This project will achieve a quantitative understanding and description of instabilities of the current-voltage characteristics of amorphous silicon Thin Film Transistors (a-Si TFTs), and will link these phenomena with the deep defect states in the a-Si bandgap. Studies of current-voltage characteristics of TFTs in the subthreshold regime (at gate voltages substantially smaller than threshold) and, especially, studies of the leakage current can be very useful for understanding degradation phenomena. Dr. Globus will analyze the results of the time and temperature dependence measurements of current-voltage characteristics under the voltage stress, annealing at elevated temperatures, and relaxation after quenching. She will study the leakage current in a-Si and poly-Si TFT; derive information about the density of states in a-Si:H and poly-Si using measured data in subthreshold regime; and will obtain more detailed information about the density of states in a-Si:H, the structure of defect absorption modes, the energy levels, and optical spectra of defects from IR optical measurements on a-Si and poly-Si thin films. The understanding, and control of metastable defect formation in a-Si are essential because this process is a principal obstacle to the practical use of a-Si:H, and for the insight into fundamental physics of amorphous silicon. The interactive activities at the host institution will include teaching a course entitled "Thin Film Transistors", presenting guest lectures, and counseling and advising students. Dr. Globus will share, with the student body, her experiences as a scientist in Russia, where almost half of scientists and engineers are female. This project furthers the VPW program objectives which are (1) to provide opportunities for women to advance their careers in engineering and in the disciplines of science supported by NSF and (2) to encourage women to pursue careers in science and engineering by providing greater visibility for women scientists and engineers employed in industry, government, and academic institutions. By encouraging the participation of women in science, it is a valuable investment in the Nation's future scientific vitality.
