@article{dfa8c5a97244449cab12c25d961be78d,
title = "Systematic Study of Oxygen Vacancy Tunable Transport Properties of Few-Layer MoO3− x Enabled by Vapor-Based Synthesis",
abstract = "Bulk and nanoscale molybdenum trioxide (MoO3) has shown impressive technologically relevant properties, but deeper investigation into 2D MoO3 has been prevented by the lack of reliable vapor-based synthesis and doping techniques. Herein, the successful synthesis of high-quality, few-layer MoO3 down to bilayer thickness via physical vapor deposition is reported. The electronic structure of MoO3 can be strongly modified by introducing oxygen substoichiometry (MoO3− x), which introduces gap states and increases conductivity. A dose-controlled electron irradiation technique to introduce oxygen vacancies into the few-layer MoO3 structure is presented, thereby adding n-type doping. By combining in situ transport with core-loss and monochromated low-loss scanning transmission electron microscopy–electron energy-loss spectroscopy studies, a detailed structure–property relationship is developed between Mo-oxidation state and resistance. Transport properties are reported for MoO3− x down to three layers thick, the most 2D-like MoO3− x transport hitherto reported. Combining these results with density functional theory calculations, a radiolysis-based mechanism for the irradiation-induced oxygen vacancy introduction is developed, including insights into favorable configurations of oxygen defects. These systematic studies represent an important step forward in bringing few-layer MoO3 and MoO3− x into the 2D family, as well as highlight the promise of MoO3− x as a functional, tunable electronic material.",
keywords = "2D materials, in situ transport, molybdenum trioxide, physical vapor deposition",
author = "Hanson, {Eve D.} and Luc Lajaunie and Shiqiang Hao and Myers, {Benjamin D.} and Fengyuan Shi and Murthy, {Akshay A.} and Chris Wolverton and Raul Arenal and Dravid, {Vinayak P.}",
note = "Funding Information: This material is partially based upon work supported by the National Science Foundation under Grant No. DMR-1507810. The EELS study was conducted at the Laboratorio de Microscop?as Avanzadas, Instituto de Nanociencia de Arag?n, Universidad de Zaragoza, Spain. Some of the research leading to these results had received funding from the European Union Seventh Framework Programme under Grant Agreements 312483- ESTEEM2 (Integrated Infrastructure Initiative-I3). R.A. gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (FIS2013-46159-C3-3-P and MAT2016-79776-P) and from the European Union H2020 programs ETN project ?Enabling Excellence? Grant Agreement 642742 and ?Graphene Flagship? Grant Agreement 696656. S.H. and C.W. (DFT calculations) acknowledge support by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Grant No. DEFG02-07ER46433. This work made use of the EPIC and SPID facilities of the NUANCE Center at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. The authors would like to thank Karl Hagglund for aid in setting up the in situ nanoprobe station. The authors thank Lintao Peng for his background knowledge on transport measurement techniques and Teodor Stanev for his aid in TEM sample transfer. The authors also thank Jeffrey Cain and Jennifer DiStefano for feedback on the manuscript. Publisher Copyright: {\textcopyright} 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim",
year = "2017",
month = may,
day = "4",
doi = "10.1002/adfm.201605380",
language = "English (US)",
volume = "27",
journal = "Advanced Functional Materials",
issn = "1616-301X",
publisher = "Wiley-VCH Verlag",
number = "17",
}