Strain induced electronic transition in 1T′ MoTe₂: high pressure Raman, x-ray diffraction, resistivity measurements and first principles theoretical studies

Abstract

A detailed high pressure study is carried out on 1T′ MoTe2 using x-ray diffraction (XRD) and Raman spectroscopy measurements up to about 30.5 GPa along with a room temperature resistivity measurement up to 14.3(4) GPa and density functional theory calculations. Though high-pressure XRD measurements show no structural transition, all the lattice parameters exhibit anomalous changes in the pressure region 8.4 to 12.7 GPa. The compressibility of the sample is found to be reduced by almost four times above 12.7 GPa with respect to that below 8.4 GPa. The anomalies in the Raman mode corresponding to the out of plane vibrations of Mo atoms sitting in the unit cell surface indicate a strong electron–phonon coupling possibly mediated by differential strain inside the unit cell. A rapid decrease in resistivity value up to about 7.0(2) GPa of pressure agrees well with the increase in the density of states (DOS) at the Fermi energy with pressure. Pressure evolution of band structure, as well as DOS at the Fermi level, shows an enhancement of the metallic character of the sample. First principle calculations show increased stress in the x and y directions compared to the z-direction with the application of pressure.

Structural and electronic phase transitions in Zr$_{1.03}$Se$_{2}$ at high pressure

“…A semiconductor to metallic transition is predicted for 1T-ZrTe 2 and 2H-ZrTe 2 at pressure of 2 GPa and 6 GPa, respectively [11]. Also other recent structural investigations in MoTe 2 , WS 2 , MoSe 2 at high pressure have predicted electronic transitions driven by strain in the unit cell [7][8][9][10].…”

“…In first configuration current is sourced through 1st and 2nd leads and voltage is measured across 3rd and 4th leads, and in second configuration current is sourced through 2nd and 3rd leads and voltage is measured across 1st and 4th leads, to overcome pressure in-homogeneity. The resistivity of the sample is calculated using the simple formula [7,28]…”

“…These different morphologies lead to distinct electronic behavior, ranging from insulators, semiconductors, semimetal and even superconductors [6]. Pressure is a very effective physical parameter which can tune the electronic behavior of TMDs by modifying their crystal structures in a controlled way [7][8][9][10][11][12]. Beside these, controlling layer numbers, presence of impurities etc.…”

Significant Enhancement of NO2 Detection Response in MoTe2 Nanostructures with a 1T′-2H Structure Mixture

“…The three peaks at 163, 232, and 258 cm –1 correspond to the A g 8 , E g 1 , and A g 12 oscillation modes, respectively. E g 1 is the oscillation mode of the 2H structure, while A g 8 and A g 12 are the oscillation modes of the 1T′ structure. – Figure a exhibits only the E g 1 peak, which indicates that only the 2H structure exists in pristine MoTe 2 nanoparticles (MoTe 2 -1). Figure b,c shows the A g 8 , A g 12 , and E g 1 peaks.…”