High-performance vanadium dioxide films with low phase transition temperatures of 40-50 degrees C were successfully fabricated by applying various negative substrate bias voltages at a low substrate temperature of 250 degrees C. This low-temperature preparation method and the films' thermochromic properties may provide useful suggestions for industrial production of VO2 films for smart window applications. The effects of the negative substrate dc bias voltage on the microstructure, surface morphology, and optical and electrical performance of the VO2 films were characterized. X-ray diffraction showed that the residual compressive stress in the films increased as the substrate bias increased, and the maximum value can reach - 576 MPa. Temperature-dependent sheet resistance measurement showed that the transition temperature (tau(c)) and room-temperature sheet resistance decreased significantly with increasing substrate bias, and the lowest value of tau(c) is 38.5 degrees C. The calculated solar energy modulation ability (Delta T-sol) of the VO2 film fabricated under a substrate bias voltage of -175 V at 250 degrees C is approximately 9.73%, which may indicate strong potential for application in smart energy-efficient windows produced industrially at a low substrate temperature.