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1.
用激光分子束外延技术在SrTiO3(001)衬底上外延生长了高质量的BaTiO3< /sub>薄膜,薄膜的生长过程由反射式高能电子衍射仪(RHEED)原位实时监测,表明薄膜具有 二维层状生长模式.薄膜的晶体结构和表面形貌分别由X射线衍射和原子力显微镜表征,显示 该薄膜为完全c轴取向四方相晶体结构,其表面具有原子尺度光滑性.采用角分辨X射线光电 子谱技术(ARXPS),研究了BaTiO3薄膜表面最顶层原子种类和排列状况.结果表 明,BaTiO3
关键词:
激光分子束外延
3薄膜')" href="#">氧化物BaTiO3薄膜
最顶层表面
角分辨X射线光电子谱 相似文献
2.
利用扫描隧道显微镜(STM)系统地研究了C60薄膜在GaAs(001)表面的异质外延生长.在GaAs(001)2×4-β相表面,观察到C60薄膜以非密排面进行生长,并在生长中有结构相变产生.实验数据表明,薄膜下层面心立方(fcc)的晶格常数比C60晶体的晶格常数要大13%;而薄膜的表层结构则展示了非理想的六角密堆(hcp)结构,其表面为hcp(1100)面,生长过程是非理想的层状生长模式.在GaAs(001)-c(4×4)衬底上,C60薄膜的表面仍然是fcc(111)面,其结构参数与C60晶体一致,但C60薄膜采用了三维模式进行生长
关键词: 相似文献
3.
以反射式高能电子衍射(RHEED)作为实时监测工具,根据GaAs(100)表面重构相与衬底温度、As4等效束流压强之间的关系,对分子束外延(MBE)系统中衬底测温系统进行了校准,这种方法也适用于其他的MBE系统.为生长高质量的外延薄膜材料、研究InGaAs表面粗糙化及相变等过程提供了实验依据.
关键词:
分子束外延
反射式高能电子衍射
表面重构
温度校准 相似文献
4.
研究了在MBE系统中,GaAs(001)表面的氮化过程。GaAs(001)表面直接和间接地暴露在等离子体激发的N2气流下。两种氮化过程显示了完全不同的表面氮化结果。在打开N2发生器挡板的情况下,氮化导致GaAs(001)表面损伤,并且形成多晶结构。当增加N2气压时,损伤变得更严重。但是,在关闭N2发生器挡板的情况下,在500℃下,经过氮化将观察到(3×3)再构的RHEED花样,表面仍保持原子级的平整度。上述结果表明,不开N2发生器挡板,低温(500℃下)氮化将在GaN外延生长之前形成平整的薄层c-GaN。 相似文献
5.
6.
7.
利用脉冲激光制膜法,在多种衬底和温度条件下,系统研究了La0.5Sr0.5CoO3(LSCO)薄膜的结构和外延生长特性,在LaAlO3,SrTiO3和MgO衬底上实现了LSCO薄膜的外延生长.外延生长的薄膜具有低的电阻率和金属性导电特征.研究表明,外延生长的最佳温度范围为700—800℃,最佳衬底为LaAlO3.并着重探讨了衬底材料和淀积温度等多种因素对LSCO薄膜的生长与性
关键词: 相似文献
8.
采用分子束外延(MBE)方法, 调节生长温度、Ⅴ/Ⅲ束流比等参数在(001)GaAs衬底上生长了InAs/GaInSb超晶格薄膜.结果表明:InAs/GaInSb超晶格薄膜的最佳生长温度在385~395 ℃, Ⅴ/Ⅲ束流比为5.7 :1~8.7 :1.高能电子衍射仪(RHEED)原位观测到清晰的GaAs层(4×2)、GaSb层(1×3)和InAs层(1×2)再构衍射条纹.获得的超晶格薄膜结构质量较好.随着温度的升高, 材料的载流子浓度和迁移率均上升. 相似文献
9.
利用室温下压电调制反射光(PzR)谱技术系统测量了N掺杂浓度为0.0%—3%的分子束外延生长GaNxAs1-x薄膜,并对图谱中所观察的光学跃迁进行了指认.在GaN0.005As0.995和GaN0.01As0.99薄膜的PzR谱中观察到此前只在椭圆偏振谱中才看到的N掺杂相关能态E1+Δ1+ΔN.当N掺杂浓度达到
关键词:
压电调制反射光谱(PzR)
xAs1-x薄膜')" href="#">GaNxAs1-x薄膜
分子束外延(MBE) 相似文献
10.
LaTiO3 是一种典型的强关联电子材料, 其(110) 薄膜为通过晶格对称性、应变等的设计调控外延结构的物理性质提供了新的机会. 本文研究了SrTiO3(110) 衬底表面金属La 和Ti 沉积所引起的微观结构变化, 进而利用电子衍射信号对分子束外延薄膜生长表面阳离子浓度的灵敏响应, 发展了原位、实时、精确控制金属蒸发源沉积速率的方法, 实现了高质量LaTiO3(110) 薄膜的生长和对阳离子化学配比的精确控制. 由于LaTiO3中Ti3+ 3d 电子的库仑排斥作用, 氧原子层截止的(110) 表面更容易实现极性补偿, 因此生长得到的薄膜表面暴露出单一类型的氧截止面. 相似文献
11.
Jie Li Wei Peng Ke Chen Ping Wang HaiFeng Chu YingFei Chen DongNing Zheng 《中国科学:物理学 力学 天文学(英文版)》2013,56(12):2312-2326
Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction (RHEED), which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition (PLD) systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned La2/3Ca1/3MnO3 thin films and ReTiO3+δ/2 (Re = La, Nd; δ = 0 ~ 1) A n B n O3n+2 structures, on YSZ-buffered ‘Silicon on Insulator’ and LaAlO3 substrates, respectively, as well as the study of the initial structure and growth dynamics of YBa2Cu3O7?δ thin films on SrTiO3 substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process. 相似文献
12.
《Applied Surface Science》2001,169(1-2):47-51
Epitaxial anatase TiO2 thin films were successfully grown on (0 0 1) SrTiO3 substrates by the laser molecular-beam epitaxy (laser-MBE) method. The whole growth process is monitored by in situ reflection high-energy electron diffraction (RHEED). RHEED monitoring shows a transition from a streaky pattern to a spot pattern during deposition, indicating different growth modes of TiO2 film. The RHEED patterns are in consistent with the RHEED intensity oscillation results. The atomic force microscopy (AFM) and X-ray diffraction (XRD) investigation show that the thin films have single crystalline orientation with roughness less than three unit cells. 相似文献
13.
We have designed a compact combinatorial pulsed laser deposition (PLD) chamber as a building block of a desktop laboratory for advanced materials research. Development of small-size systems for the growth and characterization of films would greatly help in interconnecting a variety of analytical tools for rapid screening of advanced materials. This PLD chamber has four special features: (1) a drum-shaped growth chamber, (2) a waterwheel-like combinatorial masking system, (3) a multi-target system having one feedthrough, and (4) a small reflection high-energy electron diffraction (RHEED) system. The performance of this system is demonstrated by the RHEED intensity oscillation during homoepitaxial growth of SrTiO3 as well as by simultaneous fabrication of a ternary phase diagram of rare earth-doped Y2O3 phosphors. 相似文献
14.
《Surface science》1997,370(1):L158-L162
We have studied the structure of a stable vicinal SrTiO3(001) surface by UHV scanning tunneling microscopy. We find that the regular nanoscale step structure on the vicinal surface strongly influences the growth of c-axis-orientedYBa2Cu3O7 − δ (YBCO) thin films. It generates an almost periodic surface structure of the YBCO films. This substrate-mediated control of the film growth is particularly important, because the resultant YBCO microstructure leads to an in-plane anisotropy of the transport properties in the high-temperature superconducting material. 相似文献
15.
我们自行研制了具有三级差分气路可以在高气压下工作的RHEED系统(High-pressure RHEED),并利用本系统实时监测了(001)SrTiO3基片上SrTiO3:Nb、Ba0.5Sr0.5TiO3、YBa2Cu3O7单层薄膜,及Ba0.5Sr0.5TiO3/SrTiO3:Nb双层膜的生长过程.研究结果表明当镀膜室氧压高达21Pa时该系统仍然可以正常工作,并且能够获取较清晰的衍射图样.通过分析衍射图样我们发现,所有这些薄膜都是外延生长且晶体质量良好,但薄膜生长模式及表面平整度受沉积条件影响较大.在真空下薄膜基本上以层状模式生长,具备纳米级光滑的表面,且其表面平整度并不因膜厚的改变而变化;而在10Pa量级氧压下薄膜更倾向于以岛状模式生长,膜表面平整度较差,并且随膜厚的增加粗糙度上升.此外对多层薄膜而言,底层薄膜的表面和结构直接影响到顶层薄膜的质量和品质. 相似文献
16.
V. Leca G. Vişănescu C. Back R. Kleiner D. Koelle 《Applied Physics A: Materials Science & Processing》2008,93(3):779-782
Sr1−x
La
x
CuO2 (x=0.10−0.15) thin films with an infinite-layer type structure were grown on BaTiO3 buffered (001) SrTiO3 substrates by pulsed laser deposition (PLD). The evolution of the growth front was monitored, in-situ, by high-pressure reflection
high-energy electron diffraction (RHEED), while the surface morphology was analyzed by means of atomic force microscopy (AFM),
ex-situ. X-ray diffraction (XRD) was used to determine the evolution of the film structure with deposition and cooling parameters,
as well as to study the type and level of epitaxial strain in the Sr1−x
La
x
CuO2 films. The RHEED data showed that the Sr1−x
La
x
CuO2 films grow on BaTiO3/SrTiO3 following a 2D or Stranski-Krastanov mechanism, depending on the La doping level. The transition point (critical thickness
d
c) from layer-by-layer like (2D) to island (3D) growth depends on the film stoichiometry: decreasing the La doping concentration
x from 0.15 to 0.10, the critical thickness d
c increases from ∼45 nm to ∼75 nm. In order to induce superconductivity, the Sr1−x
La
x
CuO2 films were cooled down under reduction conditions. The as-deposited films showed semiconducting or metallic behavior, the
resistivity decreasing with increasing La concentration. Post-deposition vacuum annealing resulted in a superconducting transition
onset (but no zero resistance down to 4.2 K) only for some of the x=0.15 Sr1−x
La
x
CuO2 films. 相似文献
17.
T. Yu Y.-F. Chen Z.-G. Liu L. Sun S.-B. Xiong N.-B. Ming Z.-M. Ji J. Zhou 《Applied Physics A: Materials Science & Processing》1996,64(1):69-72
The semiconductive perovskite-type oxide SrFeO3-x (x<0.16) (SFO) thin films have been directly fabricated on (001)SrTiO3 and (001)LaAlO3 single crystal substrates by pulsed laser deposition(PLD) under high oxygen partial pressure of 100 Pa. The SFO thin films
were (110) oriented. The x-ray photoelectron spectroscopy (XPS) analysis showed that the surface of SFO thin film has strong
gas absorption capability. The resistance versus temperature has been measured in the temperature range from 77 K to 300 K.
The SFO thin film showed typical semiconductive property. Dependence of resistance of SFO thin film on oxygen pressure was
measured and result showed that the SFO thin film had better oxygen sensitive property.
Received: 14 May 1996/Accepted: 15 August 1996 相似文献
18.
H. Huhtinen M. Irjala P. PaturiM. Falter 《Physica C: Superconductivity and its Applications》2012,472(1):66-74
The effect of BaZrO3 (BZO) doping is systematically studied in YBa2Cu3O6+x (YBCO) thin films deposited by pulsed laser deposition (PLD) on buffered NiW substrates. Based on the structural and magnetic properties, the optimal BZO doping concentration is obtained to vary between 4 and 7.5 wt.%, depending mainly on applied magnetic field. This relatively high optimal concentration is linked to the nanograined target material and metal substrate that cause low-angle grain-boundaries and in-plane spread of YBCO crystals on NiW. Thickness dependent analysis of undoped and BZO-doped YBCO films predicts differences in growth mechanisms where early growth next to the substrate interface is 2D-type in BZO-doped films. This leads to the situation where crystallographic structure as well as superconducting properties are improved when the film develops and the thickness is increased. Therefore from the resistivity measurements a threshold thicknesses where reasonable properties occur are determined for both set of films. Measurements in thermally activated flux-flow regime (TAFF) indicate that above the threshold thickness relatively strong and isotropic vortex pinning is realized in BZO-doped YBCO films. Generally, this paper demonstrates that especially for thin film applications on NiW substrates even more compatible buffer layer structures should be utilized. 相似文献
19.
The a-axis oriented YBa2Cu3Ox(YBCO) thin films could be grown on (100) SrTiO3(STO) substrates with STO buffer layers by dc and rf magnetron sputtering either by low-ering the deposition temperature, or by using a self-template technique. For the latter, the resistivity of the thin film at 290K along the substrate [001] direction is about four times larger than that in the [010] direction. The zero resistance temperatures Tc0 are 89 K in both directions. So high quality a-axis oriented YBCO thin films can be prepared by the self-template technique. Also the Tc0 increase monotonously with the reduction of the thickness of the YBCO seed layer. 相似文献
20.
Y. Du M.-S. Zhang J. Wu L. Kang S. Yang P. Wu Z. Yin 《Applied Physics A: Materials Science & Processing》2003,76(7):1105-1108
SrTiO3 thin films were prepared on a fused-quartz substrate by pulsed laser deposition (PLD). Dense and homogeneous films with a
thickness of 260 nm were prepared. Optical constants (refractive index n and extinction coefficient k) were determined from
the transmittance spectra using the envelope method. The optical band gap energy of the films was found to be 3.58 eV, higher
than the 3.22 eV for bulk SrTiO3, attributable to the film stress exerted by the substrate. The dispersion relation of the refractive index vs. wavelength
follows the single electronic oscillator model. The refractive index and the packing density for the PLD-prepared SrTiO3 thin films are higher than those for the SrTiO3 films prepared by physical vapor deposition, sol–gel and RF sputtering.
Received: 18 March 2002 / Accepted: 7 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-25/359-5535, E-mail: mszhang@nju.edu.cn 相似文献