Structural Dependence of the Optical Properties of Cr$_{1-x}$Cu$_{x}$ Alloy Films

Cr$_{1-x}$Cu$_{x}$ ($0 < x < 1$) alloy films have been prepared by face-to-face dc sputtering of the Cr and the Cu targets on a large glass substrate (25 x 120 mm$^{2}$ in dimension), located parallel to a line connecting the Cr and the Cu targets and kept at room temperature. After deposition, the sample was cut into 12 pieces along the short side of substrate, and a set of 12 alloy films with different compositions were obtained. The composition of each alloy sample was determined at its central part by x-ray fluorescence. The structural characterization of Cr$_{1-x}$Cu$_{x}$ alloy films was performed by high-angle x-ray diffraction. The optical properties were investigated by using a spectroscopic ellipsometer at room temperature in a spectral range of 265 - 2500 nm (4.7 - 0.5 eV). It was found that the optical properties were categorized into two groups with different crystalline structures