Giant Temperature Coefficient of Resistivity and Cryogenic Sensitivity in Silicon with Galvanically Displaced Gold Nanoparticles in Freeze-Out Region Seung-Hoon Lee,† Seongpil Hwang,‡ and Jae-Won Jang*,† †
Department of Physics, Pukyong National University, Busan 48513, Republic of Korea Department of Advanced Materials Chemistry, Korea University, Sejong 30019, Republic of Korea
‡
S Supporting Information *
ABSTRACT: The temperature coefficient of resistivity (TCR) and cryogenic sensitivity (Sv) of p-type silicon (pSi) in the low-temperature region (10−30 K) are remarkably improved by increasing the coverage of galvanically displaced Au nanoparticles (NPs). By increase of the galvanic displacement time from 10 to 30 s, the average surface roughness (Ra) of the samples increases from 0.31 to 2.31 nm and the coverage rate of Au NPs increases from 3.1% to 21.9%. In the freeze-out region of the sample, an up to 103% increase of TCR and dramatically improved Sv of p-Si (∼5813%) are observed with Au coverage of 21.9% compared to p-Si without galvanically displaced Au NPs. By means of a finite element method (FEM) simulation study, it was found that the increase of surface roughness and a number of Au NPs on p-Si results in a higher temperature gradient and thermoelectric power to cause the unusual TCR and Sv values in the samples. KEYWORDS: galvanic displacement, temperature coefficient of resistivity, bolometer, cryogenic sensitivity, Au nanoparticles
S
required for their operation. To overcome the limitation of the operating temperature of bolometers, uncooled bolometers (operating at temperatures higher than that of liquid helium) using materials other than Si have been reported, including metal oxide10 and high-Tc superconductors.11 In addition, efforts to substitute Si bolometers with carbon material-based bolometers have been recently reported.12,13 As well as TCR, cryogenic sensitivity (Sv) is also useful parameter, related to measurement resolution, to evaluate performance of bolometers and cryogenic sensors.14 Sv is defined as voltage sensitivity to temperature in cryogenic temperature (
