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    Electronic passivation of PbSe quantum dot solids by trimethylaluminum vapor dosing

    Year: 2020

    Journal: Appl. Surf. Sci., Volume 513, MAY 30

    Authors: Ueda, ST; Kwak, I; Abelson, A; Wolf, S; Qian, C; Law, M; Kummel, AC

    Organizations: UC Office of the President under the UC Laboratory Fees Research Program Collaborative Research and Training Award [LFR-17-477148]; DOE Office of Science User FacilityUnited States Department of Energy (DOE) [DE-AC02-05CH11231]

    Keywords: PbSe; Quantum dots; Nanocrystals; Passivation; Scanning tunneling microscopy (STM); Scanning tunneling spectroscopy (STS); Field-effect transistors

    The inherent instability of PbSe quantum dot (QD) thin films in ambient atmospheric conditions presents a significant challenge to their use in devices. Using low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy, the electronic passivation of epitaxially-fused PbSe QD superlattices (epi-SLs) by trimethylaluminum (TMA) vapor dosing was studied. TMA dosing immobilizes loosely bound mobile adsorbates and passivates states on the surface of the QDs. X-ray photoelectron spectra of QD films prepared by dip coating show an aluminum surface concentration of <1% of a monolayer, consistent with the TMA binding only to defect sites. Field-effect transistor (FET) transport measurements of similar films confirm the impact of this trace surface state passivation. QD FETs dosed with TMA show a shift from p-channel to n-channel behavior as well as a 20-fold increase in mobility and 300-fold increase in on/off ratio compared to devices before TMA dosing. Defect passivation by TMA vapor dosing may facilitate the integration of PbSe QD solids into future optoelectronic devices.
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