Aligned and unaligned single-walled carbon nanotube bilayer films for uncooled infrared sensors

Semiconducting single-walled carbon nanotube (SWCNT) film fabrication using the dip-coating method has successfully produced a unique film with two layers of different morphologies, an upper layer of aligned SWCNT film and a lower layer of non-aligned SWCNT network film. In the upper layer, SWCNTs form SWCNT bundles of several SWCNT thicknesses, and the bundles form thin aligned SWCNT films of 2–7 nm in thickness with parallel and equally spaced bundles of SWCNTs. When a bolometer device with this bilayer film was fabricated on electrodes, the upper aligned SWCNT film was the main conductive path with a low resistivity of about 0.2 Ωcm around room temperature. The alignment film also achieved a high temperature coefficient of resistance (TCR) of more than −5%/K due to its thin thickness, which is hardly affected by the slight metallic SWCNT presence. These excellent properties of a high TCR and low resistance are advantageous for the development of innovative sensor elements. [Display omitted] •Successful fabrication of novel two-layer film of aligned and non-aligned SWCNTs.•Achievement of a high temperature coefficient of resistance (TCR) of above −5%/K.•Low resistance achieved with thin aligned SWCNT films 2–7 nm in thickness.•Demonstration of an excellent-performance bolometer with low resistance and high TCR.