Fluorine doped ZnO thin films by RF magnetron sputtering

Growth of ZnO films by reactive RF sputtering in ambients of Ar-H-2 and Ar-H-2-CHF3 has been investigated as a function of the reactive gas partial pressure (ppx%). substrate temperature and sputtering power. Use of H-2 reduces the resistivity of ZnO by a factor of 10(4), with doping through use of CHF3 giving a further factor of 10 decrease. The lowest resistivity (2.9 x 10(-3) Omega cm) was achieved using ppH(2) = 5%, ppCHF(3) = 4% in a total pressure of 5 mTorr made up with Ar. An optical transmittance of >80% in the visible range was achieved for all doped films. Analysis of Burstein-Moss shifts in measured indirect and direct band-gap values for doped films yield values for the electron and hole effective masses of 0.5 m(o) and 1.2 m(o) respectively, according to a parabolic band model. (C) 2011 Elsevier B.V. All rights reserved.