A universal method for thermal conductivity measurements on micro-/nano-films with and without substrates using micro-Raman spectroscopy

Kwon

2020

ACS Appl. Nano Mater.

Well-tailored metal nanostructure arrays possessing a large number of small nanogaps have been highlighted because of their ability to enhance optical and electrical properties. In addition, it has been demonstrated that nanostructures with two or more elements present significantly enhanced and synergistic properties compared to those with a single element. However, the precise and reliable synthesis of bimetallic nanostructures possessing multiple nanogaps with high uniformity remains a major challenge. In this study, we propose the fabrication of bimetallic nanostructure patterns with numerous uncovered and external nanogaps. Silver dot arrays (SDAs) without organic capping ligands were developed via nanoimprint lithography, and several deposited Au−Ag alloy nanogranules were directly deposited on SDAs through a fast galvanic replacement reaction, without adding any additional reducing agents or capping molecules, to produce highly accessible nanogaps. These nanogaps surrounded by two types of metal elements demonstrated an excellent surface-enhanced Raman scattering (SERS) enhancement factor of up to 1.09 × 10 9 , and the highly homogeneous SDAs led to high signal uniformity (relative standard deviation < 6.5 ± 0.3%) as well as deviceto-device reproducibility. Finally, it was demonstrated that the synthesized substrates can be used as ultrasensitive and reliable SERSbased pesticide (malachite green) detection probes, down to a 10 fM concentration.

Section: Discussionmentioning

confidence: 71%

Highly Dense and Accessible Nanogaps in Au–Ag Alloy Patterned Nanostructures for Surface-Enhanced Raman Spectroscopy Analysis

Kwon

2020

ACS Appl. Nano Mater.

“…Another approach presented [50] was to ensure that the film's thickness was higher than the laser diameter to remove the thermal effect imposed by the substrate, which thus, limits such measurements from thinner film materials. Although, a theoretical model and numerical solution [7,36,37] were presented to address these difficulties in thermal conductivity measurement of thin film material via Raman spectroscopy by thermally isolating the effect of the substrate from the film material, however, the behavior of such substrate acting as a heat sink to the film material on top was not considered as could be evidenced in a typical model of heat transfer in any multi-layer material (Figure 6).…”

Section: Methodsmentioning

confidence: 99%

“…Our analysis is based on the radial Gaussian heat distribution model. [35][36][37] Thermal conductivity for each sample, at 5 and 9% Sn content, was calculated using measurements of the sample's surface temperature, ΔT = Δ𝜔/𝜂, obtained from temperature dependency of Ge-Ge mode shift, seen in Figure 2b. Local temperature was measured at the surface of the sample by applying the heating laser power density to cause peak shift, ignoring any wide peak shifts associated with overheating.…”

Section: Thermal Conductivitymentioning

confidence: 99%

Revealing Low Thermal Conductivity of Germanium Tin Semiconductor at Room Temperature

Ayinde,

Myronov

2023

Adv Materials Inter

The low thermal conductivity of a material is a key essential parameter for its potential application in high‐performance thermoelectric devices. Unprecedently low thermal conductivity of germanium tin (Ge1−xSnx) semiconductor thin film is experimentally obtained at room temperature. The thermal conductivity decreases with increasing Sn concentration in the relaxed Ge1−xSnx binary alloy, which is explained mainly by increasing the interatomic distance between atoms via alloying. A pronounced decrease of thermal conductivity, by over 20 times, from 58 W m−1K−1 in Ge to ≈2.5 W m−1K−1 in relaxed Ge1−xSnx, with Sn content up to 9% is observed. This thermal conductivity is just ≈2 times higher than that of the state‐of‐the‐art thermoelectric material, Bismuth Selenium Telluride. Ge1−xSnx, in contrast, is a non‐toxic Group‐IV semiconductor material, that is epitaxially grown on a standard silicon wafer up to 300 mm diameter using the semiconductor industry standard epitaxial growth technique. As a result, it can lead to the creation of a long‐awaited high‐performance low‐cost thermoelectric energy generator for room‐temperature applications in human's daily life and would make a substantial contribution toward global efforts in CO2 emission‐free and green electricity generation.

“…Microstructures may enable engineered materials with unique thermal properties to allow significant enhancement or reduction of the heat flow rate [5][6][7][8][9][10]. Therefore, knowledge of thermal transport from the micrometer scale and thermal properties of microstructures is of critical importance to future technological growth.…”

Section: Introduction *mentioning

confidence: 99%

Simulation of Micro-Precoating Effect on Temperature Distribution in Plasma Thermal Spraying

Guo

2018

J. Coat. Sci. Technol.

The effect of micro-precoating on temperature distribution of the plasma thermal spraying was simulated. After the plasma thermal spraying test with SS304 as precoating, the effect of micro-precoating on the wear loss and fatigue had been studied preliminarily. Results show that the surface temperature with micro-precoating is higher than that of without micro-precoating. Meanwhile, the heat affected zone with precoating is wider which effectively restrains the microcracks forming in the succedent coating. Subsequently, the wear and fatigue of the plasma thermal spray coating are significantly increased with the optimum micro-precoating thickness.