TWI281522B - Method for preparing zinc oxide crystalline - Google Patents

Abstract

The present invention provides a method for preparing zinc oxide crystalline, which is comprising the following steps: mixing a reacting aqueous solution and a proper amount of nitric acid aqueous solution to obtain a mixing solution, heating said mixing solution to a proper temperature, and then placing a substrate into said mixing solution for appropriate time, so as to form a layer of zinc oxide crystalline on the substrate, wherein said reacting aqueous solution is consisting of zinc nitrate aqueous solution and hexamethylenetetramine aqueous solution.

Description

1281522 IX. Description of the Invention: [Technical Field] The present invention relates to a method for preparing an oxidized crystal, and more particularly to a method for preparing zinc oxide crystal by liquid phase deposition. [Prior Art] Zinc oxide (ZnO) has many special properties due to its band gap of 3.37 eV and excitation binding energy of 60 meV, for example, near-UV emission. , transparent conductivity, piezoelectricity, photocatalytic effect, chemical and thermal stability, etc. Therefore, the application of oxidation is very extensive, especially the oxidation of crystalline phase can be applied to surface acoustic waves. Surface acoustic wave filter, photonic crystals, light-emitting diodes, optical modulator waveguides, varistors, gas sensors And solar cells (solar cells) and the like. Metal-organic chemical vapor phase deposition (MOCVD), thermal evaporation, and high temperature vapor transport are known as methods for preparing zinc oxide crystals. And liquid phase deposition methods, etc., because the liquid deposition method has the advantages of simple steps, no need to use a specific instrument, and low cost, so most of the current researches are directed to the preparation of oxidized crystals by liquid deposition. L. Vayssieres et al. (L. Vayssieres, K. Keis, S. Ε · 1281522

Lindquist, A. Hagfeldt, J. Phys. Chem. B 2001, 105, 3350; L. Vayssieres, ji/v. Maier. 2003, 75, 464) first proposed the use of hexamethylenetetramine (C6H12N4) and Zinc nitrate (Zn(N03)2) is thermally decomposed in aqueous solution to directly grow highly oriented two-dimensional microrod arrays of ΖηΟ on various substrates. In the "Q·Li, V. Kumar, Y. Li, H. Zhang, TJ Marks, RPH Chang, C/zem. Maier. 2005, /7, 1001·" literature, is the use of the six molar number The aqueous solution of methylenetetramine and the aqueous solution of nitric acid are reacted at a reaction temperature of 95 ° C, and the reaction equation is presumed to be as shown in the following formulas (1) to (5): C6H12N4 + 6H20 4 6HCHO + 4NH3 (1) nh3 + H20 ^ NH4+ + OH" (2) Zn(N〇3)2 ^ ^ Zn2+ + 2N03" (3) 20H~ + Zn2 + Zn(OH)2 (4) Zn(OH)2 — ZnO(S) + H20 ( 5) First, the hexamethylenetetramine will provide the hydroxide ion (OH_) according to the reaction of the above formulas (1) and (2), and the zinc nitrate will provide the atom (Zn2) according to the above formula (3). +), then the hydroxide ion and the zinc atom will continue to react according to the above formulas (4) and (5), and finally an oxidation word will be generated, and the oxidation word will undergo a nucleation reaction and grow on top of the substrate. 'Approximately 10 hours to grow into ZnO nanorods. Oxidation requires the use of temperatures above 95 ° C as the growth temperature for two reasons: one, causing the hydrolysis of hexamethylenetetramine and dissociation of hydroxide ions, and the high temperature above 95 ° C will promote the reaction equation ( 5) Move to the right to convert Zn(OH)2 to ZnO and increase the growth rate by 1281522. However, the above reaction formulas are all carried out in an aqueous solution state, but a high temperature of 95 QC or higher may cause water and NH 3 to evaporate, and the concentration of hydroxide ions is lowered. Therefore, it takes a time to use a growth temperature of 95 ° C or higher. Columnar oxidized crystals are available for ten hours or longer. In "X. Gao, X. Li, W. Yu, CT^m. 5 2005, 709, 1155.", the zinc sulfate and ethylenediamine are mixed according to the molar ratio of 1:3:1. Ethylenediamine) and hexamethylenetetramine to prepare a precursor aqueous solution, and then heat the previous aqueous solution of the precursor to 95 ° (3, and then poured into a glass bottle with a ruthenium substrate at the bottom for growth reaction, about 1 hour. The flowerlike ZnO nanostructures are obtained, and the reaction process is as shown in the following reaction equations (6) to (9):

Zn2+ + 3NH2.(CH2)2.NH2 (I)[Zn(NH2.(CH2)2.NH2)3]2+ (6) C6H12N4 + 6H20 — 6HCHO + 4NH3 (7) NH2 (CH2)2 NH2 + 2H20 h NH3 (CH2)2 NH3 + 20H_ (8)

Zn2+ + 20H_ — Zn(OH)2 — ZnO + H20 (9) . This paper is mainly to explore whether ethylenediamine will affect the form of zinc oxide produced. Finally, it was found that when zinc sulfate/hexamethylenetetramine/ethylenediamine = 1/1/6 or when ethylene is not used In the state where the amine and the zinc sulfate concentration are 0.0001 Å, a rod-shaped zinc oxide crystal can be obtained. However, the reaction temperature of this document must be controlled at 95 ° C to obtain columnar zinc oxide crystals. It can be seen from the above that the conventional preparation method of the columnar oxidized crystals is mostly required to have a growth temperature of 95 ° C or more, and it is necessary to appropriately control the concentration of the reactants, and it takes a few tens of hours to obtain columnar crystals. There is still a need for 1281522 for the preparation of columnar oxidized crystals at lower growth temperatures and for shorter periods of time. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for preparing zinc oxide crystals at a lower growth temperature (below 80 ° C) and for a shorter period of time. Therefore, the method for preparing zinc oxide crystals of the present invention comprises the steps of: mixing a reaction aqueous solution with an appropriate amount of aqueous citric acid solution to obtain a mixed solution, heating the mixed solution to a suitable temperature, and then The substrate is placed in the mixed solution for a suitable period of time, and finally a layer of oxidized crystals is formed on the substrate, wherein the aqueous solution is composed of an aqueous solution of nitric acid and an aqueous solution of hexamethylenetetramine. The method of the present invention prepares an oxidized crystal by adding an appropriate amount of nitric acid, and can effectively lower the growth temperature to 80. (: The following and shortening time to 2 hours or less. For the method of the present case, the current estimated reaction process is as shown in the following formulas (1) to (ix): C6Hi2N4 + 6H20 6HCH0 + 4NH3 (i) NH3 + H20 (1) NH4+ + OH- (ii )

Zn(N03)2 (a) Zn2+ + 2Ν0Γ (iii) 20H_ + Zn2+ — Zn(OH)2 (iv) HN03 (I) It + NOf (v)

Zn(N03)2 + 2H20 + 2C6H12N4 (1) [Zn(H20)2(C6H12N4)2](N03)2 (vi)

Zn(N03)2 + 4H20 + 2C6H12N4 ^ [Ζη(Η20)4(〇6Η12Ν4)2](Ν〇3)2 (vii) [Zn(H2〇)2(C6Hi2N4)2](N〇3)2 + OH" — Zn(0H)2 — Z11O+H2O (viii) [Zn(H20)4(C6H12N4)2](N〇3)2 + 〇ir-> Zn(OH)2 Zn0+H20 (ix) , The hexamethylenetetramine also produces 0H_ according to the above formulas (i) and (ii), but with the concentration of H+ and strontium produced by the formula (v), the formula (iii) and the formula (iii) Iv) The reaction of 1281522 will be affected and will not continue to react to the right, meaning that the hexamethylenetetramine and zinc nitrate will not dissociate in the aqueous solution, and according to "Q. Li, V. Kumar, Y. Li, H. Zhang, T. J. Marks, R. Ρ·H· Chang, C/zem. Μα化r.2005,7 7,1001 The content of the literature, and it is speculated that this formula (vi) and (vii) Coordination complexes, with two coordination complexes as nuclei, and finally zinc oxide crystals (presumably possible mechanisms such as formula viii and formula ix). The acid can effectively promote the growth of zinc oxide crystals. [Embodiment] The present invention is used for preparing zinc oxide crystals. The method comprises the steps of: mixing a reaction aqueous solution with an appropriate amount of aqueous nitric acid solution to obtain a mixed solution, heating the mixture to a suitable temperature, and then placing a substrate in the mixed solution for a suitable period of time, and finally Forming a layer of zinc oxide crystals on the substrate, wherein the aqueous solution of the solution is composed of an aqueous solution of zinc silicate and an aqueous solution of hexamethylenetetramine. Preferably, in the mixture, the nitrate, hexamethylene The molar ratio of the tetramine to the nitric acid is 1: 1: 0.05~1 ··1 ·· 0.15. It should be noted that the crystal state and shape of the oxidation may be affected by the surrounding growth environment, so it must be properly controlled. Columnar zinc oxide crystals of different sizes can be obtained by adding nitric acid. In the method of the present invention, the mixture is heated to a lower temperature (below 80 ° C) and then placed on the substrate for zinc oxide crystals. Preferably, the mixture is heated to 50 ° C to 75 ° C; more preferably, the mixture is heated to 65 ° C to 75 ° C. In one embodiment of the invention, the mixture Being heated 1 281522 to 70oC 时间 The time during which the substrate is placed in the mixed solution can be increased as needed. Preferably, the substrate is placed in the mixed solution for 5 to 2 hours. In one embodiment of the present invention, the substrate Placed in the mixture for 2 hours

In the method of the present invention, the material of the substrate can be changed as needed. Preferably, the substrate is selected from the group consisting of a π-ν 半导体 semiconductor substrate, a III-V semiconductor substrate, and a Group IV semiconductor substrate. For example, the side III-V semiconductor substrate may be filled with indium or the like, and the π_νι group semiconductor substrate may be, but not limited to, zinc sulfide, zinc telluride, and zinc oxide. The group IV semiconductor substrate may be, without being limited to, : Shi Xi, wrong and so on. In a specific embodiment of the invention, the substrate is a gallium arsenide substrate. Optionally, the method of the present invention further comprises a substrate cleaning step of cleaning the substrate prior to placing the substrate in the mixed solution. It should be noted that the substrate cleaning step can be carried out according to procedures well known in the art and using a suitable solvent. In the method of the present invention, the substrate used may be selectively etched or removed depending on the needs of the subsequent use. Preferably, the method of the present invention further comprises a separation step of separating the oxidized singer from the substrate.曰曰ο In the method of the present invention, the zinc oxide obtained is a hexagonal plate-like junction <Example> 10 1281522 The present invention will be further illustrated by the following examples, but it should be understood that The examples are for illustrative purposes only and are not to be construed as limiting the invention. &lt;Chemicals&gt; The following examples and comparative examples were carried out by the following chemicals: 1. Zinc nitrate aqueous solution: Zinc nitrate was manufactured by Riedel_de Haen, Switzerland, model 14436, and the following zinc nitrate aqueous solution was used. The concentration is 0·1 Μ, which is obtained by adding 29.75 g of zinc nitrate to 1 L of water. 2. hexamethylenetetramine aqueous solution: hexamethylenetetramine is manufactured by Sigma-Aldrich, USA, model si3361_473, and the hexamethylenetetramine aqueous solution used below is used at a concentration of 〇·丨M. It is prepared by adding 14.19 g of hexamethylenetetramine to 1 l of water. 3 · Aqueous nitric acid solution: The acid is manufactured by Merck, Germany, model TN1701, and the aqueous solution of nitric acid used below is used at a concentration of 0.1 Μ, which is obtained by diluting a 70% by volume aqueous solution of nitric acid. iiMJ__ Colonization: Addition amount of aqueous acid solution and cerium oxide shape A 10 mL aqueous solution of citric acid was mixed with 1 〇 mL of hexamethylenetetramine to obtain a reaction aqueous solution. To the aqueous solution of the reaction, 0, 0.5, ho, 15, 2.0, 2.5, and 3.0 mL of an aqueous solution of nitric acid were separately added to obtain a mixed solution. Next, the gallium arsenide substrate is

It is manufactured by Sumitomo Electric Industries, and the thickness is about 4〇〇μηι). It is cleaned according to the following steps: cleaning with acetone for about 1 〇 1281522 minutes, then cleaning with hot sulfuric acid for about 3 minutes, then using an etchant (Sulphuric acid, hydrogen peroxide, and water were prepared by mixing according to a volume ratio of 5:1:1). The cleaning was carried out for about 1 minute, and finally dried by nitrogen gas. Then, the mixture was separately heated to 7 ° C and maintained in a constant temperature bath (manufactured by Wisdom, Taiwan, model 0B-10) for 2 minutes, and then the washed gallium arsenide substrate It was placed in the mixture for about 2 hours, and finally a layer of oxidation was formed on the gallium arsenide substrate. (Test) The gallium arsenide substrate obtained by growing the zinc oxide obtained above was washed with water, and then dried with nitrogen, and then analyzed by the following methods and instruments. The obtained results are shown in Table 1 below. 1 to 9 none (I) FESEM test: The obtained crystal is adhered to a conductive material, and a field-type scanning electron microscope (hereinafter referred to as Xl-40FEG) manufactured by Philips, the Netherlands (hereinafter referred to as "Xl-40FEG"). "FESEM"), the surface and side of the crystal and the state of connection between the crystal and the substrate were observed. (II) XRD test An X-ray diffractometer (hereinafter referred to as "XRD") manufactured by Siemens, Germany, model D5000, with a voltage of 4 〇 kv, a current of 30 mA, and a scanning range of 2 Θ = 20. ~50. The scanning rate is i ° / min, 2θ = 〇 · 1 per division. XRD analysis was performed under the conditions of automatic recording of X-ray intensity and copper target λ = 0.15406 ,, and the signal comparison was performed via the built-in database of the instrument to confirm the chemical composition. 12 1281522 (III) HRTEM test was carried out on a substrate and placed on a circular copper wire of approximately 2-3 mm diameter and 200 mesh, and manufactured by jeql jem. The 3010 high-resolution transmission electron microscope, hereinafter referred to as "HRTEM", observes the single crystal structure of the crystals with an acceleration voltage of 200 kV. Table 1 Sample No. Nitric Acid Aqueous Solution Addition (mL) --------- Zinc Shawl Acid: Form of Hexamethylene Zinc Oxide FESEM Pattern HRTEM Figure 1 0 1 : 1 : 0 --- ^ 11^曰 blade shape Figure 1 - 2 0.5 1 : 1 : 〇.〇5 ------- - Crystallization Figure 2 - 3 1.0 t : 1 : 0.10 _____— ---- _^ Crystallization Figure 3 4 1.5 1 : 1 · 〇·ΐ5 ----- Crystalline Figure 4 Figure 8 5 2.0 ! : 1 : 0.20 _______ ___ Blade Figure 5 Figure 7 6 2.5 1 : 1 : 〇·25 Leaf Shape - 7 3.0 1 : 1 : 0.30 i___一-- Leaf shape Figure 6 - (Result) From the results of Table 1, the oxidation obtained when 'the amount of nitric acid aqueous solution is 〇·5, 1.0 and 1.5 mL' is obtained. The form of zinc is columnar crystal, and it can be clearly seen from Fig. 2 to Fig. 4 and Fig. 8 that the oxidation word is hexagonal columnar crystal, and it can be found that the columnar zinc oxide is added when the addition amount of the aqueous solution is increased. The size of the crystal will decrease with increasing density and density. This is because an appropriate amount of nitric acid inhibits the dissociation of hexamethylenetetramine and nitric acid, and the addition amount of the liquid is 1,7,815,522. In summary, when nitric acid: hexamethylenetetramine: indeed zinc oxide, can be used for subsequent use.

In addition, it is worth mentioning that if the amorphous leaf-shaped zinc oxide is converted into an oxidized word in the crystalline phase, the amorphous leaf-shaped zinc oxide sample (sample No. 5, 6 and 7) can be placed. The tempering step is carried out in human oxygen, and the oxidation of the crystalline phase is obtained in about 1 hour. For example, the amorphous leaf-shaped oxidation obtained by the above sample No. 1 (without adding an aqueous solution) is reacted at different tempering temperatures, and then the oxidized oxidized words are subjected to XRD analysis. As shown in the figure, it was found that the highest strength was obtained with a tempering temperature of 3 〇〇〇c. In summary, the method for preparing an oxidized crystal of the present invention is obtained by adding an appropriate amount of an aqueous solution of nitric acid to obtain an oxidized word in a hexagonal columnar crystal, and effectively reducing the growth temperature of the oxidized word to less than 8 〇cc. And shorten the growth time to less than 2 hours. The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an FESEM diagram showing the appearance of zinc oxide prepared in sample No. 1 of a specific example of the method of the present invention, wherein the left side is a front view and the right side is a side view; 8 1281522 FIG. 2 is an FESEM diagram showing the appearance of the oxidized word obtained by the sample No. 2 of one specific example of the method of the present invention, wherein the left side is a front view and the right side is a side view; FIG. 3 is a FESEM BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a perspective view showing the appearance of an oxidized word obtained by the sample editing 3 of a specific example of the method of the present invention, wherein the left side is a front view and the right side is a side view; FIG. 4 is a twisted 8_FIG. The appearance form of zinc oxide prepared in sample No. 4 of a specific example of the invention, wherein the left picture is a front view and the right picture is a side view; Fig. 8 is a view showing the appearance of zinc oxide prepared in sample No. 5 of a specific example of the method of the present invention, wherein the left picture is a front view: 'and the right picture is a side view · Fig. 6 is a -feSEM picture 'Description of the appearance of the oxidized word prepared in sample No. 7 of a specific example of the method of the present invention, wherein the left picture is a front view: 'and the right picture is a side view; FIG. 7 is a -HRTEM chart illustrating the method of the present invention. A specific example of the amorphous state of zinc oxide prepared in sample No. 5, and FIG. 8 is a -HRTEM diagram showing the state of the zinc oxide obtained by the method of the present invention in the single crystal state; kind. Figure 9 is -XRD @, illustrating the crystal state of zinc oxide prepared in Samples 1 to 7 of the method of the present invention - and the figure is -XRD pattern, illustrating a specific example of the method of the present invention. The amorphous leaf-shaped zinc oxide prepared in sample No. 1 was crystallized under different tempering temperature.怠 怠 16 1281522 [Explanation of main component symbols] None 17

Claims (1)

1281522 -, the scope of application for patents :::::: A method for preparing zinc oxide crystals, the bed comprises the steps of: combining a reaction aqueous solution with an appropriate amount of aqueous nitric acid solution, The mixture is heated to a suitable temperature to squirt the port to obtain a mixture of the mixture for a suitable period of time, and the substrate is placed on the oxidized crystal, wherein the reaction is water-soluble = a layer is formed on the substrate and a hexamethylene group is formed. The liquid hydrazine composed of the tetraamine aqueous solution is composed of - zinc nitrate aqueous solution 2. 3. 6 · = ???========================================================= Methyltetramine: The molar ratio of the province is 1:1:0.05~...:(3). Fang: Shen = Lifan: In the '/, used to prepare zinc oxide crystals, the mixture was heated to 5 Torr. (^ 75〇c The method for preparing an oxidized crystal according to item 3, wherein the mixture is heated to 65 〇 c 〜 75 〇 c 3 = the range described in item 1 for preparation The method for oxidizing crystals, wherein the substrate is placed in the (four) liquid phase, and the phase is 0.5 to 2 small. 2 Patent Application No. 2, which is used to prepare zinc oxide crystals, wherein the substrate is selected from the group consisting of In the group consisting of: n_vector+conductor substrate, mv group semiconductor substrate, and ιν semiconductor substrate=Application for the invention of the zinc oxide crystal described in the sixth paragraph of claim 4, wherein the substrate is gallium arsenide Substrate. _中中(4) The scope described in item 1 for the production of zinc oxide crystals 18 1281522 Before the substrate is placed in the mixture, the cough substrate cleaning step is to clean the substrate in accordance with the scope of the patent. The method 'further includes a separation step, and 2 is used to prepare a body of the oxidized crystal and is separated from the substrate. The Z-knife separation step is the zinc oxide crystal 10. According to the method of claim 1, wherein the emulsifier crystal for preparing zinc oxide crystals is a hexagonal columnar crystal. 19