Professor Nasibulin and co-workers have discovered that fine treatment of single-walled carbon nanotubes (SWCNT) films with oxygen plasma allows to increase significantly the sensitivity of carbon nanotube-based bolometers. The results have been published in Nanoscale of the Royal Society of Chemistry.
SWCNTs are unique family of materials that demonstrate a number of properties that have paved many ways toward novel applications and contributed greatly to the existing ones.
Bolometer is a type of infrared photodetectors based on the resistance change by material heated under an irradiation. The SWCNTs films have been already evaluated as a promising material for bolometers due to their low thermal capacity and high thermal conductivity. The thickness of free-standing film can be up to 10 nanometers that makes CNTs-based bolometers very fast. It means that bolometric signal response rapidly to a change in radiation power.
On the other hand, one of significant limitation of nanotubes for this application is the low sensitivity of bolometers in comparison with commercial analogues. The sensitivity of bolometer is mainly defined by temperature coefficient of resistance (TCR), which is relatively low for pristine nanotubes.
The researchers have found the way to enhance greatly this characteristic by stepwise plasma treatment of SWCNTs films (up to -2.8 %/ K at liquid nitrogen temperature, which is much higher than reported values for pristine carbon nanotubes and comparable with vanadium oxides, standard sensor material for bolometers). The mechanisms underlying the effect of TCR increase are explained in detail in the paper.
The sensitivity of the bolometers based on SWCNTs films in the IR range increased up to three times at room temperature and up to 33 times at the liquid nitrogen temperature after treatment with oxygen plasma. Furthermore, the devices have ultrafast (3 ms) response time, which is much better than those of commercially available bolometers.
The reported research demonstrates a good example of rational design of material to meet demands of application.
Reference: Nanoscale, 2018, DOI:10.1039/C8NR05925J
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