Ultra‐High Optical Absorption Efficiency from the Ultraviolet to the Infrared Using Multi‐Walled Carbon Nanotube Ensembles

Abstract

The optical absorption efficiencies of vertically aligned multi-walled (MW)-carbon nanotube (CNT) ensembles are characterized in the 350-7000 nm wavelength range where CNT site densities > 1 × 10(11) /cm(2) are achieved directly on metallic substrates. The site density directly impacts the optical absorption characteristics, and while high-density arrays of CNTs on electrically insulating and non-metallic substrates have been commonly reported, achieving high site-densities on metals has been challenging and remains an area of active research. These absorber ensembles are ultra-thin (<10 μm) and yet they still exhibit a reflectance as low as ∼0.02%, which is 100 times lower than the reference; these characteristics make them potentially attractive for high-sensitivity and high-speed thermal detectors. In addition, the use of a plasma-enhanced chemical vapor deposition process for the synthesis of the absorbers increases the portfolio of materials that can be integrated with such absorbers due to the potential for reduced synthesis temperatures. The remarkable ruggedness of the absorbers is also demonstrated as they are exposed to high temperatures in an oxidizing ambient environment, making them well-suited for extreme thermal environments encountered in the field, potentially for solar cell applications. Finally, a phenomenological model enables the determinatiom of the extinction coefficients in these nanostructures and the results compare well with experiment.

Decoration of an inorganic layer with nickel (hydr)oxide via green plasma electrolysis

“…The lattice parameter analysis seen in Fig. 3(e) indicated that several areas of the hybrid layer had a lattice distance equal to 0.23 nm, which corresponds to the 011 plane of Ni(OH) 2 , whilst the area shown in Fig. 3(f) had a lattice distance of 0.21 nm, corresponding to the 002 plane of NiO.…”

“…Fig. 3(a) shows that MgO and Mg 2 SiO 4 were the major components of both samples, whilst Ni(OH) 2 and NiO made up a minor fraction of NiMO. The peak for Ni(OH) 2 was detected in several position, but the most prominent was at 2q value of 33 which was coming from diffraction of (101) plane, while NiO was at 2q value of 43.5 from the diffraction of (200) plane.…”

“…3(c) shows that the majority of the oxygen atoms on the surface belong to Ni(OH) 2 . Judging from the area below the curve, the amount of oxygen atoms corresponding to Ni(OH) 2 was larger than that for NiO, which suggested that a larger fraction of the former was present. Furthermore, it was interesting to note that the majority of Ni was incorporated as the hydroxide form, while the main matrix, MgO, was in the oxide form.…”

“…3(b) presents the XPS spectrum for Ni 2p 3/2 ; deconvolution of the spectrum showed that the Ni 2p 3/2 peak was divided into three peaks. The peak at a binding energy of 855.6 eV was assigned to NiO, [46][47][48][49] whilst the peaks at 856.2 and 857.3 eV with a shakeup satellite at a higher binding energy of $6.5 eV were ascribed to Ni(OH) 2 . 50 The spectrum of O 1s was deconvoluted to analyse the source of the oxygen atoms on the surface.…”

“…[2][3][4] In addition to high absorption capacity, an important strategy for obtaining dark-coloured materials is to incorporate particles or microstructure arrays, which restrict light in deep pores, such as carbon nanotubes.…”