sol-gel process is used. Since a precursor of a thin film to be produced is prepared as a colloid solution, the process is advantageous in that it is simple. However, in the process of removing the solvent by heat treatment of the thin film, There is a downside. Accordingly, there is a need for an improved method of manufacturing zinc oxide thin films.

In order to solve the above problems and / or limitations, it is an object of the present invention to provide a method of manufacturing a zinc oxide thin film which is not only simple compared to a conventional zinc oxide thin film manufacturing process, but also exhibits high transmittance and low resistance .

Electrostatic spraying has the advantage that the droplet size can be adjusted from micrometer to nanometer, and means for activating thin films such as light, heat, and plasma are not necessary. The electrostatic atomization method is a method of generating droplets by applying a high voltage between the nozzle and the substrate. The droplets have the same electrical polarity, so that the generated particles are electrostatically repelled, and thus the formation of a nonuniform cluster is effectively prevented . It is possible to fabricate a dense thin film by forming a uniform droplet with a relatively uniform particle size distribution, and it has many advantages such that the composition of the thin film, the growth rate of the thin film, and the substrate temperature during the growth of the thin film can be easily controlled.

Accordingly, the inventors of the present invention confirmed that a zinc oxide thin film doped with a metal atom can be manufactured using the electrostatic spraying method and the heat treatment method, and that the thin film having improved electrical and optical characteristics can be manufactured.

According to one aspect of the present invention, a precursor solution is prepared by adding zinc salt as a solvent and boron or tantalum as a dopant (Step 1), electrostatically spraying the prepared precursor solution onto a substrate to deposit zinc oxide on the substrate (Step 2); and heat treating the substrate on which the zinc oxide is deposited (step 3).

The step 1 is a step of adding a boron or tantalum as a dopant to a zinc salt to prepare a precursor solution. The solution used in electrostatic atomization includes a zinc source and a boron source or a tantalum source as a dopant, To prepare a zinc oxide thin film.

The zinc salt that can be used may be zinc acetate or zinc acetate hydrate. The solvent for the preparation of the precursor solution is not limited as long as it is a solvent capable of dissolving the zinc salt, but an alcohol can be preferably used. For example, ethanol, 2-methoxypropanol, or a mixture thereof may be used.

Further, a boron source or a tantalum source is additionally added as a dopant to the precursor solution, so that the zinc oxide thin film produced according to the present invention can be doped with boron or tantalum. As the boron source, boric acid may be used, and as the tantalum source, tantalum chloride may be used. The amount of boric acid or tantalum chloride to be added can be controlled depending on the doping amount of boron or tantalum in the zinc oxide thin film produced according to the present invention. For example, when boron or tantalum is doped with 0.1% It may be controlled by adding boron or tantalum corresponding to 0.1% molar amount to the precursor solution. The addition amount of boron or tantalum may be added in a molar amount of 0.1 to 0.9% of the zinc salt. More preferably, it may be added in a molar amount of 0.3 to 0.7%.

In the step 2, the precursor solution prepared in the step 1 is electrostatically sprayed on a substrate to deposit metal-doped zinc oxide on the substrate.

The term " electrospraying " used in the present invention means a method of generating a droplet by applying a high voltage between a nozzle and a substrate. When the high voltage is applied while passing the conductive solution through the nozzle, the ions in the nozzle and the liquid move to the liquid surface by the repulsive force and the attraction force, and the repulsive force of the electric force and the positive ions acting on the liquid surface becomes larger than the surface tension of the liquid, The droplet is sprayed. When the liquid is atomized, the specific surface area of the liquid increases, and heat and mass transfer between the dispersed liquid and the surrounding gas is facilitated. In the present invention, the zinc source contained in the precursor solution reacts with oxygen to form zinc oxide, Zinc oxide is laminated on the substrate to produce a zinc oxide thin film. The electrostatic spraying is characterized in that the process is simple since the same conditions as the vacuum condition are not necessary and can be performed in a normal atmospheric condition.

In the present invention, a voltage of 0 kV to 8 kV is preferably applied in the electrostatic spraying process, and more preferably, a voltage of 4 kV to 8 kV may be applied to perform electrostatic spraying. In addition, the distance between the nozzle and the substrate is preferably maintained at 1 cm to 5 cm, more preferably 3 cm to 4 cm.

The temperature of the substrate during electrostatic spraying is preferably maintained at 200 to 300 캜. The substrate may be a glass substrate.

The step 3) is a step of heat-treating the substrate on which the zinc oxide doped with the metal prepared in the step 2) is deposited to improve the crystallinity, transmittance and resistance of the zinc oxide thin film. The characteristics of the zinc oxide can be further improved by improving the crystallinity, grain size, etc. of the zinc oxide thin film produced in the step 2) by the heat treatment in the step 3).

The temperature of the heat treatment may be 300 ° C to 600 ° C. Also, the heat treatment time may be from 1 hour to 3 hours.

The zinc oxide thin film manufacturing method according to the present invention is characterized in that the process is simple compared to other zinc oxide thin film manufacturing methods. Particularly, it can be used under ordinary atmospheric conditions, and boron or tantalum can be easily added as a dopant.

The method of manufacturing a zinc oxide thin film doped with a metal atom according to the present invention uses an electrostatic spraying method in manufacturing a zinc oxide (ZnO) thin film having high transmittance and low resistance, thereby improving the problem of zinc oxide thin film, It is possible to provide a method of producing a thin film having a fine particle structure as well as a simple process as compared with a process of producing a zinc thin film.

Further, the manufacturing method according to the present invention can simply doping metal atoms, more specifically, boron (B) or tantalum (Ta), into the zinc oxide thin film in a simple manner. Since the zinc oxide thin film produced according to the manufacturing method of the present invention is similar to ITO in transmittance and resistance, it is possible to provide a method of replacing the conventional ITO with the zinc oxide thin film of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a configuration of an apparatus for manufacturing a zinc oxide thin film according to an embodiment of the present invention; FIG.
FIGS. 2A to 2D are XRD spectra of a zinc oxide thin film according to an embodiment of the present invention. FIG. 2A shows an XRD spectrum of a zinc oxide thin film doped with 2 at.% Of boron before and after a heat treatment, FIG. 2C shows the XRD spectrum of the zinc oxide thin film according to the boron doping concentration, and FIG. 2D shows the XRD spectrum of the zinc oxide thin film according to the tantalum doping concentration.
3 is a scanning electron microscope (SEM) image of a zinc oxide thin film doped with 2 at% of boron or tantalum according to an embodiment of the present invention.
4 is a scanning electron micrograph of a zinc oxide thin film according to the doping concentration of boron or tantalum in accordance with an embodiment of the present invention.
FIGS. 5A and 5B show resistance of a zinc oxide thin film according to a heat treatment temperature and a dopant concentration of a precursor solution according to an embodiment of the present invention. FIGS. 5A and 5B are graphs showing the dopant concentration of boron and tantalum, FIG. 5C is a graph showing the resistance value according to the dopant concentration. FIG.
6A to 6D show a carrier concentration (n) and a hole mobility (μ) of a boron or tantalum-doped zinc oxide thin film according to an embodiment of the present invention, 6C and 6D are graphs showing the carrier concentration and hole mobility according to the heat treatment temperature in the case where the concentration of tantalum is 2 at% FIG. 5 is a graph showing the carrier concentration and hole mobility of the zinc oxide thin film in the case of performing heat treatment in FIG.
7A to 7D show the transmittance of boron or tantalum-doped zinc oxide thin film according to an embodiment of the present invention. Figs. 7A and 7B are graphs showing transmittance of boron or tantalum-doped zinc oxide thin films when the concentration of boron and tantalum is 2 atomic% FIG. 7C and FIG. 7D are graphs showing the transmittance of the zinc oxide thin film when heat treatment is performed at 400 ° C. according to the concentrations of boron and tantalum, respectively. FIG. 7B is a graph showing the transmittance of zinc oxide .
8A and 8B show the optical bandgap of boron or tantalum doped zinc oxide thin film according to an embodiment of the present invention. FIGS. 8A and 8B are graphs showing the optical bandgap of boron or tantalum doped with a concentration of boron and tantalum of 2 atomic% FIG. 8C and FIG. 8D are graphs showing the heat banding effect of the direct optical bandgap in the case of the zinc oxide thin film, respectively, and FIGS. 8C and 8D are graphs showing the optical bandgap of the zinc oxide thin film in the case of performing the heat treatment at 400.degree. C. depending on the concentrations of boron and tantalum, respectively Graph.

Hereinafter, preferred embodiments and experimental examples are provided to facilitate understanding of the present invention. However, the following examples and experimental examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples and experimental examples.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a configuration of an apparatus for manufacturing a zinc oxide thin film according to an embodiment of the present invention; FIG.

A zinc oxide thin film doped with boron or tantalum in accordance with an embodiment of the present invention was manufactured by electrostatic spraying on a heated substrate 5 as shown in FIG.

First, a zinc acetate dihydrate (junsei chemical) was added to a solvent (ethanol: water = 30: 70 (v / v)) to prepare a precursor solution. At this time, the concentration of the precursor solution was adjusted to 0.05 M and boric acid (aldrich) or tantalum (V) chloride (aldrich) was added to the boron or tantalum in an amount of 1 , 0.1%, 0.3%, 0.5%, 0.7% and 0.9%, respectively, in terms of%, 2%, 3% and 4%. The precursor solution was stirred at room temperature for 1 hour using a magnetic stirrer, and a few drops of hydrochloric acid was added thereto to prepare a transparent precursor solution.

Referring to FIG. 1, an apparatus for manufacturing a zinc oxide thin film according to an embodiment of the present invention may include a nozzle 1, a pump 2, a power source 3, and a plate 4.

The nozzle 1 can be connected using a pump 2 and a tube 11. The pump 2 can use a syringe pump KD200, KD Scientific Inc., U.S.A. The tube 11 may be a silicon tube. The precursor solution was supplied to the nozzle 1 using the pump 2, and the supply rate of the precursor solution was adjusted to 0.003 mL / min.

The substrate 5 is placed on a plate 4 where the nozzle 1 and the plate 4 are electrically connected to a power supply 3. The power source 3 can apply, for example, a direct current high voltage of 5.5-5.6 kV to the nozzle 1 and the plate 4. [ As a result, a precursor solution sprayed through the nozzle 1 can be converted into aerosol particles by applying a voltage to the portion of the nozzle 1 where the droplet appears and the substrate 5. The shape of the resulting droplet may be such that a cone-jet mode appears. The substrate 5 and the end of the nozzle 1 were kept at about 4 cm.

The substrate 5 was glass, and the glass was washed with isopropyl alcohol (IPA; aldrich) and water before use.

The precursor solution was electrostatically sprayed onto the substrate 5 for 1 hour at which time the plate 4 was heated to maintain the temperature of the substrate 5 at 250 ° C. The shape of the droplet sprayed using a CCD camera (Model No. 7309P-1) using a high-resolution lens and a light source was observed.

After completion of the electrostatic spraying, heat treatment was performed at different temperatures in the range of 300 캜 to 600 캜.

The thin film was analyzed by X-ray diffractometer (XRD; D8 DISCOVER) using Cu k? Radiation (? = 1.5405 A). The surface morphology of the thin film was observed with a field emission SEM (Nova 320 and Magellan 400), and at the same time, an X-ray energy dispersive spectrometer (EDXS) Respectively. The optical properties were analyzed by UV-visible spectrometer (UV-3101PC). Electrical resistance was measured by four-point probe equipment (CMT-SR1000N, AIT, Korea). The carrier concentration and hall mobility were measured with a hall effect measurement (HMS-3000).

The results are as follows.

The element composition ratio (B / Zn and Ta / Zn ratio) of the boron or tantalum-doped zinc oxide thin film produced by the electrostatic spraying method according to an embodiment of the present invention was analyzed by EDS. The composition ratios in the precursor solution and the zinc oxide thin film are shown in Tables 1 and 2 below.

turn The B / Zn ratio (atomic%) of the precursor solution B / Zn ratio (atomic%) of the thin film One 0 0 2 One 0.9 3 2 1.9 4 3 2.8 5 4 3.9

turn Ta / Zn ratio (atomic%) of the precursor solution Ta / Zn ratio (atomic%) of the thin film 6 0 0 7 One 0.9 8 2 2.0 9 3 2.9 10 4 4.0

From Table 1 and Table 2, it was confirmed that the metal atoms contained in the precursor solution were effectively doped. In addition, it was confirmed that the heat treatment of the thin film had no great influence on the composition of the thin film.

FIGS. 2A to 2D are XRD spectra of zinc oxide thin films obtained by the electrostatic spraying method according to an embodiment of the present invention.

More specifically, FIG. 2A shows an XRD spectrum of a zinc oxide thin film doped with 2 atomic% boron after annealing at 300 ° C., annealing at 400 ° C., annealing at 500 ° C., annealing at 600 ° C., annealing after annealing at 300 ° C. FIG. 2B shows XRD spectra of the zinc oxide thin film doped with 2 at.% Of tantalum after heat treatment at 300 ° C., 400 ° C. heat treatment at 500 ° C., and heat treatment at 600 ° C.

As can be seen from FIGS. 2A and 2B, it was confirmed that all of the thin films exhibited a polycrystalline structure and a single-phase zinc oxide wurtzite structure. The thin films were preferentially oriented along the (002) crystal phase, (002) peak intensity was increased. This means that the crystallinity of the thin film is increased by heat treatment.

FIG. 2C shows the XRD spectra of the zinc oxide thin films having boron doping concentrations of 0%, 1%, 2%, 3%, and 4%, respectively. FIG. 2D shows XRD spectra of zinc oxide thin films in which the tantalum doping concentrations are 0%, 1%, 2%, 3%, and 4%, respectively. 2C and 2D show XRD spectra of the zinc oxide thin films produced by the electrostatic spraying method according to the dopant concentration in the case of heat treatment in air for 1 hour.

As can be seen in FIGS. 2c and 2d, the (002) peak intensity decreases with increasing dopant concentration. This causes crystal defects and crystal distortions by substituting atoms of different sizes in the zinc oxide crystal, and the XRD spectrum shows that in the c-axis direction perpendicular to the surface by introducing boron or tantalum atoms into the zinc oxide crystal And inhibited crystal growth.

The surface morphology of the zinc oxide thin film doped with a metal atom was analyzed by a scanning electron microscope, and the results are shown in FIG. 3 and FIG.

3 (a) to 3 (c) are graphs showing the results of (a) when the zinc oxide thin film doped with 2 atomic% boron is annealed before heating (without heat treatment) (D) to (f) show the results of scanning electron micrographs of each thin film when annealing is performed at 600 ° C for 1 hour, and FIGS. 3 (d) (F) heat treatment at 600 ° C for 1 hour, (c) heat treatment at 400 ° C for 1 hour, and (d) heat treatment before the heat treatment , And a scanning electron microscope photograph of each thin film is shown.

3 (a) to (c) and (d) to (f) show that the crystal size increases with increasing heat treatment temperature, . ≪ / RTI >

4 (a) to 4 (c) are SEM images of a zinc oxide thin film according to a dopant concentration, wherein the concentrations of boron are (a) 0 atomic%, (b) 4 (d) to 4 (f) show the surface structure of the zinc oxide thin film in the case where the concentration of tantalum is 4 atomic%, the concentration of tantalum is 0 atomic%, (e) And the surface structure of the zinc oxide thin film in the case of 4 atom%. All were subjected to heat treatment at 400 ° C for 1 hour in air.

Referring to FIGS. 4 (a) to (c) and (d) to (f), it can be seen that as the amount of boron or tantalum as the dopant increases, the crystal size decreases.

3 and 4 indicate that boron and tantalum form a new nucleation center in the vacancy of the zinc oxide crystal.

Electrical properties such as thin film resistance, hall mobility, and carrier concentration were analyzed in relation to the heat treatment temperature and the dopant concentration of the precursor solution.

5A to 5C show the resistivity of the zinc oxide thin film according to the heat treatment temperature and the dopant concentration of the precursor solution.

FIG. 5A is a graph showing a resistance value of a zinc oxide thin film according to a heat treatment temperature and a boron doping concentration, and FIG. 5B is a graph showing a resistance value of a zinc oxide thin film according to a heat treatment temperature and a tantalum doping concentration. The heat treatment is carried out in each case for 1 hour each.

Referring to FIGS. 5A and 5B, the zinc oxide thin film doped with 2 atomic% of boron exhibited the lowest resistance value at 2.16 x 10 ^-4 ? Cm when annealed at 400 ° C, and the tantalum doped with 2 atomic% The zinc oxide thin film showed the lowest resistance value at 1.195 x 10 ^-4 Ωcm when heat treated at 400 ° C. This means that the number of crystal boundaries and crystal lattice defects in the thin film decreases as the heat treatment temperature is increased to 400 DEG C and the resistance value tends to increase when the heat treatment temperature exceeds 400 DEG C, This means that the number of crystal boundaries and crystal lattice defects is increased.

On the other hand, referring to FIG. 5C, when the amount of the dopant increases to 2 atomic%, the resistance value decreases. This is because the free carrier concentration increases. When the amount of the dopant exceeds 2 atomic% Of the boron or tantalum atom in the amorphous silicon layer results in a decrease in the free carrier concentration. The minimum value of the resistivity was found to be similar to the resistance value of the metal-doped zinc oxide thin film reported in the literature, and the electrostatic atomizing method according to the present invention has an advantage that it can be performed by a simplified process under normal temperature and normal pressure conditions (T. Minami, Semicond. Sci. Techonol 20 (2005) S35).

6A to 6D relate to a carrier concentration (n) and a hole mobility (mu) of a boron or tantalum-doped zinc oxide thin film produced by the present invention.

More specifically, FIGS. 6A and 6B show the carrier concentration and the hole mobility according to the heat treatment temperature in the case where the concentration of boron and tantalum is 2 atomic%, respectively. The carrier concentration and hole mobility are directly proportional to the heat treatment temperature, which can be attributed to an increase in the crystal size and crystallinity of the thin film.

6C and 6D show the carrier concentration and the hole mobility of the zinc oxide thin film depending on the concentrations of boron and tantalum, which are dopants, when the heat treatment is performed at 400 DEG C for 1 hour in the air, respectively. The hole mobility decreases as the amount of boron or tantalum increases, which can be attributed to the decrease in crystal size of the thin film. Carrier concentration, on the other hand, increases with the amount of boron or tantalum, which can be attributed to the substitution of boron ions (B ³⁺ ) or tantalum ions (Ta ⁵⁺ ) for zinc ions (Zn ²⁺ ) . When the concentration of boron or tantalum as a dopant exceeds 2 atomic%, the carrier concentration decreases, which may be attributed to a failure in the crystal structure.

7A and 7B show the transmittance of the zinc oxide thin film according to the heat treatment temperature in the case where the concentration of the dopant boron or tantalum is 2 atomic%. The boron-doped zinc oxide thin films annealed at 400 ° C for 1 hour in air in the visible region showed a maximum transmittance of 96% and the zinc oxide thin films doped with tantalum showed a maximum transmittance of 92% . Thin films without annealing show lower transmittance than those annealed, which is related to the crystallinity of the thin film and is related to the optical scattering due to crystal boundaries and surface morphology of the thin film.

FIGS. 7C and 7D show the transmittance of the zinc oxide thin film subjected to the heat treatment at 400 ° C. according to the concentration of boron or tantalum in the visible region and the near infrared region (350 nm to 800 nm), respectively. The maximum transmittance appears when the concentration of the dopant boron or tantalum is 2 atomic%. When the concentration of the dopant exceeds 2 atomic%, the transmittance decreases because the optical scattering of the photon increases due to the crystal lattice defect generated by the doping (B. Joseph, PK Manoj, VK Vaidyan , Ceram. Int. 32 (2006) 487).

The optical bandgap of the zinc oxide thin film produced by the electrostatic atomization method according to the embodiment of the present invention is calculated from the degree of absorption, and the absorption is related to the excitation from the balance band to the conduction band. The relationship between the optical band gap Eg and the absorption coefficient is obtained from the following equation (1).

(1)

(One)

8A and 8B show the heat treatment effect of the direct optical bandgap when the concentration of the dopant boron or tantalum is 2 atomic%, respectively. The optical band gap was obtained by extrapolating the linear portion of the graph. The optical bandgap of the zinc oxide thin film subjected to the heat treatment shows a higher optical band gap than that of the zinc oxide thin film, which is related to the burstein-moss effect. It was confirmed that the optical bandgap increased from 3.19 eV to 3.37 eV as the annealing of zinc oxide doped with 2 atomic% of boron was performed at 600 ° C. Similarly, in the case of tantalum, the optical bandgap increased from 3.19 eV to 3.24 eV.

FIGS. 8C and 8D show the optical bandgap of the zinc oxide thin film subjected to the heat treatment at 400 ° C. according to the dopant boron or tantalum concentration, respectively. As the concentration of dopant increases, the absorption edge (dege) increases to a high energy region. As the concentration of boron or tantalum as a dopant increases to 4 atomic%, boron becomes 3.19 eV to 3.37 eV and tantalum The optical bandgap increases from 3.18 eV to 3.26 eV. This is because the Fermi level is increased in the conduction band and the carrier concentration is increased.

Claims (12)

1) adding a zinc salt to a solvent and boron or tantalum as a dopant to prepare a precursor solution;
2) depositing the zinc oxide thin film on the substrate by electrostatically spraying the prepared precursor solution on the substrate; And
3) heat treating the substrate on which the zinc oxide thin film is deposited
Wherein the zinc oxide thin film has a thickness of 100 nm or less.
The method of claim 1, wherein the zinc salt is zinc acetate or zinc acetate hydrate.
The method for producing a zinc oxide thin film according to claim 1, wherein the solvent is an alcohol.
Claim 4 has been abandoned due to the setting registration fee. 4. The method for producing a zinc oxide thin film according to claim 3, wherein the alcohol is ethanol, 2-methoxypropanol, or a mixture thereof.
The method of producing a zinc oxide thin film according to claim 1, wherein boron is added to the solvent as a dopant, wherein boric acid is added to the solvent.
The method of manufacturing a zinc oxide thin film according to claim 1, wherein adding tantalum as a dopant to the solvent is to add tantalum chloride to the solvent.
The zinc oxide thin film of claim 1, wherein the boron or tantalum is added in an amount of 0.1 to 0.9% of the zinc salt.
The method of any one of claims 1 to 7, wherein the electrostatic spraying of step 2) is performed by applying a voltage of 0 kV to 8 kV.
The method according to claim 8, wherein the electrostatic spraying in step 2) is performed by applying a voltage of 4 kV to 8 kV.
Claim 10 has been abandoned due to the setting registration fee. The method for producing a zinc oxide thin film according to any one of claims 1 to 7, wherein the temperature of the substrate in step 2) is 200 to 300 占 폚.
Claim 11 has been abandoned due to the set registration fee. The method for producing a zinc oxide thin film according to any one of claims 1 to 7, wherein the heat treatment temperature in step 3) is 300 ° C to 600 ° C.
Claim 12 is abandoned in setting registration fee. The method for producing a zinc oxide thin film according to claim 11, wherein the heat treatment time is from 1 hour to 3 hours.

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