Carrier-Induced Metal-to-Insulator Transition in Electrostatically Doped VO₂

Metal-to-insulator transition (MIT) in strongly correlated electronic systems such as vanadium dioxide (VO2) is known to be modulated by carrier doping. However, previous attempts show modification of carriers in VO2 are always concomitant with lattice distortions, making it challenging to decouple pure electronic contribution in MIT. In this work, we synthesize and demonstrate a pure filling-controlled MIT in VO2 using modulation-doped heterostructures. With a combination of electrical transport and hall measurements, we show that carrier concentrations in VO2 can be modulated both by varying the dopant densities in the dopant layer and by varying the thickness of the VO2 layer. The increase in carrier densities up to ∼1021 cm–3 in the insulating phase led to a decrease in transition temperatures by ∼40 K. Additionally, X-ray photoelectron spectroscopy was utilized to rule out the presence of oxygen vacancies as a source of electron donors in VO2. We further present that the modulation-doped heterostructures with an amorphous insulating spacer layer offer unambiguous evidence of pure filling-controlled MIT in VO2. Our work shows that modulation doping is a potent strategy for realizing carrier-induced condensed matter phases in other correlated electronic systems, paving the pathway for the possible development of Mott devices.