title: Quantum Dot Thin-Films as Rugged, High-Performance Photocathodes.
abstract: Typical use of colloidal quantum dots (QDs) as bright, tunable phosphors in real applications relies on engineering of their surfaces to suppress the loss of excited carriers to surface trap states or to the surrounding medium. Here, we explore the utility of QDs in an application that actually exploits their propensity toward photoionization, namely within efficient and robust photocathodes for use in next-generation electron guns. In order to establish the relevance of QD films as photocathodes, we evaluate the efficiency of electron photoemission of films of a variety of compositions in a typical electron gun configuration. By quantifying photocurrent as a function of excitation photon energy, excitation intensity and pulse duration, we establish the role of hot electrons in photoemission within the multiphoton excitation regime. We also demonstrate the effect of QD structure and film deposition methods on efficiency, which suggests numerous pathways for further enhancements. Finally, we show that QD photocathodes offer superior efficiencies relative to standard copper cathodes and are robust against degradation under ambient conditions.
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Makarov
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Lim
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Qianglu
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: John W
authors.initials: JW
authors.lastname: Lewellen
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Moody
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: István
authors.identifier: 0000-0002-9738-7728
authors.initials: I
authors.lastname: Robel
authors.affiliation: Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Jeffrey M
authors.identifier: 0000-0001-5360-4228
authors.initials: JM
authors.lastname: Pietryga
keywords: Quantum dot; electron gun; nanocrystal; photocathode; photoemission; photoinjector