Crystal Structure, Phase, and Electrical Conductivity of Nanocrystalline W_0.95Ti_0.05O₃ Thin Films

Abstract

W(0.95)Ti(0.05)O(3) films were fabricated using sputter-deposition onto Si(100) wafers in by varying the growth temperature from room temperature (RT) to 500 °C. X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDS), and Raman spectroscopy (RS) were performed to investigate the effect of temperature on the growth behavior, crystal structure, texturing, surface morphology, and chemical bonding of W(0.95)Ti(0.5)O(3) films. The results indicate that the effect of temperature is significant on the growth and microstructure of W(0.95)Ti(0.05)O(3) films. XRD results indicate that the effect of Ti is remarkable on the crystallization of WO(3). W(0)(.95)Ti(0.05)O(3) films grown at temperatures <300 °C are amorphous compared to pure WO(3) crystalline films crystallizing at 200 °C. Phase transformation is induced in W(0)(.95)Ti(0.05)O(3) resulting in tetragonal structure at ≥300 °C. The structural changes were also reflected in the intensities of -W-O-W- vibrational modes in RS measurements. The SEM imaging analysis indicates that the phase transformations are accompanied by a characteristic change in surface morphology. Room temperature electrical conductivity of W(0.95)Ti(0.05)O(3) films increases from 0.63 to 27 (Ω m)(-1) with increasing temperature from RT to 400 °C due to improved structural order. Electrical conductivity exhibit a decrease at 500 °C (7.4 (Ω m)(-1)) due to disordering induced by Ti segregation, which is confirmed by XRD and RS measurements.