A Transmission Electron Microscope Study of the Chalcocite–Djurleite Transformation in Topotactically Grown Thin Films of CuxS

Echigoya, J.; Edington, J. W.

doi:10.1002/pssa.2210720131

Cited by 4 publications

(1 citation statement)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed defects along the APBs (Figure 8b) are evidence in support of low-temperature transformation of the precursor digenite into either monoclinic chalcocite or djurleite at <103.5 • C and <93 • C, respectively [34]. The chalcocite-djurleite transformation may be continuous across lattice fringes and preserves stacking faults in the djurleite, as documented experimentally on Cu x S films [48].…”

Section: Evolution Of Sulphide Assemblagessupporting

confidence: 71%

Nanoscale Study of Clausthalite-Bearing Symplectites in Cu-Au-(U) Ores: Implications for Ore Genesis

et al. 2018

View full text Add to dashboard Cite

Symplectites comprising clausthalite (PbSe) and host Cu-(Fe)-sulphides (chalcocite, bornite, and chalcopyrite) are instructive for constraining the genesis of Cu-Au-(U) ores if adequately addressed at the nanoscale. The present study is carried out on samples representative of all three Cu-(Fe)-sulphides displaying clausthalite inclusions that vary in size, from a few µm down to the nm-scale (<5 nm), as well as in morphology and inclusion density. A Transmission Electron Microscopy (TEM) study was undertaken on foils prepared by Focussed Ion Beam and included atom-scale High-Angle Annular Dark-Field Scanning TEM (HAADF-STEM) imaging. Emphasis is placed on phase relationships and their changes in speciation during cooling, as well as on boundaries between inclusions and host sulphide. Three species from the chalcocite group (Cu 2-x S) are identified as 6a digenite superstructure, monoclinic chalcocite, and djurleite. Bornite is represented by superstructures, of which 2a and 4a are discussed here, placing constraints for ore formation at T > 265 • C. A minimum temperature of 165 • C is considered for clausthalite-bearing symplectites from the relationships with antiphase boundaries in 6a digenite. The results show that alongside rods, blebs, and needle-like grains of clausthalite within the chalcocite that likely formed via exsolution, a second, overprinting set of replacement textures, extending down to the nanoscale, occurs and affects the primary symplectites. In addition, other reactions between pre-existing Se, present in solid solution within the Cu-(Fe)-sulphides, and Pb, transported within a fluid phase, account for the formation of composite, commonly pore-attached PbSe and Bi-bearing nanoparticles within the chalcopyrite. The inferred reorganisation of PbSe nanoparticles into larger tetragonal superlattices represents a link between the solid solution and the symplectite formation and represents the first such example in natural materials. Epitaxial growth between clausthalite and monazite is further evidence for the interaction between pre-existing Cu ores and fluids carrying REE, P, and most likely Pb. In U-bearing ores, such Pb can form via decay of uranium within the ore, implying hydrothermal activity after the initial ore deposition. The U-Pb ages obtained for such ores therefore need to be carefully assessed as to whether they represent primary ore deposition or, more likely, an overprinting event. A latest phase of fluid infiltration is the recognised formation of Cu-selenide bellidoite (Cu 2 Se), as well as Fe oxides.

show abstract

Section: Evolution Of Sulphide Assemblagessupporting

confidence: 71%

Nanoscale Study of Clausthalite-Bearing Symplectites in Cu-Au-(U) Ores: Implications for Ore Genesis

et al. 2018

View full text Add to dashboard Cite

show abstract

Ore minerals down to the nanoscale: Cu-(Fe)-sulphides from the iron oxide copper gold deposit at Olympic Dam, South Australia

Ciobanu

Cook

Ehrig

2017

Ore Geology Reviews

View full text Add to dashboard Cite

Degradation of a CuxS/CdS solar cell in hot, moist air and recovery in hydrogen and air

Partain

McLeod

Duisman

et al. 1983

Journal of Applied Physics

View full text Add to dashboard Cite

A polycrystalline, thin-film CuxS/CdS solar cell was exposed to air saturated with water vapor at temperatures between 27 and 67 °C for up to 6 1/2 h. The short-circuit current decreased progressively from 11.7 to 1.02 mA/cm2. Subsequent heating in hydrogen at 150 °C for 680 h and in 170 °C air for 5 h restored the short-circuit current to 14.4 mA/cm2. Modeling of the measured quantum yield indicates that the degradation could be quantitatively explained by two effects: (1) the CuxS minority carrier electron diffusion length decreasing from 0.23 to 0.02 μm (±20%) and (2) the CuxS optical band gap increasing from 1.16 to 1.46 eV (±3%). The recovery was quantitatively modeled by the CuxS diffusion length increasing back to 0.24 μm and the CuxS band gap returning to 1.16 eV. A Burstein–Moss analysis shows the band-gap shift is due to the Fermi level penetration of the valence band as the measured hole concentration increased from 1.03(1020) cm−3 to 4.62(1021) cm−3 during degradation. A new band structure is proposed with six equivalent, indirect, valence band maxima located at 1.16 eV (±3%) below the conduction band edge followed by two direct maxima located at 1.28 and 1.8 eV (±3%) below the conduction band edge. A density-of-states effective mass ratio for holes of 2.0 (±30%) is found. The sharp decrease and recovery in diffusion length is explained by a transition between phonon-assisted and direct minority carrier recombination with changes in CuxS hole concentration.

show abstract

A Transmission Electron Microscope Study of the Chalcocite–Djurleite Transformation in Topotactically Grown Thin Films of CuxS

Cited by 4 publications

References 12 publications

Nanoscale Study of Clausthalite-Bearing Symplectites in Cu-Au-(U) Ores: Implications for Ore Genesis

Nanoscale Study of Clausthalite-Bearing Symplectites in Cu-Au-(U) Ores: Implications for Ore Genesis

Ore minerals down to the nanoscale: Cu-(Fe)-sulphides from the iron oxide copper gold deposit at Olympic Dam, South Australia

Degradation of a CuxS/CdS solar cell in hot, moist air and recovery in hydrogen and air

Contact Info

Product

Resources

About