In this paper, we report the characteristics of a thermopile infrared sensor in which a nanostructured Si–Ge thermoelectric material is used. Although the thermopile infrared sensor is capable of being operated without power consumption, a challenge has been improving its sensitivity. With the aim of improving its sensitivity, we have realized a nanostructured Si–Ge thermoelectric material with low thermal conductivity (0.8 W/m K or less) by forming nanocrystals through heat treatment of amorphous Si–Ge. The thermopile infrared sensor composed of this material exhibited a high sensitivity of 1200 V/W at a pressure of 1.0 × 10−1 Pa or less.
