Infrared interaction in surface modified thin film of carbon nanotubes

Abstract

In the entire study carried out in this thesis work, it has been established that, interfacial interaction of MWCNTs with functional materials like QDs, semiconducting NPs and metal NPs is beneficial towards improving device performances both in terms of its FOM as well as Chapter 7 134 from the technological aspects (freestanding, transparent etc.). In macro−scale (order of cm) the interfacial interactions in MWCNTs with QDs led to mechanically stable freestanding papers with improved device performances. Such papers reject the performance degradation effects from the substrate and thus find applications in a wide area, right from electrodes for energy storage devices to actuators for flexible robotic component applications. Secondly, in the micro scale (order of micron), the developed fabrication technique using spray coating and wet-transfer allowed to fabricate freestanding films. Bolometric characteristics of the MWCNTs could then be tuned using the technique. For instance, in chapter 4 it was observed that, RT TCR of suspended bolometer was ~1.17 times higher than the unsuspended one. Further, 𝑅𝑣 of the suspended bolometer obtained by this technique was also ~7.68 times higher than the unsuspended one. Apart from fabrication methodology, the interactions of MWCNTs with functional semiconducting NPs and metal NPs also revealed tunable bolometric properties. The RT TCR (modulus) of MWCNT film bolometer obtained in this thesis work was ~0.05%/K. From the studies in this thesis work it was found that RT TCR of the hybrid MWCNT systems could be varied in a range from as low as ~0.023%/K to as high as ~0.41%/K. Such variations are attributed to the global conducting nature of the MWCNT hybrid films, where the lower values are for metallic conductivities while the high ones are for the semiconducting ones. From the interaction with semiconducting NPs a RT TCR of ~0.41%/K was obtained, which was ~8.2 times higher compared to our MWCNT bolometer. While on the other hand, from the interaction with metal NPs (Au in this case), a maximum RT TCR of ~0.11%/K was obtained, which is again higher by ~2.2 times compared to MWCNT. Thus, to conclude, we find that the semiconducting NPs interacted MWCNTs depict better bolometric performance than metal NPs interacted MWCNTs bolometer with ~3.7 times higher RT TCR value. Chapter 7 135 From the last section it was understood that, Mott insulators are a very interesting IR detector materials with ultrahigh response at their transition temperature. Light−matter interaction induced phase changes pave way for further exploring the induced physical mechanism and the associated application towards photon detection. Further, to tackle the intrinsic problem of coupling with MWCNTs, a new approach was adopted using the developed fabrication technique. With the transfer technique, MWCNT film was made to act as a ‘black’ electrode with minuscule improvement in device performance.