CN101654780A - Preparation method of Bi3.2Nd0.8Ti3O12 ferroelectric film - Google Patents

Abstract

A preparation method of a Bi3.2Nd0.8Ti3O12 ferroelectric film comprises the following steps: respectively dissolving bismuth nitrate or bismuth acetate and neodymium nitrate into glacial acetic acid according to the Bi3.2Nd0.8Ti3O12 chemical formula to obtain solution A and then regulating the solution A until the pH value is less than 3 to obtain solution B; dissolving butyl titanate or tetrabutyl titanate into the glacial acetic acid to obtain solution C and then adding acetylacetone into the solution C to obtain solution D; mixing the solution B and the solution D to obtain precursor solution, coating the precursor solution on a substrate by the technology of dip coating or spin coating and cooling the coated substrate at different annealing temperatures to obtain a c-oriented film or an a-oriented film. In the method, the Bi3.2Nd0.8Ti3O12 film is deposited on the single crystal silicon substrate by a chemical solution deposition method and a metal organic solution method. The singly c-oriented Bi3.2Nd0.8Ti3O12 ferroelectric film is obtained by quick temperature rise between 650 DEG C and 1000 DEG C, and the a-oriented Bi3.2Nd0.8Ti3O12 ferroelectric film is obtained by preheating treatment at 350-400 DEG C and further annealing at 650-750 DEG C.

Description

A kind of Bi 3.2Nd 0.8Ti 3O 12The preparation method of ferroelectric membranc

Technical field

The invention belongs to field of material preparation, be specifically related to a kind of Bi _3.2La _0.8Ti ₃O ₁₂The preparation method of ferroelectric membranc.

Background technology

Bi _3.2Nd _0.8Ti ₃O ₁₂Ferroelectric membranc has the characteristics of the big and antifatigue of polarization.It is very important electron material of the class with potential using value of permanent random access memory (NVRAM) and dynamic randon access memory in (DRAM).In these are used, require film that low coercive field, high residual polarization, low leakage current and low polarization fatigue are arranged.Big residual polarization is arranged Pb-based lanthanumdoped zirconate titanates (PZT) film but anti-fatigue performance is poor.Barium titanate, barium strontium titanate ferroelectric film have preferably anti-fatigue performance but poor-performings such as residual polarization.(Wang H., Ren M.F., Effects ofOrientated Growthon Properties of Ag/Bi such as Smolenskii ₄Ti ₃O ₁₂/ p-Si Heterostructure Prepared by Sol-gel Methodwith Rapid Thermal Annealing Techniques, J.Mat.Sci.:Mat.In Eletronics, 2005,16,209-213) find bismuth layer perovskite structure pottery (SrB i ₂Ta ₂O ₉, SrBi ₂NbTaO ₉, SrB i ₄Ta ₄O ₁₅And Bi ₄Ti ₃O ₁₂Deng) have ferroelectricity and high Curie temperature and big anti-fatigue performance are arranged.But the remnant polarization of their thin-film material is then relatively low.In order to utilize Bi ₄Ti ₃O ₁₂The advantage of the high-curie temperature of ferroelectric material and big residual polarization overcomes the fatiguability characteristics, discovers lanthanum, neodymium, samarium] and ruthenium ion partly replace bismuth ion and enter the electropolarization performance that the bismuth layer can improve film, significantly improve anti-fatigue performance.Just ion Bi is thought in some researchs ₄Ti ₃O ₁₂The electropolarization direction of film is the a-axle, then thinks ion doping Bi in other researchs ₄Ti ₃O ₁₂The electropolarization direction of film is at the c-axle.But a large amount of data in literature shows that so-called orientation is actually indirect or several orientations and exists the orientation degree on certain orientation just bigger simultaneously.On the electropolarization direction, increase orientation degree and mean the increase polarization.Therefore, for the electropolarization discovery of studying such film and the film that obtains large electrode intensity, be necessary to prepare the high-orientation film of two kinds of orientations, research obtains the processing condition of various oriented films.

Summary of the invention

The object of the present invention is to provide the simple Bi of a kind of preparation technology _3.2Nd _0.8Ti ₃O ₁₂The preparation method of ferroelectric membranc can prepare single oriented film that high a-is orientated and high c-is orientated by preparation method of the present invention.

For achieving the above object, the technical solution used in the present invention is:

1) preparation precursor solution:

At first, press Bi _3.2Nd _0.8Ti ₃O ₁₂Chemical formula is got Bismuth trinitrate or bismuth acetate respectively, neodymium nitrate and butyl (tetra) titanate or tetrabutyl titanate, then Bismuth trinitrate or bismuth acetate and neodymium nitrate are dissolved in and obtain solution A in the glacial acetic acid, in solution A, add again after the Bismuth trinitrate of Bismuth trinitrate in the solution A or bismuth acetate quality 5～10% or the bismuth acetate with hydrochloric acid regulate pH＜3 solution B;

Secondly, butyl (tetra) titanate or tetrabutyl titanate be dissolved in obtain solution C in the glacial acetic acid, in solution C, add methyl ethyl diketone again and obtain solution D;

At last, solution B and solution D are mixed, in mixing solutions, regulate the concentration of mixing solutions to metal ion Ti with glacial acetic acid behind adding ethylene glycol and the citric acid again ⁴⁺Volumetric molar concentration to metal ion Ti ⁴⁺Volumetric molar concentration be that 0.01mol/l obtains precursor solution, metal ion in the precursor solution: ethylene glycol: citric acid: methyl ethyl diketone=1: (1～4): (1～2): 0.1;

2) film: adopt dip-coating or spin coating proceeding that precursor solution is coated on the substrate, after each coating with it 120-150 ℃ of drying, above-mentioned repeatedly coating and drying process are until the film that obtains required thickness;

3) annealing:

The substrate of substrate after filming from room temperature is warming up to 650～1000 ℃ of annealing 3min or directly will films with the temperature rise rate of 200～300 ℃/min after put into take out cooling from stove immediately behind 650-1000 ℃ the High Temperature Furnaces Heating Apparatus annealing 3min and obtain c-orientation Bi _3.2Nd _0.8Ti ₃O ₁₂Film;

Substrate after maybe will filming is warming up to 650-750 ℃ of annealing 3-60min with the temperature rise rate greater than 200～300 ℃/min and obtains a-orientation Bi behind 350-400 ℃ of thermal pretreatment 10min _3.2Nd _0.8Ti ₃O ₁₂Film.

The present invention is in order to reduce the viscosity of precursor solution, with precursor solution at 60-80 ℃ of gelation 30-60min; Said substrate adopts monocrystalline silicon substrate, uses dehydrated alcohol and acetone respectively to the monocrystalline silicon substrate drying in air after ultrasonic cleaning before filming.

Applied chemistry solution-deposition method of the present invention and organic metal solution method deposit Bi on monocrystalline silicon substrate _3.2Nd _0.8Ti ₃O ₁₂Film.At 650-1000 ℃ of list orientation Bi that is rapidly heated and obtains the c-orientation _3.2Nd _0.8Ti ₃O ₁₂Film.Obtain a-orientation Bi in 350-400 ℃ of thermal pretreatment and 650-750 ℃ of further annealing _3.2Nd _0.8Ti ₃O ₁₂Film.

Description of drawings

Fig. 1 (a) is 700 ℃ and 800 ℃ of Bi with c-orientation that short annealing 3min obtains _3.2Nd _0.8Ti ₃O ₁₂The XRD figure of film, Fig. 1 (b) is 400 ℃ of Bi with a-orientation that anneal 10min and obtain behind 700 ℃ of annealing 3min and 10min _3.2Nd _0.8Ti ₃O ₁₂The XRD figure of film.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in further detail.

Embodiment 1:

1) preparation precursor solution:

At first, press Bi _3.2Nd _0.8Ti ₃O ₁₂Chemical formula is got Bismuth trinitrate respectively, and neodymium nitrate and butyl (tetra) titanate are dissolved in Bismuth trinitrate and neodymium nitrate then and obtain solution A in the glacial acetic acid, in solution A, add again after the Bismuth trinitrate of Bismuth trinitrate quality 5% in the solution A with hydrochloric acid regulate pH＜3 solution B;

Secondly, butyl (tetra) titanate is dissolved in obtains solution C in the glacial acetic acid, in solution C, add methyl ethyl diketone again and obtain solution D;

At last, solution B and solution D are mixed, in mixing solutions, regulate the concentration of mixing solutions to metal ion Ti with glacial acetic acid behind adding ethylene glycol and the citric acid again ⁴⁺Volumetric molar concentration to metal ion Ti ⁴⁺Volumetric molar concentration be that 0.01mol/l obtains precursor solution, metal ion in the precursor solution: ethylene glycol: citric acid: methyl ethyl diketone=1: 1: 1: 0.1, in order to reduce the viscosity of precursor solution, with precursor solution at 60 ℃ of gelation 60min;

2) film: get monocrystalline silicon substrate, use dehydrated alcohol and acetone respectively to the monocrystalline silicon substrate drying in air after ultrasonic cleaning before filming, adopt dip-coating or spin coating proceeding that precursor solution is coated on the substrate, after each coating with it 120 ℃ of dryings, above-mentioned repeatedly coating and drying process are until the film that obtains required thickness;

3) annealing:

The substrate of substrate after filming from room temperature is warming up to 650 ℃ of annealing 3min or directly will films with the temperature rise rate of 200 ℃/min after put into take out cooling from stove immediately behind 650 ℃ the High Temperature Furnaces Heating Apparatus annealing 3min and obtain c-orientation Bi _3.2Nd _0.8Ti ₃O ₁₂Film (is seen Fig. 1 a);

Substrate after maybe will filming is warming up to 650 ℃ of annealing 60min with the temperature rise rate greater than 200 ℃/min and obtains a-orientation Bi behind 400 ℃ of thermal pretreatment 10min _3.2Nd _0.8Ti ₃O ₁₂Film (seeing Fig. 1 b).

Embodiment 2:

1) preparation precursor solution:

At first, press Bi _3.2Nd _0.8Ti ₃O ₁₂Chemical formula is got bismuth acetate respectively, and neodymium nitrate and tetrabutyl titanate are dissolved in bismuth acetate and neodymium nitrate then and obtain solution A in the glacial acetic acid, in solution A, add again after the bismuth acetate of bismuth acetate quality 5% in the solution A with hydrochloric acid regulate pH＜3 solution B;

Secondly, tetrabutyl titanate is dissolved in obtains solution C in the glacial acetic acid, in solution C, add methyl ethyl diketone again and obtain solution D;

At last, solution B and solution D are mixed, in mixing solutions, regulate the concentration of mixing solutions to metal ion Ti with glacial acetic acid behind adding ethylene glycol and the citric acid again ⁴⁺Volumetric molar concentration to metal ion Ti ⁴⁺Volumetric molar concentration be that 0.01mol/l obtains precursor solution, metal ion in the precursor solution: ethylene glycol: citric acid: methyl ethyl diketone=1: 2: 1.5: 0.1, in order to reduce the viscosity of precursor solution, with precursor solution at 70 ℃ of gelation 45min;

2) film: get monocrystalline silicon substrate, use dehydrated alcohol and acetone respectively to the monocrystalline silicon substrate drying in air after ultrasonic cleaning before filming, adopt dip-coating or spin coating proceeding that precursor solution is coated on the substrate, after each coating with it 135 ℃ of dryings, above-mentioned repeatedly coating and drying process are until the film that obtains required thickness;

3) annealing:

The substrate of substrate after filming from room temperature is warming up to 800 ℃ of annealing 3min or directly will films with the temperature rise rate of 240 ℃/min after put into take out cooling from stove immediately behind 800 ℃ the High Temperature Furnaces Heating Apparatus annealing 3min and obtain c-orientation Bi _3.2Nd _0.8Ti ₃O ₁₂Film;

Substrate after maybe will filming is warming up to 700 ℃ of annealing 30min with the temperature rise rate greater than 260 ℃/min and obtains a-orientation Bi behind 380 ℃ of thermal pretreatment 10min _3.2Nd _0.8Ti ₃O ₁₂Film.

Embodiment 3:

1) preparation precursor solution:

At first, press Bi _3.2Nd _0.8Ti ₃O ₁₂Chemical formula is got Bismuth trinitrate respectively, and neodymium nitrate and tetrabutyl titanate are dissolved in Bismuth trinitrate and neodymium nitrate then and obtain solution A in the glacial acetic acid, in solution A, add again after the Bismuth trinitrate of Bismuth trinitrate quality 10% in the solution A with hydrochloric acid regulate pH＜3 solution B;

Secondly, tetrabutyl titanate is dissolved in obtains solution C in the glacial acetic acid, in solution C, add methyl ethyl diketone again and obtain solution D;

At last, solution B and solution D are mixed, in mixing solutions, regulate the concentration of mixing solutions to metal ion Ti with glacial acetic acid behind adding ethylene glycol and the citric acid again ⁴⁺Volumetric molar concentration to metal ion Ti ⁴⁺Volumetric molar concentration be that 0.01mol/l obtains precursor solution, metal ion in the precursor solution: ethylene glycol: citric acid: methyl ethyl diketone=1: 4: 2: 0.1, in order to reduce the viscosity of precursor solution, with precursor solution at 80 ℃ of gelation 30min;

2) film: get monocrystalline silicon substrate, use dehydrated alcohol and acetone respectively to the monocrystalline silicon substrate drying in air after ultrasonic cleaning before filming, adopt dip-coating or spin coating proceeding that precursor solution is coated on the substrate, after each coating with it 150 ℃ of dryings, above-mentioned repeatedly coating and drying process are until the film that obtains required thickness;

3) annealing:

The substrate of substrate after filming from room temperature is warming up to 1000 ℃ of annealing 3min or directly will films with the temperature rise rate of 300 ℃/min after put into take out cooling from stove immediately behind 1000 ℃ the High Temperature Furnaces Heating Apparatus annealing 3min and obtain c-orientation Bi _3.2Nd _0.8Ti ₃O ₁₂Film;

Substrate after maybe will filming is warming up to 750 ℃ of annealing 3min with the temperature rise rate greater than 300 ℃/min and obtains a-orientation Bi behind 350 ℃ of thermal pretreatment 10min _3.2Nd _0.8Ti ₃O ₁₂Film.

Claims (3)

1, a kind of Bi _3.2Nd _0.8Ti ₃O ₁₂The preparation method of ferroelectric membranc is characterized in that, may further comprise the steps:

1) preparation precursor solution:

At first, press Bi _3.2Nd _0.8Ti ₃O ₁₂Chemical formula is got Bismuth trinitrate or bismuth acetate respectively, neodymium nitrate and butyl (tetra) titanate or tetrabutyl titanate, then Bismuth trinitrate or bismuth acetate and neodymium nitrate are dissolved in and obtain solution A in the glacial acetic acid, in solution A, add again after the Bismuth trinitrate of Bismuth trinitrate in the solution A or bismuth acetate quality 5～10% or the bismuth acetate with hydrochloric acid regulate pH＜3 solution B;

Secondly, butyl (tetra) titanate or tetrabutyl titanate be dissolved in obtain solution C in the glacial acetic acid, in solution C, add methyl ethyl diketone again and obtain solution D;

At last, solution B and solution D are mixed, adding behind ethylene glycol and the citric acid concentration of regulating mixing solutions with the glacial acetic acid volumetric molar concentration to the volumetric molar concentration of metal ion Ti4+ to metal ion Ti4+ again in mixing solutions is that 0.01mol/l obtains precursor solution, metal ion in the precursor solution: ethylene glycol: citric acid: methyl ethyl diketone=1: (1～4): (1～2): 0.1;

2) film: adopt dip-coating or spin coating proceeding that precursor solution is coated on the substrate, after each coating with it 120-150 ℃ of drying, above-mentioned repeatedly coating and drying process are until the film that obtains required thickness;

3) annealing:

The substrate of substrate after filming from room temperature is warming up to 650～1000 ℃ of annealing 3min or directly will films with the temperature rise rate of 200～300 ℃/min after put into take out cooling from stove immediately behind 650-1000 ℃ the High Temperature Furnaces Heating Apparatus annealing 3min and obtain the c-oriented film;

Substrate after maybe will filming is warming up to 650-750 ℃ of annealing 3-60min with the temperature rise rate greater than 200～300 ℃/min and obtains the a-oriented film behind 350-400 ℃ of thermal pretreatment 10min.

2, Bi according to claim 1 _3.2Nd _0.8Ti ₃O ₁₂The preparation method of ferroelectric membranc is characterized in that: in order to reduce the viscosity of precursor solution, with precursor solution at 60-80 ℃ of gelation 30-60min.

3, Bi according to claim 1 _3.2Nd _0.8Ti ₃O ₁₂The preparation method of ferroelectric membranc is characterized in that: said substrate adopts monocrystalline silicon substrate, uses dehydrated alcohol and acetone respectively to the monocrystalline silicon substrate drying in air after ultrasonic cleaning before filming.

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