Influence of Atmospheric Gases on the Electrical Properties of PbSe Quantum-Dot Films

We report the effects of N 2 and O 2 on the electrical properties of PbSe quantum-dot (QD) films treated with 1,2-ethanedithiol (EDT) by measuring the changes in the current−voltage characteristics of QD field-effect transistors (FETs). EDT-treated PbSe QD films at a base pressure of ∼10 −5 Torr exhibit ambipolar transport. Exposing these films to N 2 shifts the transfer characteristics toward negative gate-voltage values and increases the electron mobility. These changes could be reversed entirely by removing the N 2 gas over the FET and returning to base pressure. Oxygen exposure shifts the transfer characteristics in the opposite direction toward positive gate-voltage values. Moreover, oxygen exposure reduces charge mobility but increases film conductivity. For exposures up to ∼10 8 langmuir, these O 2 -induced changes could be reversed completely by removing the O 2 gas over the sample and returning to base pressure. However, after ∼10 10 langmuir of O 2 exposure, the changes are irreversible. The QD films then permanently become p -type and the decrease in charge mobility remains even after returning to base pressure.