Experimental electron band alignment of 1T'and 2H MoTe2/SiO2 interface using internal photoemission spectroscopy

Abstract

Unlike other two-dimensional (2D) transition metal dichalcogenides, molybdenum ditelluride (MoTe2) displays a stable biphasic character in artificially synthesizable 2H and 1T’ state. While these phases are inherently distinguished in their electronic band character (semiconducting and metallic, respectively), it is not clear how they electronically interface with technology relevant substrate where to engineer an electronic device layout. In this study, we experimentally determine the electron band alignment at interfaces between SiO2 and 1T'/2H of MoTe2 few-layers ultrathin films grown by chemical vapor deposition. We use internal photoemission spectroscopy to determine the energy barrier height between the 1T’/2H-MoTe2 Fermi level and the oxide conduction band (CB) bottom. This observation indicates the band gap opening in 2H-MoTe2 and provides an estimate of the barrier height for holes at the polytypic 1T’/2H-MoTe2 interface. In particular, by comparing the Fermi level energy in single-phase 1 T'-MoTe2 with the VB energy in 2H-MoTe2, we reveal a ≈ 0.4 eV difference, suggesting that the low Schottky barrier observed at the 1T'/2H interface results from Fermi level pinning, which is independent of interface defects and unaffected by the VdW gap. Our findings can be exploited for optimizing charge transport and device performance, facilitating the development of next-generation electronic and optoelectronic devices that harness the unique properties of both phases in MoTe2.