Properties Of TiO₂and Al₂O₃Thin Films Deposited By Rf Magnetron Sputtering

Two series of oxide-TiO2and Al2O3films, fabricated on K9glass using the GJL560CI2sputtering system, have been investigated in this paper. TiO2films were deposited by directly sputtering the TiO2target with a very high purity under argon plasma environment, while Al2O3films were obtained by reactively sputtering where the oxygen was input into the chamber during the sputtering of the pure A1target. The effects of deposition parameters, such as sputtering power, depositon pressure and argon flow, on the microstructure and properties of the films have been studied and analyzed.Some conclusions on these two kinds of films are drawn out as following, respectively.1TiO2The as-deposited TiO2films are amorphous, and they become crystallized by an annealing heat treatment at450℃. The annealed samples, characterized by an anatase crystalline structure, have different crystalline orientation, depending on the sputtering power that was used to deposit the films. The negative bias, deposition pressure as well as argon flow affect the crystalline structure of the TiO2films, as indicated by the fact that the XRD spectra of the films differ from each other.The surface morphology of the films is influenced by the processing parameters applied during the deposition. The sputtering power, ranging within40W-100W, gives the lowest surface roughness at80W, resulting a smooth surface. As the negative bias increases, the surface roughness of the films increases at first, but it decreases while even larger bias is applied. Within the range of0.8-1.6Pa, the lowest of roughness1.16nm was achieved at1.2Pa, where the value of the surface roughness is1.16nm.When the Ar flow is40seem, the largest roughness of the film is observed.The sputtering power, the negative bias and argon flow have obvious effects on the deposition rate. As the sputtering power, negative bias and argon flow increas, the deposition rate increases. However, as the work pressure increases, the depostion rate decreases.The sputtering power, the negative bias, the work pressure and the Ar flow have influences on the refractive index, but have little effects on the extinction coefficients.2Al2O3Both the as-deposited and the annealed (450℃) Al2O3films, fabricated under different conditions, are amorphous.The deposition rate which ranges from0.5-3nm/min, is dependent on the sputtering power, the negative bias, and the ration of argon to oxygen flow Compared with other parameters, the sputtering power has a larger inflence on the deposition rate. The deposition rate increases with increasesing sputtering power. The fastest depostion rate is found at100V negative bias, which varies from0to120V. As the deposition pressure changes increasingly within0.2-1.6Pa,the deposition rate decreases and the maximum is achieved at0.2Pa. The deposition rate increases as the ratio of oxygen to argon flow increases, and it decreases when the ratio increases further.The Sputtering power, the negative bias, the work pressure and the ratio of argon to oxygen affect the refractive index of Al2O3films. As sputtering power increases, the refractive index increases but then decreases when the sputtering power furtherly increases. The refractive indice decrease with increasing wavelength within the visible range. The refractive index increases as the negative bias increases up to100V, after which the refractive index decreased a little. In case of0.2Pa, the refractive index decreases sharply with the increasing wavelength. Within the range of0.5-1.6Pa, the refractive index of Al2O3film decreases with increasing depositon pressure.The influence of work parameters to extinction coefficient are different. With sputtering power increasing the extinction coefficient k is first increases, then decreases, when power increases to300W extinction coefficient become O, the change trend of the extinction coefficient in different sputtering power to the wavelength is different, sputtering power in150W and300W, the extinction coefficient is not change with wavelength. In addition to negative bias for80V, extinction coefficient approximate is0, the extinction coefficient of the film in other negative bias is all0.In different negative bias, the extinction coefficient in different wavelength of the film didn’t change. In addition to working pressure for0.2Pa, the extinction coefficient in the200-400nm sharply reduce, the extinction coefficient with the wavelength in other work pressure is approximate constant. The extinction coefficient of the film in different argon oxygen ratio with wavelength are no relationship, are all zero. The effects of deposition pressure and the ratio of oxygen to argon on the refractive index of the films are similar to the results presented above. The deposition parameters have only negligible effects on the extinction coefficient of Al2O3thin films.