Selected Electrical Properties Of Rf Sputtered Al2o3 Cr2o3 Thin Films

An investigation was made into the effect of rf magnetron deposition parameters on the resulting properties of chromium oxide thin films. The films were sputtered in an argon/ oxygen plasma environment with the main deposition parameters being the argon and oxygen flow rate, chamber pressure, deposition-time and the deposition power (forward and back). Tire effect of the sputter deposition regime which is controlled by the sputtering hysteresis phenomenon i.e. the reactive and metallic regimes, are expected to have a significant effect on the properties of the sputtered films and will have to be taken into account. The films were deposited on a range of substrates such as silicon, glass micro-slides and stainless steel 304 and the composition of the mainly amorphous sputtered films was determined through XPS, EDX and XRD. Optical characterisation and determination of optical constants was undertaken by transmission/reflection spectrophotometry, ellipsometry and Raman and FTIR analysis. Two designs of a solar thermal absorber (multilayer interference and tandem absorber) were designed and fabricated based on the optical constants measured by the methods previously stated and their performance analysed. The surface energy was calculated through measurement of the contact angle with three different liquids and the corrosion resistance of the films measured by OCP, linear sweep and EIS analysis in 3.5wt% NaCI solution. The mechanical properties were measured by nanoindentation, from which the hardness and elastic modulus of the samples could be obtained. The electrical properties were measured using a four point probe to calculate the thin film resistivity and the Kelvin probe analysis was used to measure the work function of the samples.

The physical and electrical properties of aluminum oxide films deposited on silicon by rf sputtering from an alumina target in an argon atmosphere were investigated as a function of sputtering power density in the range from 0.5 to 3 W/sq cm. The deposition rates ranged from 20 to 80 A/min. The density, index of refraction, and dielectric constant of the films increased while the etch rate decreased with increasing power density. The surface charge at the aluminum oxide-silicon interface was typically larger than 10 to the 12th. This charge increased with increasing sputtering power density and could be reduced to 7-8 x 10 to the 11th e/sq cm by annealing. The films exhibited trapping instabilities at room temperature but no polarization was observed under biastemperature stress. The characteristics of composite layers of thermally grown silicon dioxide and sputtered aluminum oxide layers on silicon were also investigated and found to exhibit low surface charge densities, no hysteresis, and a 'contact potential' as well as charge stored at the interface between the two insulators. (Author).

During the last few years, sputtering has become a very important industrial technique for depositing thin films. Typical applications include metalization and passivation in the electronics industry, the deposition of complex cermets, glasses, and plastics, and the formation of coatings for corrosion, abrasion, and wear resistance. However, relatively little work has been reported on the growth of compound semiconducting films by sputtering.

In this book we have discussed the preparation and characterization of CdO thin films using RF reactive magnetron sputtering technique. The deposition parameters such as oxygen partial pressure, substrate temperature and film thickness are optimized for producing good quality films. Systematic characterization of as deposited and annealed films has been discussed from the crystal structure, surface morphology, film composition, optical and electrical properties. The films prepared under optimized conditions are tested for gas sensing characteristics towards ammonia gas.