Effect of the Oxygen Flux Ratio on the Structural and the Optical Properties of Silver-oxide Films Deposited by Using the Direct-current Reactive Magnetron Sputtering Method

Using values of the oxygen flux ratio (OFR = [O2]/[Ar]) ranging from 0 to 0.5, authors deposited a series of silver-oxide (Ag(x)O) films on glass substrates by direct-current reactive magnetron sputtering (DC sputtering) at a substrate temperature of 150 degrees C. The effect; of the OFR, on the film's structural and optical properties was systematically investigated by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. The Ag(x)O films deposited clearly show an evolution of the film's phase structure from the biphased (Ag + Ag(2)O) structure to the biphased (AgO + Ag(2)O) structure and then to the single-phased (Ag(2)O) structure as value of the OFR increases. Accordingly, the film's surface morphology, related to the film's crystalline structure, clearly changes from a loose and porous surface structure to a compact surface structure and then to a pyramid-like surface structure with increasing value of the OFR. The novel porous structure may be attributed to the interruption of the silver's growth course by the AgO on the film's surface. Notably, a single-phased Ag(2)O film is deposited by DC-sputtering at OFR = 0.5 due to the dual effects of thermal decomposition of the AgO phase and a combination reaction of AgO and Ag to Ag(2)O. The oscillations both in the film's reflectivity and transmissivity spectra are strengthened with increasing OFR, indicating an evolution from the metallic behavior of the biphased (Ag + Ag(2)O) film to the dielectric behavior of the biphased (Ag(2)O + AgO) film and the single-phased Ag(2)O film. The fitted optical absorption edges of the Ag(2)O and the Ag(x)O films deposited at values of the OFR, of 0.5 and 0.33 are approximately 2.43 eV and 2.34 eV, respectively. The absorption edges are closely related to the direct interband transitions.