Field-effect modulation of conductance in VO$_2$ nanobeam transistors with HfO$_2$ as the gate dielectric

Field-effect transistors have been fabricated from VO$_2$ nanobeams using HfO$_2$ as the gate dielectric. When heated up from low to high temperatures, VO$_2$ undergoes an insulator-to-metal transition. We observe a change in conductance (6 \%) of our devices induced by gate voltage when the system is in the insulating phase. The response is reversible and hysteretic, and the area of the hysteresis loop becomes larger as the rate of gate sweep is slowed down. A phase lag exists between the response of the conductance and the gate voltage. This indicates the existence of a memory of the system involving a timescale of a few minutes. The origin of such slow processes may lie in the coupling between the dipolar arrangement and the strain state of the VO$_2$ crystal.