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The results of measurements of electronic conductivity and the Seebeck coefficient, as well as X-ray phase analysis, electron microscopy, differential scanning calorimetry (DSC) and studies of the heat capacity of nanocrystalline NaxCu2-xS (x = 0.05, 0.075, 0.10) and Na0.125Cu1.75S semiconducting alloys in the temperature interval of 300 - 600 K are presented. At ambient temperature, the alloys under study consist of three phases: monoclinic Na2Cu4S3, hexagonal Chalcocite Cu2S and rhombohedral digenite Cu9S5. Measurements show that the Seebeck coefficient increases, and the conductivity decreases with increasing sodium concentration in the alloys. Thermal effects near the temperatures of 360 K, 450 K and 640 K have been observed by the DSC method.

An organic reagent-assisted method has been developed for the synthesis and assembly of copper sulfide, cadmium sulfide and silver sulfide nanocrystallites at low temperature under hydro- or solvothermal conditions. Nanowire-like aggregates (with an average diameter of 120 nm and length of 2 μm) assembled by digenite phase copper sulfide nanoparticles, nanotube-like aggregates (with diameters ranging from 40 to 200 nm and lengths from 400 nm to 4 μm) and nanovesicle-like aggregates (with size ranging from 50 to 180 nm) assembled using djurleite phase copper sulfide nanoparticles have been obtained using triethylenediamine, tramethylethylenediamine and di-n-butylamine as the linking agents, respectively. A cetyltrimethyl-ammonium bromide-assisted solvothermal process with CdCl2 and thiourea as the reactants and ethylenediamine as the solvent has been proposed to control the length of the CdS nanorods from 300 nm to 4.5 μm and construct novel CdS nanorod-based structures, including polydentate wire-like architectures and polydentate sphere-like architectures composed of dozens of CdS nanorods of 10 nm in width and 100 nm in length. A CH3(CH2)11SH-template method has been adopted to realize the synthesis and the simultaneous assembly of silver sulfide nanocrystallites with AgNO3 and Na2S as reactants. By changing the reaction temperature and the dodecylthiol concentration, two-dimensional orthogonal and hexagonal-like ordered silver sulfide nanoparticle arrays and quasi-orthogonal silver sulfide nanorod arrays can be obtained. This organic reagent-assisted route is very simple and can be extended to the synthesis and assembly of other semiconductor sulfide nanocrystals.

Thin films of copper sulphide with thickness up to m were deposited at C on glass substrates from a solution containing copper(II) chloride, sodium thiosulphate and dimethylthiourea. As prepared and after annealing at C in (100 millitorr), these films showed x-ray diffraction patterns matching that of the mineral covellite (CuS). Annealing the films for 1 h each at C and C in nitrogen resulted in their conversion to S (digenite) and S (chalcocite), respectively. The reduction in sulphur content of the films is evident in the x-ray florescence spectra. The sheet resistance of the films varied with annealing temperature. For a film of m thickness, the observed sheet resistance values are: (as prepared), (C), (C) and (C). The low sheet resistance (and thus the high conductivity, ) leads to a high near-infrared reflectance for the films, 65% (CuS) and 40% (S), at a wavelength of 2500 nm. Analyses of the optical band gap of the films indicate an indirect gap of 1.55 eV for CuS and S and 1.4 eV for S.

The structure of a non-stoichiometric copper compound Cu1.8S (digenite) has been studied by X-ray diffraction. Although digenite has a cubic anti-fluorite structure, satellite reflections were seen along the (111)c axis. Single-crystal X-ray diffraction data, including first- and second-order satellites, were collected using a four-circle diffractometer. A rhombohedral twinning model was used to determine the modulation densities of the copper ions. The final R-factor is about 10% including the main and satellite reflections. The present analysis shows that the crystal is composed of domain-like structures: in each domain, the dimensions of the regular lattice, formed from copper ions, are slightly larger than those of the basic sulphur lattice. The origin of this domain-like structure, based on the Frenkel-Kontorova model, is attributed to the non-stoichiometry and apparently smaller cation-anion interaction.

Thin polycrystalline films of chalcocite ( approximately Cu2S), djurleite ( approximately Cu1.96S) and digenite ( approximately Cu1.84S) have been obtained by sputtering in an Ar/H2 atmosphere and their optical constants n( lambda ) and alpha ( lambda ) have been determined in the 400-1000 nm spectral range. Using the values of the optical constants found previously, the determination of diffusion lengths and lifetimes of minority carriers of both heterojunction components and the surface recombination velocity is achieved. The method used adjusts a theoretical expression of the spectral short-circuit current to the experimental values by a minimisation 'Simplex' method. The results are compared with those obtained by Partain and co-workers (1983) during degradation of CuxS/CdS solar cells.

Conventional vacuum evaporation of Cu1.8S produces films with conductivities σ ranging from 10-3 to 103 (Ωcm)-1 which arc an increasing function of the distance from the evaporator. The films with σ less than 101 (Ωcm)-1 contain precipitations of Cu. The films with low conductivities are chalcocite and the highest conductivity of the chalcocite film is probably 100 (Ωcm)-1. The films with σ of 102–103 (Ωcm)-1 consist of djurleite and digenite. The hole mobilities in films with several 102 (Ωcm)-1 are 1.1–0.6 cm2/V sec corresponding to the hole densities of 6×1020–9×1021 cm-3. The mobilities in films are only several times smaller than those in bulky Cu2-xS. The films with σ as low as 10-3 (Ωcm)-1 become conductive by sweeping out excess Cu by a field applied during deposition. In the films under the deposition, Cu ions migrate through the activation process with an energy of about 0.2 eV.

Electrical conductivity measurements have been made on copper sulfide crystals of compositions ranging from Cu1.8S to Cu2.0S and indium-doped Cu1.8S in the temperature region between 20°C and 220°C. Conductivity of Cu2-xS varied from 0.07 ohm-1cm-1 to 2400 ohm-1cm-1 as the deviation from stoichiometry increased from x=0 to x=0.2. It was found that Cu1.8S (digenite) and Cu1.96S (djurleite) undergo phase transitions at 90°C and at 93°C respectively. The transition temperature of Cu2S (chalcocite) increased from 98°C to 108°C as conductivity decreased from 52 ohm-1cm-1 to 0.07 ohm-1cm-1. An analysis of mixed conduction at β phase of low conductivity copper sulfide has shown that ionic conductivity is independent of the composition or the number of impurity cations in this material, and exhibits a temperature dependence with activation energy of 0.24 eV. Finally it is emphasized, after the discussion of the relation between electrical properties and crystal structure of copper sulfides, that the composition and crystalline phase are well characterized by the electrical conductivity in these materials.

Four examples of an extensive development of slip lines on crystal faces are described. They are synthetic UO2, digenite (Cu2 xS), diamond and natural sphalerite. The slip lines are considered to be formed during growth, not by external stresses but by internal stresses due to distortion in crystals. It is suggested that the distortion is caused either by the existence of foreign impurity atoms or by excess or deficiency of constitutional atoms.