Photosensitive semiconducting p-type tin(II) sulfide thin films with a band gap of 1.03 ± 0.09 eV have been manufactured in compliance with green chemistry principles using the one-pot approach. To extend the range of sulfidizers suitable for chemical deposition of thin nanostructured SnS films, the efficiency of using sodium thiosulfate solutions has been shown. It has been found that thin SnS films with good adhesion to a dielectric substrate and a coherent scattering region size of ⁓30 nm can be synthesized through hydrolytic decomposition of thiosulfate ions. The conditions for synthesis of SnS have been justified by thermodynamic analysis of ionic equilibria. Quantum-chemical calculations have shown that the p-type conductivity of the synthesized SnS films is most likely due to tin vacancies.

Abstract—Ultrafine ZnO–ZnS powder with d-metal oxide additions, namely, V2O5, MnO, Fe2O3, CoO, NiO, and CuO are studied. The alloying of the ZnO–ZnS system with d metals changes the morphology of the synthesized powders. The particle size distribution obeys a lognormal law. An addition of d metal oxide upon the synthesis of ZnO–ZnS composite shifts the maximum of the particle-size distribution to the larger sizes. The more probable particle size in the samples alloyed with iron and cobalt (530 nm) exceeds that of unalloyed samples (320 nm) by more than 1.6 times. All the synthesized samples are found to be characterized by excess oxygen. The zinc, sulfur, and oxygen contents in the unalloyed ZnO–ZnS compositions is 48.0, 12.8, and 39.2 at

The results of the measurements of electrical and Hall resistivities on polycrystalline PbS films doped with iodine obtained through hydrochemical deposition are presented. The analysis of the temperature dependence of resistivity points out the crossover from the hopping mechanism due to thermal delocalization in the impurity band to the variable range hopping mechanism. The increase in the iodine content in the films leads to an increase in the impurity ionization energy. It has been established that the temperature dependence of resistivity over a wide temperature range obeys the inverse Arrhenius law, which is characteristic of disordered polycrystalline films with different sizes and orientations of crystallites relative to the substrate, as confirmed by AFM topography, Raman spectra and X-ray diffraction measurements. We found that the type of charge carrier changes from electrons to holes with an increase in the iodine content. Additionally, for a wide range of iodine doping, the concentration of charge carriers is low, indicating the possible occurrence of a self-compensation mechanism due to the formation of impurity defects.

Photosensitive nanocrystalline SnS films with a size of coherent X-ray scattering regions of about 30 nm were obtained by chemical bath deposition. It has been demonstrated that the deposition time affects significantly both microstructure and thickness of the film as well as the size of the particles' agglomerates forming the film. The current sensitivity of the obtained films was studied. All synthesized films, regardless of the duration of synthesis, reveal p-type conductivity due to Sn vacancies. Atomic force microscopy measurements and fractal approach provide a detailed description of the processes occurring during film formation. The characteristics of the fabricated SnS films are potentially useful for design of advanced absorbing layers within thin film solar cells.

Two-phase thin-film composites consisting of CdxPb1 – xS (0.007 ≤ x ≤ 0.068) substitutional solid solutions with a B1 cubic structure (sp. gr. Fm3̅m ) and amorphous cadmium sulfide (CdS) have been produced by chemical deposition. The surface topography of the films has been studied by atomic force microscopy, and the results have been used to calculate surface microtopography parameters. A correlation has been found between the composition and functional properties of thin CdS–PbS films. The sensitivity of CdxPb1 – xS/CdS two-phase films to ammonia (NH3) in air has been assessed for the first time. The room-temperature detection limit for ammonia has been determined to be 10 ppm (6.22 mg/m3).

CdS–PbS nanocrystalline films with a thickness of 0.5 to 1.2 µm are obtained by Chemical Bath Deposition (CBD) from an ammonium-citrate reaction mixture by varying the concentrations of different cadmium salts CdAn n ( An is CH 3 COO − , NO_3^ - , SO_4^2 - ) within 0.01–0.08 mol/L. The morphology and surface topography of the films are studied by scanning electron and atomic-force microscopy. The film’s composition is determined by energy-dispersive analysis. A nonlinear change in the content of the main CdS–PbS film elements and their morphological characteristics is shown. The influence of the anionic component of the salt CdAn n on the cadmium content in thin film layers is established. This effect correlates with the lyotropic series of anions: SO_4^2 - > NO_3^ - > CH 3 COO − . A mechanism for the anion nucleophilic addition to the thiocarbonyl atom of thiourea is proposed. As a result, a nucleophilic attack promotes thiourea activation by weakening the carbon–sulfur bond. Based on the results of comprehensive study of the morphology and the fractal analysis of the surface of the CdS–PbS semiconductor layers, we conclude that the studied films are predominantly formed by particle–cluster diffusion-limited aggregation (DLA).

Thin films of CdxPb1 – xS (0 ≤ x ≤ 0.094) substitutional solid solutions of cubic structure B1 (space group Fm) were prepared by chemical deposition and characterized by X-ray diffraction, scanning electron microscopy, EDX elemental analysis, and Raman spectroscopy. Once the cadmium sulfate concentration in the batch reached some critical value (0.1 mol/L), the films formed involved two autonomous phases: CdxPb1 – xS substitutional solid solutions and hexagonal cadmium sulfide CdyS of structure В4 (space group P63mc). The method and its parameters as proposed are efficient for manufacturing heterostructures in the CdS–PbS system in one-pot deposition.

Установлено ингибирующее действие йодида аммония NH 4 I на кинетику роста пленки сульфида свинца при варьировании его исходной концентрации в растворе в пределах 0.05–0.40 М. Введение ингибитора способствует уменьшению размеров зерен, увеличению до ~13% частиц нанодиапазона и до 3.7 ат. % йода в составе пленок PbS в зависимости от условий синтеза. По результатам рентгеновских исследований установлено, что синтезированные слои сохраняют кубическую структуру B 1 (пр. гр. \(Fm\bar {3}m\) ). При повышении концентрации ингибирующей добавки в растворе наблюдается увеличение параметра кристаллической решетки сульфида свинца от 0.59315(1) до 0.59442(3), что связано с замещением серы йодом в кристаллической решетке PbS. Максимум спектральной чувствительности и "правая" граница фотоответа пленок PbS сдвигаются в коротковолновую область – с 2.5 до 2.2 мкм и с 3.0 до 2.8 мкм соответственно, что может быть следствием образования широкозонной фазы PbI 2 . Низкотемпературными исследованиями пленок, осажденных в присутствии 0.15 и 0.25 моль/л NH 4 I, определены значения термической ширины запрещенной зоны, составившие 0.46 и 0.51 эВ при энергии активации примесных акцепторных уровней соответственно 0.135 эВ и 0.153 эВ. Легированные йодом пленки PbS имеют относительно высокую вольт-ваттную чувствительность к ИК-излучению за счет инверсии зон проводимости ( n → p ) при аномально малых значениях постоянной времени.

The results of studies of the morphology and photoelectric characteristics of nanostructured thin-film photoresistors based on Cd x Pb 1 – x S obtained by modifying their composition are analyzed. The surface morphology of photosensitive elements is analyzed by scanning electron microscopy and high-resolution transmission electron microscopy. Auger-electron microscopy is used to determine the elemental composition of thin the films and the distribution of elements according to thickness. Photoresistors are prepared by physical sputtering and chemical-bath deposition from aqueous solutions with various additives. To increase the sensitivity, oxygen is introduced into films of the composition Cd 0 Pb 1 S: into physically sputtered layers by high-temperature annealing and into chemically deposited layers by the addition of oxidants. To obtain Cd x Pb 1 – x S layers, hydrochemical deposition from an ammonium-citrate reaction mixture is used with varying concentrations of cadmium sulfate in the range of 0.01–0.1 mol/L.

Ammonium iodide (NH4I) has been shown to have an inhibiting effect on the growth kinetics of lead sulfide films at initial NH4I concentrations in solution from 0.05 M to 0.40 M. The addition of the inhibitor leads to a decrease in grain size, an increase in the fraction of nanoparticles in the PbS films to similar to 13%, and an increase in the iodine content of the films to 3.7 at %, depending on growth conditions. X-ray diffraction characterization has shown that the films have a B1 cubic structure (sp. gr. Fm (3) over barm). Increasing the inhibitor concentration in solution leads to an increase in the lattice parameter of the lead sulfide from 0.59315(1) to 0.59442(3) nm, due to iodine substitution for sulfur in the PbS crystal lattice. The spectral sensitivity peak and the long-wavelength edge of the photoresponse of the PbS films shift to shorter wavelengths from 2.5 to 2.2 and from 3.0 to 2.8 mu m, respectively, which is attributable to the formation of the wide-band-gap phase PbI2. Using low-temperature measurements, the thermal band gap of the films grown in the presence of 0.15 and 0.25 mol/L NH4I has been determined to be 0.46 and 0.51 eV. The respective activation energies for acceptor impurity levels are 0.135 and 0.153 eV. The iodine-doped PbS films offer a relatively high voltage responsivity in the IR spectral region owing to an n- to p-type conversion, in combination with an anomalously short response time.

Thin films of Cd x Pb 1 – x S (0 ≤ x ≤ 0.094) substitutional solid solutions of cubic structure B 1 (space group Fm 3 m ) were prepared by chemical deposition and characterized by X-ray diffraction, scanning electron microscopy, EDX elemental analysis, and Raman spectroscopy. Once the cadmium sulfate concentration in the batch reached some critical value (0.1 mol/L), the films formed involved two autonomous phases: Cd x Pb 1 – x S substitutional solid solutions and hexagonal cadmium sulfide Cd y S of structure В 4 (space group P 6 3 mc ). The method and its parameters as proposed are efficient for manufacturing heterostructures in the CdS–PbS system in one-pot deposition.

Pb1+хS thin films of 190-360 nm thickness have been synthesized on glass substrates by chemical bath deposition from aqueous solutions using different thioamides (thiourea, N-allylthiourea, thioacetamide) as sulfur precursors. The obtained films are polycrystalline semiconductors with n-type conductivity. The effect of the sulfur origin on the crystalline structure, morphology and formation mechanism of Pb1+хS thin films is analyzed. The formal rate constants of Pb1+хS formation reactions are determined. Quantum-chemical calculations approve that a lead superstoichiometry in the obtained films may be attributed to types of point defects: atomic vacancies in the sulfur sublattice and the lead doping the sulfur sublattice. A correlation is established between the amount of lead excess and the optical band gap of Pb1+хS: the greater the excess of lead is, the wider the band gap is. The fractal analysis of Pb1+хS thin films evidences the film growth obeying model of a cluster-by-cluster association in three-dimensional space.

Министерство науки и высшего образования Российской Федерации Российское химическое общество им.Д.И.Менделеева Секция по химической термодинамике и термохимии Научного совета РАН по физической химии Сибирское Отделение Российской Академии Наук Институт неорганической химии им.А.В.Николаева СО РАН

Polycrystalline films of Cd x Pb 1-x S (0≤ x≤0.05) substitutional solid solutions with a cubic structure B1 (Fm3m space group) containing amorphous cadmium sulfide were obtained by chemical bath deposition. Upon reaching a critical concentration of the cadmium salt in the reactor, the films consisted of substitutional solid solution and cubic CdS with the B3 structure (F43m space group). Scanning electron microscopy established the morphological features associated with the secondary nucleation and formation of the cadmium sulfide phase. The structural characteristics of the films have been calculated by a full-profile analysis of X-ray diffraction patterns. We have revealed the correlation between phase and elemental composition of Cd x Pb 1-x S/CdS films with their voltage and current photosensitivity. Based on the received data, we have assumed the role of the individual CdS phase for the photoconductivity mechanism of Cd x Pb 1-x S solid solutions. Keywords: chemical bath deposition, thin films, solid solutions, cadmium sulfide, photosensitivity, current-voltage characteristics.

The concentration conditions for the deposition of lead sulfide and hydroxide in a citrate-ammonia reaction system by varying the pH value and the concentration of the ammonium iodide dopant are calculated. Kinetic studies of the process of conversion of lead salt into sulfide by varying the concentration of NH4I in solution within the range of 0.0-0.4 M show an inhibitory effect of ammonium iodide, which reduces the constant of the effective rate of the conversion process by almost 20 times. Thin films of lead sulfide with a thickness of 100 to 650 nm are synthesized by chemical bath deposition in the presence of NH4I on sitall and glass substrates. The introduction of NH4I into the reaction mixture decreases the size of crystallites forming the films and increases the fraction of nanoparticles to 17%. The films deposited during 90 min contain 48.5-51.7 at% of lead, 47.4-47.9 at% of sulfur, and up to 3.7 at% of iodine; the content of iodine can reach 17.1 at% in the initial period of deposition (after 20 min of deposition). The calculated fractal dimension of the surface of the iodine-doped PbS(I) films (Dc = 2.04-2.14) corresponds to the process of film formation by the cluster-cluster aggregation mechanism with small sticking probability (reaction-limited cluster aggregation model (RLCA)). According to the X-ray diffraction data, the PbS(I) films have a cubic structure of the NaCl (B1) type; an increase in the concentration of NH4I in the solution results in an increase in the lattice parameter from 0.59315(1) to 0.59442(3) nm, which is probably due to the substitution of sulfur ions for iodine ones. According to optical studies, the introduction of ammonium iodide into the reaction mixture leads to a shift of the absorption edge to the high-energy region and the appearance of an additional (impurity) band. The PbS films deposited in the presence of NH4I do not require additional photosensitization operations and show a relatively high volt-watt sensitivity to IR radiation at anomalously small values of the time constant.

Evolution of the morphology, composition, structural characteristics (lattice constant, microstrains, texturing), and optical and photoelectric properties of PbS films produced by chemical deposition in the presence of ammonium iodide and chromium (III) chloride at concentrations of up to 0.02 M is studied. According to the data of elemental analysis by energy-dispersive X-ray spectroscopy, the Cr content in PbS films nonmonotonically depends on the CrCl 3 concentration, and the highest content is 1.08 at %. The size distribution of particles is monomodal, and the average size of particles forming the films varies from ~100 to ~225 nm at a nanoparticle content of 2–6%. The introduction of NH 4 I and CrCl 3 into the reactor preserves the B 1 cubic structure of PbS and yields an increase in the band gap E g by 0.16–0.20 eV, a decrease in the dark resistance R d , and an increase in the voltage sensitivity U s . The dependences of E g and U s on the chromium-salt concentration in the reaction bath are of extreme character, with a maximum at 0.016 M of CrCl 3 , which is due to the nonmonotonic incorporation of chromium into the PbS lattice. The results of studies of the current–voltage characteristics of PbS(I) and PbS(I, Cr) thin-film layers are in good agreement with the data on the structural, optical, and photosensitivity properties.

Polycrystalline films of CdxPb1−xS (0 ≤ x ≤ 0.05) substitutional solid solutions with a cubic structure B1 (Fm3 ̅m space group) containing amorphous cadmium sulfide were obtained by chemical bath deposition. Upon reaching a critical concentration of the cadmium salt in the reactor, the films consisted of substitutional solid solution and cubic CdS with the B3 structure (F43 ̅m space group). Scanning electron microscopy established the morphological features associated with the secondary nucleation and formation of the cadmium sulfide phase. The structural characteristics of the films have been calculated by a full-profile analysis of X-ray diffraction patterns. We have revealed the correlation between phase and elemental composition of CdxPb1−xS/CdS films with their voltage and current photosensitivity. Based on the received data, we have assumed the role of the individual CdS phase for the photoconductivity mechanism of CdxPb1−xS solid solutions.