Comparison of Telluropentathionates as Precursors for the Formation of Semiconductive Copper Chalcogenide Layers

Abstract

The processes of obtaining semiconductive and electrically conductive layers of mixed copper chalcogenides Cu_xS–Cu_yTe 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, Cu_1.9375S, anilite, Cu_1.75S, digenite, Cu_1.80S, villamanite, CuS₂, covelite, CuS, three copper telluride phases Cu₄Te₃, Cu_1.85Te, 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 Cu_3.18Te₂, 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, Cu_1.9375S, geerite, Cu_1.6S, orthorhombic digenite, Cu_1.8S, and tellurium sulfide TeS₇; the Cu–Te–S layers formed using H₂TeS₄O₆ solution have binary phases such as chalcocite, Cu₂S, djurleite, Cu_1.9375S, anilite, Cu_1.75S, digenite, Cu_1.80S, copper telluride Cu_1.85Te, 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 Cu_xS–Cu_yTe 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.

DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1909