2023 年 21 巻 4 号 p. 324-330
A VO2 film with a thickness of 400 nm was deposited on indium-tin-oxide/glass substrate by the inductively coupled plasma-assisted radio frequency magnetron sputtering method. A temperature-dependent Raman spectrum exhibits mixed VO2 M2 and triclinic (T) phases at room temperature. A resistance change of more than one order of magnitude is achieved in out-of-plane direction in the prepared sample. The current-voltage (I-V) characteristics of the prepared sample are investigated by varying the contact probe force on the VO2 side from 1 to 30 gf. At low probe forces, a multi-step like I-V characteristic is obtained. On the other hand, when the probe force is increased, the I-V characteristic similar to the usually reported I-V in VO2 is obtained. Moreover, it was found that the hysteresis width of the I-V characteristics became larger with increasing the probe force. In oscillation measurements, the self-sustained electrical oscillation was obtained until 20 gf. At 20 gf, the oscillation region became smaller than 1 and 5 gf. However, the oscillation was not found at 30 gf. This is responsible for the large hysteresis width in the I-V characteristics. The results suggested that there is a strong correlation between the hysteresis behavior of the I-V characteristics and the oscillation characteristics. We believe that the findings of the present study will contribute to the further acceleration of the application of the VO2 films in various fields.
