Optical, electrical and structural properties of Al–Ti and Al–Cr thin films
Njoroge, W. K.
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The influence of Ti and Cr on the optical, electrical and structural properties of thin Al films was studied with the goal of maintaining the high reflectance of thin Al films, but to reduce the thermal, and thus also, electrical conductivity. The optical properties were measured using optical spectroscopy in the range from 9000 cm−1 (1111 nm) to 50 000 cm−1 (200 nm), while the resistivity was determined using the van der Pauw-method. For Ti and Cr concentrations up to 15 at.%, the reflectance at 12 050 cm−1 (830 nm) was hardly affected, while the sheet resistance increased linearly with both the Ti and Cr concentration. Resistivity measurements during annealing show that Al–Ti films are stable up to 200°C, while Al–Cr films are stable up to 300°C. Above these temperatures, phase separation takes place. X-Ray reflectometry, X-ray diffraction, atomic force microscopy and Rutherford backscattering are used to corroborate these findings. The comparison of the two alloys helps to decide which film is more suitable as a reflective layer in erasable or rewritable optical data storage applications.