Layer Number Dependence Of Charge Density Wave Phase Transition Between Nearly-Commensurate And Incommensurate Phases In 1t-Tas2

The charge density wave (CDW) phase transition between the nearly commensurate (NCCDW) and incommensurate (ICCDW) phases in 1T-TaS2 around 350 K was investigated by electrical resistance measurement and Raman spectroscopy in terms of the number of layers of the samples. Temperature hysteresis Delta T decreases in the NCCDW-ICCDW phase transition as the number of layers decreases, which is in contrast to the transition between the commensurate CDW (CCDW) and NCCDW phases around 180 K, as previously reported. The different Delta T trend can be explained by the different origins. The difference in the layer-number dependence of Delta T between the NCCDW-ICCDW and CCDW-NCCDW region is mainly explained by the difference in the CDW superstructure along the out-of-plane direction between the CCDW and ICCDW phases. The results will be helpful for the development of device applications using CDW phase transition at room temperature. In addition, the baseline of Raman spectra below 70 cm(-1) is proposed as a conventional probe to investigate CDW transitions.