Influence of oxygen vacancies in ALD HfO_(2-x) thin films on non-volatile resistive switching phenomena with a Ti/HfO_(2-x)/Pt structure

摘要

Graphical abstractDisplay OmittedHighlights•Oxygen vacancies in ALD HfOxthin film were modulated by varying oxidant pulse time.•Resistive switching behaviors are governed by connection/disruption of filament via reduction/oxidation.•Conduction mechanism clearly depends on amount of oxygen vacancies.AbstractWe report a modulation of oxygen vacancies profile in atomic layer deposition (ALD) HfO2-xthin films by reducing oxidant pulse time (0.7 s–0.1 s) and study its effect on resistive switching behavior with a Ti/HfO2-x/Pt structure. Hf 4f spectra of x-ray photoelectron microscopy (XPS) and depth profile confirm varied oxygen vacancies profiles by shifts of binding energies of Hf 4f5/2 and Hf 4f7/2 main peaks and its according HfO2-xsub-oxides for each device. The ultraviolet photoelectron spectroscopy (UPS) confirms different electron affinity (χ) of HfO2and HfO2-xthin films, implying that barrier height at Ti/oxide interface is reduced. Current transport mechanism is dictated by Ohmic conduction in fully oxidized HfO2thin films - Device A (0.7 s) and by Trap Filled Space Charge Limited Conduction (TF-SCLC) in less oxidized HfO2-xthin films - Device B (0.3 s) and Device C (0.1 s). A switching mechanism related to the oxygen vacancies modulation in Ti/HfO2-x/Pt based resistive random access memory (RRAM) devices is used to explain carefully notified current transport mechanism variations from device-to-device. A proper endurance and long-time retention characteristics of the devices are also obtained.