Studies are reported on the transformation of M1-phase vanadium dioxide into the stable M2 structure for a micro-fabricated device. The device is composed of a VO2 channel of length 50 μm, width 40 μm, and thickness 120 nm, and electrical contacts made of titanium and gold. Transformation is achieved in the channel region between electrical contacts by heating the entire structure to 40 C and simultaneously driving current. The channel is observed to partially transform along its length. Micro-Raman measurements reveal the two regions to be the M1 and M2-phases of VO2. X-ray photoemission measurements show the presence of gold in both regions, but with higher content in the M2 material. The M1 portion of the channel is found to undergo a phase transition to the conductive R phase at ∼ 63 C based on resistance and micro-Raman measurements as temperature is increased. The M2-phase is found to remain stable to temperature cycling between 25 and 120 C. We attribute both the reduced M1→R phase transition temperature and the stable formation of M2-phase VO2 to the presence ofgold.
- Raman spectroscopy
- metal-insulator phase transition
- vanadium dioxide