Sub‐THz characterisation of multi‐walled carbon nanotube thin films using vector network analyser

Abstract

A vector network analyser is used to study the electrical properties of multi-walled carbon nanotube (MWCNT) thin films deposited on a fused quartz substrate in the sub-terahertz (THz) frequency ranges of 220-325 GHz (WR3.4) and 325-500 GHz (WR2.2). The experiment is performed in free space. The complex permittivity of the MWCNT thin films is extracted using the Nicholson-Ross-Weir method. The refractive index and conductivity are then determined from the extracted permittivity. The method is validated by comparison with values obtained using THz time-domain spectroscopy

Terahertz free‐space dielectric property measurements using time‐ and frequency‐domain setups

“…Some free‐space methods comprise a vector network analyzer (VNA) with pairs of vector network analyzer extenders (VNAXs) and standard gain horns (SGHs) . The measurement frequency of these methods can reach up to 1.1 THz, and they should be able to achieve higher frequencies when the corresponding VNAXs and SGHs are available in the future.…”

“…However, the complex relative permittivity is not expressed explicitly, and thus some necessary procedures need to be carried out to resolve the problem. For References , the calculations are carried out using iterative algorithms. The iterative calculations require considerable computational resources and computation time, which grow worse if approximate property values are not known.…”

Electrical characterization of silver nanowire-graphene hybrid films from terahertz transmission and reflection measurements

“…Therefore, a non-contact and non-destructive technique are needed in practice. 15 Among modern techniques, terahertz time-domain spectroscopy (THz-TDS) is known for years to be a precise tool for noncontact characterization of samples like semiconductor wafers, 16 paint films, 17 art and historical pieces, 18 biological tissues, 19 etc.…”

Electric Properties of Graphene-Based Conductive Layers from DC Up To Terahertz Range

“…Much effort has also been spent on investigating an electronic band structure [4] of graphene motivated with the search of new applications both in electronics [5] and photonics [6]. As a part of this effort attempts at measuring dielectric properties of graphene in the sub-THz frequency band with vector network analyzers (VNA) [7], time-domain spectrometers (TDS) [8], or in the microwave band using waveguide setups [9] have been undertaken. Thus, thanks to the work done in the past, dielectric properties of raw graphene are considered to be known already.…”

“…The authors assumed that the major changes in the behavior of the inks occurs in the sub-THz and the THz bands; thus, they concentrated on these portions of the electromagnetic (EM) spectrum while providing only limited number of data points in dc and the microwave bands as required to better fit the model. Another reason to provide only limited number of data points below the sub-THz band (i.e., dc-250 GHz) was apparent poor accuracy and repeatability of millimeter-band material characterization methods based on onwafer techniques like those employed in [12] or a requirement for large samples in case of transmission-based approaches similar to [7] that would soon become prohibitive at frequencies in the lower mm-band and below.…”