The investigation of III-V semiconductors using SuperSTEM

[摘要] In recent years, the performance of electron microscopes has been greatly improved through the implementation of practical aberration correction technology. This has allowed the creation of instruments that can form A-scale electron probes at acceleration voltages of only 100kV. As an example, SuperSTEM 1 was the first UK based aberration-corrected 100kV field emission gun scanning transmission electron microscope (FEG-STEM) that was capable of achieving a spatial resolution of 1A. Instruments, such as SuperSTEM 1, permit a wide range of nanostructures to be studied at scales that were not previously possible in commercial microscopes. The introduction of aberration-corrected instruments has been an important development for the characterisation of state of the art semiconductor materials. For instance, some III-V semiconductor structures already incorporate layers that are only a single atom in width. However, due to the limitations of the techniques that have been previously used to characterise such materials, it remains unclear exactly how successful growth methods (such as MBE i.e. molecular beam epitaxy) actually are at producing sharp interfaces. Hence, the ability to study semiconductor materials at the atomic scale has become ever more crucial for technological and economic reasons. In this project, SuperSTEM 1 was used to study several MBE grown III-V semiconductor nanostructures. These materials have applications in present, and possibly future, semiconductor devices. However, in order to improve the performance of such devices, a more in-depth appraisal of the associated growth techniques is necessary. Hence, the aim of this project was to provide atomic scale information on the composition and interfacial sharpness of the various layers that were present in the MBE grown III-V semiconductor nanostructures. This project also required a greater understanding of some aspects of probe scattering and the HAADF (high angle annular dark field) imaging technique due to the exceptional A-scale spatial resolution of SuperSTEM.

[发布机构] University:University of Glasgow

[关键词] Electrical engineering, Condensed matter physics