Identifying the Role of Domains in Metal-Insulator Transitions in Individual Nanowires of Tungsten-Doped $VO_{2}$

Though it is well known that the metal-insulator transition (MIT) in $VO_{2}$ can be achieved by a variety of external parameters, an understanding of how different parameters drive such a transition has remained relatively unknown. We report transport and Raman spectroscopic characteristics on voltage ($V$)- and temperature ($T$)-driven MIT in individual, single-crystal, tungsten-doped $VO_{2}$ nanowires. From transport analyses we discuss the $T$-dependent features in $I$ vs $V$ curves; specifically hysteresis gaps and resistance jump features seen in sub-micron devices. From Raman spectroscopic analyses we discuss the Raman intensity of $A_{g}$ modes while driving the temperature and voltage across the transition. We conclude that driving $T$ supports a slow transition to the rutile (R) metallic phase with a wide temperature range of mixed insulating, monoclinic (M1) and R states due to the population of metallic domains. $V$-driven transition does not appear evolve via the formation of domains, but is activated when $V$ is sufficiently large above a $T$-dependent threshold.