The properties of individual inverted gate, thin film transistors (TFT) with a range of channel width to length from 2/2 to 4780/4 fabricated on 5 mu m thick polyimide substrates have been investigated. In addition to the room temperature properties, the effects of illumination, bias stress and temperature have been measured. The current as a function of voltage of the TFTs scale linearly with transistor size and the threshold voltages are independent of size. Illumination of the transistors increases the off current and decreases the threshold voltage. Gate characteristics were determined for transistors before and after a bias stress of V-GS = 20 V for t = 10, 10(2), 10(3) and 10(4) s. The threshold voltage shifted to larger voltages and the on/off ratio decreased with application time. Gate and transfer characteristics of the TFTs were measured every 25 degrees C from 25 degrees C to 125 degrees C, The threshold voltages decreased with increasing temperature while held effect mobilities increased. (C) 2000 Elsevier Science B.V. All rights reserved.