Roscopy s electric field vectors eii and es are aligned along the a- or c-axes. An optical microscopy image of the flake studied by Raman spectroscopy is shown in Figure 2c, when the room with the flake studied by Raman spectroscopy is shown in Figure 2c, while the room image temperature Raman spectra recorded for the as-prepared and air aged WTe2 flake are temperature Raman spectra recorded for the as-prepared and air aged WTe2 flake are given in Figure 2d. Raman active modes with peaks centered at 105.0 cm-1 given in Figure 2d. A total of 5 Raman active modes with peaks centered at 105.0 cm-1 , -1 126.five cm-1 157.2 cm-1 and 205.3 cm-1 have been recorded. The Raman active -1 , 126.five cm-1 , 157.two cm-1 , and 205.3 cm-1 have been recorded. The Raman active 110.five cm 110.five cmNanomaterials 2021, 11,5 ofmodes are labelled as Aq and Bq , where q = 1, 2 and p Z to uniquely recognize the eight Raman mode. Right here, the 5 detected Raman peaks are assigned for the A5 , A4 , B1 , A2 , and two two two A1 allowed Raman active modes [50,51]. Upon comparison with all the calculated resonances, two it is actually located that the experimental A4 is blue shifted, though the other 4 Raman active 2 modes are red shifted resulting from the tension built up when the flake is transferred onto the rigid substrate. Upon measurement, the sample has been exposed to air for seven days then Raman spectra have already been recorded. The Raman spectrum for the air aged sample, represented by the dashed curve in Figure 2d is found to show the permitted Raman modes with the optical phonons as recorded for the pristine flake. No peaks connected to oxides of Te or W are detected, confirming the chemical stability from the WTe2 flakes. three.two. Out-of-Plane Magnetotransport Low-T/high- H magnetotransport measurements are carried out around the samples S1 and S2 inside a Janis Super Variable Temperature 7TM-SVM cryostat (Janis Cryogenics, Cholesteryl sulfate sodium Westerville, OH, USA) equipped with a 7 T superconducting magnet. Prior to the measurements, the Ohmic nature on the Pt contacts to the WTe2 flakes is confirmed by the linear I – V traits measured with a higher precision Keithley 4200 SCS dc source-measure unit (SMU). The longitudinal resistance Rxx as a function of T and H has been measured by employing a lock-in amplifier (LIA) ac strategy. The Iac is sourced from a Standord Research SR830 LIA, though the generated voltage Vxx is measured within a phase locked mode as a function of T and H. The applied existing is limited to 10 to reduce Joule heating and subsequent thermogalvanic effects due to the constraints imposed by the low Cucurbitacin D Purity & Documentation dimensionality from the samples. The lock-in expand function is employed to improve the sensitivity in the LIA. All measurements happen to be performed at a frequency of 127 Hz. The selected reference axes for the applied H, for E as a consequence of Iac , and for the l and w dimensions in the specimens – identified to characterize the transverse magnetoresistance MR and also the longitudinal magnetoresistance MR -are shown in Figure 3a,b, respectively. In Figure 3a, would be the angle between H applied along the c-axis along with the ab-plane, whilst E is oriented along w. The H has been recorded for = 0 and 90 . The MR for S1 and S2 are measured by applying an in-plane magnetic field H at an angle w.r.t. E, even though E is always applied along w. Therefore, you can find two doable configurations on the relative orientations of E, H w.r.t. w, namely: (i) H ( E w) and (ii) H ( E w) . The evolution of longitudinal resistance Rxx as a function of T in the.