Scientists discover new class of semiconducting entropy-stabilized materials
Semiconductors are important materials in numerous functional applications such as digital and analog electronics, solar cells, LEDs, and lasers. Semiconducting alloys are particularly useful for these applications since their properties can be engineered by tuning the mixing ratio or the alloy ingredients. However, the synthesis of multicomponent semiconductor alloys has been a big challenge due to thermodynamic phase segregation of the alloy into separate phases. Recently, University of Michigan researchers Emmanouil (Manos) Kioupakis and Pierre F. P. Poudeu, both in the Materials Science and Engineering Department, utilized entropy to stabilize a new class of semiconducting materials, based on GeSnPbSSeTe high-entropy ourchalcogenide alloys, a discovery that paves the way for wider adoption of entropy-stabilized semiconductors in functional applications.
Entropy, a thermodynamic quantity that quantifies the degree of disorder in a material, has been exploited to synthesize a vast array of novel materials by mixing eachcomponent in an equimolar fashion, from high-entropy metallic alloys to entropy-stabilized ceramics. Despite having a large enthalpy of mixing, these materials can surprisingly crystalize in a single crystal structure, enabled by the large configurational entropy in the lattice. Kioupakis and Poudeu hypothesized that this principle of entropy stabilization can be applied to overcome the synthesis challenges of semiconducting alloys that prefer to segregation into thermodynamically more stable compounds. They tested their hypothesis on a 6-component II-VI chalcogenide alloy derived from the PbTe structure by mixing Ge, Sn, and Pb on the cation site, and S, Se, and Te on the anion site.
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