We present an analysis of the electronic properties of an MoS 2 monolayer (ML) and bilayer (BL) as-grown on a highly ordered pyrolytic graphite (HOPG) substrate by physical vapour deposition (PVD), using lab-based angle-resolved photoemission spectroscopy (ARPES) supported by scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) for morphology and elemental assessments, respectively. Despite the presence of multiple domains (causing in-plane rotational disorder) and structural defects, electronic band dispersions were clearly observed, reflecting the high density of electronic states along the high symmetry directions of MoS 2 single crystal domains. In particular, the thickness dependent direct-to-indirect band gap transition previously reported only for MoS 2 layers obtained by exfoliation or via epitaxial growth processes, was found to be also accessible in our PVD grown MoS 2 samples. At the same time, electronic gap states were detected, and attributed mainly to structural defects in the 2D layers. Finally, we discuss and clarify the role of the electronic gap states and the interlayer coupling in controlling the energy level alignment at the MoS 2 /substrate interface.

Electron band alignment at interfaces of SiO2 with directly synthesized few-monolayer (ML) thin semiconducting MoS2 films is characterized by using field-dependent internal photoemission of electrons from the valence band of MoS2 into the oxide conduction band. We found that reducing the grown MoS2 film thickness from 3 ML to 1 ML leads to ≈400 meV downshift of the valence band top edge as referenced to the common energy level of the SiO2 conduction band bottom. Furthermore, comparison of the MoS2 layers grown by a H-free process (sputtering of Mo in sulfur vapor) to films synthesized by sulfurization of metallic Mo in H2S indicates a significant (≈500 meV) electron barrier increase in the last case. This effect is tentatively ascribed to the formation of an interface dipole due to the interaction of hydrogen with the oxide surface.

Structure and properties of W O 3 -doped Pb 0.97 La 0.03 ( Zr 0.52 Ti 0.48 ) O 3 ferroelectric thin films prepared by a sol-gel process J. Appl. Phys. 98, 034104 (2005); 10.1063/1.1999834 Effects of lanthanum doping on the dielectric properties of Ba ( Fe 0.5 Nb 0.5 ) O 3 ceramicWe have investigated the effect of Ti and Mg dopants on the structural properties and band-gap energies of Ba 0.5 Sr 0.5 TiO 3 ͑BST͒ thin films grown on LaAlO 3 substrates. The transmission spectra of these BST thin films measured by ultraviolet-visible spectrophotometer show that the band-gap energies are strongly dependent on the dopant concentration. Based on the structural analyses and theoretical calculation, the variation of the band-gap energies can be attributed to the combined effects of stress, grain size, and phase transformation in Ti-and Mg-doped BST thin films.