Van Der Waals Epitaxy of GaSe on WSe2

GaSe layers were grown on the van der Waals (0001) planes of WSe2 (van der Waals epitaxy). The substrate (0001) plane was cleaned in UHV by heating to 400°C. GaSe was deposited from resistively heated Knudsen cells at T=300° C. After annealing at 450°C an epitaxial GaSe overlayer is formed as evidenced by X-ray diffraction, scanning tunneling microscopy, low energy electron diffraction and photoelectron spectroscopy.

Spectroscopic signatures of a bandwidth-controlled Mott transition at the surface of 1T-TaSe2

High-resolution angle-resolved photoemission data show that a metal-insulator Mott transition occurs at the surface of the quasi-two-dimensional compound 1T-TaSe2. The transition is driven by the narrowing of the Ta 5d band induced by a temperature-dependent modulation of the atomic positions. A dynamical mean-field theory calculation of the spectral function of the half-filled Hubbard model captures the main qualitative feature of the data, namely, the rapid transfer of spectral weight from the observed quasiparticle peak at the Fermi surface to the Hubbard bands, as the correlation gap opens up.

Use of molybdenum telluride as a substrate for the imaging of biological molecules during scanning tunnelling microscopy

Scanning tunnelling microscopy was used to image biological molecules including supercoiled deoxyribonacetic acid and specific retrovirus enzymes, the reverse transcriptases of the avian myeloblastosis virus, the moloney murine leukaemia virus and the human immunodeficiency virus. Measurements were carried out on graphite and Group VI transition metal dichalcogenide layered crystals. Images obtained with graphite could not be unequivocally interpreted and attachment appears to occur solely at surface defect sites. The layered crystal MoTe2 shows different imaging properties. The bimolecules are clearly visible, distributed over the semiconductor surface, and the molecular shapes and dimensions show good correlation with structure predictions.