Toward High-Precision Control of Transformation Characteristics in VO2 through Dopant Modulation of Hysteresis

Metal-insulator transition materials such as VO2 have garnered much attention in the field of neuromorphic devices because of their nonlinear behavior and orders of magnitude scale property changes. Of interest is the ability to control their transformation and hysteresis through dopants. However, a deep understanding of the effect of each dopant on the VO2 system remains lacking. Here, we utilize an optical technique to investigate the changes produced by substitutional tungsten and interstitial boron dopants when compared to an undoped VO2 system. Tungsten demonstrates the ability to decrease the transition temperature, reduce hysteresis, and increase the transformation width. Boron also shows small increases to the transformation width but is accompanied by a larger hysteresis and unique relaxation effects. Single-particle imaging demonstrates that broader hysteresis observed in ensemble calorimetry measurements results from variations of dopant incorporation among populations of particles. Additionally, both dopants seem to negate the size effects observed in undoped particles because of their ability to enhance or suppress point defect concentrations and thereby improve the consistency of hysteresis. Both effects are essential for utilizing VO2 in practical applications such as neuromorphic devices requiring precise control of transformation characteristics.