Ultrathin 2 nm gold as impedance-matched absorber for infrared light

Abstract

Thermal detectors are a cornerstone of infrared and terahertz technology due to their broad spectral range. These detectors call for efficient absorbers with a broad spectral response and minimal thermal mass. A common approach is based on impedance-matching the sheet resistance of a thin metallic film to half the free-space impedance. Thereby, one can achieve a wavelength-independent absorptivity of up to 50%. However, existing absorber films typically require a thickness of the order of tens of nanometers, which can significantly deteriorate the response of a thermal transducer. Here, we present the application of ultrathin gold (2 nm) on top of a surfactant layer of oxidized copper as an effective infrared absorber. An almost wavelength-independent and long-time stable absorptivity of 47(3)%, ranging from 2 μm to 20 μm, can be obtained. The presented absorber allows for a significant improvement of infrared/terahertz technologies in general and thermal detectors in particular.

Plasmonic metal nanostructures with extremely small features: new effects, fabrication and applications

“…Resonance peaks at wavelengths of 1.5~5 μm are shifted by hundreds of nanometres and amplitude-modulated by tens of percent through gating using relatively low voltages. Combined with a large-scale fabrication approach, the fabricated films can find applications in transparent conductors, plasmon-enhanced spectroscopy, optical biosensing and electrochromic devices.Beyond the new plasmonic effects and applications mentioned above, UTMFs imply broader future applications in the fields of optoelectronics, nonlinear optics, plasmon-enhanced detection and sensing, thermal manipulation, two photon emission and plasmonic color printing [79][80][81]. 5.…”

Thermal Transport and Frequency Response of Localized Modes on Low-Stress Nanomechanical Silicon Nitride Drums Featuring a Phononic-Band-Gap Structure

“…Further control of the tensile stress reduction potentially allows even higher δRs to be achieved than presented here. Addition of a suitable absorbing layer on top of the PnC presents an additional path towards greater responsivities [28]. Even larger band gaps can be opened through variation of the PnC design, which might lead to modes with even higher localization [35].…”

“…As such, all simulations take emission into account with an emissivity = 0.05, calculated using optical data of 50-nm SiN membranes [28]. Further investigation into the effect of thermal radiation on the responsivity of membrane resonators can be found in Piller et al [27].…”

Simultaneous measurement of temperature and refractive index based on an SPR Silicon core fiber sensor with a fused silica grating design

“…In our article, the proposed fiber sensor achieved only 2 nm ultra-thin Au film coating. Although it was very challenging to fabricate a metal thinfilm of only 2 nm thick, the low-pressure chemical vapor deposition (LPCVD) method is still used technique [34].…”