Germanium tin oxide thin films for uncooled infrared detectors

Abstract

Microbolometer is a class of infrared detector whose resistance changes when the temperature changes. In this work, we deposited and characterized Germanium Oxide thin films mixed with Sn (Ge—Sn—O) for uncooled infrared detection. Ge—Sn—O were deposited by co-sputtering of Sn and Ge targets in the Ar+O environment using a radio frequency sputtering system. Optical characterization shows that the absorption in Ge—Sn—O was most sensitive in the wavelength ranges between 1.0-3.0 μm. The transmission data was further used to determine the optical energy band gap (0.678 eV) of the thin-film using Tauc's equation. We also found the variations of absorption coefficient (1.4802×105 m-1-1.0097×107 m−1), refractive index (1.242-1.350), and the extinction coefficient (0.3255-8.010) for the wavelength ranges between 1.0-3.0 μm. The thin film's resistivity measured by the four point probe was found to be 4.55 Ω-cm and TCR was in the range of −2.56-−2.25 (%/K) in the temperature range 292-312K. In light of these results it can be shown that this thin film is in keeping with the current standards while also being more cost and time effective.

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