Pyrite band diagram calculated using the quasiparticle self-consistent GW (QSGW) approximation. Gray shading refers to Fe character and solid black refers to S character. VBM = valence-band maximum, and CBM = conduction-band minimum.
FTIR spectra of doped and undoped pyrite. (a) Ni-doped pyrite.(b) Co-doped pyrite. The spectrum for Co-doped sample with 3100 ppm Co has no data below 0.3 eV because it was mounted on glass, which is opaque below 0.3 eV. (c) As-doped pyrite. The energy labels in (c) correspond to small semi-periodic peaks.
Electrical properties of undoped and doped pyrite. (a) Hall carrier concentration vs. 1000/T (K−1). (b) Hall mobility vs. T (K−1). (c) Log resistivity vs. 1000/T (K−1).
Fit of the Ni-doped Hall data to the statistical model used to infer the defect concentration and energy in the bandgap. The inserted figure shows the energy positions of the defect levels, their concentration, and how the Fermi energy changes as a function of temperature.
Comparison of QSGW calculated valence band DOS with absorption peaks in the As-doped optical spectra offset by 0.06 eV. With this offset the peaks in the calculated DOS show fair correspondence with the optical absorption peaks suggesting absorption is from photo-activated electrons to an effective acceptor level at 0.06 eV above the VBM.
XANES spectra for four As-doped pyrite samples with As in different valence states as indicated by the As K-edge inflection-point energies (vertical dashed lines).
Measured pyrite lattice parameters.
Dopant concentrations measured using SIMS for Ni-doped, Co-doped, and Undoped pyrite, and using RBS for As-doped pyrite.
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