Discharge diagnosis and controlled deposition of SnOx : F films by DC-reactive sputtering from a metallic tin target

Fluorine-doped tin oxide (SnOx:F) films on glass substrates have been prepa red by reactive magnetron DC-sputtering in Ar-O-2-Freon plasma from a metal lic tin target. We studied the relationship between the discharge character istics and film properties and found the discharge conditions in which the films belong to the SnO2 or to the SnO stoichiometry, by proposing a phase diagram for this system. We showed that the film stoichiometry is closely r elated to the tin valence changes at the target. We found that there is a n arrow voltage band and a limit value in the oxygen content where the films have SnO2 stoichiometry; outside this region SnO films are obtained. We stu died the crystallinity and the optical properties of the SnO2 films. The re sults show that crystalline films have cassiterite-like diffraction pattern s with preferred orientation in the (110) planes. The crystallinity of the films is improved when the discharge voltage and oxygen content increase. A thermal annneling of the amorphous films at 500 degrees C leaves them in t he crystalline cassiterite-like form. The films have a transmittance of sim ilar to 80% in the visible region of the spectrum and a uniform thickness. (C) 1999 Elsevier Science S.A. All rights reserved.