Copper Sulfide Thin Films Research Articles

Studies on surface deformation of copper sulphide thin films by holographic interferometry technique

Holographic interferometry technique used to study the surface deformation of electrodeposited copper sulphide thin films on stainless steel substrate is here presented. It is concerned with the formation and interpretation of fringe patterns, which appears when a wave generated at some earlier time and stored in a hologram is later reconstructed by interfering with comparison wave. The proposed technique uses double exposure holographic interferometry (DEHI) together with simple mathematical relation, which allows immediate finding of stress, mass deposited and thickness of thin film. It must be further noted that, fringe spacing changes with time of deposition as well as solution concentration. The structural study (XRD) is carried out for the confirmation.

Optimization of the synthesis and characterizations of chemical bath deposited Cu2S thin films

Semiconducting copper sulphide (Cu2S) thin films have been deposited on various substrates (SnO2:F/glass, glass) by the simple and economical chemical bath deposition technique. The depositions were carried out during a deposition time of about 32.5 min in the pH range of 9.4 to 11. The synthesized Cu2S thin films were characterized using various techniques without any annealing treatment. X-ray diffraction study shows that Cu2S films exhibit the best crystallinity for pH = 10.2. For this pH value, Auger electron spectroscopy investigations show that Cu2S thin films grown on an SnO2/glass substrate exhibit stochiometric composition with [Cu]/[S] concentrations ratio equal to 2.02. Using the Kelvin method, the work function difference (Фmaterial– Фprobe) for the Cu2S films deposited on SnO2/glass substrates at the optimum pH value was found to be equal to 145 meV. Hall measurements confirm the p-type electrical conductivity of the obtained films. The electrical resistivity was of the order of 3.85 × 10−4 Ω-cm. The transmission and reflection coefficients vary in the range of [35–60] % and [5–15] % respectively, in the visible range, and the band gap energy is about 2.37 eV.

Preparation and characterization of patterned copper sulfide thin films on n-type TiO 2 film surfaces

Micro-arrayed patterns of p-type copper sulfide (Cu x S) thin films with positive and negative features were deposited onto the surfaces of n-type TiO 2 semiconductor films via a selective nucleation and growth process from aqueous solution. The surface functional molecules of the UV photo-oxidised patterned SAMs were utilized to direct the nucleation and growth of Cu x S crystallites. The resultant Cu x S/TiO 2 composite films with negative and positive Cu x S patterns on the TiO 2 film surface were investigated using SEM, XRD, XPS and a 3D Surface Profiler. It is demonstrated that regular and compact patterned films of Cu 2S crystallites had been deposited onto the n-type TiO 2 surface, with sharp edges demarcating the boundaries between the patterned Cu 2S region and the TiO 2 film region. The UV–vis spectra for three Cu 2S/TiO 2 films exhibit a wide absorption between 300 nm and 450 nm. The maximum wavelength differences in the spectra of Cu 2S/TiO 2 films and TiO 2 film were attributed to the added absorption of Cu 2S films at 302 nm and the unchanged adsorption of TiO 2 films. The absorption intensities of the Cu 2S/TiO 2 films could be varied in the UV–vis range using the Cu 2S patterned features (positive, negative).

Characterization of Electrodeposited Copper Sulphide Thin Films

Copper Sulphide (CuS) thin films were electrodeposited onto indium doped tin oxide coated conducting glass (ITO) substrates from an aqueous acidic bath containing CuSO4, Na2S2O3 and EDTA. The deposition mechanism was investigated using cyclic voltammetry. The appropriate potential region in which the formation of stoichiometric CuS thin films occurs was found to be -500 mV versus SCE and the solution pH was maintained at 3.0 p 0.1. X-ray diffraction studies revealed that the deposited films are found to be cubic structure with preferential orientation along (111) plane. Optical absorption measurements were used to estimate the band gap value of CuS thin films deposited at different bath temperatures. Surface morphology and film composition was analyzed using an energy dispersive x-ray analysis (EDAX) set up attached with scanning electron microscope (SEM), respectively. The experimental observations are discussed in detail.

CuS-based thin films for architectural glazing applications produced by co-evaporation: Morphology, optical and electrical properties

Copper sulphide thin films in the 90–300 nm thickness range have been deposited on soda–lime glass substrates by thermal co-evaporation of Cu and S. Depending on the film thickness, the optical transmittance in the visible region is of about 50% for the thinnest film and 19% for the thickest film, with the corresponding near-infrared transmittance dropping from 11% to near-zero at 2500 nm as the film thickness increases from 90 to 300 nm. A resistivity of ρ ~ 10 − 4 Ω cm has been obtained for the films. The optoelectronic properties of the films remained practically unchanged after one year stored under laboratory ambient. The optical properties obtained for selected CuS-based films make them suitable for their use as effective solar control glazings in warm climates.

Effect of Different Substrates on Performance of Copper Sulfide Thin Film Ammonia Gas Sensor

Copper sulfide (Cu1.4S) thin films have been grown on Silicon (Si), silicon dioxide (SiO2), stainless steel (SS) and fluorine doped tin oxide (FTO) coated glass substrates by solution growth technique (SGT) at room temperature. The effect of substrate on surface morphology is studied by probing surface morphology using scanning electron microscope (SEM) and atomic force microscope (AFM). It is observed that particle size of copper sulfide is larger on silicon and smaller on FTO substrates. Ammonia gas detection testing is carried out by fabricating resistive sensor element and measuring (in-situ) current-voltage (l-V) curves during gas adsorption. In addition, effect of ambient temperature on response of sensor is also studied. Copyright © 2009 American Scientific Publishers All rights reserved.

Properties of CuS thin films treated in air plasma

Copper sulfide thin films were grown by chemical deposition and post treated in air plasma during 20 min. Air plasma was generated by alternating current discharge at a pressure of 4 × 10 2 Pa. The power discharge was maintained at an output of 220 V and a current of 0.2 A. Thermal annealing at 300 °C was performed for comparison. X-ray diffraction shows that plasma treatment results in phase transformation of Cu 39S 28 (as grown) to CuS (treated by plasma). The copper lost is confirmed by X-ray fluorescence. No significant change in the optical band gap was observed due to plasma action. In addition, the electrical conductivity increases in one order of magnitude. On the other hand, the samples under plasma condition show a parallel growth to the substrate and an increase in the surface uniformity. The plasma etching removes copper due to its affinity with oxygen to form CuO, as is corroborated by optical emission spectroscopy.

Enhancement in sensitivity of copper sulfide thin film ammonia gas sensor: Effect of swift heavy ion irradiation

The studies are carried out on the effect of swift heavy ion (SHI) irradiation on surface morphology and electrical properties of copper sulfide (CuxS) thin films with three different chemical compositions (x values). The irradiation experiments have been carried out on CuxS films with x=1.4, 1.8, and 2 by 100 MeV gold heavy ions at room temperature. These as-deposited and irradiated thin films have been used to detect ammonia gas at room temperature (300 K). The SHI irradiation treatment on x=1.4 and 1.8 copper sulfide films enhances the sensitivity of the gas sensor. The results are discussed considering high electronic energy deposition by 100 MeV gold heavy ions in a matrix of copper sulfide.

Electrical characterization of 100 MeV heavy ion irradiated Au/p-Cu1.4S Schottky barrier diodes

Interface states play a vital role in Fermi-level pinning in Schottky barrier diodes. Here, we have modified the surface of copper sulfide by using 100 MeV Au8+ swift heavy ions. On this modified surface, a Schottky diode was fabricated using gold metal. This leads to an interface with different ‘interface states’, affecting the charge transport and diode properties. I–V measurements showed that the current decreases with increase in ion fluence from 1011 to 1013 ions cm−2, and barrier height increases while ideality factor decreases. These results are explained by taking into account the presence of free copper at the surface and grain boundaries of copper sulfide thin films and its diffusion into the matrix.

Fabrication and characterization of positive and negative copper sulfide micropatterns on self-assembled monolayers

Positive and negative micropatterned copper sulfide thin films were successfully fabricated through chemical bath deposition methods. The thin films were deposited on patterned Si substrates with two different self-assembled monolayers (SAMs), i.e., NH 2/CH 3 and NH 2/OH terminated silane, respectively. Under an optimal depositing condition, the copper sulfide thin films were selectively deposited on NH 2 regions. The resultant Cu 2S crystal films, in positive and negative circle patterns, respectively, were verified by SEM, XPS, XRD spectra. UV–vis spectrum analysis demonstrated that the prepared Cu 2S films exhibited high optical transmission in the visible light regions (vis) and near-infrared region (NIR), and a low band gap of 2.48 eV.

Copper sulphide (CuxS) as an ammonia gas sensor working at room temperature

Abstract A solution growth technique (SGT) has been used to deposit Cu x S ( x = 1, 1.4, and 2) thin films on glass substrates at room temperature (300 K). These as-deposited thin films are characterized for their structural, optical and electrical properties by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), scanning electron microscopy (SEM) and atomic force microscopy (AFM), optical absorption and current–voltage ( I – V ) measurements. XRD shows that the Cu x S layer grew with hexagonal and monoclinic phases for x = 1 and 2, respectively. SEM and AFM show the nano-particles ( x = 1 and 1.4) and nano-discs ( x = 2) formation. The optical band gaps ( E g ) of thin films are 1.26 eV (CuS), 1.96 eV (Cu 1.4 S), and 2.31 eV (Cu 2 S). In addition, surface wettability is studied by using double-distilled water drops for contact angle measurements. It is observed that the contact angle for Cu 1.4 S is larger than those for CuS and Cu 2 S films. It suggests that the x = 1.4 films have high-surface energy. Ammonia gas sensors are fabricated by using these copper sulphide thin films with silver metal contacts. Based on the time-dependent experimental results nanostructured Cu x S serve as sensor material for the detection of NH 3 molecules at room temperature.

Gigantic irradiation effect of 100 MeV Au8+ swift heavy ions on the copper sulfide thin films with different chemical compositions

Gigantic deformations were found for the copper sulfide (Cu1.4S and Cu2S) thin films irradiated with 100 MeV Au8+ swift heavy ions (SHI) for 1011 and 1012 ions cm−2 fluencies. It was observed that the deformation due to SHI is dependent on the chemical composition of the film. The optical band gap (E g) of the Cu1.4S was blue shifted, whereas that of Cu2S was red shifted. The surface modifications were also different for these two compositions. These effects were studied by using the atomic force microscopy and scanning electron microscopy. The results are explained in the light of thermal spike model.

Copper sulfides obtained by spray pyrolysis — Possible absorbers in solid-state solar cells

Copper sulfide (Cu x S, x = 1.8–2) thin films were deposited at 285 °C by spray pyrolysis from aqueous and alcoholic solutions of copper (II) chloride and thiourea with different Cu:S molar ratio. The XRD analysis showed that deposited films are chemically close to chalcocite (Cu 2S) or to mixtures of copper-rich phases (Cu 2S, Cu 1.8S, Cu 1.9375S) in which chalcocite or digenite (Cu 1.8S) is predominant. The films containing the single phase Cu 2S are denser and more homogenous than the films formed by two or more phases. The current–voltage ( I– V) dark curves showed the diode behavior of the films, depending on the film thickness.

Growth characteristics and effect of thickness on optical properties of iron copper sulphide (FeS<sup>2</sup>CuS<sup>3</sup>) thin films

Thin films of iron copper sulphide (FeS2CuS3) were produced by chemical bath deposition technique on glass substrate. The optical and electrical properties of the films were investigated using ultraviolet-visible spectrophotometer and Fourier transforms infrared spectrometer. The energy band gap of the film ranged between 1.80 - 2.10 eV, which fell within the band gaps of Cu2S and FeS2 thin films. The thickness and electrical conductivity of the films ranged between 3.96 - 4.18 μm and 3.57 x 102 - 4.04 x 102 W-1m-1 respectively. There was a corresponding decrease in thickness with electrical conductivity. The optical transmittance of the films decreased with increased film thickness. Since the average transmittance of film was greater than 45 % in the ultraviolet-near infrared regions and exhibited poor transmittance in the ultraviolet regions, the thin films of FeS2CuS3 could be used for solar cell fabrication and as effective coatings for poultry houses. Journal of Applied Science and Technology Vol. 10(1&2) 2005: 53-59

Formation Processes of Chemically Deposited Copper Sulfide Thin Films

Copper sulfide thin films and particles were prepared by chemical bath deposition. Bath compositions were altered as well as mechanical processes such as stirring of solutions during the deposition process to determine the effect on resulting films. The films and particles that were formed homogeneously in the bath solutions were analysed by Raman spectroscopy, electron microscopy, X-ray diffraction and electrochemistry. By changing one of the complexing agents, films and particles with varying copper:sulfur ratios were formed. Films that were deposited while the solution stirred formed a thinner layer than those in which the solution was static during the deposition process. The effect of changing specific parameters included an improvement in adhesion properties, a decreased amount of particulate growth within the bath solution, a decrease in the thickness and roughness of the resulting films, and a change in stoichiometry, although these property changes were not always observed in the same system.

Use of an Evaporated Gold SERS Substrate to Detect 2-Mercaptobenzothiazole on Sulfide Mineral Surfaces

The interaction of 2-mercaptobenzothiazole (MBT) with the sulfide mineral surfaces, chalcopyrite (CuFeS2), chalcocite (Cu2S) and synthetic copper sulfide (CuxS) thin films, was investigated by Raman spectroscopy. Gold was evaporated onto the sulfide surface to facilitate surface enhancement of Raman scattering. Raman and gold-induced SERS spectra from mineral surfaces exposed for various times to solutions of different MBT concentrations, recorded before and after gold decoration, were used to elucidate the mechanism of collector adsorption. Spectra were identified with MBT bonded to copper atoms in the mineral surface and not to bonding to the gold overlayer. Spectra obtained from each sulfide surface displayed the band arising from the NCS ring stretch vibration of MBT downshifted from its position from CuMBT. The shift was similar to that found previously for MBT chemisorbed on a copper metal electrode. MBT chemisorbs to copper atoms in the mineral surfaces through the exocyclic sulfur atom.

Formation Processes of Chemically Deposited Copper Sulfide Thin Films

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Optical and mechanical characteristics of clear and solar control laminated glass using zinc sulphide and copper sulphide thin films

Due to their structural integrity, laminated sheet glass is used in safety, security and transportation applications. In the simplest form, it is produced at temperature of 130–140 °C under a pressure of 10–16 kg/cm 2, applied to a glass–polyvinyl butyral (PVB)–glass sandwich for 30 min to a few hours. In this work, we report that the presence of a coating of ZnS thin film (40–80 nm) applied by chemical bath deposition on 2-mm-thick sheet glass improves the adhesion strength of laminated glass by about 20%, from 11.08±0.85 to 13.29±1.8 MPa. The optical transmittance of the laminated glass with ZnS thin film in the visible region is about 80%, essentially the same as that of the simple glass–PVB–glass laminate. The addition of a CuS thin film of 100–150 nm in thickness over the ZnS coating confers solar radiation control properties to the glass laminate: visible transmittance of 22% to 40% and very low transmittance, <10%, in the near infrared region, with the adhesion strength maintained at 12–14 MPa, which is above that of glass–PVB–glass laminates. These results may be of interest toward developing architectural glazings for tropical hot climates, and which can withstand windstorms efficiently.

Synthesis, vibrational spectra and X-ray structures of copper(I) thiourea complexes

Complex formation of thiourea with copper takes place as an intermediate step in the preparation of copper sulfide thin films by spray pyrolysis starting from aqueous solutions of copper(II) chloride and thiourea. The stoichiometry of the complex and that of the resulting thin film primarily depends on the molecular ratio of the starting materials. For comparison, the structures of all copper(I) thiourea complexes found in the Cambridge Structural Database are classified in this paper. In addition, syntheses, structural (single crystal XRD also at low temperature 193 K) and spectroscopic studies (FTIR and Raman) of six copper–thiourea complexes are now reported. The copper to thiourea stoichiometric ratio is 1:3 in four of these complexes, but their structures are basically different as dimerization or polymer formation takes place depending on whether the water of crystallisation is present or absent. The structure of bis(μ-thiourea)tetrakis(thiourea)dicopper(I) dichloride dihydrate, [Cu 2(tu) 6]Cl 2 · 2H 2O ( 1) was determined at room and also at low temperature. Bis(μ-thiourea)tetrakis(thiourea)dicopper(I) dibromide dihydrate, [Cu 2(tu) 6]Br 2 · 2H 2O ( 2) is isomorphous with 1, like the anhydrous compounds chlorotris(thiourea)copper(I), [Cu(tu) 3]Cl ( 3) and bromotris(thiourea)copper(I), [Cu(tu) 3]Br ( 4) are isomorphous. In the third isomorphous pair of complexes the copper to thiourea stoichiometric ratio is 1:1, viz. chloro(thiourea)copper(I) hemihydrate, [Cu(tu)]Cl · 0.5H 2O ( 5) and bromo(thiourea)copper(I) hemihydrate, [Cu(tu)]Br · 0.5H 2O ( 6). During the preparation of chloro(thiourea)copper(I) hemihydrate ( 5) a reaction by product α,α ′-dithiobisformamidinium dichloride, [SC(NH 2) 2] 2Cl 2 ( 7) was identified and structurally characterized which made it possible to suggest a reaction path leading to complex formation.

Modified chemical deposition and physico-chemical properties of copper sulphide (Cu 2S) thin films

Semiconducting stoichiometric copper sulphide (Cu 2S) thin films were deposited using modified chemical deposition method. The preparative conditions such as concentration, pH of cationic and anionic precursors, adsorption, reaction and rinsing time durations, complextant, etc. were optimized to get stoichiometric Cu 2S thin films. The structural, surface morphological, compositional, optical and electrical characterization were carried out with the help of X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Rutherford back scattering (RBS), optical absorbance/transmittance, electrical resistivity and thermoemf studies. The films were found to be nanocrystalline. Absorbance of the film was high (10 4 cm −1) with optical band gap of 2.35 eV. The electrical resistivity was of the order of 10 −2 Ω cm with p-type electrical conductivity.