Atomic layer deposition effect on the electrical properties of Al2O3-passivated PbS quantum dot field-effect transistors

We have investigated the effect of atomic layer deposition (ALD) on the electrical properties of colloidal PbS quantum dot field-effect transistors (PbS QD-FETs). Low-temperature Al2O3 ALD process was used to fill up the pore spaces of PbS QD films containing 1, 2-ethanedithiol ligands. Upon deposition of Al2O3 on PbS film, the PbS QD-FETs showed ambipolar behavior. The treated film retained this property for over 2 months, despite of exposure to air. This change in the electrical properties of the PbS QD-FETs is attributed to the formation of electron channels in the Al2O3-passivated PbS film. We conclude that these electron transport channels in the AlxOy-PbS film are formed due to substitution of the Pb sites by Al metal and chemical reduction of Pb2+ ions, as determined by an analysis of the depth profile of the film using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. (C) 2015 AIP Publishing LLC.