Structural and optical properties of sulfurized Cu2ZnSnS4 thin films from Cu–Zn–Sn alloy precursors

This study reports the preparation of Cu₂ZnSnS₄ (CZTS) thin films by magnetron sputtering deposition with a Cu–Zn–Sn ternary alloy target and sequential sulfurization. The effects of substrate temperatures on the structural, morphological, compositional as well as optical and electrical properties were characterized. The results showed the CZTS thin films prepared by sulfurization at substrate temperature of 570 °C yielded secondary phases along with CZTS compound. The relatively good properties of CZTS thin film were obtained after sulfurization at substrate temperature of 550 °C. This CZTS film showed compact structure with large grain size of 900 nm, direct optical band gap of 1.47 eV, optical absorption coefficient over 10⁴ cm^?1, resistivity of 4.05 Ω cm, carrier concentration of 8.22 × 10¹⁸ cm^?3, and mobility of 43.38 cm² V^?1 S^?1.     

CuIn(S,Se)2 thin films prepared by selenization and sulfurization of sputtered Cu–In precursors

CuIn(S,Se)₂(CISSe) thin films have been prepared onto soda-lime-glass (SLG) substrates by selenization and sulfurization of magnetron sputtered Cu–In precursors. The results indicate that the properties of the CISSe films are strongly dependent on the post-annealing treatment. After annealing at 400 °C for 20 min, the CISSe films have formed tetragonal (chalcopyrite) crystal structure and the diffraction peaks of the films shift systematically to the left with the temperature varying from 400 °C to 500 °C. EDAX study reveals that the compositions of CISSe films are Cu_0.83In_1.17S_1.67Se_0.3, Cu_0.86In_1.13S_1.61Se_0.4 and Cu_0.82In_1.15S_1.54Se_0.49 after annealing at 400 °C, 450 °C and 500 °C, respectively. The direct optical band gaps of the films slightly decrease from 1.44 ev to 1.32 ev with the increase of the temperature from 400 °C to 500 °C, and the optical absorption coefficient is over 10⁵ cm⁻¹. The films annealed at 400 °C–500 °C are all found to be p-type and the resistivity is almost 10⁻²–10⁻³ Ω cm. The carrier mobility of the film at 500 °C is almost as high as 1.701 cm²/V S.     

Preparation of CuInSe2 thin films by selenization of co-sputtered Cu–In precursors

CuInSe2 thin films have been prepared by high Se vapor selenization of co-sputtered Cu–In alloy precursors within a partially closed graphite container. Cu–In alloys with different compositions were investigated. X-ray diffraction (XRD) analysis of the films showed mainly CuIn2 and Cu11In9 phases and the Cu11In9 peak intensity was found to increase as the alloy composition tended towards Cu-rich. A linear dependence of the alloy composition on the Cu/In deposition power was observed from energy dispersive analysis by X-rays (EDX). A three-fold volume expansion was exhibited by all the CuInSe2 films after selenization at 500–550 °C. Scanning electron microscopy (SEM) analysis of the films showed large and densely packed crystal structures with sizes above 5 m. The CuInSe2 films exhibited single phase chalcopyrite structure with preferential orientation in the (1 1 2) direction. The EDX composition analyses of the films showed Cu/In ratio ranging from 0.43 to 1.2, and Se/(Cu+In) ratios from 0.92 to 1.47. The measured film resistivities varied from 10-1 to 105 cm. The Cu–In alloy precursors with Cu/In ratio less than 0.70 were found to form CuIn3Se5 a defect chalcopyrite compound. All films were Se rich, with the exception of samples with very high Cu content.© 1998 Kluwer Academic Publishers     

Synthesis of Cu2ZnSnS4 films from sequentially electrodeposited Cu–Sn–Zn precursors and their structural and optical properties

The Cu₂ZnSnS₄ (CZTS) films are successfully prepared using a process of sequentially electrodeposited Cu–Sn–Zn precursors by a novel electrolyte formula and optimized parameters on Mo substrate, succeeded by annealing in saturated sulfur atmosphere. The results show that the Cu/Sn/Zn precursor sequence is strict, and optimized electro-deposition parameters are as follows: ?0.6 V, 5 min for Cu, ?1.2 V, 2 min for Sn, and ?1.35 V, 10 min for Zn. Layered precursors firstly alloy into Cu₆Sn₅ and CuZn binary phases under low annealing temperature. Then Cu₆Sn₅ and CuZn alloys decompose in sulfur atmosphere, and form CuS, SnS and ZnS binary phases. Cu₂SnS₃ ternary phase forms through reaction between CuS and SnS with increasing the temperature. Finally, the CZTS film is synthesized through reaction among binary and ternary sulfides. The photoluminescence peak from the CZTS films synthesized at 550 °C for 1 h is about at 1.49 eV.     

Growth and optical properties of Sn–Si nanocomposite thin films

The growth and optical properties of nanocomposite thin films comprising of nanocrystalline Sn and Si are reported. The nanocomposite films are produced by thermal annealing of bilayers of Sn and Si deposited on borosilicate glass substrates at various temperatures from 300 to 500 °C for 1 h in air. X-ray diffraction reveals that the as-deposited bilayers consist of nanocrystalline Sn films with a crystallite size of 30 nm, while the Si thin films are amorphous. There is onset of crystallinity in Si on annealing to 300 °C with the appearance of the (111) peak of the diamond cubic structure. The crystallite size of Si increases from 5 to 18 nm, whereas the Sn crystallite size decreases with increase in annealing temperature. Significantly, there is no evidence for any Sn–Si compound, and therefore it is concluded that the films are nanocomposites of Sn and Si. Measured spectral transmittance curves show that the films have high optical absorption in the as-deposited form which decreases on annealing to 300 °C. The films show almost 80 % transmission in the visible-near infrared region when the annealing temperature is increased to 500 °C. There is concomitant decrease in refractive index from 4.0, at 1750 nm, for the as-deposited film, to 1.88 for the film annealed at 500 °C. The optical band gap of the films increases on annealing (from 1.8 to ~2.9 eV at 500 °C). The Sn-Si nanocomposites have high refractive index, large band gap, and low optical absorption, and can therefore be used in many optical applications.     

Composition control in Cu2ZnSnS4 thin films by a sol–gel technique without sulfurization

Kesterite Cu₂ZnSnS₄ (CZTS) thin films with a smooth, compact and crack-free morphology are obtained via a sol–gel method without sulfurization process. Non-toxic ethylene glycol is selected as solvent, while Cu(CH₃COO)₂, Zn(CH₃COO)₂, SnCl₂·2H₂O and thiourea are used as raw materials. Chemical composition dependence of CZTS films on pre-annealing and post-annealing process is comprehensively investigated. The analysis of energy dispersive X-ray indicates that composition control of CZTS films can be easily realized by the preparation of precursor solution and varying the annealing conditions.     

Fabrication and characterization of dual sputtered Pd–Cu alloy films for hydrogen separation membranes

In this paper, submicron thin Pd–Cu alloy films are deposited using a dual sputtering technique, which allows a high composition control of the layer. The composition, surface morphology and phase structure of the sputtered layers are investigated by energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractiometry (XRD). For example, the XRD data prove that the Pd–Cu layers are an alloy of Pd and Cu. Subsequently, the characterized Pd–Cu alloy layers are deposited on a silicon support structure to create a 750-nm thin Pd–Cu membrane for hydrogen separation. The reported membrane obtained a high flux of 1.6 mol H₂/m² s at a temperature of 725 K, while the selectivity is at least 500 for H₂/He.     

Mechanism of grain refinement of an Al–Zn–Mg–Cu alloy prepared by low-frequency electromagnetic casting

Low-frequency electromagnetic casting (LFEC) process had been developed and is being used for the past several years with the application of an induction coil placed outside the conventional direct chill (DC) casting mould. It has been demonstrated that the LFEC process has a significant grain refining effect on aluminium alloys. In the present study, temperature measurement and direct quenching from liquid and/or semi-solid were carried out to study the temperature field during casting process and to understand the mechanism of the grain-refining effect of the LFEC process. The experimental results showed that in contrast to the conventional DC casting process, the liquid melt from the launder, during the LFEC process, is cooled with very high cooling rate directly to 3–6 °C below the liquidus, and the temperature field of the entire melt in the mould, and the hot top is quite uniform, which results in the enhanced heterogeneous nucleation and improved survival rate of the nuclei. This is believed to be the main reason why the LFEC process can significantly refine the grain size of aluminium alloys.     

Preparation and characterization of nanoporous Cu6Sn5/Cu composite by chemical dealloying of Al–Cu–Sn ternary alloy

In this article, a new ternary Al–Cu–Sn alloy system has been exploited to fabricate nanoporous Cu₆Sn₅/Cu composite slices through chemical dealloying in a 20 wt% NaOH solution at an elevated temperature. The microstructure of the sliced nanoporous Cu₆Sn₅/Cu composite was characterized using x-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy. The experimental results show that multi-phase precursor alloy comprises α-Al, Sn, and θ-Al₂Cu phases. The new phase Cu₆Sn₅ emerges through dealloying, and the as-dealloyed samples have three-dimensional (3D) structure composed of large-sized channels (hundreds of nanometers) and small-sized channels (tens of nanometers). Both the large- and small-sized pores are 3D, open and bicontinuous. The synergetic dealloying of α-Al and θ-Al₂Cu in the three-phase Al–Cu–Sn alloy and fast surface diffusion of Cu atoms and Sn atoms result in the formation of Cu₆Sn₅/Cu composite with bimodal channel size distributions. In addition, the dealloying duration plays a significant role in the formation of Cu₆Sn₅ and the length scales of the small-sized ligament/channels at a settled temperature.     

Microhardness properties of Cu–W amorphous thin films

Pure copper, pure tungsten and amorphous Cu₅₀W₅₀ and Cu₆₆W₃₄ alloy films were deposited by the direct current magnetron sputtering technique on cooled glass substrates. The film microhardness has been investigated as a function of alloy composition and substrate potential bias during deposition. The microhardness exhibited a maximum at Cu concentrations close to 50 at%, similar to the case of completely miscible binary alloys. The ion bombardment caused by the negative substrate polarization increased the film microhardness. The annealing of the amorphous Cu–W films up to 250 °C in vacuum increased the film microhardness by 10–20% apparently owing to the formation of the W(Cu) crystalline phase dispersed within a predominantly amorphous film matrix.     

Growth of YBa2Cu3O7−x thin films by ion beam sputtering

Polycrystalline, superconducting YBa₂Cu₃O_7−x films have been grown by ion beam sputtering (IBS) of bulk stoichiometric ceramic target. We found that the superconducting properties of the films are very sensitive to the choice of the substrates and post-deposition annealing conditions. Films deposited on SrTiO₃ substrates were found to be the best with a critical onset transition temperature, T_c to be as high as 95 K with a maximum current carrying capacity in superconducting state of 1.5 × 10⁵ A/cm² which is close to the best reported value for single-crystal YBa₂Cu₃O_7−x films.     

Effect of creep-aging processing on corrosion resistance of an Al–Zn–Mg–Cu alloy

Creep-aging forming, combining both the aging treatment and forming process, has recently drawn much attention of researchers. In this study, the effects of creep-aging processing on the corrosion resistance of an Al–Zn–Mg–Cu alloy are studied. Results show that the corrosion resistance of the studied Al–Zn–Mg–Cu alloy is sensitive to creep-aging processing parameters (creep-aging temperature and applied stress). With the increase of creep-aging temperature, the corrosion resistance first increases and then decreases. Increasing the applied stress can deteriorate the electrochemical corrosion resistance and improve the exfoliation corrosion resistance. The creep-aging processing can change the size and distribution of precipitates in the aluminum matrix, which significantly affects the corrosion resistance. The discontinuous grain boundary precipitates and narrow precipitate-free zones can enhance the corrosion resistance.     

Shape memory behavior of Fe–Pd alloy thin films prepared by dc magnetron sputtering

Fe–Pd films have been deposited onto fused quartz and silicon substrates by dc magnetron sputtering. When an arc-melted and homogenized Fe–30at.% Pd alloy disk was used as a sputtering target, Fe–Pd films fabricated was shown to contain about 24 at.% Pd under the deposition condition used. The target configuration was then modified by placing Pd wires on the target so as to control the Pd content of films with an accuracy of 1 at.% Pd. Fe–Pd films containing 28.5 at.% Pd underwent a thermoelastic fcc-to-fct martensite transformation after annealing at 900 °C followed by quenching into iced water. Apparently, the reverse transformation was also thermoelastic and the thermoelastic transformations occurred repeatedly upon thermal cycling. Some of the Fe–28.5at.% Pd films were peeled off from the quartz substrate and they showed SM effects upon heating after deformation. A diaphragm-shaped free-standing film was also fabricated on a thin Si substrate. This film showed attractive transformation characteristics, including a narrow transformation hysteresis loop of about 4 °C and a small temperature difference between M_f and A_f (about 10 °C) in addition to M_s (43 °C) close to room temperature. This diaphragm-shaped film showed a reversible ballooning behavior with a maximum strain of about 0.05% upon thermal cycling.     

Effects of synthesis temperature on CuIn(S,Se)2 thin films prepared by one-step evaporation of Cu–In precursors

CuIn(S,Se)₂ thin films were grown on soda-lime glass substrates by one-step evaporation Cu–In precursors processes. Effects of synthesis temperature on the structural and optical properties of CuIn(S,Se)₂ absorption layers were studied. The changes of surface morphology among different samples were observed by field-emission scanning electron microscopy. From X-ray diffraction images and Raman spectra, the CuIn(S,Se)₂ films had good crystallinity quality when the synthesis temperature was 550 °C. The FWHM of (112) peaks decreased from 0.537° to 0.180°, and secondary phase Cu_x(S,Se) disappeared when the synthesis temperature increased from 300 to 550 °C. The Raman spectra of the films also showed the CuIn(S,Se)₂ A₁ mode peaks existed chalcopyrite, and the blue shift of the CuIn(S,Se)₂ A₁ mode peaks from 289 to 284 cm^?1. The optical properties of the films were showed by transmission spectra, and the energy band gap of the CuIn(S,Se)₂ thin films fabricated at 550 °C is 1.34 eV.     

Enhanced mechanical properties and corrosion behavior of Zn–30Sn–2Cu high-temperature lead-free solder alloy by adding Sm

Journal of Materials Science: Materials in Electronics - Zn–30Sn–2Cu–xSm (x?=?0, 0.1, 0.3, 0.5, and 1.0 wt%) solders were prepared to investigate its...     

Preparation and properties of electroless Ni–Zn–P alloy films

Electroless deposition of Ni–Zn–P layers was studied on steel electrodes by varying the bath temperature (40–90°C), pH and chemical composition. The deposition parameters were optimized. Alloys containing 70–86 wt % Ni, 6–20 wt % Zn and 6–10 wt % P are obtained at 20 m h^–1 and 85°C. Corrosion measurements were performed in aerated 5% sodium chloride solution, the corrosion potential and current density are, respectively, –0.49 V/SCE and 2.6 A cm^–2.     

Hot tensile deformation behaviors and constitutive model of an Al–Zn–Mg–Cu alloy

The hot tensile deformation behaviors of an Al–Zn–Mg–Cu alloy are studied by uniaxial tensile tests under the deformation temperature of 340–460 °C and strain rate of 0.01–0.001 s⁻¹. The effects of deformation temperature and strain rate on the hot tensile deformation behaviors and fracture characteristics are discussed in detail. The Arrhenius-type constitutive model is developed to predict the peak stress under the tested deformation condition. The results show that: (1) The true stress–true strain curves under all the tested deformation conditions are composed of four distinct stages, i.e., elastic stage, uniform deformation stage, diffusion necking stage and localized necking stage. The flow stress decreases with the increase of deformation temperature or the decrease of strain rate. (2) The elongation to fracture increases with the increase of deformation temperature. Under the tested conditions, the strain rate sensitivity coefficient varies between 0.1248 and 0.2059, which indicates that the main deformation mechanism is the lattice diffusion-controlled dislocation climb. (3) The localized necking causes the final fracture of specimens under all the deformation conditions. Microvoids coalescence is the main fracture mechanism under relatively low deformation temperatures. With the increase of deformation temperature, the intergranular fracture occurs. (4) The peak stresses predicted by the developed model well agree with the experimental results, which indicate the validity of the developed model.     

Influence of high-pressure torsion on microstructural evolution in an Al–Zn–Mg–Cu alloy

A commercial age-hardenable Al-7136 alloy was successfully processed by high-pressure torsion (HPT) at room temperature through 1/8 to 4 turns. Microhardness measurements showed significant hardening even after 1/8 turn with the average hardness value reaching a maximum after 1 turn and then slowly decreasing. Higher hardness values were attained by processing the alloy through one pass of equal-channel angular pressing in a supersaturated condition at room temperature and then applying HPT for 1 or 2 turns. Microstructural observations revealed the possibility of achieving true nanometer grain sizes of <100 nm after processing at room temperature. There were variations in hardness with imposed strain due to the fragmentation and subsequent growth of precipitates during processing.