Establishing a relation between surface roughness and non-volatile resistive switching in VO 2 − x -based devices: A temperature dependent study

Temperature dependent resistive switching (RS) and non-volatile characteristics are systematically studied in Ag/VO 2 − x /Si MOS devices. Oxygen deficient VO 2 films were deposited on n -type Si (100) substrates at room temperature using rf magnetron sputtering of VO 2 target in pure argon plasma. Broad endothermic response seen in DSC indicates beginning of phase transition at much lower temperature influencing the I − V properties. Synchrotron-based GIXRR studies show increase in surface roughness with temperature affecting the RS properties due to enhanced lattice distortion with partial surface reordering at ∼ 90 ∘ C . The interface roughness remains nearly constant with temperature. Temperature dependent C − V and I − V studies reveal strong link between vacancy dynamics, semiconductor to metal transition (SMT), and RS behavior. RS nature changes with temperature from analog to digital one originated from stoichiometric deviations specifically oxygen deficient VO 2 , evident from temperature dependent XPS. C − V measurements further indicate role of oxygen vacancies (OVs) and interfacial reactions on accumulation capacitance and flat-band voltage. Overall, the results highlight the effect of surface roughness and crucial role of OVs in RS phenomena. These findings not only enhance the understanding of defect-assisted switching in correlated oxides but also offer valuable design ideas for developing VO 2 -based non-volatile memory and neuromorphic devices. • An extended endothermic peak during ramp up cycle proves initiation of phase transition well below 67 °C, likely originated from oxygen deficiency, lattice stress etc. • GIXRR analysis reveals an increase in surface roughness near the semiconductor–metal transition at ∼ 60 ° C . • Temperature dependent XPS reveals coexistence of V 3 + and V 4 + states in VO 2 − x at room temperature confirming intrinsic oxygen vacancies formed during deposition and presence of V 3 + states at higher temperatures. • I − V characteristics show analog switching at RT, initiation and stability of digital switching well below the transition temperature and up to 175 °C.