RETRACTED ARTICLE: HFCVD Application for Growth of Monoclinic Tungsten Trioxide Crystal Nano-walls

Abstract

In this research the hot filament chemical vapor deposition technique application for growth of monoclinic tungsten trioxide crystal nano-walls on Si substrates without using catalysts was presented. The products were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and four-point probe instrument. The FESEM images and XRD patterns show that crystallinity of the samples was improved when the substrate temperature increases to 800 °C. The peaks intensity of WO3 are enhanced by increasing the substrate temperature, which can be understood based on the fact that the thermal energy enable atoms to diffuse, as a result, a more perfect crystal structure was obtained. From FESEM images, it can be seen that by increasing the temperature the nano-walls structure appears and continues to grow sharper. The width of the nano-walls is in the range of 80–300 nm and lengths of them are about 5 μm. The electrical measurement results show that the resistivity decreased with increasing the substrate temperature, in such a way high crystallinity samples with sheet resistance of 36 Ω/sq and sharper nano-walls morphology were obtained with a temperature of 800 °C. Also measurements of binding energies of both the XPS spectra W4f and O1s core-level electrons indicated that the sample is stoichiometric with maximum substrate temperature.