We obtained the band gap energy in different parts of a US thin film processed in a large area (450 cm(2)) by photomodulation (PM) at room temperature. This sample of large area was divided in several parts and we studied eight of them symmetrically distributed in order to determine the corresponding PM-signals. The film was grown on conducting glass (SnO2:F-7 Omega/square) by radio frequency-planar magnetron sputtering method and processed with a substrate temperature at 250 degreesC, a deposition time of 60 min, a radio frequency power of 300 W and with an Ar pressure of 20 mTorr. The results were compared with those obtained by optical transmission and are important from the point of view of getting a good uniformity in large samples. (C) 2003 Elsevier Science B.V. All rights reserved.