Electron transport of WS2 transistors in a hexagonal boron nitride dielectric environment

Abstract

We present the first study of the intrinsic electrical properties of WS2 transistors fabricated with two different dielectric environments WS2 on SiO2 and WS2 on h-BN/SiO2, respectively. A comparative analysis of the electrical characteristics of multiple transistors fabricated from natural and synthetic WS2 with various thicknesses from single- up to four-layers and over a wide temperature range from 300 K down to 4.2 K shows that disorder intrinsic to WS2 is currently the limiting factor of the electrical properties of this material. These results shed light on the role played by extrinsic factors such as charge traps in the oxide dielectric thought to be the cause for the commonly observed small values of charge carrier mobility in transition metal dichalcogenides.

MoS2/WS2 Heterojunction for Photoelectrochemical Water Oxidation

“…41,42 Similarly, Raman characterization of 60 nm WS 2 films shows an energy difference between the in-plane E 1 2g and the out-of-plane A 1g modes comprised between 66±0.2 cm -1 and 68 ±0.2 cm -1 (Figure 2a and S5d, f and h), suggesting the formation of a nanosheets network with electronic coupling comparable to mono-and a few-layers. 43,44 Analogous to bilayer 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 and ~ 526 nm in WS 2 , overall suggesting a predominant contribution from few -layered nanosheets. 37,48 The absorption peak positions were extracted by fitting the UV-Vis spectra, which were corrected to the scattering due to the thickness of the films (~ 60 nm) and fitted using a combination of Lorentzian functions ( Figure …”

Electronic transport properties of transition metal dichalcogenide field-effect devices: surface and interface effects

“…The detrimental effects of the substrate may be alleviated in several ways. 39,123,127 Alternatively, sandwiching the MX 2 channel with hBN layers can also reduce scattering from charged impurities and roughness.…”

“…36,139,159 n-Type doping of few-layer MoS 2 by physisorption has been achieved by immersing the sample in a solution of polyethyleneimine (PEI) 151 or benzylviologen. 39,122,123,125 The combination of adlayer deposition and substrate modification possibly allows fine control of doping densities over a wide range. Both n-type and p-type doping can be realized by simply drop-casting solutions of NADH and TCNQ, respectively, on monolayer MoS 2 .…”

“…16 Charge transport properties of bulk TMD crystals have been extensively studied since the early work by Fivaz and Mooser. Mono-and fewlayer FETs from the isoelectronic compounds of MoS 2 such as MoSe 2 , 32-34 WSe 2 , 35,36 WS 2 , [37][38][39] and MoTe 2 40,41 have also been successfully demonstrated. FETs from bulk 29 and few-layer 30 TMD crystals were demonstrated more recently followed by the pioneering work on monolayer MoS 2 FETs 12 and logic gates 31 by Kis's group.…”

Full-range electrical characteristics of WS2 transistors

“…These values are similar with activation energies and electron mobilities found in WS 2 -based electric double layer. 23 It must be pointed out that this approach is valid to solely model the channel conduction by excluding the contact resistance.…”