Low-temperature grown vertically aligned carbon nanotube array for an optimal infrared bolometer

Abstract

Vertically aligned carbon nanotube (VACNT) arrays have been explored as an absorber of thermal-type photodetectors. A long and dense VACNT array absorbs a wide spectral range of incident light with high absorption rate, but has a high thermal mass that results in a low response speed. To achieve a small thermal mass, a shorter and less dense VACNT array is needed. In addition, the high temperature needed to grow the VACNTs is detrimental to the functional sensing materials of the photodetector. The height, density, and growth temperature of VACNTs need to be optimized to achieve a working absorber that has high absorption rate and a high response speed. In this work, a low-temperature plasma enhanced chemical vapor deposition process is used to prepare various VACNT arrays with different heights and densities by controlling the CNT growth parameters. The absorption coefficients of the resulting samples are measured with Fourier transform infrared spectroscopy. An effective medium theory (EMT) is adopted to establish a working model of the VACNTs. Using experimentally extracted CNT density and height as fitting parameters, the EMT model is fitted to obtain theoretical absorption coefficients, which are found to be comparable to the experimentally measured absorption coefficients. Our experimental and theoretical investigations pave the way for future studies to integrate CNTs with infrared photodetectors.

Carbon Nanotube-Based Uncooled Bolometers: Advances and Progress

“…Parallelly, there have been positive efforts on the laboratory scale by other groups, such as low-temperature synthesis and lithography-free synthesis of periodic arrays, to grow these aligned forests with potential applications for optimal BMs. 183,184 Besides the introduction and development of new, unique device fabrication techniques and optimizing MWCNT forests, steps have also been taken to improve the bolometric performance with CNT hybrids. These hybrids include coupling CNTs with other nanomaterials, organic molecules, and so on.…”

“…Figure21ashows the blackbody characteristics of various black coatings, and Figure21bshows an SEM image of a CNT μBM pixel reported from the group. Parallelly, there have been positive efforts on the laboratory scale by other groups, such as low-temperature synthesis and lithography-free synthesis of periodic arrays, to grow these aligned forests with potential applications for optimal BMs 183,184. Besides the introduction and development of new, unique device fabrication techniques and optimizing MWCNT forests, steps have also been taken to improve the bolometric performance with CNT hybrids.…”

“…Figure a shows the blackbody characteristics of various black coatings, and Figure b shows an SEM image of a CNT μBM pixel reported from the group. Parallelly, there have been positive efforts on the laboratory scale by other groups, such as low-temperature synthesis and lithography-free synthesis of periodic arrays, to grow these aligned forests with potential applications for optimal BMs. , …”

“…Recently, Wang et al demonstrated a low-temperature PECVD process for growing vertically aligned CNTs. Growth temperatures varying in the range of 480–530 °C were reported Chirality control : An unbiased synthesis leads to the growth of mixed chirality nanotubes, which, in turn, degrades the bolometric properties, particularly, the TCR.…”

“…Recently, Wang et al demonstrated a low-temperature PECVD process for growing vertically aligned CNTs. Growth temperatures varying in the range of 480–530 °C were reported …”