Self-heating and external strain coupling induced phase transition of VO₂ nanobeam as single domain switch.

Besides by temperature, this transition can also be driven by manipulation of various external stimuli, such as pressure, metal doping, photo-carrier injection and electric fi eld, which have a profound effect on the phase transition. However, to date most works have been carried out based on epitaxial thin fi lms or bulk crystals, in which the spatially inhomogeneous polycrystalline domains, local internal strain, and defects in the system result in the discontinuous and irregular phase domain structures when the transition occurs. If one takes the case of the temperature-induced transition process as an example, the system resistance decreases gradually over a wide temperature range, indicating the reordering of the introduced strain and secondary arrangement of phases within twoor three-dimensional structures. Therefore, it is diffi cult to realize independent control of temperature and strain, which may limit the application of VO 2 in novel devices. Recently work by Cao et al. on one-dimensional VO 2 nanobeams brought the possibility to eliminate the irregular distribution of domains. [ 2 ] Single crystal, fi ne diameter and anisotropy with strain-sensitive growth direction ( c R , caxis of rutile phase) make the formed metallic (M)/insulating (I) domain periodically aligning along the axis direction. Particularly, compared to the multiple-domain transition, the phase switch of a nanobeam based on a single domain has more potential applications in functional devices such as phase-change memories, [ 3 ]