The Dynamic Mixed Metal–Insulator Phase in Self‐Heated Needle‐Like VO2 Single Crystals

Abstract

Reported herein is the mixed metal–insulator phase induced in needle‐like VO2 single crystals by direct current (DC) electric currents applied at ambient temperature; it appears in the current‐controlled negative differential resistivity (CC‐NDR) regime of the nonlinear I–V characteristic governed by self‐heating. In this regime, the I–V characteristic is stable for RL ≥ |dV/dI|max, (RL—the load resistance); for lower RL, portions of I–V are unstable and switching occurs between initial and final steady states (SSs). In high‐quality needle‐like VO2 single crystals (cross‐sectional area < 2 × 10−5 cm2) the SS NDR regime is “unique,” whereas crossing from the insulating to the mixed phase I(V) is almost—or perfectly—smooth, the dissipation power (P = IV) versus current bends and this bend is accompanied by the appearance of insulating domains sliding along the metallic background in the sense of the current. The periodic domain emission, the variation of the dynamic parameters (domains’ frequency and sliding velocity) over the steady‐state NDR regime, and the energetics of the process are discussed. These results show that the process of domain emission and sliding is fairly expensive at low frequencies but there is some evidence that the process becomes more efficient at higher frequencies.