Comparison of Telluropentathionates as Precursors for the Formation of Semiconductive Copper Chalcogenide Layers
Keywords:telluropentathionates, polyamide, copper chalcogenide layers, composition, conductivity
The processes of obtaining semiconductive and electrically conductive layers of mixed copper chalcogenides CuxS–CuyTe by the sorption-diffusion method on polyamide 6 using solutions of potassium and sodium telluropentathionates, K2TeS4O6 and Na2TeS4O6, and of telluropentathionic acid, H2TeS4O6, as precursors of chalcogens (Te and S) are compared. The concentration of sorbed chalcogens increases with the increase of the duration of treatment and concentration of precursor solution in cases of all precursors used. Copper chalcogenide layers are formed on the surface of polyamide after the treatment of chalcogenized polymer with Cu(II/I) salt solution. The concentration of copper in the layer increases with the increase of initial chalcogenization duration. XRD spectra of PA films treated for different time with solutions of telluropentathionates and then with Cu(II/I) salt solution showed the maxima characteristic of the copper sulfide and copper telluride phases, tellurium sulfide TeS7 and of elemental tellurium. Six copper sulfide phases, chalcocite, Cu2S, djurleite, Cu1.9375S, anilite, Cu1.75S, digenite, Cu1.80S, villamanite, CuS2, covelite, CuS, three copper telluride phases Cu4Te3, Cu1.85Te, rickardite, Cu7Te5, and tellurium sulfide TeS7 were identified in the layers formed using (0.025 – 0.1) mol/dm3 solutions of potassium telluropentathionate. Three phases of copper tellurides, tetragonal Cu3.18Te2, hexagonal Cu2Te and orthorhombic vulcanite, CuTe, were found in the films on PA surface formed using sodium telluropentathionate solutions, among them four phases of copper sulfides such as orthorhombic anilite, Cu7S4, monoclinic djurleite, Cu1.9375S, geerite, Cu1.6S, orthorhombic digenite, Cu1.8S, and tellurium sulfide TeS7; the Cu–Te–S layers formed using H2TeS4O6 solution have binary phases such as chalcocite, Cu2S, djurleite, Cu1.9375S, anilite, Cu1.75S, digenite, Cu1.80S, copper telluride Cu1.85Te, elemental tallurium and tellurium sulfide TeS7. The phase composition of layers changes depending on the nature of telluropentathionate used for PA chalcogenization and conditions of treatment in precursor’ solutions. The value of electrical sheet resistance of chalcogenide layers formed using (0.05 – 0.1) mol/dm3 K2TeS4O6 solutions varies from 256 kW/cm2 to 1.6 kW/cm2 and of those formed using Na2TeS4O6 solutions – from 3.14·103 kW/cm2 to ~1.34 kW/cm2; the use of H2TeS4O6 as precursor leads to the formation of electrically conductive CuxS–CuyTe layers with electrical resistance in the range of
(4.34·103 – 1.2) kW/cm2; the sheet resistance depends on the conditions of PA interaction with initial chalcogenization solutions.
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