The effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited ZnTe thin films

The present paper reports the effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited zinc telluride (ZnTe) thin films. X-ray diffraction (XRD) analysis of the films, deposited on glass substrates, revealed that they have cubic structure with strong (111) texture. Room temperature deposits are tellurium rich and an increase in the substrate temperature up to 553 °K results in stoichiometric films. Electrical conductivity has been observed to increase with the increase in substrate temperature, accompanied by increase in the carrier concentration and the mobility of the carriers. The optical bandgap energy and the thermal activation energy of the films have also been evaluated.     

Effect of annealing temperature on structural, electrical and optical properties of B-N codoped ZnO thin films

The B-N codoped p-type ZnO thin films have been prepared by radio frequency magnetron sputtering using a mixture of nitrogen and oxygen as sputtering gas. The effect of annealing temperature on the structural, electrical and optical properties of B-N codoped films was investigated by using X-ray diffraction, Hall-effect, photoluminescence and optical transmission measurements. Results indicated that the electrical properties of the films were extremely sensitive to the annealing temperature and the conduction type could be changed dramatically from n-type to p-type, and finally changed to weak p-type in a range from 600 °C to 800 °C. The B-N codoped p-type ZnO film with good structural, electrical and optical properties can be obtained at an intermediate annealing temperature region (e.g., 650 °C). The codoped p-type ZnO had the lowest resistivity of 2.3 Ω cm, Hall mobility of 11 cm²/Vs and carrier concentration of 1.2 × 10¹⁷ cm^− 3.     

In-situ TEM observations of abnormal grain growth, coarsening, and substrate de-wetting in nanocrystalline Ag thin films

Abnormal grain growth is studied in nanocrystalline sputtered Ag films. Eighty nanometer thick Ag films are DC sputter deposited onto back-etched amorphous silicon nitride membranes. Specimens are annealed in a heating stage in an in-situ TEM for various temperatures and hold times. With the same specimen, we proceed to higher temperatures after the apparent halt of growth for sufficiently long hold times. The grain size distribution of the as-deposited films is bi-modal, with large abnormal grains with 100 nm diameters, embedded in a matrix of smaller grains of 15 nm diameters. Coarsening begins at temperatures of approximately 100°C, and quickly reaches a plateau. The growth process restarts only after sufficient temperature increases, and plateaus at each succeeding temperature. Using a variation of the Mullins–Von Neumann law, the activation energy for the abnormal growth is found to be 0.274 eV, consistent with the value reported for pore formation during electromigration via surface diffusion in Ag. Grain growth appears to stop above temperatures of 350°C, eventually leading to triple junction pore formation at 350°C and de-wetting of the film from the substrate at 600°C. The de-wetting is the high temperature limit of the thermal grooving which cancels the driving force for grain growth at the lower temperatures. TEM images as evidence of this effect are presented, along with observations on the pore formation that support surface diffusion as the mass transport mechanism for grooving, pore fomation, and as the limiting mass transport mechanism for the grain growth.     

Effects of substrate temperature on structural, electrical and optical properties of As-doped ZnO films

As-doped ZnO films were prepared by co-sputtering ZnO and Zn₃As₂ targets on glass substrates at various temperatures from 250 to 500 °C. The effects of substrate temperature on structural, electrical and optical properties of the films were investigated. The films grown at temperatures from 250 to 400 °C were c-axis oriented and those deposited above 400 °C exhibited poor crystallinity. Hall measurement showed that p-type ZnO:As films were prepared at different temperatures. With increasing the substrate temperature from 250 to 500 °C, the optical band gap (E_g) first decreased, and then increased. The E_g changes upon the substrate temperature were due to the effect of substrate temperature on the crystallinity of ZnO films.     

Microstructure and electrical properties of ultrathin gold films prepared by DC sputtering

Ultrathin gold films with different thicknesses were prepared by direct current magnetron sputtering technique and analyzed by X-ray diffraction, atomic force microscopy, transmission electron microscopy and temperature-varying four-wire technique. For thicknesses d < 24.1 nm, both D_{avg {111}} and D_{avg {220}} increase rapidly with the thickness. For 24.1 ≤ d ≤ 97.8 nm, D_{avg {220}} increases at a slower rate than before but D_{avg {111}} remains the same. Surface morphology analysis shows that, as the thickness increases, the average particle size changes from 22.1 to 54.3 nm; at the same time, rms roughness decreases to a minimum and then increases. The electrical properties of the thin films from 80 to 300 K were measured. The results show that the temperature coefficient of resistance of the thin films is positive, and increases from 2.2 × 10⁻⁴ to 8.5 × 10⁻⁴ K⁻¹ with increasing film thickness.     

Fabrication by electrostatic spray deposition and structural investigation of ultra thin and dense zirconia films

The aim of this work was to prepare ultra thin and dense zirconia films by electrostatic spray deposition to be applied in microelectronic devices. In this paper, the influence of the precursor solution was investigated on the morphology of zirconia films, in terms of salt concentration starting from zirconium acetylacetonate and solvent composition based on butyl carbitol and/or ethanol. The microstructure of zirconia films was studied by Scanning and Transmission Electron Microscopies. The as-deposited films, less than 20 nm in thickness, were found to be amorphous. A film densification, leading to its thickness decrease to 7 nm, occurred through a thermal treatment at 600 °C under helium. A partial crystallization was observed and the structure of the film was found to be mainly tetragonal, according to electron diffraction. An appearance of 6 mol% monoclinic phase was detected by Raman microspectrocopy.     

Growth and characterization of electrodeposited Cu(In,Al)Se2 thin films

Thin films of CuIn_1 − xAl_xSe₂ were grown using a cathodic electrodeposition technique. The CuIn_1 − xAl_xSe₂ films were electrodeposited on SnO₂ coated glass from aqueous baths containing different Al contents using deposition potentials ranging from − 650 mV to − 850 mV versus a saturated calomel electrode. The electrodeposited films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays, atomic force microscopy, and UV-VIS-NIR spectroscopy. The results show that single phase CuIn_1 − xAl_xSe₂ films with Al content x around 0.27-0.33 having good stoichiometry can be produced in the above potential range. XRD and SEM studies show that films deposited at − 650 mV and − 750 mV have good crystallinity while those grown at − 850 mV have comparatively poorer crystallinity. SEM studies show that the particle size of the films grown at − 650 and − 750 mV is in the micron range but is around 100 nm when grown at − 850 mV. Optical studies show that the optical band gap shifts with Al content from 1.21 eV for x = 0.27 to about 1.42 eV for x = 0.33. The as-grown as well as vacuum annealed films were n-type in conductivity with resistivity in the range 3-5 × 10⁻³ Ω cm.     

Microstructure and electrical properties of RuO2-CeO2 composite thin films

RuO₂-CeO₂ composite thin films are deposited on various Si substrates by a radiofrequency magnetron sputtering technique. Compacted polycrystalline pellets of the nanostructured CeO₂-RuO₂ composite system are used as standard samples for comparative electrical analyses. All films and composite samples are analyzed by X-ray diffraction and transmission electron microscopy. Electrical measurements of radiofrequency sputtering of thin films are performed as a function of the RuO₂ fraction and of the temperature (between 25 and 400 °C). A nonlinear variation in the electrical conductivity of the RuO₂-CeO₂ composite thin films as a function of the RuO₂ volume fraction (Φ) is observed and discussed. It is interpreted in terms of a power law (in (Φ − Φc)^m ), where m and Φc are parameters characteristic of the distribution of the conducting phase in a composite medium.     

Growth of nanocomposite in eutectic Cu-Ag films

Eutectic composition Cu-Ag alloy thin films were prepared by co-deposition at room temperature onto oxidized Si substrates by thermal evaporation. Morphological development, structure and phase state of the films were investigated by transmission electron microscopy. The films possess fibre morphology 10-30 nm in diameter and strong <111> texture is present. The fibres are nanocrystalline composed of 2-3 nm size zones of Cu and Ag rich solid solution phases and a model for morphological development and phase separation is described. In the early stages of growth phase separation occurs by nucleation in melted islands and a eutectic of randomly oriented crystallites forms. In later stages of growth the phase separation takes place by spinodal decomposition. It results in a strain stabilized unique morphology corresponding to an intermediate stage of phase separation.     

Physical and electrical properties of thin films produced by Low Energy Cluster Beam Deposition of mixed InxSb1−x clusters

We present a new gas-aggregation cluster source with two independent crucibles, one for indium and another one for antimony. This source was used to produce mixed In_xSb_1−x clusters in the nanometer range size (typically 4 nm), which were deposited at room temperature on amorphous carbon or glass substrates by low energy cluster beam deposition technique (LECBD). The film composition was analysed by energy dispersive X-ray (EDX) spectroscopy. The morphology and structure of the films were studied by transmission electron microscopy (conventional and high resolution) and selected area electron diffraction (SAED) at different compositions. Semiconducting InSb clusters could be produced by controlling the temperature of the two crucibles. The electrical properties of the films were studied at a film thickness of 20 nm. The conductivity versus temperature appeared to be thermally activated for all compositions.     

The influence of annealing temperature on the structural, electrical and optical properties of ion beam sputtered CuInSe2 thin films

CuInSe₂ (CIS) thin films were prepared by ion beam sputtering deposition of copper layer, indium layer and selenium layer on BK7 glass substrates followed by annealing at different temperatures for 1 h in the same vacuum chamber. The influence of annealing temperature (100-400 °C) on the structural, optical and electrical properties of CIS thin films was investigated. X-ray diffraction (XRD) analysis revealed that CIS thin films exhibit chalcopyrite phase and preferential (112) orientation when the annealing temperature is over 300 °C. Both XRD and Raman show that the crystalline quality of CIS thin film and the grain size increase with increasing annealing temperature. The reduction of the stoichiometry deviation during the deposition of CIS thin films is achieved and the elemental composition of Cu, In and Se in the sample annealed at 400 °C is very near to the stoichiometric ratio of 1:1:2. This sample also has an optical energy band gap of about 1.05 eV, a high absorption coefficient of 10⁵ cm⁻¹ and a resistivity of about 0.01 Ω cm.     

Structural properties of epitaxial SrCuO2 thin films on SrTiO3 (001) substrates

Thin films of SrCuO₂ with tetragonal structure have been epitaxially grown on SrTiO₃ (001) substrates by high-oxygen pressure sputtering technique. The interface structure between SrCuO₂ and SrTiO₃ and configuration of defects in SrCuO₂ thin films have been characterized by means of high-resolution transmission electron microscopy. Two types of film-substrate interface structure coexist and are determined as bulk-SrO-TiO₂-Sr(O) -CuO₂-Sr-bulk and bulk-SrO-TiO₂-SrO-Sr(O) -CuO₂-Sr-bulk. The planar faults with double SrO atomic layers in {100} planes in SrCuO₂ thin films are observed, which mainly arise from the coalescence of these two types of film-substrate interface structure. Meanwhile, planar faults in {110} planes are observed in thin films and structural models are proposed.     

Electrochemical composite deposition of Sn–Ag–Cu alloys

The dominant materials used for solders in electronic assemblies over the past 60 years have been Pb–Sn alloys. Increasing pressure from environmental and health authorities has stimulated the development of various Pb-free solders. One of the most promising replacements is eutectic or near-eutectic Sn–Ag–Cu alloys produced by electrodeposition. In this study, simple and “green” Sn–Cu-citrate solutions with suspended Ag particles have been developed and optimized for electrochemical composite deposition of eutectic and near-eutectic Sn–Ag–Cu solder films. Different plating conditions, including solution concentration, current density, agitation and additives, are investigated by evaluating their effects on plating rate, deposit composition and microstructure.     

Behavior of Cu nanoparticles ink under reductive calcination for fabrication of Cu conductive film

Cu nanoparticle ink was prepared from Cu nanoparticles that were coated with a gelatin layer at an average diameter of 46 nm. The Cu nanoparticle ink was applied on the polyimide substrate. Conductive films were fabricated using the Cu nanoparticle ink with a two-step annealing process consisting of oxidative pre-heating at 200 °C under 10 ppm O₂-N₂ mixed gas flow and reductive calcination at 250 °C under 3 vol.% H₂-N₂ mixed gas flow showed a low resistivity of 5 μΩ cm. The hydrolysis of the remaining gelatin layer by H₂O vapor, which was formed during the reduction of the Cu oxide by 3 vol.% H₂-N₂ mixed gas, was suggested. The results suggest the possibility of the removal of the gelatin layer without oxidative pre-heating and simultaneous sintering of Cu nanoparticles in reductive calcination.     

Effects of calcination temperature on the morphology, structure and photocatalytic activity of titanate nanotube thin films

"Titanate nanotube thin films were synthesized on titanium substrate via a simple hydrothermal method. The as-prepared film was composed of Na₂Ti₃O₇, and then transformed into H₂Ti₄O₉·H₂O after acid washing process. However, H₂Ti₄O₉·H₂O was thermally unstable. The effect of calcination temperature on its morphology (nanotube, nanosheet, nanorod or a lotus-root-like appearance), structure and photocatalytic activity was carried out by annealing the films at 300-900 °C in the static air and then analyzing by X-ray diffraction, scanning electron microscope and transmission electron microscope. Based on the results, the possible evolution mechanisms were discussed for no-acid (washed with distilled water) and acid washed (washed with dilute HNO₃) samples, respectively. Finally, the photocatalytic activity of acid washed films calcined at different temperatures was evaluated by photodegradation of methyl orange (MO) under ultraviolet light. The results indicated that the film obtained at 500 °C showed the highest rate for decomposing MO solution, which could be explained by its unique surface morphology and crystal structure.     

C-Ti nanocomposite thin films: Structure, mechanical and electrical properties

Carbon-titanium nanocomposite thin films were deposited by DC magnetron sputtering on oxidized silicon substrates in argon. The films were prepared at different deposition temperatures between 25 and 800 °C. Transmission electron microscopy was used to determine the structure of the films. All the C-Ti nanocomposites consisted of columnar TiC structure with average column width ∼10 and 20 nm and a thin carbon matrix. The thickness of the carbon matrix between adjacent TiC columns was ∼2-5 nm.Mechanical properties (hardness, reduced modulus) of C-Ti films showed a distinct variation depending on the deposition temperature. Films deposited at 200 °C had the highest hardness ∼18 GPa and the highest reduced modulus ∼205 GPa.Temperature dependence of the film resistance was measured between 80 and 330 K. C-Ti nanocomposites have a non-metallic conduction mechanism characterized by a negative temperature coefficient of resistivity (TCR). The most negative TCR was observed for films showing high hardness and reduced modulus of elasticity.     

Surface morphological, structural, electrical and optical properties of annealed vanadyl tetra tert-butyl 2, 3 naphthalocyanine thin films

Vanadyl Tetra Tert-Butyl 2, 3 Naphthalocyanine (VTTBNc) thin films have been grown at room temperature by physical vapor deposition technique. The article describes the role of air and vacuum annealing on VTTBNc thin film surface morphology, structure, electrical conductivity and optical absorbance on the basis of respective measurements like atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray Diffractogram (XRD), DC electrical conductivity with integrated electrodes and UV-visible absorption spectra.     

Structural and electrical properties of amorphous carbon-sulfur composite films

In this paper, we discuss the synthesis of carbon-sulfur composite (a-C:S) films by vapour phase pyrolysis of maleic anhydride and sulfur. Structural changes in the system are analysed by scanning electron microscopy and powder X-ray diffraction. Microhardness test depicts an increase in the value of hardness with an increase in sulfur concentration. Electrical conductivity of composite samples varies with sulfur concentration. Magnetoresistance (MR) measurements show a drastic increase in the value of MR for the samples prepared at < 900°C. Thermal stability of these samples is analysed by thermogravimetric analysis, which depends on the host structure and the amount of intercalated species.     

Physico-chemical and electrical properties of InSe films

Thin films of InSe were obtained by vacuum evaporation of polycrystalline material onto well cleaned glass substrates. After deposition on a cold substrate the samples were placed in a vacuum-sealed Pyrex tube for the annealing process. Physico-chemical and electrical properties of the InSe layers have been investigated. RBS and X-ray diffraction measurements showed that the InSe phase could be obtained. Electrical properties of the InSe layers are studied for different annealing temperatures. Conductivity measurements show that the behaviour of the films is sensitive to their thermal environment. The conductivity is controlled by grain boundaries.     

The effect of carbon content on the microstructure of hydrogen-free physical vapour deposited titanium carbide films

Titanium carbide (TiC) coatings for tribological applications were deposited on high speed steel. Several coatings with different titanium to carbon ratio were deposited by means of physical vapour deposition in which titanium was evaporated and carbon was sputtered. The coatings were characterised using analytical electron microscopy. It was observed that the change in titanium to carbon ratio significantly changed the microstructure of the coatings. The low carbon containing coatings consisted of columnar grains exhibiting a preferred crystallographic orientation whereas the coating with highest carbon content consisted of randomly ordered TiC grains in an amorphous carbon matrix. Energy filtered transmission electron microscopy revealed a change in Ti/C ratio as the distance from the substrate increased. The titanium to carbon ratio was observed to increase with distance from the substrate until a stable level was reached. This is due to a variation in the titanium evaporation during the early stages of film growth. This change of the titanium to carbon ratio affected the columnar growth in the initial stage of coating growth for the coatings with low carbon content.