Doping dependence of laser-induced transverse thermoelectric voltages in the perovskite Nd_(2-x)Ce_xCuO_4 thin films

摘要

Large laser-induced thermoelectric voltages (LITVs) are measured in the electron-doped Nd_(2-x)Ce_(x-) CuO_4 thin films grown on the vicinal-cut SrTiO_3 substrates by pulsed laser deposition. The dependence of LITV signals upon the doping carrier density is investigated by changing the Ce content of the films. The optimum Ce dopant corresponding to the largest voltage is found and is attributed to the two-dimensional transport behaviors of the localized electrons. The shorter laser irradiation always induces the larger voltage signals in samples with richer Ce content, suggesting the optimum dopant level is sensitive to the wavelength of excitation source. Thus, the behaviors of LITV signals are resulted from both effects of the aniso-tropic thermoelectric transport and the optical properties of the thin films. The doping dependence related with an anisotropic charge transport may come from the change in carrier density and the modification in energy band configuration.