Effect of heat treatment on the current induced dynamic mixed metal-insulator phase in needle-like VO₂ single crystals.

Sliding domains in the current induced mixed metal insulator phase of VO₂ single crystals are very sensitive on the crystal quality. Following measurements aimed to test this sensitivity were performed on an initially virgin needle-like crystal:
1. d.c. I-V measurements under steady state conditions (adequate load resistance in the NDR regime) carried out at ambient temperature on a VO₂ single crystal under the microscope while sliding domains were recorded on videos.
2. R(T) measured during three heating-cooling cycles between room temperature and 355 K.
3. Repeated d.c. I-V measurements under same conditions as in 1 with video recording of sliding domains.
The results show:
a. Slow cyclings through the transition have a healing effect on the sample: R(T) becomes reproducible and the activation energy in the insulating state is highest.
b. The damping term in u(J) (u- sliding velocity and J-current density) after heat treatment, is practically zero in contrast to its finite value before.
c. The energetics of sliding domains emission, determined by P(f) (P=IV- the power, f- the frequency) show that the energy per domain emission decreases with increasing f before heat treatment, but remains high and constant thereafter. This motivates studying samples with controlled imperfections.