Study of electronic and structural properties of Si/Ge thin film nanostructures
by
Shilpa Tripathi, UGC-DAE CSR, Indore, India
→
Europe/Berlin
room 456, bldg. 25f
room 456, bldg. 25f
Description
It is well known that the materials consisting of solids with nanometer dimensions exhibit unusual properties as compared to corresponding bulk materials. The advances in growth and characterization techniques for these nanostructures provide a means to control the physical/chemical properties at atomic scale. This level of control has facilitated the growth of novel semiconductor structures, the structural parameters being at the command of the designer. In particular, the optical and electronic properties of semiconductor nanostructures (such as Si and Ge) can be tailored to a large extent by tuning their size. This is of immense importance, since one can achieve a wide range of optical and electronic properties from the same substance by only changing its size/dimensions. In the past, Si was the dominating material for electronic industry. However, the fact that the band gap of Si is indirect has limited the use of Si in present optoelectronic applications. The use of heterostructured thin films and nanoparticles may help alleviate this limitation which would pave the way to the full integration of optoelectronic with digital logic and memory devices. In addition to the academic interest which the Si/Ge thin films and multilayers have attracted, the flexibility in controlling the layer designs by deposition methods heralded a new era in technological design: by suitably choosing the composition, layer thicknesses, doping and strain configurations in such structures, the so-called electronic band structure may be tailored to give new optical and electronic features. These can be fine-tuned and have found utilitarian value in a wealth of technological applications.
This has motivated the present work to investigate the semiconductor system consisting of Si/Ge multilayers. In addition, systematic thickness dependent studies on electron beam evaporated single layers of Si and Ge as well as on Si/Ge bilayers are also performed to establish self-standards. Its main relevance to the rest of the study lies in revealing the way in which researchers can address the relevant areas of semiconductor devices effectively by preparing variable band gap materials starting from a multilayer route. The individual layers thicknesses were optimized to utilize these thicknesses for creating some novel bilayer and multilayer structures. Therefore, present work explores the structural, optical and electronic properties of electron beam evaporated amorphous/polycrystalline Si/Ge thin films and MLS prepared under ultra high vacuum (UHV) environment.
