Defense Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Indika U. Arachchige

Abstract

Ge1-xSnx alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge1-xSnx thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in lattice constants. Moreover, little is known about the chemical factors that govern the growth of Ge1-xSnx nanoalloys and the effects of quantum confinement on structure and optical properties. A synthesis has been developed to produce phase pure Ge1-xSnx nanoalloys which provides control over both size and composition. Three sets of Ge1-xSnx nanocrystals have been studied, 15–23 nm, 3.4–4.6 nm and 1.5–2.5 nm with Sn compositions from x = 0.000–0.279. Synthetic parameters were explored to control the nucleation and growth as well as the factors that have led to the elimination of undesired metallic impurities. The structural analysis of all nanocrystals suggests the diamond cubic structure typically reported for Ge1-xSnx thin films and nanocrystalline alloys. As-synthesized Ge1-xSnx nanoalloys exhibit high thermal stability and moderate resistance against sintering up to 400–500 °C and are devoid of crystalline and amorphous elemental Sn impurities.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

12-16-2016