Fluorine doped ZnO thin films by RF magnetron sputtering

摘要

Growth of ZnO films by reactive RF sputtering in ambients of Ar-H_2 and Ar-H_2-CHF_3 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 CHF_3 giving a further factor of 10 decrease. The lowest resistivity (2.9×10~-3Ωcm) 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_0 and 1.2 m_0 respectively, according to a parabolic band model.