CN1142316C - A kind of doped barium niobium titanate film material and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of film materials. The invention provides a method for preparing a multifunctional niobium-doped barium titanate (BaNb _x Ti _1-x O ₃ ) film material by doping niobium (Nb) in barium titanate (BaTiO ₃ ). With the different niobium content, the film material has different characteristics. When the niobium content of the film is low, its ferroelectric and pyroelectric properties are strong. With the increase of niobium content, its conductivity is enhanced, and it becomes Metallic oxide conductive thin film material. The thin film material provided by the invention has wide applications in electronic devices, optics, light detection and the like.

Description

A kind of Nb-doped barium titanate film and preparation method thereof

The invention belongs to the thin-film material field.

Barium titanate (BaTiO ₃) be a kind of multifunctional material, he is a kind of representative ferroelectrics, has good piezoelectricity, electric light and non-linear optical property.The aspect such as selling off at storer, optical detection, light has a wide range of applications.As document 1:M.Sayer andK.Sreenivas, Science, 247 (1990) 1056; With document 2:Gene H.Hearting, J.Vac.Sci.Technol.A, 9 (1991) 414.People utilize at BaTiO ₃In adulterated method, improve and change BaTiO ₃Some characteristic.As document 3: Chinese patent, the patent No.: ZL 93104553.3.Document 4:J.Y.Chang, C.F.Chu, C.Y.Huang, R.R.Yueh, J.Appl.Phys., 85 (1999) 2318.Document 3 and document 4 are preparation single crystal material, and doping content only is the ppm magnitude.

Nb-doped barium titanate (the BaNb that the purpose of this invention is to provide a kind of highly doped multiple function _xTi _1-xO ₃) thin-film material.It not only can change BaTiO ₃Ferroelectric, photoelectricity and optical characteristics, especially make it become a kind of type material with conductive characteristic.

The object of the present invention is achieved like this:

BaNb provided by the invention _xTi _1-xO ₃Film is to adopt Nb to substitute the adulterating method of a part of Ti, is finished by preparation target and preparation film two portions operation.

BaNb _xTi _1-xO ₃Film characteristics is different and different along with the concentration of doping Nb, and when doping content is low, when just the value of x was less than normal, characteristics such as the ferroelectric and electric light of film etc. were stronger; When the doping content height, when promptly the value of x increased, the electroconductibility of film was stronger.Therefore can choose x by the requirement of characteristic carries out stoicheiometry.The span of x is: 0.005-0.5.

It is high-purity material more than 99.95% that the chemical feedstocks of target should be chosen purity, and can select for use different materials to carry out chemical formulation: these starting material can be pure metal or their compound.They are oxidized to oxide compound in high temperature or their compound thermal degradation is an oxide compound.Its resultant solid phase composition is BaNb _xTi _1-xO ₃Film can be used radio-frequency sputtering, magnetron sputtering, and electron beam evaporation, laser molecular beam epitaxy, several different methods such as laser deposition and molecular beam epitaxy are made.The combination of its formula for raw stock can for:

BaCO ₃+Nb ₂O ₃+TiO ₂ (1)

BaO+Nb ₂O ₃+TiO ₂ (2)

BaCO ₃+Nb ₂O ₅+TiO ₂ (3)

BaCO ₃+Nb+TiO ₂ (4)

BaCO ₃+Nb ₂O ₃+Ti (5)

BaO+Nb+Ti (6)

Etc. multiple combination, target can generate BaNb by sintering reaction in air or oxygen or mixed-gas atmosphere _xTi _1-xO ₃All stoicheiometries are: Ba: Ti: Nb=1: (1-x): x

Concrete preparation method is as follows:

One, preparation target

From above-mentioned 6 kinds of chemical formulations, choose any one kind of them,, press chemistry than the good required various raw materials of the accurate weighing of difference by the size of required target size.Different masking techniques has different requirements with method to target, and following three kinds of system Target processes are generally arranged:

1. the preparation of composite target material

Laser molecular beam epitaxy, the general composition targets that adopt of film-forming methods such as pulsed laser deposition and magnetron sputtering that is to say as far as possible the contained element of thin-film material all according to chemical composition is prepared into composite target material than mixed sintering together more.

If select above-mentioned chemical formulation 2 or 6 for use, can be directly with the BaO that weighs up, Nb ₂O ₃, TiO ₂Or BaO, Nb, Ti mixes, and grinds repeatedly, behind the raw material thorough mixing, the grinding tool of putting into required target size is pressed and to be formed type, then pressure is formed the material of type and is put into High Temperature Furnaces Heating Apparatus, heat to 700 ℃～1100 ℃ sintering 12-36 hour.After the material that sintering is intact took out, crushing grinding-pressure was formed type-(700 ℃～1100 ℃) sintering 12-36 hour again.In order to obtain even high-quality target, said process can repeat 2-5 time.Last material of again pressure being formed type is placed in 900 ℃～1300 ℃ the High Temperature Furnaces Heating Apparatus sintering 20-50 hour and is prepared into target.

If select above-mentioned chemical formulation 1,3,4 or 5 for use, before several raw materials mix, earlier the carbonate compound that weighs up is put into containers such as crucible, 600 ℃～1000 ℃ High Temperature Furnaces Heating Apparatus heating 12-20 hour, take off C and handle, can whether purify by the weight discrimination C of raw material.After treating that c purifies, by above-mentioned system target process several raw materials are mixed, grind, press knot, sintering again, be prepared into composite target material at last with chemical formulation 2 or 6.

2. separate the preparation of target

For some masking techniques such as electron beam evaporations, because it adopts the mode of continuous heating evaporation, thereby, be easy to make the chemical composition generation of film to depart from for the different compound of fusing point, preferably the element to different melting points evaporates respectively.So target need be by different element prepared compositions from target.

The preparation method who separates target is the same with the preparation technology of composite target material, and it is not that all raw material is mixed, but is prepared into BaO, Nb respectively by element ₂O ₃(or Nb ₂O ₅) and TiO ₂Three are separated target.

3. separate preparation with composite target material

The BaNb of c orientation _xTi _1-xO ₃Film is by a BaO layer and a Nb _xTi _1-xO ₂Layer is formed a BaNb _xTi _1-xO ₃The primitive unit cell layer.For the laser molecular beam epitaxy masking technique of can atomic scale accurately controlling layer growth, BaO and Nb just can alternately grow respectively _xTi _1-xO ₂Layer prepares BaNb _xTi _1-xO ₃Thereby can be prepared into a BaO and a Nb to target by aforesaid preparation target method _xTi _1-xO ₂Two targets.

Two, preparation film

BaNb _xTi _1-xO ₃Film can be selected SrTiO for use ₃, BaTiO ₃, LaAlO ₃, ZrO ₂Do substrate etc. the monocrystal material that lattice parameter is comparatively mated, also can the add buffer layer bigger for mismatch carries out transition.Adopt different film-forming method such as laser molecular beam epitaxy, pulsed laser deposition, magnetron sputtering, electron beam evaporation and molecular beam epitaxy and technology preparation.For BaNb _xTi _1-xO ₃Film, except that its doping content plays the conclusive effect film characteristics, the influence of oxygen vacancy also is clearly.Therefore can press 70Pa～10 at 400～900 ℃ of base reservoir temperatures, oxygen by the common process of various masking techniques ^-5Under the condition of Pa, select processing condition such as optimum growh speed, prepare BaNb _xTi _1-xO ₃Film.Also can with other material alternating growth, the preparation layered film material.

The BaNb of the present invention's preparation _xTi _1-xO ₃Film is along with the change of doping content has different characteristics, and when doping content was low, it had well ferroelectric, photoelectricity and optical characteristics, has good electroconductibility when doping content is high.BaNb provided by the invention _xTi _1-xO ₃Film is at electron device, and aspects such as optical detection and optical element have widely to be used.

The invention will be further described below in conjunction with embodiment:

Embodiment 1:

Select chemical formulation 2 for use, choose x=0.2, the target of the thick about 4mm of preparation Φ 30mm.900 ℃ sintering temperatures 15 hours.Altogether crushing grindings-pressure is formed type-sintering 3 times, last sintering temperature at 1200 ℃ 48 hours.Make BaNb _0.2Ti _0.8O ₃Target.

Select the SrTiO of 10mm * 10mm * 0.5mm for use ₃(001) do substrate, 620 ℃ of base reservoir temperatures, oxygen presses 1 * 10 with laser molecular beam epitaxy ^-4Under the Pa condition, preparation thickness 5000 BaNb _0.2Ti _0.8O ₃Film.

High energy electron diffraction and X-ray diffraction prove, the BaNb of our preparation _0.2Ti _0.8O ₃Film is the monocrystal thin films of c orientation, has extraordinary epitaxy single-crystal phase.The resistivity that records film with the standard four probe method reaches 7 * 10 ^-5Ω cm, n type carrier concentration is 10 ²²Cm ^-3And observe stronger characteristics such as pyroelectricity.Estimate that this material not only can make its ferroelectric response accelerate, light is sold off characteristic and is strengthened, and also has characteristics such as superconduction.The feature measurement of different levels of doping thin-film material carries out.The result who observes proves, BaNb _xTi _1-xO ₃Be multi-functional and have the novel film material of widespread use.

Embodiment 2:

Press embodiment 1 and make, select chemical formulation 1 for use, choose x=0.005, the preparation target is before raw material mixes, earlier with BaCO ₃Under 850 ℃ of temperature, took off C20 hour.Preparation thickness 2000 BaNb _0.005Ti _0.995O ₃Film.

Embodiment 3:

Press embodiment 1 and make, use pulsed laser deposition, 700 ℃ of base reservoir temperatures, oxygen is pressed under the 20Pa condition, preparation thickness 4000 BaNb _0.2Ti _0.8O ₃Film.

Embodiment 4:

Press embodiment 1 and make, use magnetically controlled sputter method, at 650 ℃ of base reservoir temperatures, Ar and O ₂Under the mixed pressure 15Pa condition, prepare 3000 BaNb _0.2Ti _0.8O ₃Film.

Embodiment 5:

Press embodiment 1 and make, select chemical formulation 3 for use, choose x=0.5, the preparation target.Before raw material mixes, earlier with BaCO ₃Under 1000 ℃ of temperature, took off C10 hour.The BaNb of the thick 5mm of preparation Φ 50mm _0.5Ti _0.5O ₃Target.Select the LaAlO of Φ 40mm * 0.5mm for use ₃Do substrate, preparation thickness 2000 BaNb _0.5Ti _0.5O ₃Film.

Embodiment 6:

Press embodiment 1 and make, at the SrTiO of 20mm * 20mm * 0.5mm ₃2000 BaNb grow earlier in the substrate _0.2Ti _0.8O ₃Film is then at BaNb0 _.2Ti _0.8O ₃Growth 4000 BaTiO on the film ₃Film is at last again at BaTiO ₃Growth 2000 BaNb on the film _0.2Ti _0.8O ₃Film.At BaTiO ₃The two-layer BaNb up and down of film _0.2Ti _0.8O ₃Film is done the usefulness of electrode.

Embodiment 7:

Select chemical formulation 4 for use, prepare isolating BaO, NbO and TiO ₂Three targets.Under 900 ℃ of temperature with BaCO ₃Sintering took off C in 20 hours.And then choose 1000 ℃ sintering temperature respectively, and crushing grindings-pressure is formed type-sintering 2 times altogether, and last sintering temperature at 1300 ℃ 36 hours is made BaO, Nb ₂O ₃And TiO ₂Three are separated target.

Separate the targets electron beam evaporation epitaxial chamber of packing into three, select 30mm * 30mm * 1mm ZrO for use ₂Do substrate, evaporate three targets respectively, press 5 * 10 at oxygen with three electron beams ^-4Pa under the condition that substrate temperature is 580 ℃, regulates the energy of three electron beams, the BaNb of preparation different levels of doping _xTi _1-xO ₃Film.

Embodiment 8:

Press embodiment 1 and make sintering BaO and Nb: Ti=3: 7 Nb ₂O ₃+ TiO ₂Target utilizes the real-time monitoring of reflection high energy electron diffraction, with laser molecular beam epitaxy stratiform control ground alternating growth BaO and Nb _0.3Ti _0.7O ₂, preparation BaNb _0.3Ti _0.7O ₃Film.

Embodiment 9:

Select chemical formulation 6 for use, only the TiO of a thick 3mm of Φ 20mm of sintering ₂Target is with TiO ₂Target is packed into and is equipped with the MBE chamber of electron beam evaporation, Ba and Sb is respectively charged into two electron gun stoves of molecular beam epitaxy again, prepares the BaNb of different levels of doping with molecular beam epitaxy _xTi _1-xO ₃Film.

Embodiment 10:

Press embodiment 7 and make, select chemical formulation 5 for use.

Claims (10)

1. A barium niobium titanate-doped thin film, characterized in that its molecular formula is BaNb _x Ti _1-x O ₃ , where x ranges from 0.005 to 0.5. 2. A method for preparing the barium niobium titanate thin film according to claim 1, characterized in that: comprising the following steps: 1) Preparation of composite target: The chemical raw materials of the target are high-purity materials with a purity of more than 99.95%, which are Ba, Nb, Ti pure metals or their compounds BaO, Nb ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaCO ₃ , choose a chemical formula, and accurately weigh the various raw materials required according to the size of the required target material according to the atomic ratio Ba:Ti:Nb=1:(1-x):x, and the All the weighed raw materials are mixed together, repeatedly ground, and after being fully mixed, put into a grinding tool of the required size for pressing and forming, and then put the pressed and formed materials into a high-temperature furnace, and heat them in an oxygen atmosphere to Sinter at 700°C to 1100°C for 12-36 hours, take out the sintered material, crush and grind it, press it into shape, repeat the process of pressing, sintering, and grinding 2-5 times, and finally press the The formed material is sintered in a high-temperature furnace at 900°C to 1300°C for 20-50 hours to prepare a target; If the selected raw materials contain carbonic acid compounds, put the weighed carbonic acid compounds into the crucible before mixing several raw materials, and heat them in a high-temperature furnace at 600°C to 1000°C for 12-20 hours for de-C treatment. After cleaning, the above-mentioned target making process is carried out, and finally a composite target is prepared; 2) Preparation of thin film: For the preparation of BaNb _x Ti _1-x O ₃ thin film, SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , ZrO ₂ and other single crystal materials with relatively matched lattice constants can be used as substrates. The buffer layer is transitioned and prepared by laser molecular beam epitaxy, pulsed laser deposition, radio frequency sputtering, magnetron sputtering, electron beam evaporation or molecular beam epitaxy. According to the conventional process of film forming technology, the substrate temperature BaNb _x Ti _1-x O ₃ thin films were prepared at 400-900°C, maintaining an oxygen pressure of 70Pa-10 ^-5 Pa, and selecting the optimum growth rate. 3. The method for preparing the niobium-doped barium titanate thin film of claim 1 according to claim 2, characterized in that: The combination of raw material formula can be: BaCO ₃ +Nb ₂ O ₃ +TiO ₂ (1) BaO+Nb ₂ O ₃ +TiO ₂ (2) BaCO ₃ +Nb ₂ O ₅ +TiO ₂ (3) BaCO ₃ +Nb+TiO ₂ (4) BaCO ₃ +Nb ₂ O ₃ +Ti (5) BaO+Nb+Ti (6). 4. The method for preparing the niobium-doped barium titanate thin film of claim 1 according to claim 2, characterized in that: the target atmosphere in step 1) can also directly select air or Ar and O with a mixed pressure of _15Pa of mixed gas. 5. A method for preparing the barium niobium titanate thin film according to claim 1, characterized in that: comprising the following steps: 1) Preparation of separation targets: The chemical raw materials of the targets are high-purity materials with a purity of more than 99.95%, which are Ba, Nb, Ti pure metals or their compounds BaO, Nb ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaCO ₃ , in an oxygen atmosphere, sinter BaCO ₃ at a temperature of 900°C for 20 hours to decarbonize, and then select a sintering temperature of 1000°C respectively, crushing and grinding-pressing molding-sintering twice, and finally at 1300°C Sintering at high temperature for 36 hours to make three separate targets of BaO, Nb ₂ O ₃ and TiO ₂ ; 2) Preparation of thin film: For the preparation of BaNb _x Ti _1-x O ₃ thin film, SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , ZrO ₂ and other single crystal materials with relatively matched lattice constants can be used as substrates. The buffer layer is transitioned and prepared by the film-making methods and technologies of laser molecular beam epitaxy, pulsed laser deposition, radio frequency sputtering, magnetron sputtering, electron beam evaporation or molecular beam epitaxy, according to the conventional processes of various film-making technologies, The substrate temperature is 400-900°C, the oxygen pressure is maintained at 70Pa-10 ^-5 Pa, and the optimum growth rate is selected to prepare BaNb _x Ti _1-x O ₃ monolayer films or BaNb _x Ti _1-x grown alternately with the above materials O ₃ multilayer film. 6. The method for preparing the niobium-doped barium titanate thin film according to claim 1, characterized in that: The combination of raw material formula can be: BaCO ₃ +Nb ₂ O ₃ +TiO ₂ (1) BaO+Nb ₂ O ₃ +TiO ₂ (2) BaCO ₃ +Nb ₂ O ₅ +TiO ₂ (3) BaCO ₃ +Nb+TiO ₂ (4) BaCO ₃ +Nb ₂ O ₃ +Ti (5) BaO+Nb+Ti (6). 7. The method for preparing the niobium-doped barium titanate thin film of claim 1 according to claim 5, characterized in that: the target atmosphere in step 1) can also directly select air or Ar and O with a mixed pressure of _15Pa of mixed gas. 8. A method for preparing the barium niobium titanate thin film according to claim 1, characterized in that it comprises the following steps: 1) Preparation of separation and composite targets: The chemical raw materials of the targets are high-purity materials with a purity of more than 99.95%, which are Ba, Nb, Ti pure metals or their compounds BaO, Nb ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ and BaCO ₃ are prepared into two targets of BaO and Nb _x Ti _1-x O ₂ respectively: in an oxygen atmosphere, BaCO ₃ is sintered at 900°C for 20 hours to remove carbon, and then the sintering temperature is selected to be 1000°C. Co-crushing and grinding-pressing molding-sintering twice, and finally sintering at 1300°C for 36 hours to make a BaO separation target; then choose a chemical formula, according to the size of the required target, by atom Ratio Ba:Ti:Nb=1:(1-x):x Accurately weigh the various raw materials required, mix all the weighed raw materials together, grind them repeatedly, mix them thoroughly, and put them into the required size Then put the pressed and formed material into a high-temperature furnace, heat it to 700°C-1100°C in an oxygen atmosphere, and sinter for 12-36 hours. After taking out the sintered material, Crushing and grinding, pressing and forming, the process of pressing, sintering and grinding can be repeated 2-5 times, and finally the pressed and formed material is sintered in a high-temperature furnace at 900 ° C to 1300 ° C for 20-50 hours Prepared as Nb _x Ti _1-x O ₂ target; If the selected raw materials contain carbonic acid compounds, put the weighed carbonic acid compounds into the crucible before mixing several raw materials, and heat them in a high-temperature furnace at 600°C to 1000°C for 12-20 hours for de-C treatment. After cleaning, the above-mentioned target making process is carried out, and finally a Nb _x Ti _1-x O ₂ composite target and a BaO separation target are prepared; 2) Preparation of thin film: For the preparation of BaNb _x Ti _1-x O ₃ thin film, SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , ZrO ₂ and other single crystal materials with relatively matched lattice constants can be used as substrates. The buffer layer is transitioned and prepared by the film-making methods and technologies of laser molecular beam epitaxy, pulsed laser deposition, radio frequency sputtering, magnetron sputtering, electron beam evaporation or molecular beam epitaxy, according to the conventional processes of various film-making technologies, The substrate temperature is 400-900°C, the oxygen pressure is maintained at 70Pa-10 ^-5 Pa, and the optimum growth rate is selected to prepare BaNb _x Ti _1-x O ₃ monolayer films or BaNb _x Ti _1-x grown alternately with the above materials O ₃ multilayer film. 9. The method for preparing the niobium-doped barium titanate thin film according to claim 1, characterized in that: The combination of raw material formula can be: BaCO ₃ +Nb ₂ O ₃ +TiO ₂ (1) BaO+Nb ₂ O ₃ +TiO ₂ (2) BaCO ₃ +Nb ₂ O ₅ +TiO ₂ (3) BaCO ₃ +Nb+TiO ₂ (4) BaCO ₃ +Nb ₂ O ₃ +Ti (5) BaO+Nb+Ti (6). 10. The method for preparing the niobium-doped barium titanate thin film according to claim 1, characterized in that: the target atmosphere in step 1) can also be directly selected from air or Ar and _O2 with a mixed pressure of 15Pa of mixed gas.