title: Crystal growth and characterization of the narrow-band-gap semiconductors OsPn₂ (Pn = P, As, Sb).
abstract: Using metal fluxes, crystals of the binary osmium dipnictides OsPn2 (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn6 octahedra, as well as [Pn2(4-)] anions. Raman spectroscopy shows the presence of P-P single bonds, consistent with the presence of [Pn2(-4)] anions and formally Os(4+) cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2 and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn2 dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a Pn-Pn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment.
authors.affiliation: Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Bugaris
authors.forename: Christos D
authors.initials: CD
authors.lastname: Malliakas
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Shoemaker
authors.forename: Dat T
authors.initials: DT
authors.lastname: Do
authors.forename: Duck Young
authors.initials: DY
authors.lastname: Chung
authors.forename: Subhendra D
authors.initials: SD
authors.lastname: Mahanti
authors.forename: Mercouri G
authors.initials: MG
authors.lastname: Kanatzidis