Preparation of WO3 network squares for ultrasensitive photodetectors

Three-dimensional WO3 network squares have been fabricated on a large scale by a hydrothermal method at 160 degrees C without any template or surfactant. The characterization of the network squares with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicates a single crystalline hexagonal structure with a square of side length up to 20 mu m. The influence of pH value on the morphology of the final product has been studied, indicating that more uniform WO3 network squares can be obtained at pH 1.7. A possible growth mechanism involves the Ostwald ripening, oriented attachment and etching effect. The UV-vis reflection spectrum indicates a band gap of similar to 3.2 eV. The photodetector based on a single WO3 network square shows remarkable photosensitivity under intermittent illumination of the simulated sunlight, which could mainly be attributed to the specific network structure of WO3 and the Schottky contacts. (C) 2011 Elsevier B. V. All rights reserved.