Polyethylene terephalate film is highly desirable material, having properties which include high strength with low weight and with high visual transparency, therefore its study is concenred about high value packaging applications. Pysical vapor depostions(PVD) techniques offer a means of depositing refractory materials onto polymeric substrates at low temperature as well as the advantage of performing accurately controllable deosition. Ceramic coatings deposited on polymers are suitable in packaging applications where high gas-barrier properties are needed. The purpose of this work is to investigate some of the basic properties of sputtered alumina coatings and to show their dependence on the plasma time and the rf power.