title: Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS2Transistors.
abstract: Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS2), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS2. Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS2bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Matsunaga
authors.forename: Ayaka
authors.initials: A
authors.lastname: Higuchi
authors.affiliation: Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States.
authors.forename: Guanchen
authors.initials: G
authors.lastname: He
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Yamada
authors.forename: Peter
authors.initials: P
authors.lastname: Krüger
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ochiai
authors.affiliation: Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Vajtai
authors.affiliation: Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Pulickel M
authors.initials: PM
authors.lastname: Ajayan
authors.affiliation: Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Bird
authors.affiliation: Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi 332-0012, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Aoki
keywords: bandgap modification; electron beam exposure; field effect transistors; first-principles calculations; molybdenum disulfide; potential barrier; scanning probe microscopy