低温凝聚InSb膜相变过程中的时间效应和超导电性

本文研究了低温凝聚InSb膜相变过程中出现的时间效应和超导电性,获得了几个重要结果:(a)低温凝聚InSb膜从发生第一次电导跃变以后到第二次电导跃变之前,样品处于同一非晶金属态,并且具有相同的超导转变温度T_c;(b)T_c和退火温度T_a的关系十分类似于电导随T_a的变化关系;(c)随着第二次电导峰值后的电导下降,在某些特殊的相变区R(T)超导转变中,样品由完全的超导电性逐渐过渡到部分的超导电性;(d)相变过程中存在显著的时 关键词：     

非晶态InSb及其亚稳中间相的霍耳效应和超导电性

实验研究了非晶态InSb及其结晶相变过程中的霍耳效应。结果表明,金属型非晶态InSb以电子导电为主,半导体型非晶态InSb以空穴导电为主;金属型非晶态InSb中的第一电导跃变是一种由类液非晶态到类点阵非晶态的结构弛豫过程;第三电导跃变是富In或富Sb固溶体相在半导体InSb晶界上析出并集中所引起的;金属型非晶态InSb的三种不同的结晶相变类型具有鲜明不同的输运性质;第二电导跃变峰所对应的亚稳金属相超导T_c的提高,可能主要起因于电子浓度的增加。 关键词：     

非晶态InSb及其亚稳中间相的霍耳效应和超导电性

实验研究了非晶态InSb及其结晶相变过程中的霍耳效应. 结果表明, 金属型非晶态InSb以电子导电为主, 半导体型非晶态InSb 以空穴导电为主; 金属型非晶态InSb中的第一电导跃变是一种由类液非晶态到类点阵非晶态的结构弛豫过程; 第三电导跃变是富In或富Sb 固溶体相在半导体InSb 晶界上析出并集中所引起的; 金属型非晶态I站b 的三种不同的结晶相变类型具有鲜明不同的输运性质; 第二电导跃变峰所对应的亚稳金属相超导Tc的提高, 可能主要起因于电子浓度的增加. 关键词：     

非晶态InSb和亚稳中间相的输运性质及其与超导电性的关系

低温凝聚 InSb 膜底板温度的改变可以诱导金属-半导体转变.金属型非晶 InSb 以电子导电为主,半导体型非晶 InSb 则以空穴导电为主;金属型非晶 InSb,在液 N_2温度和1kG磁场下呈现出电子-电子相互作用行为;金属型非晶 InSb 的结构弛豫,不仅可以导致近程有序度的提高,而且可能导致电子结构的变化;第一电导跃变主要起源于电子迁移率的大幅度增加,系统由类液非晶态弛豫到类点阵非晶态;金属型非晶 InSb 中,不同的结晶相变类型表现出不同的输运行为;金属型非晶 InSb 和亚稳中间相是载流浓度(n_o～10~(81)cm~(-3))最低的超导体系之一.且亚稳中间相的超导 Tc 与态密度有关,高的 Tc 值对应于高的态密度;准二维的层状结构对超导电性有利.     

低温凝聚InSb膜相变过程中的结构及其超导电性

本文研究了低温凝聚LnSb膜相变过程中的结构变化及其对超导电性的影响,由X射线衍射分析发现一系列新结果,从而解释了低温凝聚InSb膜相变过程中的电导及相应的T_c本文指出对应于第二电导峰值的T_c是六方晶系(InSb)H的层状导电机制所致。 关键词：     

亚稳中间相的电导和其反常超导相变的机理

我们系统地测得了在低温凝聚InSb膜亚稳中间相的不同结构下其σ(T_a)与温度T的关系,发现相应于某些特定σ(T_a)的相变区,样品超导转变的R(T)曲线出现奇异的反常现象。本文提出一个类半导体相和亚稳金属相的混合态模型来解释这些现象,并且按此模型做了理论计算,理论曲线和实验数值较好地符合。 关键词：     

系列退火条件下Bi2201相超导电性的进化

通过对Pb掺杂Bi2201相超导样品进行系列条件下的真空退火处理,固定退火时间,调节退火温度,使得样品氧含量随退火温度升高而降低,从而使样品载流子浓度随退火温度升高而依次降低,进而影响样品超导电性.我们系统研究了退火条件、正常态电阻率和超导电性之间的关联,确定了样品最高超导转变温度的退火条件,讨论了Bi2201相超导样品在系列退火条件下其超导电性的进化,并获得了该体系最高超导转变温度Tconset=43K.     

聚偏氟乙烯在不同衬底上的结晶行为研究

利用滴涂法制备聚偏氟乙烯(PVDF)薄膜,分别以载玻片、铜片、聚四氟乙烯(PTEF)为衬底研究衬底、退火时间和退火温度对PVDF薄膜结晶行为的影响。实验表明PVDF在PTEF基体上更容易结晶,这是因为PTEF是非极性基体,PVDF分子链运动在界面不受限制,能够充分地重排,利于晶体的生长;延长退火时间,PVDF分子链能够充分进行重排,形成规整的结构,提高结晶性;同时提高退火温度也有利于PVDF薄膜的结晶。另外,基体作用、退火时间和退火温度不会改变PVDF晶体结构,但会不同程度地影响α和β相的含量。     

退火对TiO2薄膜形貌、结构及光学特性影响

利用射频磁控溅射技术在熔融石英基片上制备TiO<,2>薄膜,采用X射线衍射、扫描电子显微镜(SEM)、拉曼光谱以及透过谱研究了退火温度和退火气氛对TiO<,2>薄膜的结构、形貌和光学特性的影响.实验结果表明:在大气环境下退火,退火温度越.高,薄膜晶化越好,晶粒明显长大,温度高于700℃退火的薄膜,金红石相已明显形成.实验还发现,退火气氛对金红石相的形成是非常重要的,拉曼光谱反应出Ar气氛退火,抑制了金红石晶相的发育,薄膜仍以锐钛矿相为主.Ar气氛退火的薄膜在可见光范围内的透过率比大气退火的要低,并且由透过率曲线推知:金红石的光学带隙约为2.8 eV,比锐钛矿的光学带隙小0.2 eV.     

两种扩展Harper模型的波包动力学

本文通过二次矩M₂(t)和概率分布W_n(t)数值地研究了两种扩展Harper模型的波包动力学,得到了这两种模型中各个相、各条临界线以及三相点的波包扩散情况.对于第一种扩展Harper模型,发现两个金属相中波包是弹道扩散的,在绝缘体相中波包不扩散,而在三相点以及各条临界线上波包是反常扩散的.同时,发现金属相—金属相转变的临界线上的波包动力学行为与金属相—绝缘体相转变的临界线上的相同,但三相点的动力学行为与各临 关键词： 金属绝缘体转变 扩展Harper模型 波包动力学     

Der Einfluß der Unterlage auf die Struktur und Leitfähigkeit metallischer Aufdampfschichten

The influence of the substrate on the electrical conductance and on the structure of condensed metal films is investigated. Ag, Cu and Sn films are condensed at different temperatures onto two identical quartz plates. One of them was prenucleated at room temperature. At low condensation temperatures the influence of the metallic prenucleation on the structure of the film is very strong. Surprisingly we find the same influence if the prenucleation and the film are of the same metal. The influence of the nucleation on the electrical conductance of the film is not so strong. Gold films are condensed onto different dielectric substrates at room temperature. From measurements of the electrical conductivity we find that a fraction of the conduction electrons are specularly reflected at the boundaries of the film. This fraction depends on the substrate material and the annealing temperature of the film.     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

Zum Einsatz metallischer Leitfähigkeit während der Kondensation von Metallschichten

Ag-, Cd-, Tl-, Pb- and Bi-films are condensed at constant deposition rates onto crystalline quartz. Film conductance is measured as a function of the mass condensed. During the growth of the film metallic conductivity appears at a “critical” thickness. This critical thickness is constant at low temperatures and begins to rise exponentially at a certain temperature which depends on the condensation energy of the metal. For metals with low thermal conductivity a large critical thickness is found at low temperatures. If the substrate is pre-sensitized with silver the critical thickness of lead films is reduced considerably while amorphous bismuth films show just the opposite behaviour.     

Order-disorder phase transition in CoPd thin films

The thin films of a CoPd alloy in the equiatomic composition region are prepared by condensation at different substrate temperatures. The substrate temperature is varied from the liquid nitrogen temperature to +280°C. At low substrate temperatures, the crystal structure of the condensed films is the single-crystal blocks of the hexagonal close-packed (hcp) phase. As the substrate temperature is further increased, the domains characterized in the initial state by the microdiffraction patterns in the form of a diffuse halo appear in the films, and these domains have a clear-cut boundary with the regions indicated by point reflections in the electron diffraction patterns. At substrate temperatures from +150 to 160°C, the CoPd alloy films in the equiatomic composition region are fully amorphous. The given state is a polymorphic transformation of the martensitic type. It arises in the martensitic transformation of the low-temperature hcp phase to the high-temperature fcc phase.     

高温退火对蓝宝石基片的表面形貌和对CeO2缓冲层以及Tl-2212超导薄膜生长的影响

研究了蓝宝石(1102)基片在不同温度和时间下退火时表面形貌和表面相结构的变化,以及它对CeO₂缓冲层和Tl-2212超导薄膜生长的影响.原子力显微镜(AFM)研究表明,在流动氧环境中1000℃温度下退火,蓝宝石(1102)的表面首先局部区域形成台阶结构,然后表面形成叠层台阶结构,随着退火时间的延长,表面发生了台阶合并现象,表面形貌最终演化为稳定的具有光滑平台的宽台阶结构.XRD测试表明,通过高温热处理可以大幅度提高蓝宝石基片表面结构的完整性.在1000℃温度下热处理20 h的蓝宝石 关键词： Tl-2212超导薄膜 蓝宝石 缓冲层     

Crystallization and thermochromism of annealed heterostructures containing titanium and tungsten oxide films

Crystalline phases in heterostructures containing titanium and tungsten oxide films are studied after step annealing in vacuum at temperatures between 500 and 750°C. The films are deposited on a silica glass substrate by dc reactive magnetron sputtering. It is found that crystalline phases in single layers and bilayer structures form in a different way. In the latter, crystallization is influenced by the order of layer arrangement on the substrate. Thermochromism in structures annealed in vacuum is due to the oxygen-deficient phase WO_{3 ? x} belonging to the hexagonal syngony. This phase intensely grows as the temperature rises from 650 to 750°C.     

New phases in the phase transition in amorphous InSb films

In this paper the structures in the process of the phase transition in amorphous InSb film condensed at low temperature are studied by X-ray diffraction experiments. The highest T_c = 4.18 K is as a result of hexagonal phase. The results of the conductance and the critical temperature are explained by means of the experiments of X-ray diffraction in the process of phase transition.