Title: Bi$_2$Se$_3$ Thin film topological insulators as a field effect transistor

Topological insulators are materials with insulating bulk and conducting surfaces. Bi$_2$Se$_3$ is one such material. However, perfect Bi$_2$Se$_3$ topological insulators have yet to be realized because imperfections in thin film growth and intrinsic se-vacancies lead to conduction in the bulk. This project explores the use of gating to eliminate bulk conduction. We demonstrate that back gating in an 8QL Bi$_2$Se$_3$ film results in reduced carrier density when negative gate voltage is applied. We also present a study of SiO$_2$ as a gate insulator for top gating Bi$_2$Se$_3$.