IR emission and electrical conductivity of Nd/Nb-codoped TiOx (1.5 < x < 2) thin films grown by pulsed-laser deposition

Abstract The effect of the co-doping with Nd and Nb on electrical and optical properties of TiO x films is reported. The role of oxygen vacancies on the physical properties is also evidenced. The films are grown by pulsed-laser deposition onto (001) sapphire and (100) silicon substrates. The substrate temperature was fixed at 700 °C. To obtain either stoichiometric (TiO 2 ) or highly oxygen deficient (TiO x with x  −1 and 10 −6  mbar, respectively. 1%Nd-1%Nb, 1%Nd-5%Nb and 5%Nd-1%Nb co-doped TiO 2 were used as bulk ceramic target. Composition, structural and morphological properties of films determined by Rutherford backscattering spectroscopy, X-ray diffraction and scanning electron microscopy, are correlated to their optical (UV–vis transmission and photoluminescence) and electrical properties (resistivity at room temperature). The most intense Nd 3+ emission in the IR domain is obtained for stoichiometric films. Codoping Nd-TiO x films by Nb 5+ ions is found to decrease the photoluminescence efficiency. The oxygen pressure during the growth allows to tune the optical and electrical properties: insulating and highly transparent (80% in the visible range) Nd/Nb codoped TiO 2 films are obtained at high oxygen pressure, while conductive and absorbent films are grown under low oxygen pressure (10 −6  mbar).