JP2003109975A - Bi2Te3 SINGLE-CRYSTAL THIN FILM AND METHOD OF MANUFACTURING THE SAME - Google Patents
Bi2Te3 SINGLE-CRYSTAL THIN FILM AND METHOD OF MANUFACTURING THE SAMEInfo
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- JP2003109975A JP2003109975A JP2001300486A JP2001300486A JP2003109975A JP 2003109975 A JP2003109975 A JP 2003109975A JP 2001300486 A JP2001300486 A JP 2001300486A JP 2001300486 A JP2001300486 A JP 2001300486A JP 2003109975 A JP2003109975 A JP 2003109975A
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- substrate
- single crystal
- temperature
- thin film
- growth
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- 239000013078 crystal Substances 0.000 title claims abstract description 112
- 239000010409 thin film Substances 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 229910002899 Bi2Te3 Inorganic materials 0.000 title 1
- 239000000758 substrate Substances 0.000 claims abstract description 100
- 238000000034 method Methods 0.000 claims abstract description 52
- 238000000137 annealing Methods 0.000 claims abstract description 12
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 238000000151 deposition Methods 0.000 claims description 4
- 230000001678 irradiating effect Effects 0.000 claims description 2
- 238000001451 molecular beam epitaxy Methods 0.000 abstract description 22
- 229910016272 Bi2 Te3 Inorganic materials 0.000 abstract 6
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 229910052594 sapphire Inorganic materials 0.000 description 17
- 239000010980 sapphire Substances 0.000 description 17
- 239000000463 material Substances 0.000 description 14
- 238000002128 reflection high energy electron diffraction Methods 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 10
- 229910052797 bismuth Inorganic materials 0.000 description 9
- 229910052714 tellurium Inorganic materials 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 239000010408 film Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000000356 contaminant Substances 0.000 description 3
- 230000007812 deficiency Effects 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007734 materials engineering Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Crystals, And After-Treatments Of Crystals (AREA)
- Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ソリッドステート
エアコンを実現するペルチェ素子、排熱エネルギーの回
収に使用される熱電発電素子、及び温度センサーなどの
熱電変換素子に用いられるＢｉ2Ｔｅ3単結晶薄膜及びそ
の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Peltier device for realizing a solid state air conditioner, a thermoelectric power generating device used for recovering exhaust heat energy, and a Bi 2 Te 3 single crystal used for a thermoelectric conversion device such as a temperature sensor. A thin film and a manufacturing method thereof.
【０００２】[0002]
【従来の技術】従来の空調装置や冷却装置には、フロン
冷媒を用いることが多かったが、最近、環境問題が大き
な問題となり、前記空調装置や冷却装置のフロンレス
化、熱交換効率の向上による省エネルギー化が要求され
ている。ここで、熱電変換素子は、熱エネルギーと電気
エネルギーの可逆的な直接変換素子として有望ではある
が、従来は変換効率が低かったため、広く普及するには
至らなかった。2. Description of the Related Art Freon refrigerants have often been used in conventional air conditioners and cooling devices, but recently environmental problems have become a serious problem, and the use of freonless air conditioners and cooling devices and improvement of heat exchange efficiency Energy saving is required. Here, the thermoelectric conversion element is promising as a reversible direct conversion element of heat energy and electric energy, but it has not been widely spread because of its low conversion efficiency in the past.
【０００３】熱電変換素子の変換効率を改善する方法と
して、熱電変換材料によって厚さ数十Åという極めて薄
い膜を形成し、この膜よりもバンドギャップ幅が広い材
料で膜を挟み込む量子井戸構造が採用されている。この
技術は、L.D.Hicks 及び M.S.Dresselhausが、"Effect
of quantum-well structures on the thermoelectricfi
gure of merit”,Phys.Rev.B 47,19,pp.12727-12731(19
93)という文献に発表したものである。前記量子井戸構
造を実現するには、基板等の下地層における原子配列の
影響を反映しながら上層が成長していくエピタキシャル
単結晶成長を行う必要がある。一方、室温近傍の温度に
おいて用いられる熱電変換材料としては、Bi2Te3系材料
が一般的である。このBi2Te3系材料で量子井戸構造を実
現するためには、原子レベルで平坦な単結晶薄膜を積層
しなければならない。As a method for improving the conversion efficiency of a thermoelectric conversion element, a quantum well structure in which an extremely thin film having a thickness of several tens of liters is formed of a thermoelectric conversion material and the film is sandwiched by a material having a wider band gap width than this film is known. Has been adopted. This technology was developed by LDHicks and MS Dresselhaus in "Effect
of quantum-well structures on the thermoelectricfi
gure of merit ”, Phys.Rev.B 47,19, pp.12727-12731 (19
93). In order to realize the quantum well structure, it is necessary to perform epitaxial single crystal growth in which the upper layer grows while reflecting the influence of the atomic arrangement in the underlying layer such as the substrate. On the other hand, as a thermoelectric conversion material used at a temperature near room temperature, a Bi 2 Te 3 based material is generally used. In order to realize a quantum well structure with this Bi 2 Te 3 based material, it is necessary to stack flat single crystal thin films at the atomic level.
【０００４】エピタキシャル単結晶を成長させるには、
基板材料として、その成長させようとする目的生成物の
結晶構造及び格子定数に近い材料を用いる必要がある
が、目的生成物がBi2Te3の場合には好適な基板材料が見
当たらない。結晶構造や格子定数が比較的近いサファイ
ア(Al2O3)基板の格子面（０００１）でもBi2Te3の格子
定数と８．６％の差異がある。従って、サファイア基板
上にBi2Te3単結晶薄膜を、単結晶薄膜成長法として一般
的な分子線エピタキシー(Molecular Beam Epitaxy:MBE)
法によって成長させると、目的生成物であるBi2Te3は多
結晶となってしまい、平坦な単結晶薄膜を作製すること
が困難であった。To grow an epitaxial single crystal,
As the substrate material, it is necessary to use a material having a crystal structure and a lattice constant close to that of the target product to be grown, but when the target product is Bi 2 Te 3, a suitable substrate material cannot be found. Even the lattice plane (0001) of a sapphire (Al 2 O 3 ) substrate having a relatively close crystal structure and lattice constant has a difference of 8.6% from that of Bi 2 Te 3 . Therefore, a Bi 2 Te 3 single crystal thin film on a sapphire substrate, a general molecular beam epitaxy (MBE) as a single crystal thin film growth method.
When grown by the method, the target product Bi 2 Te 3 becomes polycrystal, and it is difficult to form a flat single crystal thin film.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、前記課題を
解決し、分子線エピタキシー法を用いて、原子レベルで
平坦な単結晶薄膜を、簡単でかつ安価なコストで作製で
きるBi2Te3単結晶薄膜の製造方法を提供することを目的
とする。[SUMMARY OF THE INVENTION The present invention is to solve the above problems, using a molecular beam epitaxy method, a flat single-crystal thin film at the atomic level, it can be produced in a simple and inexpensive cost Bi 2 Te 3 It is an object to provide a method for manufacturing a single crystal thin film.
【０００６】[0006]
【課題を解決するための手段】本発明に係るＢｉ2Ｔｅ3
単結晶薄膜の製造方法は、前記目的を達成するため、密
閉された容器内に配置した基板上にBi2Te3エピタキシャ
ル単結晶を成長させる方法であって、Bi2Te3蒸気圧が前
記容器内の圧力よりも小さくなる基板温度で、Bi2Te3を
基板上に堆積させるバッファ成長段階と、Bi2Te3蒸気圧
が前記容器内の圧力よりも大きくなる温度まで前記基板
温度を上げたのち、更に、Bi2Te3蒸気圧が前記容器内の
圧力よりも小さくなる温度まで前記基板温度を下げるア
ニール段階とを含んでなる方法である。この方法によれ
ば、原子レベルで平坦なBi2Te3エピタキシャル単結晶薄
膜を作製することができる。Bi 2 Te 3 according to the present invention
A method for producing a single crystal thin film is a method for growing a Bi 2 Te 3 epitaxial single crystal on a substrate arranged in a sealed container in order to achieve the above object, wherein Bi 2 Te 3 vapor pressure is the container. A buffer growth step of depositing Bi 2 Te 3 on the substrate at a substrate temperature lower than the internal pressure, and raising the substrate temperature to a temperature at which the Bi 2 Te 3 vapor pressure becomes higher than the internal pressure of the container. After that, the method further comprises an annealing step of lowering the substrate temperature to a temperature at which the vapor pressure of Bi 2 Te 3 becomes smaller than the pressure in the container. According to this method, an atomically flat Bi 2 Te 3 epitaxial single crystal thin film can be produced.
【０００７】前記基板としては、Bi2Te3と結晶構造及び
格子定数が近いもの、例えばサファイア（Ａｌ2Ｏ3）か
らなる基板などが好ましい。また、前記容器内の圧力
は、特に限定されないが、例えば、１０-6〜１０-8Ｐａ
の範囲が好ましい。そして、前記バッファ成長段階及び
アニール段階は、各々、一回ずつ行っても良いが、安定
した薄膜を作製するには、例えば二回などの複数回繰り
返して行うことが望ましい。さらに、バッファ成長段階
の処理時間は、好ましくは、５〜１２０秒間であり、更
に好ましくは、１０〜６０秒間である。なお、アニール
段階の処理時間は、１〜１０分間であり、更に好ましく
は、３〜５分間である。As the substrate, a substrate having a crystal structure and a lattice constant close to that of Bi 2 Te 3 , for example, a substrate made of sapphire (Al 2 O 3 ) is preferable. The pressure in the container is not particularly limited, but is, for example, 10 −6 to 10 −8 Pa.
Is preferred. The buffer growth step and the annealing step may each be performed once, but it is preferable to repeat the buffer growth step a plurality of times, for example, twice in order to form a stable thin film. Further, the processing time of the buffer growth stage is preferably 5 to 120 seconds, more preferably 10 to 60 seconds. The treatment time in the annealing step is 1 to 10 minutes, more preferably 3 to 5 minutes.
【０００８】また、本発明に係るＢｉ2Ｔｅ3単結晶薄膜
の製造方法の一態様では、前記バッファ成長段階におい
て、Bi 分子線及びTe 分子線を前記基板上に照射するこ
とにより、Bi2Te3を基板上に堆積させる方法である。Bi
2Te3を基板上に堆積させる方法は、特に限定されない
が、例えば、分子線エピタキシー法を好適に用いること
ができる。このように、基板としてサファイア基板を用
いれば、該サファイア基板上に低温で堆積させた多結晶
を含むBi2Te3薄膜は、基板温度を上昇させると単結晶化
され、基板表面がＢｉ2Ｔｅ3単結晶で覆われることによ
って、一様でかつ良好なＢｉ2Ｔｅ3単結晶の成長が分子
線エピタキシー法によって可能となる。Further, in one aspect of the method for producing a Bi 2 Te 3 single crystal thin film according to the present invention, the Bi 2 Te beam is irradiated onto the substrate during the buffer growth step, so that Bi 2 Te is irradiated. This is a method of depositing 3 on the substrate. Bi
The method of depositing 2 Te 3 on the substrate is not particularly limited, but for example, the molecular beam epitaxy method can be preferably used. Thus, when a sapphire substrate is used as the substrate, the Bi 2 Te 3 thin film containing polycrystals deposited on the sapphire substrate at a low temperature is single-crystallized when the substrate temperature is raised, and the surface of the substrate is Bi 2 Te 3. By being covered with 3 single crystals, uniform and good growth of Bi 2 Te 3 single crystals is possible by the molecular beam epitaxy method.
【０００９】さらに、本発明は、前述した方法によって
製造したＢｉ2Ｔｅ3単結晶薄膜である。結晶方位が制御
されたBi2Te3単結晶膜は、微細加工によるマイクロ熱電
変換モジュールの素材としても有用である。単結晶薄膜
の成長法として一般的な分子線エピタキシー法によって
Ｂｉ2Ｔｅ3のエピタキシャル単結晶薄膜を作製できるた
め、特別な装置等を必要とせずに、簡単かつ安価なコス
トで行うことができる。Further, the present invention is a Bi 2 Te 3 single crystal thin film produced by the above-mentioned method. Bi 2 Te 3 single crystal film with controlled crystallographic orientation is also useful as a material for micro thermoelectric conversion module by microfabrication. Since a Bi 2 Te 3 epitaxial single crystal thin film can be produced by a general molecular beam epitaxy method as a method for growing a single crystal thin film, it can be performed easily and at low cost without requiring a special device or the like.
【００１０】そして、本発明は、前述したＢｉ2Ｔｅ3単
結晶薄膜を用いた熱電変換素子である。この熱電変換素
子とは、熱エネルギーと電気エネルギーを可逆的に直接
変換するものであり、ソリッドステートエアコンに用い
られるペルチェ素子、排熱エネルギーの回収に用いる熱
電発電素子、及び温度センサーなどがある。The present invention is also a thermoelectric conversion element using the above-mentioned Bi 2 Te 3 single crystal thin film. The thermoelectric conversion element reversibly directly converts thermal energy and electric energy, and includes a Peltier element used in a solid state air conditioner, a thermoelectric power generation element used to recover exhaust heat energy, and a temperature sensor.
【００１１】[0011]
【発明の実施の形態】以下に、本発明の実施の形態に係
るＢｉ2Ｔｅ3単結晶薄膜及びその製造方法について、図
面を用いて詳細に説明する。この実施の形態において
は、分子線エピタキシー法（以下、MBE法という）を用
いて、サファイア基板上にBi2Te3エピタキシャル単結晶
の薄膜を生成させる一例について説明をする。BEST MODE FOR CARRYING OUT THE INVENTION A Bi 2 Te 3 single crystal thin film according to an embodiment of the present invention and a method for manufacturing the same will be described below in detail with reference to the drawings. In this embodiment, an example of forming a thin film of Bi 2 Te 3 epitaxial single crystal on a sapphire substrate using a molecular beam epitaxy method (hereinafter referred to as MBE method) will be described.
【００１２】［分子線エピタキシー装置］本発明に用い
る分子線エピタキシー装置（以下、MBE装置という）の
構造を図１に概略的に示す。このMBE装置２０は、真空
容器１によって外部から遮断され、内部は１０-7Paの圧
力に保持されている。前記真空容器１は、排気ダクト２
を介して、ターボ分子ポンプ又はクライオポンプなどの
高真空排気手段（図示せず）に接続されており、目的生
成物であるBi2Te3薄膜を成長させるための基板３は、基
板ホルダー４に保持されている。基板ホルダー４には、
図示しない加熱手段及び温度調節機能が設けられている
ため、基板３の温度を任意の設定温度に保持することが
できる。また、Ｋセル(Knudsen Cell)７ａ，７ｂが基板
３に向けて配設されており、このＫセル内にるつぼ８
ａ，８ｂ、加熱ヒーター９ａ，９ｂ、及び開閉可能なシ
ャッター１０ａ，１０ｂが設けられている。Bi（ビスマ
ス）ソース５及びTe（テルル）ソース６は、Ｋセル７
ａ，７ｂ内のるつぼ８ａ，８ｂに充填されており、ソー
ス加熱ヒーター９ａ，９ｂで加熱されるように構成され
ている。[Molecular Beam Epitaxy Device] The structure of a molecular beam epitaxy device (hereinafter referred to as MBE device) used in the present invention is schematically shown in FIG. The MBE device 20 is shut off from the outside by the vacuum container 1, and the inside is kept at a pressure of 10 −7 Pa. The vacuum container 1 has an exhaust duct 2
The substrate 3 for growing a Bi 2 Te 3 thin film, which is a target product, is connected to a substrate holder 4 by being connected to a high vacuum evacuation means (not shown) such as a turbo molecular pump or a cryopump through the substrate holder 4. Is held. The substrate holder 4 has
Since the heating means and the temperature adjusting function (not shown) are provided, the temperature of the substrate 3 can be maintained at an arbitrary set temperature. Further, K cells (Knudsen Cell) 7a, 7b are arranged toward the substrate 3, and the crucible 8 is provided in the K cell.
a, 8b, heaters 9a, 9b, and shutters 10a, 10b that can be opened and closed are provided. Bi (bismuth) source 5 and Te (tellurium) source 6 are K cells 7
The crucibles 8a and 8b in a and 7b are filled and heated by the source heaters 9a and 9b.
【００１３】この加熱によって、高真空中で蒸発したソ
ース５，６は、分子線２２ａ，２２ｂとなり、真空容器
１中の残留ガス分子に衝突することなく基板３の表面上
に到達し、薄膜成長の材料供給源となる。そして、Ｋセ
ル７ａ，７ｂに開閉可能に配設されたシャッター１０
ａ，１０ｂを開閉制御することにより、基板３の表面に
元素を選択的に供給することができ、所望の組成材料か
らなる薄膜を成長させることができる。また、真空容器
１の上部側壁には、反射高速電子線回折(Reflection Hi
gh Energy Electron Diffraction:以下、RHEEDという)
電子銃１１ａと、該電子銃１１ａに対向してRHEEDスク
リーン１１ｂが配設されている。By this heating, the sources 5 and 6 evaporated in the high vacuum become the molecular beams 22a and 22b, reach the surface of the substrate 3 without colliding with the residual gas molecules in the vacuum container 1, and grow the thin film. It becomes the material supply source. Then, the shutter 10 arranged to be openable / closable on the K cells 7a and 7b.
By controlling the opening and closing of a and 10b, the element can be selectively supplied to the surface of the substrate 3, and a thin film made of a desired composition material can be grown. Also, on the upper side wall of the vacuum container 1, reflection high-energy electron diffraction (Reflection Hi
gh Energy Electron Diffraction: RHEED)
An electron gun 11a and a RHEED screen 11b are arranged facing the electron gun 11a.
【００１４】前記薄膜の成長は、RHEED像によって、基
板３上の成長表面を実時間で観測することができる。RH
EED電子銃１１ａから２〜３°の角度で基板３表面に電
子線２１を照射すると、RHEEDスクリーン１１ｂの裏面
に塗布された蛍光面に、成長表面の結晶構造情報を含有
した反射電子線２１が照射される。この蛍光パターンを
観察することで、基板３上で成長する結晶表面状態を知
ることができる。なお、真空容器１の上端部には、真空
容器１内部の真空度を測定する真空度測定手段１２が配
設されている。この真空度測定手段１２としては、例え
ば電離真空計などを好適に用いられる。The growth of the thin film can be observed in real time on the growth surface on the substrate 3 by the RHEED image. RH
When the front surface of the substrate 3 is irradiated with the electron beam 21 from the EED electron gun 11a at an angle of 2 to 3 °, the reflected electron beam 21 containing the crystal structure information of the growth surface is formed on the fluorescent surface coated on the back surface of the RHEED screen 11b. Is irradiated. By observing this fluorescence pattern, it is possible to know the state of the crystal surface growing on the substrate 3. A vacuum degree measuring means 12 for measuring the degree of vacuum inside the vacuum vessel 1 is provided at the upper end of the vacuum vessel 1. As the vacuum degree measuring means 12, for example, an ionization vacuum gauge or the like is preferably used.
【００１５】［基板］基板３は、前述したように、エピ
タキシャル成長させる目的生成物の結晶構造に近い単結
晶が用いられる。本発明における目的生成物Bi2Te3単結
晶は、図２に示す三方晶系に属し、ａ0＝4.3852Å，ｃ0
＝30.483Åの格子定数を有する。ｃ軸方向への結晶成長
を考えると、同じ晶系である三方晶あるいは六方晶で、
かつ、ｃ（０００１）面内の格子定数ａ0が近い材料が
基板材料として望ましい。これに加えて、材料の入手性
や表面研磨性などの物理的要因を考慮すると、サファイ
ア単結晶が三方晶で格子定数ａ0＝4.763Å，ｃ0＝13.00
3Åであり、Bi2Te3単結晶の格子定数に比較的近いａ0を
有する。しかし、サファイア単結晶とBi2Te3単結晶とに
おけるａ0の差異は、約８．６％におよぶため、両者の
ヘテロ接合界面で歪を生じることになり、良質な単結晶
を育成する上で阻害要因となる。[Substrate] As described above, the substrate 3 is a single crystal having a crystal structure close to that of the target product to be epitaxially grown. The target product Bi 2 Te 3 single crystal in the present invention belongs to the trigonal system shown in FIG. 2, and a 0 = 4.3852Å, c 0
It has a lattice constant of = 30.483Å. Considering the crystal growth in the c-axis direction, the same crystal system, trigonal or hexagonal,
In addition, a material having a lattice constant a 0 close to that in the c (0001) plane is desirable as the substrate material. In addition to this, in consideration of physical factors such as availability of materials and surface polishability, the sapphire single crystal is a trigonal crystal with lattice constants a 0 = 4.763Å, c 0 = 13.00.
3Å and has a 0 relatively close to the lattice constant of Bi 2 Te 3 single crystal. However, since the difference in a 0 between the sapphire single crystal and the Bi 2 Te 3 single crystal is about 8.6%, strain is generated at the heterojunction interface between the two, which leads to the growth of a good single crystal. It becomes an obstacle factor.
【００１６】［蒸気圧］図３に示すのは、ソース源であ
るBi,Teおよび目的生成物であるBi2Te3の蒸気圧曲線で
ある。MBE装置は、１０-7Paに設定された真空容器内の
背圧に対して、ソースを加熱することで蒸発させ、これ
によって、分子線を発生させて基板表面に材料を供給す
る装置である。また、ソース蒸気圧が１０-7Paオーダー
で、かつBi蒸気圧とTe蒸気圧の比率がBi2Te3の化学量論
組成比２：３よりややTeの比率が高い程度とする。Teの
比率を高くするのは、同一温度に対する蒸気圧はBiより
もTeの方が遙かに高く、生成されたBi2Te3からの昇華に
よるTe欠損を防ぐためである。さらに、Biソース５とTe
ソース６の温度は、好ましくは、ＴBi＝５６０℃、ＴTe
＝３２０℃である。基板表面温度は高いほうが不安定分
子が再蒸発して良質な結晶が得られやすいが、目的生成
物の蒸気圧が真空容器背圧より低くなるようにしなけれ
ばならない。したがって、Bi2Te3蒸気圧曲線から、後述
するバッファ成長I，IIにおいては、基板表面温度は約
２７０℃以下に設定しなくてはならないことがわかる。[Vapor Pressure] FIG. 3 is a vapor pressure curve of Bi, Te as a source and Bi 2 Te 3 as a target product. The MBE device is a device that evaporates by heating the source against the back pressure in the vacuum container set to 10 −7 Pa, thereby generating a molecular beam and supplying the material to the substrate surface. . The source vapor pressure is on the order of 10 −7 Pa, and the ratio of Bi vapor pressure to Te vapor pressure is slightly higher than the stoichiometric composition ratio of Bi 2 Te 3 of 2: 3. The reason for increasing the ratio of Te is that the vapor pressure at the same temperature is much higher in Te than in Bi, and Te deficiency due to sublimation from Bi 2 Te 3 produced is prevented. In addition, Bi source 5 and Te
The temperature of the source 6 is preferably T Bi = 560 ° C., T Te
= 320 ° C. The higher the surface temperature of the substrate, the easier the unstable molecules are re-evaporated to obtain good quality crystals, but the vapor pressure of the target product must be lower than the back pressure of the vacuum container. Therefore, it can be seen from the Bi 2 Te 3 vapor pressure curve that the substrate surface temperature must be set to about 270 ° C. or lower in buffer growth I and II described later.
【００１７】［本発明に係るBi2Te3単結晶薄膜の作製方
法］次いで、図４を用いて、本発明に係るBi2Te3単結晶
薄膜を成長させる手順を説明する。まず、図１に示すMB
E装置２０を用い、１０-7Pa以下の高真空雰囲気下で基
板３を温度Tb１まで加熱することによって、基板３の表
面における汚染物質を蒸発及び除去する（Pb１工程：サ
ーマルクリーニング）。次いで、基板表面の温度をTb２
となるように温度調整を行なう（Pb２工程：温度調
整）。[Method for Producing Bi 2 Te 3 Single Crystal Thin Film According to the Present Invention] Next, the procedure for growing the Bi 2 Te 3 single crystal thin film according to the present invention will be described with reference to FIG. First, the MB shown in Figure 1
By using the E device 20 and heating the substrate 3 to a temperature Tb1 in a high vacuum atmosphere of 10 −7 Pa or less, contaminants on the surface of the substrate 3 are evaporated and removed (Pb1 step: thermal cleaning). Next, the temperature of the substrate surface is set to Tb2.
The temperature is adjusted so that (Pb2 step: temperature adjustment).
【００１８】さらに、充分に時間が経過して各部の設定
温度が熱平衡状態に達したら、Biシャッター１０ａとTe
シャッター１０ｂを開き、基板表面にBi,Teソース５，
６による分子線２２ａ，２２ｂを照射してBi2Te3を成長
させ、成長時間tb３が経過した段階でBiシャッター１０
ａのみを閉じる。なお、このときの基板温度Tb2では、B
i2Te3蒸気圧が真空容器背圧よりも小さくなっている（P
b３工程：バッファ成長Ｉ）。そして、基板温度を、Bi2
Te3蒸気圧が真空容器背圧よりも大きくなるTb３まで昇
温し、Tb３に達したら速やかに加熱を停止して基板３を
温度Tb４となるよう調整する。この基板温度Tb４では、
Bi2Te3蒸気圧は真空容器背圧よりも小さくなっている
（Pb４工程：アニールＩ）。Further, when the set temperature of each part reaches a thermal equilibrium state after a sufficient time has passed, the Bi shutter 10a and the Te
The shutter 10b is opened, and Bi, Te source 5,
Bi 2 Te 3 is grown by irradiating the molecular beams 22a and 22b of 6 with the Bi shutter 10 at the stage when the growth time tb3 has passed.
Close only a. At the substrate temperature Tb2 at this time, B
i 2 Te 3 Vapor pressure is lower than vacuum container back pressure (P
Step b3: buffer growth I). Then, the substrate temperature is set to Bi 2
The temperature of the vapor of Te 3 is raised to Tb3 at which the vapor pressure of the vacuum container becomes larger than the back pressure of the vacuum container, and when Tb3 is reached, heating is immediately stopped and the temperature of the substrate 3 is adjusted to Tb4. At this substrate temperature Tb4,
The vapor pressure of Bi 2 Te 3 is smaller than the back pressure of the vacuum container (Pb 4 step: annealing I).
【００１９】ここで再びBiシャッター１０ａを開き、分
子線２２ａを基板３に照射し、時間ｔb５だけ薄膜成長
を行なったらBiシャッター１０ａを閉じる。このときの
温度Tb4においても、Bi2Te3蒸気圧は真空容器背圧より
も小さくなっている（Pb５工程：バッファ成長II）。次
いで、基板温度を、Bi2Te3蒸気圧が真空容器背圧よりも
大きくなる温度Tb５まで昇温する（Pb６工程：アニール
II）。Here, the Bi shutter 10a is opened again, the substrate 3 is irradiated with the molecular beam 22a, and after the thin film growth is performed for the time tb5, the Bi shutter 10a is closed. Even at the temperature Tb4 at this time, the vapor pressure of Bi 2 Te 3 is smaller than the back pressure of the vacuum container (Pb5 step: buffer growth II). Next, the substrate temperature is raised to a temperature Tb5 at which the vapor pressure of Bi 2 Te 3 becomes larger than the back pressure of the vacuum container (Pb6 step: annealing
II).
【００２０】そして、基板温度が、Tb５に達したら、速
やかに加熱を停止し、基板３を結晶成長温度Tb４となる
よう温度調整をすると同時に、Biシャッター１０ａを開
けて分子線２２ａを照射し、所望の膜厚が得られる結晶
成長時間tb７だけBi2Te3結晶を成長させる（Pb７工程：
結晶成長）。最後に、結晶成長を終えた後に、Biシャッ
ター１０ａとTeシャッター１０ｂを閉じて基板３上に成
長した試料を徐冷して成長プロセスが終了する（Pb８工
程：徐冷）。When the substrate temperature reaches Tb5, the heating is immediately stopped, the temperature of the substrate 3 is adjusted to the crystal growth temperature Tb4, and at the same time, the Bi shutter 10a is opened and the molecular beam 22a is irradiated. The Bi 2 Te 3 crystal is grown for a crystal growth time tb7 that gives a desired film thickness (Pb7 step:
Crystal growth). Finally, after the crystal growth is completed, the Bi shutter 10a and the Te shutter 10b are closed to gradually cool the sample grown on the substrate 3 and the growth process ends (Pb8 step: slow cooling).
【００２１】Pb３工程からPb７工程までTeシャッター１
０ｂを開状態とし、アニール時にはBiとTeの蒸気圧の差
から基板３上に成長したBi2Te3のTe欠損が生じるのを防
止する。Teの蒸気圧は充分に高いため、基板温度Tb2〜T
b5の範囲内で基板３上にTe単相の結晶成長が進行するこ
とはない。Te shutter 1 from Pb3 process to Pb7 process
0b is opened to prevent Te deficiency of Bi 2 Te 3 grown on the substrate 3 from occurring due to the difference in vapor pressure between Bi and Te during annealing. Since the vapor pressure of Te is sufficiently high, the substrate temperature Tb2 ~ T
Within the range of b5, the Te single phase crystal growth does not proceed on the substrate 3.
【００２２】本発明の実施の形態に係る方法により成長
させたBi2Te3単結晶薄膜試料のＸ線回折結果は、図５に
示すとおりである。Ｘ線回折のピークについては、４
１．６８°がサファイア基板の（０００６）面、４４．
６２°がBi2Te3の（０００１５）面、５４．３５°がBi
2Te3の（０００１８）面に相当する。サファイアおよび
Bi2Te3のｃ面以外の回折ピークは観測されていないた
め、サファイア基板表面のｃ（０００１）面上に、Bi2T
e3のｃ軸が基板面と垂直な方向に単結晶成長しているこ
とが確認できる。The X-ray diffraction results of the Bi 2 Te 3 single crystal thin film sample grown by the method according to the embodiment of the present invention are shown in FIG. For the X-ray diffraction peak, 4
1.68 ° is the (0006) plane of the sapphire substrate, 44.
62 ° is Bi 2 Te 3 (000 15 ) plane and 54.35 ° is Bi
This corresponds to the (000 18 ) plane of 2 Te 3 . Sapphire and
Since no diffraction peaks other than the c-plane of Bi 2 Te 3 were observed, Bi 2 T 3 was not observed on the c (0001) plane of the sapphire substrate surface.
It can be confirmed that the single crystal has grown in a direction in which the c-axis of e 3 is perpendicular to the substrate surface.
【００２３】［Bi2Te3単結晶の成長過程］図６〜図９
は、本発明に係る成長プロセスによるBi2Te3単結晶の成
長過程を模式的に示したものである。図６に示すよう
に、サファイア基板３にBi分子線２２ａとTe分子線２２
ｂを照射すると、基板３の表面でBi2Te3３０が生成され
て堆積していく。このとき、図７に示すように、サファ
イア３１とBi2Te3３０は結晶格子定数が大きく異なるた
め、両者の界面に生じる歪を吸収しきれず、多くの結晶
核が島状構造３２を形成したり、基板の結晶構造を反映
せずランダムな方向に結晶が配向している多結晶３３と
なる。図８に示すように、Bi2Te3蒸気圧が真空容器背圧
よりも大きくなるように基板表面を昇温させると、島状
構造３２や多結晶３３などを構成する不安定分子は、基
板３の表面から再蒸発し、また格子欠陥が埋まっていく
ために、Bi2Te3単結晶３０がサファイア基板３の表面を
覆う。一旦、基板３の表面がBi2Te3単結晶３０で覆われ
ると、図９に示すように、Bi2Te3蒸気圧が真空容器背圧
よりも小さくなる基板温度になっても、基板３とBi2Te3
単結晶３０との間に、格子定数の不整合が無くなったも
のと同等の状態になる。このため、Bi2Te3単結晶３０の
表面に更にBi分子線２２ａとTe分子線２２ｂを照射する
と、Bi2Te3単結晶の成長が持続的に進む。[Growth Process of Bi 2 Te 3 Single Crystal] FIGS. 6 to 9
FIG. 3 schematically shows the growth process of Bi 2 Te 3 single crystal by the growth process according to the present invention. As shown in FIG. 6, the Bi molecular beam 22a and the Te molecular beam 22 are formed on the sapphire substrate 3.
When b is irradiated, Bi 2 Te 3 30 is generated and deposited on the surface of the substrate 3. At this time, as shown in FIG. 7, since the crystal lattice constants of sapphire 31 and Bi 2 Te 3 30 are significantly different, the strain generated at the interface between them cannot be absorbed completely, and many crystal nuclei form the island structure 32. Alternatively, the polycrystal 33 has crystals oriented in random directions without reflecting the crystal structure of the substrate. As shown in FIG. 8, when the surface of the substrate is heated so that the vapor pressure of Bi 2 Te 3 becomes larger than the back pressure of the vacuum vessel, unstable molecules constituting the island-shaped structure 32, the polycrystal 33, etc. The surface of No. 3 is re-evaporated and the lattice defects are filled, so that the Bi 2 Te 3 single crystal 30 covers the surface of the sapphire substrate 3. Once the surface of the substrate 3 is covered with the Bi 2 Te 3 single crystal 30, as shown in FIG. 9, even if the substrate temperature at which the Bi 2 Te 3 vapor pressure becomes lower than the vacuum container back pressure is reached, the substrate 3 And Bi 2 Te 3
The state is the same as that in which there is no lattice constant mismatch with the single crystal 30. Therefore, when the surface of the Bi 2 Te 3 single crystal 30 is further irradiated with the Bi molecular beam 22a and the Te molecular beam 22b, the growth of the Bi 2 Te 3 single crystal proceeds continuously.
【００２４】このように、本発明によれば、サファイア
基板３上に低温で堆積した多結晶を含むBi2Te3薄膜は、
基板３を昇温することにより単結晶化され、基板表面が
Bi2Te3単結晶で覆われることで、MBE法を用いて一様で
良好なBi2Te3エピタキシャル単結晶成長が可能になる。As described above, according to the present invention, the Bi 2 Te 3 thin film containing polycrystalline deposited on the sapphire substrate 3 at a low temperature is
By raising the temperature of the substrate 3, the single crystal is formed, and the substrate surface is
By covered by Bi 2 Te 3 single crystal, it is possible to uniform and favorable Bi 2 Te 3 epitaxial single crystal grown by the MBE method.
【００２５】[0025]
【実施例】次いで、実施例によって本発明を具体的に説
明する。EXAMPLES Next, the present invention will be specifically described by way of examples.
【００２６】［本発明例］まず、図４に示すように、１
０-7Pa以下の高真空雰囲気下において、基板３を温度Tb
１（７００℃）まで加熱して、基板３の表面の汚染物質
を蒸発及び除去した（Pb１工程）。次いで、基板３を温
度Tb２（１７０℃）となるまで温度調整を行なった（Pb
２工程）。そして、各部の設定温度が熱平衡状態に達し
たら、基板３の表面にBi,Te各ソース分子線２２ａ，２
２ｂを照射するため、Biシャッター１０ａとTeシャッタ
ー１０ｂを開いてBi2Te3３０を成長させ、成長時間tb３
（３０秒間）が経過した段階でBiシャッター１０ａを閉
じた（Pb３工程）。[Invention Example] First, as shown in FIG.
The substrate 3 is heated to a temperature Tb in a high vacuum atmosphere of 0 -7 Pa or less.
By heating to 1 (700 ° C.), contaminants on the surface of the substrate 3 were evaporated and removed (Pb1 step). Next, the temperature of the substrate 3 was adjusted to the temperature Tb2 (170 ° C.) (Pb
2 steps). Then, when the set temperature of each part reaches a thermal equilibrium state, Bi, Te source molecular beams 22a, 2
In order to irradiate 2b, Bi shutter 10a and Te shutter 10b are opened to grow Bi 2 Te 3 30, and the growth time tb 3
When (30 seconds) has elapsed, the Bi shutter 10a was closed (Pb3 step).
【００２７】さらに、基板温度を、Bi2Te3蒸気圧が真空
容器背圧よりも大きくなるTb３（３４５℃）まで昇温
し、この３４５℃に達したら速やかに加熱を停止して基
板３を温度Tb４（２５５℃）となるよう調整した。な
お、基板温度Tb４では、Bi2Te3蒸気圧は真空容器背圧よ
りも小さくなった（Pb４工程）。そして、再びBiシャッ
ター２２ａを開き、時間ｔb５（５分間）だけ薄膜の成
長を行なったのちBiシャッター１０ａを閉じた（Pb５工
程）。Further, the substrate temperature is raised to Tb3 (345 ° C.) at which the vapor pressure of Bi 2 Te 3 becomes larger than the back pressure of the vacuum container, and when the temperature reaches 345 ° C., the heating is immediately stopped and the substrate 3 is heated. The temperature was adjusted to Tb4 (255 ° C). At the substrate temperature Tb4, the vapor pressure of Bi 2 Te 3 became smaller than the back pressure of the vacuum container (Pb4 step). Then, the Bi shutter 22a was opened again, the thin film was grown for the time tb5 (5 minutes), and then the Bi shutter 10a was closed (Pb5 step).
【００２８】次いで、基板温度を、Bi2Te3蒸気圧が真空
容器背圧よりも大きくなるTb５（４０５℃）まで昇温し
た（Pb６工程）。この４０５℃に達したら、速やかに加
熱を停止して基板３を結晶成長温度Tb４（２５５℃）と
なるよう調整すると同時に、Biシャッター１０ａを開け
て、所望の膜厚が得られる結晶成長時間Tb７のBi2Te3結
晶成長を行った（Pb７工程）。最後に、結晶成長を終え
た後に、Bi,Teシャッター１０ａ，１０ｂを閉じて基板
３上に成長した試料を徐冷して成長プロセスを終了させ
た（Pb８工程）。Pb３工程からPb７工程までTeシャッタ
ー１０ｂは開状態で、アニール時にはBiとTeの蒸気圧の
差から基板３上に成長したBi2Te3３０のTe欠損が生じる
のを防止した。Teの蒸気圧は充分に高いため、基板温度
Tb2〜Tb5で基板３上にTe単相の結晶成長が進行すること
はなかった。Then, the substrate temperature was raised to Tb5 (405 ° C.) at which the vapor pressure of Bi 2 Te 3 was larger than the back pressure of the vacuum vessel (Pb6 step). When the temperature reaches 405 ° C., the heating is immediately stopped to adjust the substrate 3 to the crystal growth temperature Tb4 (255 ° C.), and at the same time, the Bi shutter 10a is opened to obtain the crystal growth time Tb7. Bi 2 Te 3 crystal growth was performed (Pb7 step). Finally, after the crystal growth was completed, the Bi, Te shutters 10a, 10b were closed, and the sample grown on the substrate 3 was gradually cooled to complete the growth process (Pb8 step). From the Pb3 process to the Pb7 process, the Te shutter 10b was in an open state, and during annealing, the Te deficiency of Bi 2 Te 3 30 grown on the substrate 3 was prevented from occurring due to the difference in vapor pressure between Bi and Te. Since the vapor pressure of Te is high enough, the substrate temperature
Crystal growth of the Te single phase did not proceed on the substrate 3 at Tb2 to Tb5.
【００２９】図１０〜図１３は、本発明例による方法で
Bi2Te3単結晶膜を成長させた場合の、各段階におけるRH
EED写真である。バッファ成長Ｉ（Pb３工程）の終了段
階では、図１０に示すように、スポットパターンと同心
円状パターンが混じっており、島状構造を有する単結晶
と多結晶とが混在している。また、図１１に示すよう
に、アニールＩ（Pb４工程）においては、RHEEDパター
ンに縦縞のストリークパターンが現れたが、このパター
ンは、成長試料の表面が原子レベルで平坦な単結晶とな
ったことを示している。図１２に示すように、アニール
II（Pb５工程）後には、さらに明瞭なストリークパター
ンが得られ、良好な単結晶成長が進んだことが判る。一
旦、成長試料表面がBi2Te3３０の平坦な単結晶に覆われ
ると、図１３の結晶成長（PB７工程）終了後におけるRH
EED写真が示すように、ストリークパターンが保持され
ており、表面が平坦なBi2Te3単結晶薄膜が得られたこと
が判る。10 to 13 show a method according to an example of the present invention.
RH at each stage when growing Bi 2 Te 3 single crystal film
EED photo. At the end stage of the buffer growth I (Pb3 step), as shown in FIG. 10, the spot pattern and the concentric pattern are mixed, and the single crystal having the island structure and the polycrystal are mixed. Further, as shown in FIG. 11, in the annealing I (Pb4 step), a streak pattern of vertical stripes appeared in the RHEED pattern, but this pattern was that the surface of the grown sample was a flat single crystal at the atomic level. Is shown. As shown in FIG. 12, annealing
After II (Pb5 step), a clearer streak pattern was obtained, indicating that good single crystal growth proceeded. Once the surface of the grown sample is covered with the flat single crystal of Bi 2 Te 3 30, the RH after the crystal growth (PB7 step) of FIG. 13 is completed.
As shown in the EED photograph, it was found that the streak pattern was retained and a Bi 2 Te 3 single crystal thin film having a flat surface was obtained.
【００３０】図５は、本発明例により成長させたBi2Te3
単結晶薄膜試料のＸ線回折結果を示すグラフである。Ｘ
線回折ピークは、４１．６８°がサファイア基板の（０
００６）面、４４．６２°がBi2Te3の（０００１５）
面、５４．３５°がBi2Te3の（０００１８）面に相当す
る。サファイアおよびBi2Te3のｃ面以外の回折ピークは
観測されておらず、サファイア基板表面のｃ（０００
１）面上に、Bi2Te3のｃ軸が基板面と垂直な方向に単結
晶成長していることが確認できた。FIG. 5 shows Bi 2 Te 3 grown according to the present invention.
It is a graph which shows the X-ray-diffraction result of a single crystal thin film sample. X
The line diffraction peak of 41.68 ° is (0
006) plane, 44.62 ° is (000 15 ) of Bi 2 Te 3
The 54.35 ° plane corresponds to the (000 18 ) plane of Bi 2 Te 3 . No diffraction peaks other than the c-plane of sapphire and Bi 2 Te 3 were observed, and the c (000
It was confirmed that single crystals were grown on the 1) plane in a direction in which the c-axis of Bi 2 Te 3 was perpendicular to the substrate surface.
【００３１】［比較例］以上説明した本発明例と比較す
るために、比較例として、従来のMBE法によるBi2Te3成
長プロセスを行った。図１４は、この比較例の成長プロ
セスの手順を概略的に示すグラフである。まず、１０-7
Pa以下の高真空雰囲気下で、基板３を温度Ta1（７００
℃）まで加熱して、基板表面の汚染物質を蒸発及び除去
し（Pa1工程：サーマルクリーニング）、基板３を結晶
成長温度Ta2（２５５℃）となるように温度調整を行な
った（Pa2工程）。次いで、充分に時間が経過して、各
部の設定温度が熱平衡状態に達したら、基板表面にBi,T
e各ソース分子線２２ａ，２２ｂを照射するため、Biシ
ャッター１０ａとTeシャッター１０ｂを開いて、成長時
間ta３だけBi2Te3３０を基板３の表面に成長させた（Pa
３工程：結晶成長）。結晶成長後に各シャッター１０
ａ，１０ｂを閉じ、基板３上に成長させた試料を徐冷し
た（Pa４工程）。[Comparative Example] In order to compare with the example of the present invention described above, a Bi 2 Te 3 growth process by the conventional MBE method was performed as a comparative example. FIG. 14 is a graph schematically showing the procedure of the growth process of this comparative example. First, 10 -7
In a high vacuum atmosphere of Pa or less, the substrate 3 is heated to the temperature Ta1 (700
C.) to evaporate and remove contaminants on the surface of the substrate (Pa1 step: thermal cleaning), and the temperature of the substrate 3 was adjusted to the crystal growth temperature Ta2 (255 ° C.) (Pa2 step). Then, when the set temperature of each part reaches a thermal equilibrium state after sufficient time has passed, Bi, T
e In order to irradiate each source molecular beam 22a, 22b, Bi shutter 10a and Te shutter 10b are opened, and Bi 2 Te 3 30 is grown on the surface of substrate 3 for growth time ta3 (Pa
3 steps: crystal growth). After each crystal growth, each shutter 10
After closing a and 10b, the sample grown on the substrate 3 was gradually cooled (Pa4 step).
【００３２】また、Bi2Te3の成長条件は、ソース温度が
ＴBi＝５６０℃，ＴTe＝３２０℃であり、基板表面温度
がTa２＝２５５℃である。この条件下で、成長時間ta３
＝３０secだけ、サファイア単結晶の格子面（０００
１）面上に成長させたものである。The growth conditions for Bi 2 Te 3 are that the source temperature is T Bi = 560 ° C., T Te = 320 ° C., and the substrate surface temperature is Ta 2 = 255 ° C. Under this condition, the growth time ta3
= 30 sec, the lattice plane of sapphire single crystal (000
1) It was grown on the surface.
【００３３】図１５は、従来のMBE成長プロセスにより
成長させたBi2Te3の表面をRHEEDで観察した写真であ
る。RHEEDパターンは整列したスポットパターンと同心
円状パターンが混在しており、成長試料の表面に、ある
程度結晶方位が揃った島状構造の単結晶と、ランダムな
方向を向いた多結晶とが混在した状態となっていること
がわかる。このように、従来のMBE成長プロセスにおい
ては、サファイアとBi2Te3の格子定数が大きく相違して
いるため、良質なBi2Te3単結晶膜を得るのは困難であっ
た。FIG. 15 is a photograph of the surface of Bi 2 Te 3 grown by the conventional MBE growth process, observed by RHEED. The RHEED pattern is a mixture of aligned spot patterns and concentric patterns, and a state in which a single crystal with an island-like structure in which the crystal orientation is aligned to some extent and polycrystals oriented in random directions are mixed on the surface of the growth sample. You can see that. As described above, in the conventional MBE growth process, it is difficult to obtain a good quality Bi 2 Te 3 single crystal film because the lattice constants of sapphire and Bi 2 Te 3 are significantly different.
【００３４】[0034]
【発明の効果】本発明によれば、一般的な分子線エピタ
キシー法を用いて、Ｂｉ2Ｔｅ3のエピタキシャル単結晶
薄膜を簡単でかつ安価なコストで作製することができ
る。According to the present invention, an epitaxial single crystal thin film of Bi 2 Te 3 can be easily manufactured at a low cost by using a general molecular beam epitaxy method.
【図１】本発明に係るＢｉ2Ｔｅ3単結晶薄膜の作製に用
いる分子線エピタキシー装置を示す断面図である。FIG. 1 is a cross-sectional view showing a molecular beam epitaxy apparatus used for producing a Bi 2 Te 3 single crystal thin film according to the present invention.
【図２】三方系晶の結晶構造を示す概念図である。FIG. 2 is a conceptual diagram showing a crystal structure of a trigonal system crystal.
【図３】本発明に係る単結晶薄膜の作製に用いるＢｉ，
Ｔｅ及びＢｉ2Ｔｅ3の蒸気圧曲線である。FIG. 3 shows Bi, which is used for producing a single crystal thin film according to the present invention.
3 is a vapor pressure curve of Te and Bi 2 Te 3 .
【図４】本発明に係るＢｉ2Ｔｅ3エピタキシャル単結晶
薄膜の工程を示す概念図である。FIG. 4 is a conceptual diagram showing a process of a Bi 2 Te 3 epitaxial single crystal thin film according to the present invention.
【図５】本発明に係るＢｉ2Ｔｅ3単結晶薄膜のＸ線回折
結果を示すグラフである。FIG. 5 is a graph showing an X-ray diffraction result of a Bi 2 Te 3 single crystal thin film according to the present invention.
【図６】本発明に係るＢｉ2Ｔｅ3単結晶の成長過程にお
いて、単結晶の成長開始時の状態を示す概念図である。FIG. 6 is a conceptual diagram showing a state at the start of growth of a single crystal in the growth process of the Bi 2 Te 3 single crystal according to the present invention.
【図７】本発明に係るＢｉ2Ｔｅ3単結晶の成長過程にお
いて、単結晶の成長核及び多結晶が成長した状態を示す
概念図である。FIG. 7 is a conceptual diagram showing a state in which a growth nucleus of a single crystal and a polycrystal are grown in the growth process of the Bi 2 Te 3 single crystal according to the present invention.
【図８】本発明に係るＢｉ2Ｔｅ3単結晶の成長過程にお
いて、アニーリングによる単結晶化が起こった状態を示
す概念図である。FIG. 8 is a conceptual diagram showing a state in which single crystallization by annealing has occurred in the growth process of the Bi 2 Te 3 single crystal according to the present invention.
【図９】本発明に係るＢｉ2Ｔｅ3単結晶の成長過程にお
いて、単結晶が成長した状態を示す概念図である。FIG. 9 is a conceptual diagram showing a state in which a single crystal has grown in the growth process of the Bi 2 Te 3 single crystal according to the present invention.
【図１０】実施例中の本発明例において、Ｐｂ３工程の
終了段階におけるＢｉ2Ｔｅ3単結晶のＲＨＥＥＤ写真で
ある。FIG. 10 is a RHEED photograph of a Bi 2 Te 3 single crystal at the end stage of the Pb3 process in the example of the present invention in Examples.
【図１１】実施例中の本発明例において、Ｐｂ４工程に
おけるＢｉ2Ｔｅ3単結晶のＲＨＥＥＤ写真である。FIG. 11 is a RHEED photograph of a Bi 2 Te 3 single crystal in the Pb4 step in the example of the present invention in Examples.
【図１２】実施例中の本発明例において、Ｐｂ５工程後
におけるＢｉ2Ｔｅ3単結晶のＲＨＥＥＤ写真である。FIG. 12 is a RHEED photograph of the Bi 2 Te 3 single crystal after the Pb5 step in the example of the present invention in Examples.
【図１３】実施例中の本発明例において、Ｐｂ７工程後
におけるＢｉ2Ｔｅ3単結晶のＲＨＥＥＤ写真である。FIG. 13 is a RHEED photograph of the Bi 2 Te 3 single crystal after the Pb7 step in the example of the present invention in Examples.
【図１４】実施例中の比較例における分子線エピタキシ
ー法の工程を示す概念図である。FIG. 14 is a conceptual diagram showing a step of a molecular beam epitaxy method in a comparative example in the examples.
【図１５】実施例中の比較例において、従来のMBE成長
プロセスにより成長中のＢｉ2Ｔｅ 3単結晶表面のＲＨＥ
ＥＤ写真である。FIG. 15 shows the conventional MBE growth in the comparative example of the examples.
Bi growing by process2Te 3RHE of single crystal surface
It is an ED photograph.
１ 真空容器 ２ 排気ダクト ３ 基板 ４ 基板ホルダー ５ Ｂｉソース ６ Ｔｅソース ７ａ，７ｂ Ｋセル ８ａ，８ｂ るつぼ ９ａ，９ｂ ソース加熱ヒーター １０ａ Ｂｉシャッター １０ｂ Ｔｅシャッター １１ａ ＲＨＥＥＤ電子銃 １１ｂ ＲＨＥＥＤスクリーン １２ 真空度測定手段 ２０ 分子線エピタキシー装置 ２２ａ Ｂｉ分子線 ２２ｂ Ｔｅ分子線 ３０ Ｂｉ2Ｔｅ3 ３１ サファイア ３２ 島状構造 ３３ 多結晶DESCRIPTION OF SYMBOLS 1 vacuum container 2 exhaust duct 3 substrate 4 substrate holder 5 Bi source 6 Te source 7a, 7b K cell 8a, 8b crucible 9a, 9b source heating heater 10a Bi shutter 10b Te shutter 11a RHEED electron gun 11b RHEED screen 12 vacuum degree measuring means 20 molecular beam epitaxy apparatus 22a Bi molecular beam 22b Te molecular beam 30 Bi 2 Te 3 31 sapphire 32 islands 33 polycrystalline
───────────────────────────────────────────────────── フロントページの続き (72)発明者 上村 税男 静岡県沼津市西野317 学校法人 東海大 学 開発工学部素材工学科内 Ｆターム(参考） 4G077 AA03 BE26 DA05 EA02 EA05 ED06 EF03 HA20 SC03 5F103 AA04 BB04 BB16 BB55 DD30 GG01 HH04 LL20 NN01 NN04 PP02 PP03 RR08 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Takuo Uemura 317 Nishino, Numazu City, Shizuoka Prefecture Tokai University Faculty of Development Engineering, Department of Materials Engineering F-term (reference) 4G077 AA03 BE26 DA05 EA02 EA05 ED06 EF03 HA20 SC03 5F103 AA04 BB04 BB16 BB55 DD30 GG01 HH04 LL20 NN01 NN04 PP02 PP03 RR08
Claims (4)
2Te3エピタキシャル単結晶を成長させる方法であって、 Bi2Te3蒸気圧が前記容器内の圧力よりも小さくなる基板
温度で、Bi2Te3を基板上に堆積させるバッファ成長段階
と、Bi2Te3蒸気圧が前記容器内の圧力よりも大きくなる
温度まで前記基板温度を上げたのち、更に、Bi2Te3蒸気
圧が前記容器内の圧力よりも小さくなる温度まで前記基
板温度を下げるアニール段階とを含んでなるＢｉ2Ｔｅ3
単結晶薄膜の製造方法。1. Bi on a substrate placed in a closed container
A method for growing a 2 Te 3 epitaxial single crystal, comprising a buffer growth step of depositing Bi 2 Te 3 on a substrate at a substrate temperature at which the vapor pressure of Bi 2 Te 3 becomes smaller than the pressure in the container, and a Bi growing step. After increasing the substrate temperature to a temperature at which the vapor pressure of 2 Te 3 is larger than the pressure inside the container, further lowering the substrate temperature to a temperature at which the vapor pressure of Bi 2 Te 3 becomes smaller than the pressure inside the container. Bi 2 Te 3 comprising an annealing step
Method for manufacturing single crystal thin film.
子線及びTe 分子線を前記基板上に照射することによ
り、Bi2Te3を基板上に堆積させることを特徴とする請求
項１に記載のＢｉ2Ｔｅ3単結晶薄膜の製造方法。2. The Bi 2 Te 3 is deposited on the substrate by irradiating the substrate with a Bi 2 molecular beam and a Te 2 molecular beam in the buffer growth step. 2 Te 3 Single crystal thin film manufacturing method.
よって製造したことを特徴とするＢｉ2Ｔｅ3単結晶薄
膜。3. A Bi 2 Te 3 single crystal thin film produced by the method according to claim 1 or 2.
結晶薄膜を用いたことを特徴とする熱電変換素子。4. A thermoelectric conversion element comprising the Bi 2 Te 3 single crystal thin film according to claim 3.
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|---|---|---|---|
| JP2001300486A JP2003109975A (en) | 2001-09-28 | 2001-09-28 | Bi2Te3 SINGLE-CRYSTAL THIN FILM AND METHOD OF MANUFACTURING THE SAME |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101091973B1 (en) * | 2010-08-17 | 2011-12-08 | 한국표준과학연구원 | Forming method of thermoelctric thin film and manufacturing apparatus of thermoelctric thin film |
| CN104818523A (en) * | 2015-05-01 | 2015-08-05 | 河南鸿昌电子有限公司 | Crystal pulling method for crystal bar |
| CN106399937A (en) * | 2016-06-17 | 2017-02-15 | 中国科学院电工研究所 | Method for preparing preferred-orientation bismuth telluride thermoelectric thin film |
| CN114457415A (en) * | 2022-01-25 | 2022-05-10 | 哈尔滨理工大学 | PLEES preparation system of laser pulse enhanced molecular beam epitaxy system |
-
2001
- 2001-09-28 JP JP2001300486A patent/JP2003109975A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101091973B1 (en) * | 2010-08-17 | 2011-12-08 | 한국표준과학연구원 | Forming method of thermoelctric thin film and manufacturing apparatus of thermoelctric thin film |
| CN104818523A (en) * | 2015-05-01 | 2015-08-05 | 河南鸿昌电子有限公司 | Crystal pulling method for crystal bar |
| CN106399937A (en) * | 2016-06-17 | 2017-02-15 | 中国科学院电工研究所 | Method for preparing preferred-orientation bismuth telluride thermoelectric thin film |
| CN106399937B (en) * | 2016-06-17 | 2018-07-27 | 中国科学院电工研究所 | A method of preparing preferred orientation bismuth telluride thermal electric film |
| CN114457415A (en) * | 2022-01-25 | 2022-05-10 | 哈尔滨理工大学 | PLEES preparation system of laser pulse enhanced molecular beam epitaxy system |
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