Bismuth incorporation and lattice contraction in GaSbBi and InSbBi
III–V-Bi compounds have received considerable attention recently due to a number of interesting material properties. For example, adding a small amount of Bi atoms in conventional III–Vs leads to a large bandgap reduction that occurs predominately in the valence band, about 88 meV/%Bi in GaAsBi. The Bi incorporation affects only the valence band structures and has little influence on electrons. Compared with dilute nitrides, the electron mobility of dilute GaAsBi is much less affected and photoluminescence intensity increases with the Bi incorporation. Dilute GaAsBi also introduces a large spin-orbit split and it has been suggested to use this property to suppress Auger recombination for 1.55 µm lasers on GaAs [1]. So far most experimental studies have been focused on growth of GaAsBi [2], but very little on GaSbBi and InSbBi. Here we report growth of dilute GaSbBi and InSbBi using molecular beam epitaxy (MBE). We have optimized growth conditions aiming at achieving maximum Bi incorporation. Surprisingly X-ray diffraction (XRD) revealed lattice contraction in GaSbBi and InSbBi although Bi atoms have a large atomic radius.
Surface morphology and Bi incorporation in GaSbBi(As)/GaSb films
Several GaSbBi(As)/GaSb films were grown to investigate the effects of Bi on GaSb surface morphology and bulk composition as a function of growth conditions. Scanning electron microscopy of the surface shows several biphasic droplets consisting of Ga- and Bi-rich phases ≈1μm in diameter form on the surface. Some of these droplets exhibit more unusual features such as facets, sub-droplets, and droplet etching into the underlying film. Bi droplet coverage shows a direct increase with increasing Bi:Ga and Bi:Sb BEP ratios. Rutherford backscatter and X-ray diffraction analyses of these films show Bi concentration of up to 12% and a concurrently increasing unintentional As concentration of up to 9.3%, suggesting the presence of a strain auto-compensation mechanism during film growth. Once Bi concentration reaches 10–12%, Bi incorporation saturates, with excess Bi atoms instead accumulating in the droplets.
What is an archival education?1
This article introduces the approach to Master's level archival education adopted at the University of Manitoba. It is intended as a contribution to the recently renewed discussion of graduate archival education in the UK and Ireland. The author maintains that recent major developments in the accessibility, uses, and very conception of archives powerfully underscore the distinctiveness of archival work. These developments foster continued collaboration between archivists and those in related professions such as records management, but, more importantly, reinforce their longstanding distinctiveness. The article discusses why and how the University of Manitoba has responded to the increasingly complex challenges facing archivists and archival educators in this evolving setting with an archival, conceptual, historical, and research-oriented curriculum.