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Optical photothermal infrared spectroscopy (O-PTIR) was used to characterize a terrestrial rock sample as a demonstration of the technique’s enhanced spatial resolution as it corresponds to minerology and the detection of organics. Traditional reflectance-based infrared techniques are limited by the wavelength of the infrared light interacting with the surface along with additional optical dispersion issues. However, because of the nature in which the infrared spectrum is measured via O-PTIR, these traditional issues are eliminated. This is possible through the recent developments of high intensity quantum cascade-based infrared lasers capable of scanning the mid infrared spectrum (3000–500 cm−1). Individual O-PTIR and diffuse reflectance data were collected on a terrestrial rock sample and compared to a recent discovery of NASA JPL’s Perseverance Rover regarding inclusions of comparable size. In addition, an O-PTIR map of a particularly dense area of proteinaceous material in the terrestrial sample was collected, further exemplifying the capability. This technique has significant potential for use regarding future returned Mars samples and in situ planetary surface science when considering the spatial resolution, sensitivity, and negligible sample preparation. 

Abstract Bismuth telluride is the working material for most Peltier cooling devices and thermoelectric generators. This is because Bi₂Te₃(or more precisely its alloys with Sb₂Te₃for p‐type and Bi₂Se₃for n‐type material) has the highest thermoelectric figure of merit,zT, of any material around room temperature. Since thermoelectric technology will be greatly enhanced by improving Bi₂Te₃or finding a superior material, this review aims to identify and quantify the key material properties that make Bi₂Te₃such a good thermoelectric. The largezTcan be traced to the high band degeneracy, low effective mass, high carrier mobility, and relatively low lattice thermal conductivity, which all contribute to its remarkably high thermoelectric quality factor. Using literature data augmented with newer results, these material parameters are quantified, giving clear insight into the tailoring of the electronic band structure of Bi₂Te₃by alloying, or reducing thermal conductivity by nanostructuring. For example, this analysis clearly shows that the minority carrier excitation across the small bandgap significantly limits the thermoelectric performance of Bi₂Te₃, even at room temperature, showing that larger bandgap alloys are needed for higher temperature operation. Such effective material parameters can also be used for benchmarking future improvements in Bi₂Te₃or new replacement materials.