Zinc oxide - a transparent, conducting IR-reflector prepared by rf-magnetron sputtering

Al doped zinc oxide thin films with different electrical and optical properties have been developed by both non-reactive and reactive rf-magnetron sputtering in Ar and Ar + H-2 atmospheres, respectively. The thin films prepared under Ar + H2 gas ambient at substrate temperatures of 100degreesC and 300degreesC show high conductivity and improved IR-reflectivity. The lowest resistivity obtained is 4.5 x 10(-4) Omega cm at 300degreesC. The transmission of the ZnO: Al film in the visible range is above 90% and that at 1400 nm is only 3.2%. Most of the IR-region is thus reflected. The carrier concentration of this transparent, conducting ZnO film prepared under Ar + H-2 atmosphere is 2.3 x 10(21) cm(-3). Tranmission electron micrographs reveal that the average crystallite of the sample deposited under Ar + H-2 ambient is smaller compared to those prepared under Ar ambient. The (100), (002) orientations of ZnO with wurtzite structure are observed from transmission electron diffraction pattern.