ORCID Profile
0000-0003-4864-0472
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Publisher: AIP Publishing
Date: 25-01-2021
DOI: 10.1063/5.0036872
Abstract: Scattering-type scanning near-field optical microscopy (s-SNOM) allows for the characterization of optical properties of s les at the nanoscale, well below the diffraction limit of the interrogating wavelength. Typically, it relies on a model for the probe-s le interaction to extract complex optical constants of the s le. Here, we propose an s-SNOM calibration method that allows for the extraction of these constants without prior knowledge of the probe geometry nor the details of the probe-s le interactions. We illustrate the technique using terahertz time-domain spectroscopy-based s-SNOM to extract the optical properties of several organic and inorganic materials and differently doped regions of a standard silicon random access memory s le. The accuracy of the technique is comparable to that of conventional far-field techniques while additionally providing spatial distribution of optical constants at the nanoscale. The source-independent nature of the proposed technique makes it directly applicable for s-SNOM measurements in other spectral ranges.
Publisher: IOP Publishing
Date: 16-11-2021
Abstract: Significant efforts have recently been invested in assessing the physical and chemical properties of microbial nanowires for their promising role in developing alternative renewable sources of electricity, bioelectronic materials and implantable sensors. One of their outstanding properties, the ever-desirable conductivity has been the focus of numerous studies. However, the lack of a straightforward and reliable method for measuring it seems to be responsible for the broad variability of the reported data. Routinely employed methods tend to underestimate or overestimate conductivity by several orders of magnitude. In this work, synthetic peptide nanowires conductivity is interrogated employing a non-destructive measurement technique developed on a terahertz scanning near-field microscope to test if peptide aromaticity leads to higher electrical conductivity. Our novel peptide conductivity measurement technique, based on triple standards calibration method, shows that in the case of two biopolymer mimicking peptides, the s le incorporating aromatic residues (W6) is about six times more conductive than the negative control (L6). To the best of our knowledge, this is the first report of a quantitative nano-scale terahertz s-SNOM investigation of peptides. These results prove the suitability of the terahertz radiation-based non-destructive approach in tandem with the designer peptides choice as model test subjects. This approach requires only simple s le preparation, avoids many of the pitfalls of typical contact-based conductivity measurement techniques and could help understanding fundamental aspects of nature’s design of electron transfer in biopolymers.
Publisher: Walter de Gruyter GmbH
Date: 03-04-2023
Abstract: Terahertz (THz) waves are a highly sensitive probe of free carrier concentrations in semiconducting materials. However, most experiments operate in the far-field, which precludes the observation of nanoscale features that affect the material response. Here, we demonstrate the use of nanoscale THz plasmon polaritons as an indicator of surface quality in prototypical quantum devices properties. Using THz near-field hyperspectral measurements, we observe polaritonic features in doped silicon near a metal-semiconductor interface. The presence of the THz surface plasmon polariton indicates the existence of a thin film doped layer on the device. Using a multilayer extraction procedure utilising vector calibration, we quantitatively probe the doped surface layer and determine its thickness and complex permittivity. The recovered multilayer characteristics match the dielectric conditions necessary to support the THz surface plasmon polariton. Applying these findings to superconducting resonators, we show that etching of this doped layer leads to an increase of the quality factor as determined by cryogenic measurements. This study demonstrates that THz scattering-type scanning near-field optical microscopy (s-SNOM) is a promising diagnostic tool for characterization of surface dielectric properties of quantum devices.
Publisher: American Chemical Society (ACS)
Date: 18-05-2023
Publisher: University of Queensland Library
Date: 2022
DOI: 10.14264/04F4869
Publisher: AIP Publishing
Date: 30-08-2021
DOI: 10.1063/5.0061078
Abstract: Superconducting quantum circuits are one of the leading quantum computing platforms. To advance superconducting quantum computing to a point of practical importance, it is critical to identify and address material imperfections that lead to decoherence. Here, we use terahertz scanning near-field optical microscopy to probe the local dielectric properties and carrier concentrations of wet-etched aluminum resonators on silicon, one of the most characteristic components of the superconducting quantum processors. Using a recently developed vector calibration technique, we extract the THz permittivity from spectroscopy in proximity to the microwave feedline. Fitting the extracted permittivity to the Drude model, we find that silicon in the etched channel has a carrier concentration greater than buffer oxide etched silicon and we explore post-processing methods to reduce the carrier concentrations. Our results show that near-field THz investigations can be used to quantitatively evaluate and identify inhomogeneities in quantum devices.
No related grants have been discovered for Xiao Guo.