Electrical and mechanical properties of SnO2:Nb films for touch screens

SnO2:Nb (Nb: 0-3.0 wt%) films were deposited on glass substrates by RF sputtering process. Electrical, optical and mechanical properties of the films as-deposited and post-annealed are measured in order to examine the feasibility for using as an electrode of the resistive touch screen with an analogue-type. X-ray diffraction (XRD) measurements of sintered SnO2:Nb specimen and the Rietvelt analysis of the XRD pattern were also carried out in order to find the doping effect of Nb to SnO2. Glancing angle XRD patterns of SnO2:Nb films showed a single phase of SnO2 with rutile structure. Average optical transmittance of the films in visible range was > 80%. For the films deposited at 300degreesC, the resisitivity decreases to 1 x 10(-1) Omega cm with increasing Nb concentration to 2.0 wt%. After the post-annealing of the films at 300degreesC in air and N-2, the resistivity of the films decreased to 3 x 10(-2) and 7 x 10(-3) Omega cm, respectively. These properties of the post-annealed films satisfy the requirements for an electrode of the touch screen. From the results of XRD measurements and the Rietvelt analysis for the sintered SnO2:Nb specimen, it is found that Sn ions are substituted by Nb ions for sintered SnO2:Nb powder with Nb less than or equal to 2 wt%. For the films, it is assumed that electron carriers were not generated by the substitution of Sn to Nb but by the oxygen vacancies induced by the distortion of the lattice. (C) 2002 Elsevier Science Ltd. All rights reserved.