In-situ observation of 1T-TaS2−xSex charge density waves

Anion-doped 1T-TaS2−xSex (x = 0−2) charge density waves (CDW's) at room temperature (RT) phase were studied using STM and electron diffraction (ED). It was found that with increasing Se concentration the anion-doped 1T-TaS2−xSex at RT phase varied the CDW's from a nearly commensurate to commensurate state, with this phenomenon being particularly reported for 1T-TaS0.4Se1.6. The 2D-FFT spectrum of the STM image and ED pattern distinctly showed that 1T-TaS0.4Se1.6 had a “3×1” commensurate CDW superstructure. Several translation boundaries, i.e., where shifts of the CDW rows are clearly visible, were also observed in 1T-TaS0.4Se1.6. Investigations of interfacial interactions of CDW's are also presented with specific emphasis on commensurate 1T-TaSe2 CDW's using a H2O cluster model. After rinsing with H2O, all 1T-TaS2−xSex CDW's contour heights were remarkably enhanced, this being a result of the physically adsorbed tetrahedral (H2O)n clusters and the charge transfer from CDW to adsorbed H2O. On a clean surface with few crystal defects, a hydrated CDW in H2O showed a triple CDW. However, results were focused on an observed single hydrated CDW in H2O which was aligned along a step due to the primary interactions of H2O molecules with active step sites. The formation of single hydrated CDW's in H2O is concluded to originate from the presence of step sites and the preferential orientation of sequential chains of (H2O)n along the step sites.