Tungsten Ditelluride: a layered semimetal

Abstract

Tungsten ditelluride (WTe2) is a transition metal dichalcogenide (TMD) with physical and electronic properties that make it attractive for a variety of electronic applications. Although WTe2 has been studied for decades, its structure and electronic properties have only recently been correctly described. We experimentally and theoretically investigate the structure, dynamics and electronic properties of WTe2, and verify that WTe2 has its minimum energy configuration in a distorted 1T structure (Td structure), which results in metallic-like transport. Our findings unambiguously confirm the metallic nature of WTe2, introduce new information about the Raman modes of Td-WTe2, and demonstrate that Td-WTe2 is readily oxidized via environmental exposure. Finally, these findings confirm that, in its thermodynamically favored Td form, the utilization of WTe2 in electronic device architectures such as field effect transistors may need to be reevaluated.

Single- and few-layer WTe2and their suspended nanostructures: Raman signatures and nanomechanical resonances

“…The Raman measurement system used in this study is integrated into a home-built optical interferometry for ultrasensitive detection of motions of the suspended samples, as illustrated in Fig. 1c ) [15,16,17,18,19]. These results confirm that comparatively high crystal quality of our WTe 2 flakes is preserved throughout measurements.…”

“…These results confirm that comparatively high crystal quality of our WTe 2 flakes is preserved throughout measurements. We compare our measured Raman results with theoretical predictions [15,16,17,18,19], in which A 1 , A 2 , B 1 , and B 2 Raman modes are expected for WTe 2 . In our measurement, it is expected that only A 1 and A 2 Raman modes would appear since the laser polarization is mostly ) exhibit high intensity among measured peaks and are well matched to the predicted Raman modes [15,16,17,18].…”

“…We observe a total of 12 Raman modes, all predicted by theoretical calculations [15,16,17,18,19], and their evolution over number of layers. We also extract WTe 2 crystal's mechanical properties such as the Young's modulus (E Y ) and pre-tension levels from nanomechanical resonance measurements.…”

“…Similar to studies on other forerunners of 2D crystals, Raman spectroscopy has been a very important means for characterization. While early Raman studies of WTe 2 (on SiO 2 substrates) have identified up to 7 Raman modes, many theoretically predicted modes remain yet to be observed [15,16,17,18,19]. In addition, suspended WTe 2 structures can offer better control over material properties in WTe 2 such as mechanically engineering the magnetoresistance through manipulating strain.…”

Thickness-dependent electronic structure in WTe2 thin films

“…We begin by characterizing the film quality to confirm that no obvious degradation happens during the sample fabrication and storage [27][28][29][30] and that they are of high enough quality to reveal the intrinsic electronic structure. Figures 1(a) all samples shown in Figs.…”