Analyzing the Bolometric Performance of Vanadium Oxide Thin Films Modified by Carbon Nanotube Dispersions

The influence of carbon nanotube (CNT) dispersions on the electrical properties and noise signal amplitude of $V{O}_x$ films is investigated. For a critical range of the CNT dispersion density on $V{O}_x$ films, the intrinsic properties of the $V{O}_x$ films are modified by the CNTs. The CNT concentrations reported in this work are about 0.3 $\mathsf{\mu }$g/cm${}^2$ and 1.6 $\mathsf{\mu }$g/cm${}^2$, allowing for low density and high density dispersions on the $V{O}_x$ film surface to be investigated. These values are higher than the percolation threshold of about 0.12 $\mathsf{\mu }$g/cm${}^2$ for these films. The composite film exhibits a significant reduction in the temperature coefficient of resistance (TCR) (from ≈3.8% $K^{-1}$ to ≈0.3% $K^{-1}$) for high density dispersions. In contrast, while $V{O}_x$–CNT composites with low density single wall CNT dispersions exhibit no significant change in TCR values, an approximate two orders of magnitude reduction in the low frequency 1/f noise is measured. The noise signal amplitude measured at 0.1 V and at 1.0 Hz reduces from 6 × ${10}^{-5}$$V/\sqrt{(}Hz)$ for $V{O}_x$ films to 5 × ${10}^{-7}$$V/\sqrt{(}Hz)$ for the low density SWCNT dispersion on $V{O}_x$ film and to 3 × ${10}^{-6}$$V/\sqrt{(}Hz)$ for the low density MWCNT dispersion on $V{O}_x$ film. The CNT concentration is the critical factor for yielding the observed changes in conductivity and low frequency noise. The results presented in this work provide a better understanding of $V{O}_x$-based composites, thereby enabling the development of new, versatile and functional materials for device applications.