CN1138870C - A kind of antimony-doped strontium titanate thin film and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of film materials. The present invention prepares a multi-performance antimony-doped strontium titanate (SrSb _x Ti _1-x O ₃ ) film by adopting an alternative method of doping antimony (Sb) in strontium titanate (SrTiO ₃ ) through two-part process of preparing target material and preparing thin film Materials, where Sr:Ti:Sb=1:(1-x):x. With the different antimony content, the film material has different characteristics. When the antimony content is low, its dielectric and pyroelectric properties are strong. When the antimony content is high, its conductivity is enhanced and it becomes a metallic oxide. Conductive film material. The thin film material of the invention can be used as an electrode and to prepare a photorefractive element or a photodetector.

Description

A kind of Sb-doped strontium titanate film and preparation method thereof

The invention belongs to the thin-film material field.

Strontium titanate (the SrTiO of isometric system ₃) crystal is as infrared optical material, is used to make optical elements such as special optical window, prism and infrared optics lens.Since high-temperature superconductor occurred, people had produced great interest to the film and the super crystal lattice material of oxide compound.SrTiO ₃Crystal is by widely as the substrate of preparation high-temperature superconductor and other sull.Up to the present, for SrTiO ₃The development work of crystal and film is still being carried out, as document 1, and Michio Naito, Hideki Yamamoto, Hisashi Sato, Physica C, 305 (1998), 233.Develop have a superconducting characteristic mix niobium (Nb) SrTiO ₃, as document 2, Arnold Leitner, Charles T.Rogers, John C.Price, David A.Rudman, David R.Herman, Appl.Phys.Lett., 72 (1998), 3065.Human SrTiO is also arranged ₃Material preparation dielectric, ferroelectric superlattice, as document 3, H.Tabata and T.Kawai, Appl.Phys.Lett., 70 (1997), 321.

The purpose of this invention is to provide a kind of Sb-doped strontium titanate (SrSb with multiple performances such as dielectric, pyroelectricity, conductions _xTi _1-xO ₃) thin-film material and preparation method thereof.SrSb provided by the invention _xTi _1-xO ₃Film is to adopt Sb to substitute the adulterating method of a part of Ti, is finished by preparation target and preparation film two portions operation.

SrSb _xTi _1-xO ₃Film characteristics is different and different along with the concentration of doping Sb, and when doping content is low, when promptly the value of x was less than normal, characteristics such as the dielectric of film and pyroelectricity were stronger; When the doping content height, when promptly the value of x increased, the electroconductibility of film was stronger.Therefore can adopt the replacement method to choose x by the requirement of characteristic and carry 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 is chosen purity, and these high-purity materials can be Sr, Sb, Ti pure metal or their compound S rO, Sb ₂O ₃, Sb ₂O ₅, TiO ₂, SrCO ₃They are oxidized to oxide compound in high temperature or their compound thermal degradation is an oxide compound.Its resultant solid phase composition is SrSb _xTi _1-xO ₃Its film can be used laser molecular beam epitaxy, radio-frequency sputtering, and pulsed laser deposition, electron beam evaporation, methods such as molecular beam epitaxy are made.For example: formula combination can for:

SrCO ₃+Sb ₂O ₃+TiO ₂ (1)

SrO+Sb ₂O ₃+TiO ₂ (2)

SrCO ₃+Sb ₂O ₅+TiO ₂ (3)

SrCO ₃+Sb+TiO ₂ (4)

SrCO ₃+Sb ₂O ₃+Ti (5)

SrO+Sb+Ti multiple combinations such as (6) can generate SrSb by sintering reaction in air or oxygen or mixed-gas atmosphere _xTi _1-xO ₃All stoicheiometries are: Sr: Ti: Sb=1: (1-x): x.

Concrete preparation method is as follows:

1, 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, thereby following three kinds of system Target processes are arranged:

1) 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 radio-frequency 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 SrO that weighs up, Sb ₂O ₃, TiO ₂Or SrO, Sb, 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 was ground again, pressed and formed type, in 700 ℃～1100 ℃ sintering 12-36 hour.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, repeat above-mentioned system target process again, be prepared into composite target material at last with chemical formulation 2 or 6.

2) preparation of separation 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 SrO, Sb respectively by element ₂O ₃(or Sb ₂O ₅) and TiO ₂Three are separated target.

3) preparation of separation and composite target material

The SrSb of c orientation _xTi _1-xO ₃Film is by a SrO layer and a Sb _xTi _1-xO ₂Layer is formed a SrSb _xTi _1-xO ₃The primitive unit cell layer.For the laser molecular beam epitaxy masking technique of can atomic scale accurately controlling layer growth, SrO and Sb just can alternately grow respectively _xTi _1-xO ₂Layer prepares SrSb _xTi _1-xO ₃Thereby can be by 1) described method, be prepared into a SrO and a Sb _xTi _1-xO ₂Two targets.

2, preparation film

Preparation SrSb _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, radio-frequency sputtering, electron beam evaporation and molecular beam epitaxy and technology preparation.For SrSb _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 SrSb _xTi _1-xO ₃Film, also can with other material alternating growth, preparation assembly of thin films material.

The SrSb of the present invention's preparation _xTi _1-xO ₃Film has good electroconductibility, and observes strong infrared Absorption and pyroelectricity characteristic, estimates that also have light sells off, characteristics such as ferroelectric and superconduction.This film can be used as the electrode of electronics and functional device, also may prepare light and sell off element or photo-detector etc.

The present 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.In air atmosphere and 900 ℃ sintering temperature 15 hours.Altogether crushing grindings-pressure is formed type-sintering 3 times, last sintering temperature at 1200 ℃ 48 hours.Make SrSb _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, the SrSb of preparation thickness 5000_ _0.2Ti _0.8O ₃Film.

High energy electron diffraction and X-ray diffraction prove, prepared SrSb _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 10 ^-4Ω cm, n type carrier concentration is 10 ²¹Cm ^-3Observe characteristics such as pyroelectricity, estimate to also have characteristics such as ferroelectric and superconduction.

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 SrCO ₃Under oxygen atmosphere and 850 ℃ of temperature, took off C 20 hours.The SrSb of preparation thickness 2000_ _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, the SrSb of preparation thickness 4000_ _0.2Ti _0.8O ₃Film.

Embodiment 4:

Press embodiment 1 and make, use radio-frequency (RF) sputtering method, at 650 ℃ of base reservoir temperatures, Ar and O ₂Under the mixed pressure 15Pa condition, the SrSb of preparation 3000_ _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 SrCO ₃Under 1000 ℃ of temperature, took off C 10 hours.The SrSb of the thick 5mm of preparation Φ 50mm _0.5Ti _0.5O ₃Target.Select the LaAlO of Φ 40mm * O.5mm for use ₃Do substrate, the thick SrSb of preparation thickness 2000_ _0.5Ti _0.5O ₃Film.

Embodiment 6:

Press embodiment 1 and make, at the SrTiO of 20mm * 20mm * 0.5mm ₃The SrSb of elder generation's growth 2000_ in the substrate _0.2Ti _0.8O ₃Film is then at SrSb _0.2Ti _0.8O ₃The BaTiO of growth 4000_ on the film ₃Film is at last again at BaTiO ₃The SrSb of growth 2000_ on the film _0.2Ti _0.8O ₃Film.At BaTiO ₃The two-layer SrSb 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 SrO, SbO and TiO ₂Three targets.Under 900 ℃ of temperature with SrCO 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 SrO, Sb 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 SrSb of preparation different levels of doping _xTi _1-xO ₃Film.

Embodiment 8:

Press embodiment 1 and make sintering SrO and Sb: Ti=3: 7 Sb 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 SrO and Sb _0.3Ti _0.7O ₂, preparation SrSb _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, SrO and Sb is respectively charged into two electron gun stoves of molecular beam epitaxy again, prepares the SrSb of different levels of doping with molecular beam epitaxy _xTi _1-xO ₃Film.

Embodiment 10:

Press embodiment 7 preparations, select chemical formulation 5 for use.

Claims (10)

1. An antimony-doped strontium titanate thin film, characterized in that its molecular formula is SrSb _x Ti _1-x O ₃ , where x ranges from 0.005 to 0.5. 2. A method for preparing the antimony-doped strontium titanate thin film according to claim 1, characterized in that it comprises 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 Sr, Sb, Ti pure metals or their compounds SrO, Sb ₂ O ₃ , Sb ₂ O ₅ , TiO ₂ , SrCO ₃ , choose a chemical formula, and accurately weigh the various raw materials required according to the size of the target target according to the atomic ratio Sr:Ti:Sb=1:(1-x):x, and 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: SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , and ZrO ₂ can be used as substrates for the preparation of SrSb _x Ti _1-x O ₃ thin films. The buffer layer is transitioned and prepared by pulse laser deposition, radio frequency sputtering, electron beam evaporation or molecular beam epitaxy. The pressure is 70Pa～10 ^-5 Pa, and the optimal growth rate is selected to prepare a SrSb _x Ti _1-x O ₃ single-layer film or a SrSb _x Ti _1-x O ₃ multi-layer film alternately grown with the above materials. 3. The method for preparing the antimony-doped strontium titanate thin film of claim 1 according to claim 2, characterized in that: The combination of raw material formula can be: SrCO ₃ +Sb ₂ O ₃ +TiO ₂ (1) SrO+ _Sb2O3 + _TiO2 ( ₂ ) SrCO ₃ +Sb ₂ O ₅ +TiO ₂ (3) SrCO ₃ +Sb+TiO ₂ (4) SrCO ₃ +Sb ₂ O ₃ +Ti (5) SrO+Sb+Ti (6). 4. The method for preparing the antimony-doped strontium 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 antimony-doped strontium titanate thin film according to claim 1, characterized in that it comprises 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 Sr, Sb, Ti pure metals or their compounds SrO, Sb ₂ O ₃ , Sb ₂ O ₅ , TiO ₂ , SrCO ₃ , in an oxygen atmosphere, sinter SrCO ₃ at a temperature of 900°C for 20 hours to remove carbon, and then select a sintering temperature of 1000°C, 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 SrO, Sb ₂ O ₃ and TiO ₂ ; 2) Preparation of thin film: SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , and ZrO ₂ can be used as substrates for the preparation of SrSb _x Ti _1-x O ₃ thin films. The buffer layer is transitioned and prepared by pulse laser deposition, radio frequency sputtering, electron beam evaporation or molecular beam epitaxy. The pressure is 70Pa～10 ^-5 Pa, and the optimal growth rate is selected to prepare a SrSb _x Ti _1-x O ₃ single-layer film or a SrSb _x Ti _1-x O ₃ multi-layer film alternately grown with the above materials. 6. The method for preparing the antimony-doped strontium titanate thin film according to claim 1, characterized in that: The combination of raw material formula can be: SrCO ₃ +Sb ₂ O ₃ +TiO ₂ (1) SrO+ _Sb2O3 + _TiO2 ( ₂ ) SrCO ₃ +Sb ₂ O ₅ +TiO ₂ (3) SrCO ₃ +Sb+TiO ₂ (4) SrCO ₃ +Sb ₂ O ₃ +Ti (5) SrO+Sb+Ti (6). 7. The method for preparing the antimony-doped strontium 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. 8. A method for preparing the antimony-doped strontium 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 Sr, Sb, Ti pure metals or their compounds SrO, Sb ₂ O ₃ , Sb ₂ O ₅ , TiO ₂ and SrCO ₃ were prepared into two targets of SrO and Sb _x Ti _1-x O ₂ respectively: in an oxygen atmosphere, sinter SrCO ₃ at a temperature of 900°C for 20 hours to remove carbon, and then select a sintering temperature of 1000°C, Co-crushing and grinding-pressing molding-sintering twice, and finally sintering at 1300°C for 36 hours to make SrO separation targets; then choose a chemical formula, according to the size of the target required, by atom Ratio Sr:Ti:Sb=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 a Sb _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 Sb _x Ti _1-x O ₂ composite target and a SrO separation target are prepared; 2) Preparation of thin film: SrTiO ₃ , BaTiO ₃ , LaAlO ₃ , and ZrO ₂ can be used as substrates for the preparation of SrSb _x Ti _1-x O ₃ thin films. The buffer layer is transitioned and prepared by pulse laser deposition, radio frequency sputtering, electron beam evaporation or molecular beam epitaxy. The pressure is 70Pa～10 ^-5 Pa, and the optimal growth rate is selected to prepare a SrSb _x Ti _1-x O ₃ single-layer film or a SrSb _x Ti _1-x O ₃ multi-layer film alternately grown with the above materials. 9. The method for preparing the antimony-doped strontium titanate thin film according to claim 1, characterized in that: The combination of raw material formula can be: SrCO ₃ +Sb ₂ O ₃ +TiO ₂ (1) SrO+ _Sb2O3 + _TiO2 ( ₂ ) SrCO ₃ +Sb ₂ O ₅ +TiO ₂ (3) SrCO ₃ +Sb+TiO ₂ (4) SrCO ₃ +Sb ₂ O ₃ +Ti (5) SrO+Sb+Ti (6). 10. The method for preparing the antimony-doped strontium titanate thin film of claim 1 according to claim 8, 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.