Polycrystalline T- and H-Nb₂O₅ Thin Films Prepared by Pulsed Laser Deposition: Impact of Laser Fluence

Polycrystalline structures of T-Nb₂O₅ and a remarkable H-Nb₂O₅ structure were successfully obtained in this work. This was achieved using a Nd:YAG laser in a pulsed laser deposition system at laser fluence values of 9.3, 13.4, 16.2, 21, and 25.2 J cm⁻². Raman bands of the prepared films are shown and discussed. The optical bandgaps were estimated at 4.81 eV, 4.73 eV, 3.41 eV, 3.29 eV, and 3.21 eV. Photoluminescence (PL) analyses showed agreement with the estimated indirect bandgaps calculated from Tauc’s plot for each prepared film. The surface average roughness and root-mean-square (RMS) roughness were also determined and are discussed. The surface morphology as illustrated by field-emission scanning electron microscopy (FE-SEM) reveals the obvious impact of laser energy density on the prepared films. Energy-dispersive x-ray (EDX) analyses revealed the highest stoichiometry attributed to a laser fluence of 21 J cm⁻².