The origin of an anomalous, low 2θ peak in x-ray diffraction spectra of MoS2 films grown by ion beam assisted deposition

Abstract

The origin of a previously reported anomalous low 2θ x-ray diffraction peak from MoS2 thin films grown by ion beam assisted deposition was investigated. The anomalous peak, observed in a film grown on Si(100), was removed by ion irradiating the film with 180 keV Ar++ ions to a dose of 1 × 1015 ions/cm2. Microstructures of the two films were investigated using x-ray diffraction and cross-section transmission electron microscopy. Diffraction data and bright-field images indicated that the low 2θ peak was due to a local interplanar expansion of the crystal structure normal to MoS2 basal planes. This expansion was attributed to molecular defects.