摘要:

The general term metallic glasses is now generally accepted to define a class of amorphous alloys obtained by rapid solidification from the liquid state. This definition corresponds exactly to the definition of a glass in general, except that in the case of well known silicate glasses the liquid does not require a rapid rate of cooling to prevent crystallization, and that is not the case for metallic glasses. The first metallic glass, an alloy of gold and silicon, was synthesized at Caltech in the summer of 1959. During the last 20 years, the interest in metallic glasses has increased steadily. There is still widespread interest in both theoretical and experimental studies of metallic glasses. About 10 years ago the potential importance of metallic glasses as a class of new materials with unusual physical properties was recognized by industry. It will take a long time before production of metallic glasses can be measured in tons, but it is encouraging to see that an increasing number of industrial research centers are involved in studies of metallic glasses.

ISSN:1071-1023    

DOI:10.1116/1.582490

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Recent developments in the field of molecular beam epitaxy (MBE) have rekindled interest in the subject of pseudomorphism: the stabilization of metastable phases by epitaxy. These developments have led to the growth of metastable films of α‐Sn, α‐Sn:Ge alloys, and BaxCa1−xF2solid solutions. Unlike the early examples of pseudomorphism, these films are relatively thick, i.e., ≳0.5 μm. This has permitted the first quantitative study of strain anisotropy in pseudomorphic films by the technique of double‐crystal x‐ray diffraction. The growth and investigation of such films using MBE techniques is a new and fertile area of materials research driven by the potentially useful properties which the films exhibit. In contrast with the relative ease with which α‐Sn, α‐Sn:Ge, and fluoride solid solutions can be grown by MBE, attempts to prepare metastable InSb1−xBixsolid solutions have encountered major problems due to the surface segregation of competing liquid eutectic phases on the growth surface. These developments are reviewed and future directions of research in the field of pseudomorphic growth by MBE are discussed.

ISSN:1071-1023    

DOI:10.1116/1.582491

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

It is now well admitted that most quaternary III–V compounds show unstable regions in the temperature range commonly used in epitaxy. For instance, according to these authors, the InGaAsP alloy, lattice matched to InP and with emitting wavelength 1.3 μm should be unstable at temperatures below 700 °C. Liquid phase epitaxy, however, is commonly performed down to 600 °C. As this growth technique occurs close to thermodynamical equilibrium, such growth should not take place. It was clearly demonstrated that the substrate stabilizing effect is responsible for this paradoxical behavior. Another LPE substrate effect pointed out by Stringfellow is known as the ‘‘pulling effect.’’ Results will be presented showing the connection between these effects in the system InGaAsP/InP and particularly InGaAs/InP. ‘‘Stabilized’’ GaAsSb was also successfully epitaxially grown on InP, in the immiscibility region, from the liquid phase. Microscopic compositional periodical modulations are observed in standard InGaAsP epilayers, if growths are performed below a critical temperature. This phenomena, also related to solid instability, can be interpreted in terms of liquid–solid interfacial spinodal decomposition.

ISSN:1071-1023    

DOI:10.1116/1.582493

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We propose that the observed V‐shaped dependence of the direct gapE0(x) in (GaAs)1−xGe2xalloys is due to an order–disorder phase transition that occurs at the minimum of the ‘‘V.’’ In disordered Ge‐rich alloys, the stable phase is one in which either Ga or As atoms can occupy nominal cation and nominal anion sites with approximately equal probability; in ordered GaAs‐rich material, Ga (As) atoms preferentially occupy nominal cation (anion) sites. We calculate the order parameter for this transition using a three‐component spin Hamiltonian and mean‐field theory and evaluate the band structure of the alloys using a modified virtual‐crystal approximation, which depends on the order parameter.

ISSN:1071-1023    

DOI:10.1116/1.582494

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Optically absorbing deposits have been detected by Raman scattering in native oxides on In0.76Ga0.24As0.56P0.44which were formed by thermal oxidation or by annealing electrochemically anodized films. For air oxidation at 560 °C, the Raman line shape of the absorbing deposit could represent either a two phase mixture of As and an alloy of AsxP1−xwithx∼0.7 or pure AsxP1−xwith a somewhat larger value ofx. The latter possibility seems the more likely at this time. Analysis of the Raman band shapes for air oxidation at 730 °C suggests a mixture of two immiscible AsxP1−xsolid solutions, both withx≥0.7. In no case is a simple two phase mixture of crystalline elemental arsenic and red phosphorus detected. Oxidation of the quaternary in As2O3leads to the detection of hexagonal elemental As, AsxP1−x(x>0.7), and InPO4. The detection of InPO4provides an explanation of why the detected AsxP1−xalloys are phosphorus depleted relative to the bulk substrate composition, i.e., the formation of orthophosphates such as InPO4and GaPO4deplete the potential source of elemental phosphorus. No absorbing deposits were detected in as‐grown anodic films on the quaternary, but annealing the anodic films leads to the formation of an optically absorbing layer. The Raman band shape associated with this deposit is broad and has been tentatively assigned as an AsxP1−xalloy. There is insufficient structure, however, to provide an accurate estimate ofxor to exclude the possibility that it contains some admixture of amorphous arsenic.

ISSN:1071-1023    

DOI:10.1116/1.582497

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582498

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We report the latest results of a continuing study of low pressure‐metal–organic chemical vapor deposition (LP‐MOCVD) growth of InP and Ga0.47In0.53As–InP heterojunctions and superlattices, which describe the general growth of InP and GaInAs with specific application to quantum well heterostructure. A study of the sources and control of residual impurities in InP and Ga0.47In0.53As, the effects of source purity upon residual impurities, mobility, and 2 K PL intensity are detailed. Total impurity concentrations as low as 6×1014cm−3for InP and 3×1014cm−3for Ga0.47In0.53As have been obtained. Mobility as high as=μ (300)=5350, μ (77)=60 000 cm2V−1 s−1for InP, and μ (300)=12 000, μ (77)=60 000, μ (2)=100 000 cm2V−1 s−1for GaInAs layers have been measured.

ISSN:1071-1023    

DOI:10.1116/1.582499

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Epitaxial growth of Si and Ge films onto silicide/Si and fluoride/Si structures has been reviewed. Growth conditions of epitaxial silicide films such as Pd2Si, CoSi2, and NiSi2films on Si substrates, as well as heteroepitaxial Si/CoSi2/Si structures, are presented. Crystalline quality and structural properties of the films have been analyzed by Rutherford backscattering and channeling spectroscopy, transmission electron microscopy, optical microscopy, and x‐ray diffraction analysis. Growth conditions of fluoride films such as CaF2, SrF2, and BaF2films on Si substrates are also presented. For the growth of Si and Ge overlayers on the fluoride/Si structure, the lattice matching condition between the semiconductor and fluoride films has approximately been satisfied by use of pure and mixed fluoride films.

ISSN:1071-1023    

DOI:10.1116/1.582500

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Radiation pulses from Q‐switched lasers can be used to transiently melt and modify the near surface regions of solids. Indeed the annealing is of such short duration that new, extremely rapid solidification phenomena are now amenable to study. Most work has probed the basic crystal growth behavior of elemental Si. This process is often strongly influenced by the presence of high concentrations of impurities: either growth instabilities or metastable, supersaturated solid solution formation may occur. At the highest resolidification rates (≳10 m/s) the recrystallization interface can break down with the formation of an amorphous solid phase. This paper describes the various processes which can occur and identifies limiting behavior in high speed crystal growth.

ISSN:1071-1023    

DOI:10.1116/1.582501

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Semiconductors, modulated by periodicnandpdoping, possibly with intrinsic regions in‐between (‘‘n‐i‐p‐icrystals’’) represent a new class of semiconductors, because of their tunable electronic properties. A large number of intriguing phenomena, predicted by the theory, have been observed recently on GaAs doping superlattices grown by molecular beam epitaxy. In this paper we summarize the theory and experimental results with special emphasis on the aspects of the metastability of large deviations of the carrier concentrations from thermal equilibrium. Approximate analytical expressions for the lifetime enhancement, its dependence of the ‘‘design parameters’’ and on the state of excitation are derived. A brief outlook on possible extensions of the original concept is given.

ISSN:1071-1023    

DOI:10.1116/1.582502

出版商:American Vacuum Society    

年代:1983

数据来源: AIP