Role of intrinsic defects on resistive switching in sputter-deposited and spin-coated BFO thin film devices

Resistive switching (RS) is an interesting phenomenon exhibited by certain materials. It has garnered significant attention for its potential in electronic device fabrication, particularly in nonvolatile memories. This study explores the RS characteristics of lead-free bismuth ferrite (BFO) material using two deposition techniques: Physical Vapor Deposition technique (sputtering) and Chemical Solution Deposition technique (spin-coating). Spincoating, known for its cost-efficiency and scalability, contrasts with sputtering, which offers better uniformity and less variability among RS devices. This manuscript examines the performance of RS devices fabricated using spin-coating and sputtering techniques of ferroelectric BFO material, while exploring the influence of intrinsic defects on various device performance parameters. X-ray Photoelectron Spectroscopy analysis demonstrated presence of more oxygen vacancies and bivalent iron defects in the spin-coated BFO thin film devices. Specifically, the Urbach energy, a measure of defect density, of spin-coated BFO thin films was found to be significantly higher 259 + 0.16 meV, showing a 100% increase compared to sputtered films (129 +0.87 meV). This discrepancy is attributed to differing annealing durations introducing intrinsic defect states in spin-coated films. The ITO/BFO/Pt thin film devices displayed moderate memory window of 60 + 13 and 600 + 27 for spin-coated and sputtered BFO thin films, respectively. The presence of intrinsic defects was found to affect the memory window of the devices. Spin-coated BFO thin film devices exhibit higher cell-to-cell variability (20 %) while sputterdeposited devices reveal lower variability, around 5 %, attributed to the less uniformity and higher defects in the former compared to the latter. Interestingly, a reciprocal relationship was observed between Urbach energy, intrinsic defects and memory window. A reduction in Urbach energy in sputtered BFO thin films leads to an enhanced memory window, in contrast to spin-coated BFO thin films, which exhibit higher Urbach energy. This suggests that Urbach energy may serve as an early indicator of memory performance. The intrinsic defects have been shown to degrade the memory performance of BFO-based thin film devices. Both deposition methods demonstrated stable endurance up to 105 cycles with less cell-to-cell variability which is highest reported for dopant-free BFO thin film devices. This confirms BFO as a promising material for resistive non-volatile memory applications across different fabrication techniques. (c) 2001 Elsevier Science. All rights reserved.