In this study, thin‐film microstructures of polymorphous niobium pentoxide were
successfully prepared at a low temperature. Spin coating was employed to deposit the
colloidal suspension before and after ultrasonic vibration. The deposited films were
characterised and analysed by X‐ray diffraction, scanning electron microscopy, and
spectrophotometry for optical investigation. Results show that the films prepared before
ultrasonic vibration possess a smooth and uniform surface. By contrast, films that
underwent further ultrasonic vibration exhibit an earth rock‐like structure and a highly
oriented, void‐ and crack‐free surface. Both film structures indicate the formation of a
monoclinic structure. Low energy gap values of approximately 2.5 eV and 2.25 eV are
suitable for heterojunction optoelectronic applications; this condition was proven by the
typical I‐V behaviours of the prepared heterojunction on the silicon substrate.
