Investigation of structural,optical and morphological properties of copper doped zinc sulphide nanoparticles

Semiconductor nanoparticles doped with transition metal ions can influence the transition probabilities and electronic structure. The undoped and copper doped zinc sulphide nanoparticles with various concentrations are synthesized by wet chemical co-precipitation method. These nanoparticles are characterized by using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), UV–visible (UV–vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, conductivity measurement and time-resolved photoluminescence studies. X-ray powder diffraction analysis reveals that the synthesized samples have cubic zinc blende structure. The Scanning Electron Microscope shows the synthesized nanoparticles are agglomerated. The UV–visible spectra reveal the absorption edge is red shifted. The FT-IR spectra show vibrational peaks around 617 cm⁻¹ which indicate the presence of Cu–S stretching modes. The AC conductivity measurement confirms the semiconducting nature and shows a marked increase in conductivity as the doping concentration of copper increases. The photoluminescence shows that the emission at 426 nm may be due to transition from the conduction band to the zinc vacancies. These transition metal ions doped semiconductor nanoparticles have important applications in solid state lighting, imaging, and other photonic devices.     

GeTe phase change material and Ti based electrode: Study of thermal stability and adhesion

Phase change memories use a specific phase change material (PCMat) as a resistor element for information storage. To obtain good reliability and performances of the device, interface between PCMat and electrodes needs to be optimized.In this work, we study the adhesion between the electrode material and GeTe PCMat by a mechanical characterization (four-point bending). Our results show that a thin titanium interfacial layer drastically enhances the adhesion energy. Using X-Ray Diffraction and Secondary Ion Mass Spectroscopy, strong chemical interactions between titanium and tellurium is evidenced. In particular, after a 400 °C anneal, Ti₃Te₄ formation is observed. This chemical affinity probably explains the improvement of adhesion between the electrode and GeTe.     

Phase equilibria and solidification properties of Sn-Cu-Ni alloys

Ternary Sn-Cu-Ni alloys were prepared and annealed at 240°C. The annealed alloys were metallographically examined and the equilibrium phases formed were identified on the basis of compositional determinations and x-ray diffraction (XRD) analysis. The isothermal section of the ternary Sn-Cu-Ni system at 240°C was proposed on the basis of experimental results of this study and related information on phase equilibrium available in the literature. The binary compounds, Cu₆Sn₅, Ni₃Sn₂, and Ni₃Sn₄, have very extensive ternary solubility. Continuous solid solutions form between Cu and Ni as well as between Cu₃Sn and Ni₃Sn. In addition to the isothermal section, the liquidus projection of the Sn-Cu-Ni system was determined based on results from the existing literature. Interfacial reactions between Sn-Cu alloys and Ni substrate and the primary solidification phases of various Sn-Cu-Ni alloys were also examined in this study.     

Molecular beam epitaxy of CdSe and the derivative alloys Zn1−x Cd x Se and Cd1−x M x Se

We report the epitaxial growth of CdSe, Zn_1−x Cd _x Se (0 ≤x ≤ 1) and Cd_1−x Mn _x Se (0 ≤x ≤ 0.8) on (100) GaAs. X-ray diffraction (XRD), electron diffraction and transmission electron microscopy (TEM) indicate that all the epilayers have the cubic (zinc-blende) structure of the GaAs substrate. The energy gaps of these materials were measured using reflectivity measurements. We also report the growth of ZnSe/Zn_1−x Cd _x Se superlattices. TEM and XRD measurements show that high quality modulated structures with sharp interfaces are possible.     

Microstructural Investigation of Bilayer Growth of In- and Ga-Rich InGaN Grown by Chemical Vapor Deposition

Epitaxial InGaN with an In content of up to 89% was grown on a GaN template on a sapphire substrate using metalorganic chemical vapor deposition. The grown layer showed a bilayered structure of In- and Ga-rich InGaN parallel to the growth plane, as confirmed by both x-ray diffraction and electron microscopy. High-angle annular dark-field images revealed that pyramidal Ga-rich InGaN had formed on the top of the In-rich InGaN layer with an abrupt interface. Nucleation of the In-rich InGaN was believed to be related to threading dislocations stemming from the GaN buffer layer.     

Structural and electrical characterization of platinum (~15 at%) doped nickel silicides on Si(100) and SiGe/Si(100) substrates

Ni(Pt~15 at%)Si/Si(100) and Ni(Pt~15 at%)SiGe/SiGe/Si(100) films corresponding to rapid thermal annealing (RTA1) temperatures of 220, 230 and 240 °C with constant RTA2 (at 420 °C) have been investigated for sub 20 nm devices. X-ray reflectometry (XRR), X-ray diffraction (XRD), four point probe, and atomic force microscopy (AFM) techniques were employed for the characterization of NiSi and NiSiGe films. XRR results indicated that NiSi and NiSiGe film thicknesses increased with RTA1 temperatures. NiSi films densities increased with layer thickness but NiSiGe films displayed an opposite trend. The diffractograms revealed that NiSi and NiSiGe layers contain identical phases and possessed fiber texture at 220 °C. Whereas, the peaks shift were observed for NiSi (211) and NiSi (021) at higher RTA1 temperatures which appear due to Pt diffusion (hexagonal structures of larger grain size were noted). NiSiGe crystallites self-alignment was observed because of strained SiGe/Si(100) substrate. At 240 °C, NiSiGe layer showed the smallest crystallites. This is believed to be due to Pt distributed along the silicide grain boundaries which obstructs silicide grain growth. NiSi and NiSiGe sheet resistance decreased significantly with increase in RTA1 temperatures and found to correlate with multiple grain orientation. AFM revealed a smooth-stable surface morphology for all films.     

Synthesis and characterization of Manganese doped Tungsten oxide by Microwave irradiation method

The aim of this article is to synthesis tungsten oxide (WO₃) nanoparticle along with Manganese (3 wt% and 10 wt%) by Microwave irradiation method. The physical properties of the synthesized Manganese doped Tungsten oxide materials were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscope (TEM), UV-Diffuse Reflectance Spectroscopy, SEM-EDAX and Photoluminescence studies. The predominant peaks obtained in X-ray diffraction pattern reveal the crystalline nature of the nanoparticles and the structure belongs to Monoclinic for pure and Mn doped WO₃. FTIR analysis shows the presence of Tungsten and oxygen in the synthesis material and verified with EDAX. TEM analysis shows both pristine and Mn doped WO₃ nanopaticles. They are having spherical shaped morphology with average particle size from 35 to 40 nm. UV-DRS revealed that the bandgap energy for pure and Manganese doped WO₃ are discussed in this article. The Scanning Electron Microscope analysis shows the plate like morphology for pure WO₃ and the morphology were decreased by doping Manganese. The defects and oxygen deficiencies were analysed by photoluminescence spectroscopy.     

Effect of tin content on the electrical and optical properties of sprayed silver sulfide semiconductor thin films

Silver sulfide (Ag₂S) thin films have been deposited on glass substrates by t spray pyrolysis using an aqueous solution which contains silver acetate and thiourea as precursors. The depositions were carried out at a substrate temperature of 250 °C. Structural studies by means of X-ray diffraction show that all tin (Sn)-doped Ag₂S thin films crystallized in a monoclinic space group with noticeable changes in the crystallites' orientation. The discussion of some structural calculated constants has been made with Sn doping in terms of microhardness measurements. Moreover, the optical analysis via the transmittance, reflectance as well as the photocurrent reveals that the direct band gap energy (E_gd) decreases (E_gd varies from 2.34 to 2.16 eV) and the indirect band gap energy (E_gi) increases (E_gi varies from 0.98 to 1.09 eV) slightly as a function of Sn content. Electrical study shows that Sn doping changes the electrical conductivity and proves the thermal activation of electrical conduction.     

Some electrical and optical properties of a-Si:F:H alloys

Amorphous Si:F:H with desirable properties for photovoltaic applications can be fabricated by the glow discharge of SiF₄ and H₂. The preparation conditions influence the properties of the resultant alloy. For instance, altering the ratio of SiF₄ to H₂ from 80 to 5 can alter the localized state density from 10¹⁹cm⁻³eV−1 to ≃ 10¹⁶cm⁻³eV-1, respectively. The conduction mechanisms are altered and there are vast changes in the photoconductivity as the density of recombination centers is decreased. The lower density of states achieved in the a-Si:F:H alloy reflects in the ease of doping. In addition, the lower density of states in a-Si:F:H alloy should result in a wider depletion region than reported for the a-Si:H alloy when fabricated within the device configuration. Results of C-V measurements using Au Schottky barrier devices confirm this.     

Antimony sulfide (Sb2S3) thin films by pulse electrodeposition: Effect of thermal treatment on structural,optical and electrical properties

Antimony sulfide films have been deposited by pulse electrodeposition on Fluorine doped SnO₂ coated glass substrates from aqueous solutions containing SbCl₃ and Na₂S₂O₃. The crystalline structure of the films was characterized by X-ray diffraction, Raman spectroscopy and TEM analysis. The deposited films were amorphous and upon annealing in nitrogen/sulfur atmosphere at 250 °C for 30 min, the films started to become crystalline with X-ray diffraction pattern matching that of stibnite, Sb₂S₃, (JCPDS 6-0474). AFM images revealed that Sb₂S₃ films have uniformly distributed grains on the surface and the grain agglomeration occurs with annealing. The optical band gap calculated from the transmittance and the reflectance studies were 2.2 and 1.65 eV for as deposited and 300 °C annealed films, respectively. The annealed films were photosensitive and exhibited photo-to-dark current ratio of two orders of magnitude at 1 kW/m² tungsten halogen radiation.     

Metal-induced lateral crystallization of a-Si thin films by Ni-Co alloys and the electrical properties of poly-Si TFTs

We have introduced a new process in metal-induced lateral crystallization (MILC). By adding Co to the Ni-MILC process, the electrical characteristics of MILC poly-Si TFTs were considerably improved. In particular, a considerable decrease of TFT leakage current were achieved in both n-type and p-type devices.     

Phase equilibria and the related properties of Sn-Ag-Cu based Pb-free solder alloys

We have recently developed a thermodynamic database for micro-soldering alloys which consists of the elements Pb, Bi, Sn, Sb, Cu, Ag, Zn, and In. In this paper, the phase equilibria and the related thermodynamic properties of the Sn-Ag-Cu base alloys are presented using this database, alloy systems being one of the promising candidates for Pb-free solders. The isothermal section diagrams of the Sn-Ag-Cu ternary system were experimentally determined by SEM-EDS, x-ray diffraction and metallographic techniques. Based on the present results as well as the previous data on phase boundaries and thermochemical properties, thermodynamic assessment of this system was carried out. The isothermal and vertical section diagrams, liquidus surface, mass fractions of the phase constitution, etc., were calculated. The predictions of surface energy and viscosity were also investigated. Moreover, a non-equilibrium solidification process using the Scheil model was simulated and compared with the equilibrium solidification behavior in some Sn-Ag-Cu base alloys. Calculated results based on the Scheil model were incorporated into a three-dimensional solidification simulation and the prediction of practical solidification procedures was performed.     

Influence of rapid thermal annealing on morphological and electrical properties of RF sputtered AlN films

Aluminum nitride films were deposited, at 200 °C, on silicon substrates by RF sputtering. Effects of rapid thermal annealing on these films, at temperatures ranging from 400 to 1000 °C, have been studied. Fourier transform infrared spectroscopy (FTIR) revealed that the characteristic absorption band of Al–N, around 684 cm⁻¹, became prominent with increased annealing temperature. X-ray diffraction (XRD) patterns exhibited a better, c-axis, (0 0 2) oriented AlN films at 800 °C. Significant rise in surface roughness, from 2.1 to 3.68 nm, was observed as annealing temperatures increased. Apart from these observations, micro-cracks were observed at 1000 °C. Insulator charge density increased from 2×10¹¹ to 7.7×10¹¹ cm⁻² at higher temperatures, whereas, the interface charge density was found minimum, 3.2×10¹¹ eV⁻¹cm⁻², at 600 °C.     

Effect of Bi doping on structural,morphological, optical and ethanol vapor response properties of SnO2 nanoparticles

The gas sensing behavior of thick films of Bi doped SnO₂ has been investigated towards ethanol vapor. The screen printing technique was used to prepare the thick films. The films were sintered at 650 °C for 2 h. The structural, surface morphological, optical and gas sensing properties of undoped and Bi doped SnO₂ thick films have been studied. X-ray diffraction and Raman spectroscopy confirmed that the films consisted exclusively of tetragonal tin oxide, without any impurity phases. FE-SEM studies revealed the formation of highly porous microstructure with grain size in few tens of nanometers. From the optical studies, the band gap was found to be decreased with bismuth doping (3.96 eV for undoped, 3.83 eV, 3.71 eV and 3.6 eV for 1 mol%, 2 mol% and 3 mol% Bi, respectively). The 3 mol % Bi doped SnO₂ thick films exhibited the highest sensitivity to 100 ppm of ethanol vapor at 300 °C. The effect of microstructure on sensitivity, response time and recovery time of the sensor was studied and discussed.     

Analysis of morphological, structural and electrical properties of annealed TiO2 nanowires deposited by GLAD technique

The effect of annealing on vertically aligned TiO₂ NWs deposited by glancing angle deposition (GLAD) method on Si substrate using pressed and sintered TiO₂ pellets as source material is studied.The FE-SEM images reveal the retention of vertically aligned NWs on Si substrate after annealing process.The EDS analysis of TiO₂ NWs sample annealed at 600℃ in air for 1 h shows the higher weight percentage ratio of~2.6(i.e.,72.27% oxygen and 27.73% titanium).The XRD pattern reveals that the polycrystalline nature of anatase TiO₂ dominates the annealed NWs sample.The electrical characteristics of Al/TiO₂-NWs/TiO₂-TF/p-Si (NW device) and Al/TiO₂-TF/p-Si (TF device) based on annealed samples are compared.It is riveting to observe a lower leakage current of~1.32×10^-7 A/cm² at+1 V with interface trap density of~6.71×10¹¹ eV^-1cm^-2 in NW device compared to~2.23×10^-7 A/cm² in TF device.The dominant leakage mechanism is investigated to be generally Schottky emission;however Poole-Frenkel emission also takes place during high reverse bias beyond 4 V for NWs and 3 V for TF device.     

Crystallization process of perovskite modified by adding lead acetate in precursor solution for better morphology and higher device efficiency

The power conversion efficiency of 15.20% is achieved in this study for planar perovskite solar cells fabricated in air from one-step spin-coating lead chloride (PbCl₂) based precursor modified by additional adding 1% lead acetate (PbAc₂), much higher than the reference one from pure PbCl₂ precursor without modification. A higher quality perovskite film with increased coverage is the reason for this improvement. The perovskite nucleation rate and start time of nucleation are key parameters of perovskite crystallization kinetics. By adding 1% PbAc₂ to the precursor, the density of perovskite crystal nucleuses is optimized to achieve the best film and then the highest device performance.     

Effect of processing parameter on structural,optical and electrical properties of photovoltaic chalcogenide nanostructured RF magnetron sputtered thin absorbing films

The aim of this work was to develop high quality of CuIn_1−xGa_xSe₂ thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn_0.8Ga_0.2Se₂ (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×10¹⁵ lines m⁻²). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~10⁵ cm⁻¹ for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω⁻¹ cm⁻¹) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose.     

TiO2压敏陶瓷的显微分析和电学性能

研究了烧结温度对TiO2压敏陶瓷的显微结构、显微成分、势垒结构和电学性能的影响。采用SEM和EDS测试其显微结构和晶粒的化学组成。根据热电子发射理论和电学性能计算了势垒结构。在1350℃烧结的TiO2压敏陶瓷具有均匀而致密的显微结构,其晶粒大小为15μm左右,施主掺杂Nb5+在TiO2晶粒中的固溶度为1.49%;势垒高度?B为0.28eV,势垒宽度xD为48nm;压敏电压V1mA为5.25V/mm,非线性系数α为4.2,εr为1.1×104。     

Enhancement of optical and electrical properties of SILAR deposited ZnO thin films through fluorine doping and vacuum annealing for photovoltaic applications

Undoped and fluorine doped ZnO thin films were deposited onto glass substrates using successive ionic layer adsorption and reaction (SILAR) technique and then annealed at 350 °C in vacuum ambience. The F doping level was varied from 0 to 15 at% in steps of 5 at%. The XRD analysis showed that all the films are polycrystalline with hexagonal wurtzite structure and preferentially oriented along the (002) plane. Crystallite sizes were found to increase when 5 at% of F is doped and then decreased with further doping. It was seen from the SEM images that the doping causes remarkable changes in the surface morphology and the annealing treatment results in well-defined grains with an improvement in the grain size irrespective of doping level. All the films exhibit good transparency (>70%) after vacuum annealing. Electrical resistivity of the film was found to be minimum (1.32×10⁻³ Ω cm) when the fluorine doping level was 5 at%.     

Characteristics and optical properties of MgO nanowires synthesized by solvothermal method

Magnesium oxide (MgO) nanowires were synthesized by solvothermal method using magnesium nitrate hexahydrate and sodium hydroxide. Field emission scanning electron microscopy (FE-SEM) and transmission scanning electron microscopy (TEM) measurements indicate that the product consists of a large quantity of nanowires with average diameter of 20 nm and average length of several micrometers. Explorations of X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), Fourier transformer infrared spectroscopy (FTIR), selected area electronic diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) indicate that the product is high-quality cubic single-crystalline nanowires. The optical properties of the samples are investigated using UV–visible spectroscopy to study the refractive index and optical dielectric constant. The photoluminescence (PL) measurement suggests that the product has an intensive emission centered at 437 nm, showing that the product has potential application in optical devices. The advantages of our method lie in high yield, the easy availability of the starting materials and allowing their large-scale production at low cost.