SPECTROSCOPIC CHARACTERIZATION OF PROCESSING-INDUCED PROPERTY CHANGESIN DOPED ZNO FILMS

The optical response and electronic conductivity of neat and trivalent cation doped ZnO films are dependent upon film deposition parameters and subsequent post-deposition processing. As-deposited films which sh ow high resistivity can be made conducting through gas phase reduction with hydrogen at elevated temperatures or by electrochemical reductio n at room temperature using both aqueous and nonaqueous solvents. Resi stive sputter and solution deposited films which exhibit c-axis or ran dom crystallite orientation respectively, become conducting after thes e treatments and show increased infrared reflectivity owing to free ca rrier absorption. Raman measurements are used to confirm the wurtzite crystalline phase and dopant incorporation into the lattice. Optical p roperties of selected films are determined from transmission and spect roscopic ellipsometry measurements using models parameterized with pre viously determined microstructural information. Based upon the electro chemical results, a mechanism is proposed to describe the reduction pr ocess which requires the generation of atomic hydrogen as a reducing s pecies. (C) 1997 Elsevier Science S.A.