We report the size effects on the metal-insulator phase transition of vanadium dioxide (VO₂) nanowires prepared by chemical vapor deposition. The phase transition temperature can be tuned from 67 °C in the bulk VO₂ to as low as 29 °C by reducing the diameter of VO₂ nanowires to nanoscale. Temperature-dependent Raman spectra display a clear dynamic picture on the metal-insulator phase transition process of the VO₂ nanowires. Whilst, Raman study shows no remarkable strain effect on the phase transition behaviors of our samples. The increasing surface defect density with reducing nanowire size facilitates the decreasing phase transition temperature. In addition, the polarized-photocurrent effect was observed, resulting from the anisotropy of the photoresponse and also caused by the reduced dimensionality. Our results indicate that size of VO₂ nanostructures can dominate their thermoelectric and photoelectrical properties.

Bottom-contact organic field-effect transistors (OFETs) based on poly(3-hexylthiophene) with different channel lengths were fabricated under different substrate pretreatment process conditions. These OFET devices were characterized using low frequency noise (LFN) spectroscopy, and the device performance parameters were correlated with the level of LFN. It is observed that the devices with higher noise levels showed poorer device properties when compared with the devices operated at same $I_{\text{ds}}$ of the same channel length. It is also observed that the noise level increased with the increase in channel length for devices with the same pretreatment conditions, which is due to increased trapping and detrapping in the channel material interface domain. The OFET device operating around the threshold voltage $V_{\text{th}}$ will have a $1/f$ noise slope that is flatter, having a gradient that is smaller in magnitude. The threshold voltage of a device can thus be observed to be at the gate voltage in which $1/f$ noise intensity is the highest at low frequencies.