Project 2.2: Mid- & LW-Infrared Detector Arrays on Flexible Substrates

PIs: Palacios, Englund, Kong

 

There is an unmet need for compact, low-power hyperspectral imagers operating in the thermal and mid-infrared spectral regions. Project 2.2 addresses this need through spectrally tunable graphene-based filters and detector arrays that promise unprecedented performance for uncooled imagers. Building on proven physical effects in graphene, the project will develop optimized device concepts incorporating advanced material growth. The optimal device concepts will be integrated in a CMOS platform to demonstrate a high-performance hyperspectral camera, while also demonstrating flexibility of the imaging array using substrate thinning. Night vision, remote material/threat identification, hazardous gas imaging, and IR point-to-point communication are examples of applications relevant to soldiers.

 

(a) Optical Microscope image of as-grown CVD graphene on copper foil showing the single crystalline grain size of >500um.
(b) Optical Microscope image of our CVD monolayer hBN flakes transferred onto Si/SiO2 substrate.
(c) Graphene G band Raman vs 2D band Raman frequency analysis, the doping and strain information for the graphene can be analyzed. In this case, the graphene is p-doped (carrier concentration ~1012cm-2) with a very low strain (<0.05%)
(d) Raman spectrum of a single crystalline hBN flake, the peak position of hBN E2g band at 1368.9 cm-1 is the peak position for monolayer hBN, and the FWHM of 13.5cm-1 indicate high quality hBN.
(e) Raman FWHM of hBN E2g band comparison, indicating our hBN quality is getting closer to the exfoliated high quality hBN.
(f) Optical microscope image of our CVD grown TiS2 flakes on Mica (triangular, synthesized under 450C).
(g) AFM image of the TiS2 flakes (hexagonal, synthesized under 600C).
(a) Microscopic image, and (b) schematic of the new graphene-polymer thermo-mechanical bolometer developed in this project. (c) Scanning electron microscopic (SEM) image of the percolative graphene film, indicating an overlap region of around 50 nm.
Temperature responses of the graphene-polymer thermo-mechanical bolometer. (a) Gradual change temperature dependent resistance. (Type I). (b) Abrupt change temperature dependent resistance (Type II). (c) Estimated detectivities vs. response time of our devices in comparison with mainstream thermal mid-IR detectors. The inset table summarizes the typical values of temperature coefficient of resistance (TCR) of various bolometric materials.