Structural analysis of 2H-WS2 thin films by X-ray and TEM investigation

Tungsten disulfide thin films were prepared by sulfurization of <500 nm thick WO3 layers at temperatures between 973 and 1223 K using 111-oriented silicon substrates. The films were investigated by X-ray diffraction, transmission electron (TEM) and scanning electron microscopy (SEM). From XRD patterns, it was concluded that the layers consisted of crystallites of the hexagonal 2-H-WS2 phase and distinguished by a high degree of texture with the hexagonal (001) faces oriented parallel to the substrate. However, analysis of the films by cross-section TEM revealed that only the top layers of the films exhibited (001) texture while in the portion of the layer beneath the hexagonal crystallites were upright standing forming an angle with the substrate and the top layer of about 72 degrees. Convergent beam electron diffraction (CBD) studies performed along [100] indicated stacking faults of the 001 layers. In accord with XRD measurements, selected area diffraction (SAD) patterns Save no evidence of unreacted WO3 even after short sulfurization times of 30 min. (C) 1997 Elsevier Science S.A.