Physical vapor deposition of copper over Lexan

Lexan is a polymer which is light-weight and extremely smooth, and is a candidate material for radio-frequency reflecting mirrors provided that they are coated with strongly adherent copper coatings. In the present investigation copper was sputtered from a dc magnetron source and deposited on Lexan surfaces. Various pretreatments were given to the Lexan surface, e.g., being exposed to pulsed dc or rf argon plasma. During deposition the Lexan surface was biased to various pulsed voltages ranging upto − 5 kV with various repetition rates and on times. All these parameters decide whether the copper coatings are strongly adherent to the Lexan surface. The results indicate that the coatings deposited over pretreated (etched) substrates showed better adhesion to the Lexan surface and the deposited coatings in general exhibit compressive stress. XRD studies revealed polycrystalline coatings with nano-sized grains and having a preferred (111) orientation.