Amorphization of pure noble metal nanocontacts by nanosecond electrical energization

Abstract Nanosecond-width pulse voltages were applied to a pure noble metal, i.e., face-centered cubic (fcc) structure iridium (Ir), of nanometer-sized contact (NC) forms. The dynamics of structure and the variation in the conductance of the NCs in the nanosecond electrical energization were investigated by in situ high-resolution transmission electron microscopy. We demonstrated that even in the pure noble metal NCs, crystalline phases transferred to amorphous phases by the nanosecond electrical energization. The inverse phase transformation, i.e., crystallization, was also observed by subsequent energization. The results showed that the phase control can be conducted even in the pure noble metal NCs of a fcc structure. The conductance of the NCs per the unit area of cross section varied in response to their phase variation; the average conductance ratio between the crystalline and amorphous phases was 0.86. The present study revealed that the pure noble metal NCs are applicable to nanometer-sized phase-change memory devices.