Highly sensitive ultraviolet detector using a ZnO/Si layered SAW oscillator

This study elucidates a highly sensitive ultraviolet light detector using the combination of an oscillator circuit with a high-frequency amplifier, a matching network and a layered surface acoustic wave (SAW) device In this structure, a ZnO thin film is simultaneously used as an active layer for UV detection and a piezoelectric layer for exciting a high-order surface acoustic wave The microstructure and crystallization of ZnO films were investigated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SAW oscillator shows a good performance with output power of -1.14 dBm and phase noise of -947 dBc at 100 kHz Firstly, the frequency shifts of the oscillator exhibit rapid increase with the intensity of the UV light. Then the increased shifts decayed at certain UV intensity due to the saturated photogenerated carriers An extreme frequency shift of 1017 kHz was obtained as the UV intensity reached 551 mu W/cm(2) The maximum sensitivity of 8 12 ppm/(mu W/cm(2)) can be obtained in this detector (C) 2009 Elsevier B V All rights reserved