RESUMO
The fabrication of highly reflective aluminum coatings is still an important part of current research due to their high intrinsic reflectivity in a broad spectral range. By using thin seed layers of Cu, CuOx, Cr, CrOx, Au, and Ag, the morphology of sputtered (unprotected) aluminum layers and, consequently, their reflectance can be influenced. In this long-term study, the reflectance behavior was measured continuously using spectrophotometry. Particular seed layer materials enhance the reflectance of aluminum coatings significantly and reduce their long-term degradation. Combining such seed layers with evaporation processes and suitable protective layers could further increase the reflectance of aluminum coatings.
RESUMO
The potential of titanium and copper seed layers to enhance the optical properties of aluminum films for ultra-violet (UV) applications is analyzed. The seed layers significantly influence the initial layer growth of aluminum films. For the titanium-seeded aluminum, a surface roughness of 0.34 nm was observed. UV spectral reflectance measurements showed an average higher reflectivity of 4.8% for wavelengths from 120 nm to 200 nm for the aluminum film grown on the titanium seed layer. Furthermore, the titanium-seeded aluminum coatings were stable at an elevated temperature of 225°C and showed no increase in surface roughness or pinholes.