||Characterization of electronic structure around metal-insulator transition in V1-x WxO2 thin films by thermopower measurement
Katase, Takayoshi ,
Endo, KenjiOhta, Hiromichi
Journal of the Ceramic Society of Japan
311 , 2015-05 , The Ceramic Society of Japan = 日本セラミックス協会
Electronic structure across the metal-insulator (MI) transition of electron-doped V1-x WxO2 epitaxial films (x = 0-0.06) grown on alpha-Al2O3 substrates was studied by means of thermopower (S) measurements. Significant increase of vertical bar S vertical bar-values accompanied by MI transition was observed, and the transition temperatures of S (T-S) decreased with x in good linear relation with MI transition temperatures. vertical bar S vertical bar values of V1-x WxO2 films at T > T-S were constant at low values of 23 mu VK-1 independently of x, which reflects a metallic electronic structure, whereas, those at T < T-S almost linearly decreased with logarithmic W-concentrations. The gradient of -213 mu VK-1 agrees well with -k(B)/e.ln10 (-198 mu VK-1), suggesting that V1-x WxO2 films have insulating electronic structures with a parabolic density of state around the conduction band bottom.