Synthesis and electrical behavior of VO2 thin films grown on SrRuO3 electrode layers

Abstract

VO2 thin films were grown on conducting oxide underlayer SrRuO3 buffered SrTiO3 (111) and Si/SiO2 substrates, respectively, using sputtering. X-ray diffraction phi-scans revealed the epitaxial nature of the VO2 films grown on SrRuO3 buffered SrTiO3 and polycrystalline structure for films grown on SrRuO3 buffered Si/SiO2. X-ray photoelectron spectroscopy confirms a dominant presence of V4+ in both films and establishes a high-quality growth of single-phase VO2 films. Temperature and electric-field driven metal-insulator-transition in both the in-plane and out-of-plane configurations were investigated. Depending on the configuration, the resistance change across the metal-insulator-transition varies from a factor of 1.57–3. The measured resistance in each state as well as the magnitude of resistance change were similar during temperature and electric-field driven metal-insulator-transition. To shed light on the suppressed metal-insulator-transition characteristics due to the current shunting effect from conducting SrRuO3 bottom electrode, a distributed resistance network model is proposed and benchmarked against reports from the literature. The results demonstrate the growth of high-quality VO2 on conducting SrRuO3 layers and their electrical behavior, which is of particular interest for all-oxide electronic devices utilizing phase transitions such as resistive memory and neuromorphic oscillators.

Reconfigurable Resistive Switching in VO2/La0.7Sr0.3MnO3/Al2O3 (0001) Memristive Devices for Neuromorphic Computing

“…The MIT occurs at ∼340 K, as demonstrated by an abrupt drop in resistance, which agrees well with the VO 2 bulk phase transition temperature. , However, the magnitude of the phase transition in our vertical device seems much smaller than that of VO 2 thin films on insulating substrates where a lateral configuration has been commonly used for R – T measurement. , This is expected as the resistance of VO 2 in the vertical geometry is comparable to or smaller than the electrode and contact resistance, whereas the resistance of VO 2 in a lateral configuration is much larger than the electrode and contact resistance. Another possible reason for this could be the presence of defects and grain boundaries in the VO 2 film, as suggested by previous reports. , The gradual decrease in resistance below and above the phase transition temperature of 340 K can be attributed to the increased charge carrier concentration in the VO 2 thin films by the thermal effect . Especially, the decrease in overall resistance after MIT in the VO 2 could be due to a decrease in resistivity of the LSMO bottom electrode at elevated temperatures.…”

“…As seen in Figure a, the current (resistance) gradually increases (decreases) with increasing temperature from room temperature up to 60 °C. When the temperature rises above 70 °C, an abrupt increase in current is observed due to the MIT of the VO 2 . , These measurements were used to extract the activation energy ( E a ) and thermally activated conduction mechanism, as shown in Figure b. The temperature-dependent resistance of the device can be expressed as , log [ R ] = R o + E a / k T where R o is the resistance at room temperature, k is the Boltzmann constant, and T is the temperature.…”

Epitaxy of Monoclinic VO2 on Large-Misfit 3m Template Enabled by a Metastable Interfacial Layer

“…AFM surface morphology characterizations reveal root-mean-square (RMS) roughnesses of 1.51 and 1.92 nm for the CFO template and the VO 2 film (Figure d,e), respectively. Note that the RMS roughness obtained here is considerably lower than those of the VO 2 epilayers deposited on [LaAlO 3 ] 0.3 [Sr 2 AlTaO 6 ] 0.7 (111) and SrRuO 3 -buffered SrTiO 3 (111) , and are comparable with the value for the VO 2 /Al 2 O 3 (0001) film (Figure S3).…”

Nanoscale Enhancement of the Local Optical Conductivity near Cracks in Metallic SrRuO3 Film

“…Here we report how nanocracks affect the physical properties of metallic SrRuO 3 (SRO) films. SRO films are the most widely used electrode materials for oxide electronics applications. − They have a very high conductivity (∼10 3 Ω –1 cm –1 ), which means they have excellent electrical properties . They are quite stable with low reactivity with other substances .…”