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The structural, optical, and transport properties of sputter-deposited Al-Ti thin films 

have been investigated as a function of Ti alloying with a concentration ranging from

2% to 46%. The opticalreflectivity of Al-Ti films at visible and near-infrared wavelengths

decreases with increasing Ti content. X-rayabsorption fine structure measurements

reveal that the atomic ordering around Ti atoms increases with increasing Ti content

up to 20% and then decreases as a result of a transition from a polycrystallineto 

amorphous structure. The transport properties of the Al-Ti films are influenced by 

electron scattering at the grain boundaries in the case of polycrystalline films and static

defects, such as anti-site effects and vacancies in the case of the amorphous alloys. The

combination of Ti having a real refractive index (n) comparable with the extinction

coefficient (k) and Al with n much smaller than k allows us to explore the parameter

space for the free-electron behavior in transition metal-Al alloys. The free electron

model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to

an optical reflectance at near infrared wavelengths that scales linearly with the square

root of the electrical resistivity.
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