Valence-band offsets and Schottky barrier heights of layered semiconductors explained by interface-induced gap states

Mönch, Winfried

doi:10.1063/1.121220

Cited by 76 publications

(57 citation statements)

References 27 publications

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“…We note that the threshold carrier density for the metal-insulator transition in thick (B20 nm) sample 13 was about an order of magnitude lower than predicted by our model, probably due to screening effects and variations of defect density. Evidence of midgap states in MoS 2 was also reported previously 32 .…”

Section: Resultsmentioning

confidence: 52%

Hopping transport through defect-induced localized states in molybdenum disulphide

et al. 2013

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Molybdenum disulphide is a novel two-dimensional semiconductor with potential applications in electronic and optoelectronic devices. However, the nature of charge transport in back-gated devices still remains elusive as they show much lower mobility than theoretical calculations and native n-type doping. Here we report a study of transport in few-layer molybdenum disulphide, together with transmission electron microscopy and density functional theory. We provide direct evidence that sulphur vacancies exist in molybdenum disulphide, introducing localized donor states inside the bandgap. Under low carrier densities, the transport exhibits nearest-neighbour hopping at high temperatures and variable-range hopping at low temperatures, which can be well explained under Mott formalism. We suggest that the low-carrier-density transport is dominated by hopping via these localized gap states. Our study reveals the important role of short-range surface defects in tailoring the properties and device applications of molybdenum disulphide.

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Section: Resultsmentioning

confidence: 52%

Hopping transport through defect-induced localized states in molybdenum disulphide

et al. 2013

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“…Figure 1(d) shows the schematic energy band diagram of the p-n heterojunction of the rubrene and MoS 2 . The energy band gaps of the rubrene and MoS 2 in this study were 2.2 and 1.3 eV [24], respectively. The conduction band edge of MoS 2 is higher than the level of the high occupied molecular orbital (HOMO) of rubrene (5.4 eV) by approximately 1.1 eV, as shown in Fig.…”

Section: Preparation Of Hybrid Mos 2 /Rubrene-patch Tfts and Energy Bmentioning

confidence: 97%

Enhancement of photoresponsive electrical characteristics of multilayer MoS2 transistors using rubrene patches

et al. 2014

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Multilayer MoS 2 is a promising active material for sensing, energy harvesting, and optoelectronic devices owing to its intriguing tunable electronic band structure. However, its optoelectronic applications have been limited due to its indirect band gap nature. In this study, we fabricated a new type of phototransistor using multilayer MoS 2 crystal hybridized with p-type organic semiconducting rubrene patches. Owing to the outstanding photophysical properties of rubrene, the device characteristics such as charge mobility and photoresponsivity were considerably enhanced to an extent depending on the thickness of the rubrene patches. The enhanced photoresponsive conductance was analyzed in terms of the charge transfer doping effect, validated by the results of the nanoscale laser confocal microscope photoluminescence (PL) and time-resolved PL measurements.

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“…The mechanisms that shape the electronic structure of metal/MoS 2 contacts have remained more elusive due to seemingly contradictory results. For example, although Au/MoS 2 is reported to exhibit rectifying properties, both n-type and p-type characteristics have been observed in seemingly similar structures [6][7][8][9][10][11]. This is further complicated by several observations of Ohmic interfaces [4,11].…”

Section: Introductionmentioning

confidence: 75%

Influence of interface coupling on the electronic properties of theAu/MoS2junction

et al. 2015

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Thin films of Au ranging from 7-24 nm were grown on MoS 2 at room temperature using thermal evaporation and studied using scanning tunneling microscopy and ballistic electron emission spectroscopy.Topographic images show the surface morphology of Au transitions from terraced triangles to a mix of terraced hexagonal and irregular-shaped structures as film thickness exceeded 16 nm. Raman spectra reveal the presence of tensile strain in the MoS 2 with thicker Au films and is likely the driving force behind this transition. All samples exhibit a Schottky barrier significantly lower than that predicted by the Schottky-Mott model due to Fermi level pinning at the interface. The pinning mechanism is thought to be caused, in part, by the presence of gap states induced by a weakening of the interlayer Mo-S bonding in the presence of the Au film. Although relatively consistent in thinner films, the Schottky barrier increases concurrently with structural changes on the surface. At the same time, transmission through the interface begins to drop at an increased exponential rate with film thickness. These observations are consistent with a widening separation between the Au and MoS 2 that would reduce the number of gap states and cause transmission through the interface to be more characteristic of quantum tunneling. An increased separation such as this could result from changes in equilibrium conditions at the interface with increasing strain.

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Valence-band offsets and Schottky barrier heights of layered semiconductors explained by interface-induced gap states

Cited by 76 publications

References 27 publications

Hopping transport through defect-induced localized states in molybdenum disulphide

Hopping transport through defect-induced localized states in molybdenum disulphide

Enhancement of photoresponsive electrical characteristics of multilayer MoS2 transistors using rubrene patches

Influence of interface coupling on the electronic properties of theAu/MoS2junction

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