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The results of computer calculation of the probability of formation of vacancies in depth of semiconductor films directly during their growth due to the creation of structural defects by the ionic component of deposition are presented. The experimental setup has been modified for carrying out ion-stimulated growth of silicon film structures in a vacuum of 10-6 Torr and at substrate temperatures up to 1000K. The basic properties and crystalline perfection of Si/Si structures obtained by vacuum deposition and their electrical characteristics when heated in the temperature range of 300-900K were studied in comparison with typical silicon epitaxial structures. [ABSTRACT FROM AUTHOR]

Substrate type plays an important role in the growth of semiconductor films using the chemical bath deposition (CBD) method, which is a simple and cost-effective technique. The effect of the nature of the substrate on the structural, optical, morphological, and electrical properties of tin monosulfide (SnS) films on both substrates (glass and flexible) was studied for 4 h at a constant temperature of 80 °C, with a strong peak at 31.75, which corresponds to the (111) level of the prepared SnS films. The scanning electron microscope revealed that the surface of the film on the glass substrate is covered with irregular spherical granules, some of which are nanoflakes, while the surface of the film on the flexible substrate is observed to contain flower-like spherical granules that are well distributed, more compact, and of a homogeneous structure. The grain size of SnS films was found to be 2.7 µm and 3.6 µm on glass and flexible substrates, respectively. The energy bandgap varied between 2.06 eV on the glass substrate and 1.52 eV on the flexible substrate. Hall Effect measurements show the films created have p-type conductivity for both substrates. [ABSTRACT FROM AUTHOR]

ZnSnN2 is a member of class of nitride semiconductors which have the additional benefits of earth abundance and non-toxicity. For device applications, NH3 gas detecting senor, which finds use in chemical, pharmaceutical, and food process industries, are fabricated with zinc-tin-nitride (ZnSnN2) thin-films on glass substrate by making use of metal as contacts. The ZnSnN2 sensor is found extremely selective to ammonia (NH3) amongst other gases like ethanol, NO2, H2S and exhibited good detecting responses at room temperature. There are many ways to develop thin films of ZnSnN2, and hence in this work we are trying to find a cost effective, feasible and easier method of synthesis, i.e., chemical vapor deposition method. The first step was the optimization of process parameters to grow Zinc-Tin (ZnSn) thin-films. Later, optimization of the process parameters for the growth of compound ZnSnN2 was completed. The grown films are characterized by material quality using X-Ray Diffraction and UV-Vis spectroscopy. [ABSTRACT FROM AUTHOR]

The terahertz (THz) wave generation by photoconductive antennas fabricated on the low-temperature and high- temperature grown In0.5Ga0.5As semiconductor and Bi2-xSbxTe3-ySey (BSTS) topological insulator films is studied by the terahertz time-domain spectroscopy method. THz generation property of In0.5Ga0.5As layers grown by molecular beam epitaxy on GaAs substrates with (100) and (111)A crystallographic orientations is compared with THz generation capability of the BSTS films grown by the MOCVD method on a sapphire substrate. Antennas of the both types were excited by radiation of Er3+ -fiber laser at 1.56 um wavelength. THz generation by InGaAs-based antennas on (111)A GaAs substrates was 3–4 times more effective than the same antennas fabricated on the (100) wafers. It was found that the generation of THz waves was more efficient in an island film of BSTS having a total thickness of about tens nanometers with that chemical composition where the volume contribution to conductivity was suppressed. Strong amplification of the THz radiation power has been demonstrated after applying an external electric field to the topological insulator film. [ABSTRACT FROM AUTHOR]

The substitution of Sb in place of Ge in As40Se50Ge10 thin film increases the 3rd order susceptibility and nonlinear refractive index by approximately three times. The two thin films As40Se50Ge10 and As40Se50Sb10 were prepared by thermal evaporation method from the bulk sample. The two optical characterizations was done by UV-Visible spectrometer which shows the decrease in transmission due to metallic Sb substitution in place of semiconductor Ge. The linear as well as the nonlinear refractive index was found to be increased and band gap got decreased with replacement of Ge by Sb. The drastic change in linear and nonlinear optical parameters was explained on the basis of density of localized states and disorderness. The structure remained amorphous and the surface roughness is nearly same as noticed from the AFM picture. [ABSTRACT FROM AUTHOR]

Herein we report, tin (Sn) doped copper sulphide(CTS) thin films deposited on commercial glass substrates at room temperature throughin-situ chemical bath deposition. For the synthesis of CuS (CS) thin film aqueous solution of cupric chloride with thiourea was prepared. Triethanolamine was used as complexing agent. PH of the precursor solution has been adjusted using ammonium hydroxide solution. Doping was accomplished by Sn in to the chemical bath using hydrated stannic chloride solution. The structural, morphological properties of the thin films are investigated in detail. The XRD analysis revealed that both the doped and undoped films are polycrystalline in nature and was indexed to be of covellite CuS phase. Morphological characteristics showedrod shaped nanoparticles of size in range 150 nm- 250 nm for CuS film and spherical nanoparticles for the Sn doped CuS thin films whose size ranges in the same order as that of the CuS thin films. AFM revealed the rough surface topographyof the CuS film. UV-vis spectroscopy shows that optical energy band gap ofCuS thin film increases with Sn incorporation. The electrical conductivity of the pure CuS thin film is enhanced with Sn doping. The carrier concentrations determined from the Hall measurements came out to be 1017 cm−3, stating both the undoped and Sn doped CuS thin films were semiconducting in nature. [ABSTRACT FROM AUTHOR]

This study aimed to synthesize Cu3BiS3 semiconductor using chemical bath deposition (CBD) method and to investigate its application on semiconductor-sensitized solar cells using mesoporous TiO2 films. The Cu3Bi1S3 semiconductor was synthesized using two-step chemical deposition onto mesoporous TiO2 film: the deposition of Bi-S and the deposition of Cu-S. The formation of Cu3Bi1S3, proved by the XRD pattern, was achieved after annealed at 350°C for 1 hour in the nitrogen atmosphere. The band gap was measured using UV-Visible spectrophotometer and found to be 1.4 eV, an optimal band gap for solar cells application. Such process was then applied to produce liquid- junction semiconductor-sensitized solar cells. The observation involved were the dependence of solar cells on the use of different electrolytes, different solar cells’ structure, different particle sizes of mesoporous TiO2 film and different deposition time. The best solar cell obtained has power conversion efficiency (PCE) of 0.139% with current density of 6.09 mA/cm². This result indicates that CBD method can be used to synthesize Cu3BiS3 semiconductor into mesoporous TiO2 and further study needs to be done to search for the best solar cells’ structure to obtain higher PCE from Cu3BiS3 semiconductor. [ABSTRACT FROM AUTHOR]

Poly (diaminonaphthalene) doped poly (vinyl alcohol) was synthesized by in-situ chemical oxidation polymerization method. The complex conduction mechanism of obtained PDAN doped PVA films were examined by measuring DC and AC conductivity. Non-linear I-V characteristics curve confirming the semiconducting nature of the films at constant temperatures. The DC and AC conductivities of the 0.791g PDAN doped PVA films were (2.041±0.64)×10−5 Scm−1 and (6.28±0.79)×10−6 Scm−1, respectively. The DC conductivity so obtained was six folds larger than earlier reported. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide nanostructured thin films are synthesized using thermal evaporation and are plasma annealed. XRD results depict that films exhibit orthorhombic crystalline phase of vanadium oxide (i.e. V2O5). As annealing temperature increases the growth of V2O5 nanostructures increases. Scanning electron micrographs show that different morphologies are obtained with different annealing temperatures. At lower plasma annealing temperature (i.e. 350 °C), 1D nanostructures are obtained, whereas for higher annealing temperature (550 °C) the embedded nano-blocks are obtained. A TEM/HRTEM measurement is conducted, which asserts the crystalline nature of nano-blocks. There is a remarkable decrease in resistance in temperature ranging from 240 K to 480 K suggests semiconductor behavior of films. The effect of temperatures of plasma annealing on the V2O5 nanostructured thin films (NSTs) is studied. [ABSTRACT FROM AUTHOR]

Thin Film Technology has attracted attention of the numerous investigators all over the world owing to its huge applications in a variety of fields such as optics, electronics, lasers, blue-green light emitting diodes and industries also. There are a variety of deposition techniques by which a host of thin semiconductor films can be deposited. Among these deposition technologies, chemical bath deposition (CBD) is ranked as conceptually simplest and universal. In this paper, we report on the synthesis of Zn1-xCoxSe (0 = x = 0.275) thin films grown from the aqueous solutions of zinc sulphate, cobaltous sulphate and selenium metal ions in the presence of TEA as a complexing agent, hydrazine hydrate as a reducing agent and ammonia to enhance the film adherence. ZnSe and Co doped ZnSe films were prepared at 80°± 1° C; the deposition time being 90 mins. The surface of the asobtained films were smooth, uniform and hydrophobic in nature. The X-ray photoelectron spectroscopy confirmed the presence of Zn, Co and Se. As the constituent elements in the deposited films are having 2+, 2+ and 2- chemical states. Both ZnSe and Zn1-xCoxSe thin films are crystalline over the whole composition range (0 = x = 0.275) and are structurally cubic. The lattice parameter (a) and interplanar distance (d) change with the addition of Co2+ in the ZnSe host lattice. Formation of ternary alloy was confirmed from the shift in the (111) X-ray diffraction peak. AFM surface topography revealed the influence of Co2+ integration into ZnSe host lattice, the film sample with x = 0.15 being more crystalline with Sku = 5.572, maximum surface area ratio (Sdr) and highest average roughness (Sa). Increasing amount of Co2+ in the ZnSe lattice results in the sample surface transformation from mesokurtic (less sharp or crystalline) to leptokurtic (crystalline or more sharper). The advanced imaging Sobel transformation and angular spectrum techniques provided a better visibility of the fine structure and features of the various materials. [ABSTRACT FROM AUTHOR]

A dye-sensitized solar cells (DSSCs) using a nanocomposite (NC) semiconductor film, consisting of graphene layer and ZnO nanosheets (Gr-ZnO) is fabricated by electrodeposition process. The DSSCs based on Gr-ZnO NC were determined via electrochemical impedance spectra (EIS), UV-Visible diffused reflectance spectroscopy (UV-Vis), and photovoltaic performances J-V curves to substantiate the explanations. Impedance spectra shows that a smaller charge transport time constant occurs in DSSCs based on Gr-ZnO NC comparing to ZnO. This improved the electron collecting efficiency significantly, resulting in high open circuit voltage. Moreover, Gr-ZnO NC shows an efficient photoinduced charge separation and transportation can be achieved at the interface thus exhibit excellent potential for photocurrent generation compared with sole ZnO. Gr-ZnO NC obtained a maximum photocurrent response for an open-circuit voltage and a power conversion efficiency of 0.96 V and 7.01% respectively, which is doubled from sole ZnO. The fabricated Gr-ZnO NC cells show better performances compared to conventional ZnO structure reference cell. [ABSTRACT FROM AUTHOR]

Co-doped ZnO and Fe-doped ZnO diluted magnetic semiconductor films were prepared on glass substrates by chemical spray pyrolysis (CSP) method. Synthesized ZnO:Co and ZnO:Fe thin films by CSP method were compared to thin film properties. Optical analysis of the synthesized thin films was examined by spectral absorption and transmittance measurements using UV-Vis double beam spectrophotometer technique and Photoluminescence (PL) spectroscopy. Structural characterizations of the thin films were examined by using X-ray diffraction (XRD), Raman Analysis, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) techniques, respectively. Magnetic properties of the films investigated by Vibrating sample magnetometer (VSM) measurements and magnetization measurements of thin films were compared.VSM measurements of ZnO:Co and ZnO:Fe thin films showed that ferromagnetic behavior for each thin films. [ABSTRACT FROM AUTHOR]

An amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is studied. It is shown that the amplification coefficient of slow surface plasmon polaritons can reach values substantially exceeding the ohmic loss coefficient when phase matching condition is satisfied, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. [ABSTRACT FROM AUTHOR]

Au Nanoparticle (NP) decorated TiO2 thin films, prepared by a unique surfactant assisted 2D self-assembling technique with molecular level control, showed significant decrease in optical band gap as well as enhanced crystallinity compared to its sol-gel prepared pristine counterpart. Spin coated Au NP overlayers on titania in absence of surfactant, on the other hand, had no appreciable effect on either band gap or crystal structure compared to undoped TiO2 films. Apart from exhibiting band gap tuning of TiO2, this cheap, scalable technique of surfactant aided deposition of 2D layers of Au NPs on semiconducting oxides, may be used for development of multilayered structures with promising light harvesting and unidirectional energy transfer (LUET) applications. [ABSTRACT FROM AUTHOR]

This work describes a new technique to enhance photoresponse of metal chalcogenide-based semiconductor film electrodes deposited by thermal vacuum evaporation under argon gas flow from synthesized Cu2SnSe3 sources. SnSe formation with Cu-doped was obtained under higher argon gas flow rate (VA = 25 cm³/min). Higher value of photoresponse was observed for films deposited under VA = 25 cm³/min which was 9.1%. This finding indicates that Cu atoms inside the SnSe film were important to increase carrier concentrations that promote higher photoresponse. [ABSTRACT FROM AUTHOR]

In this work, CdS and In doped CdS films were prepared by ultrasonic spray pyrolysis (USP) technique and were annealed at 450 °C in an air atmoshpere. The optical constants (n and k) and thicknesses of the films were determined by spectroscopic ellipsometry. Transmission and absorbance spectra were taken by UV spectrophotometer. Optical method was used to determine the band gap value of the films. Atomic force microscope (AFM) images were taken to see the effect of annealing time on surface topography and roughness of the films. Electrical resistivities of the films were analyzed by four probe technique. As a result, the application potential of annealed CdS:In films for photovoltaic solar cells and optoelectronic applications were investigated. [ABSTRACT FROM AUTHOR]

A comprehensive study of the effect of cadmium sulfide thicknesses on its physical properties is reported. CdS thin films prepared by thermal evaporation technique with substrate temperature of 373 K, the films prepared with 50, 150, 200 and 300nm thicknesses. X-ray diffraction spectra of CdS films were polycrystalline structure of pure hexagonal phase with prepared orientation at (002). The prepared films have been investigated by D.C conductivity and thermoelectric power to study some electrical properties. D.C electrical conductivity display two stages of conductivity through whole heating temperature range. The thermal activation energy for CdS thin films found to decrease with increasing thickness. The conductivity found to increase as thicknesses increased. Thermoelectric power study shows that all prepared films are n-type semiconductor. The hopping and thermal energies decreased as thickness increased. [ABSTRACT FROM AUTHOR]

Cadmium sulfide (CdS) thin films of different thicknesses were deposited on corning glass by closed space sublimation (CSS) technique in a vacuum. Structural, electrical, optical, Fourier transform infrared (FTIR) with Raman spectrometric properties were investigated. X-rays diffraction used to identify the preferred orientation of CdS thin films as well as crystalline size, dislocation density and strain vs thickness was estimated. The electrical properties like resistivity, mobility vs thickness was calculated at room temperature. Optical properties were investigated from UV-VIS-NIR ranges which were used to calculate band gap, thickness of the films, also samples were placed at different angles in spectrophotometer to investigate the effect of angles variation on %T and band gap. Raman spectroscopy for identification of vibration modes in thin films by varying thickness. [ABSTRACT FROM AUTHOR]

We report new results on the deposition of high-density films of semiconductor nanostructures by ultrafast pulsed laser deposition (UFPLD). Such materials are of interest for advanced optoelectronic applications such as quantum dot lasers and energy harvesting devices. The deposition method utilizes the interaction of a focused chirped pulse amplified (CPA) Ti-sapphire laser beam with a solid target (a rotating semiconductor wafer) to produce a hot-dense plasma at the target surface with a power density in excess of 1014 W/cm2. The plasma then undergoes rapid expansion and the resulting condensation process produces a high density of nanoscale particles (average size of a few nm) on a substrate placed a few cm from the target. We have investigated several semiconductor quantum dot systems including silicon and germanium. We observed a significant blue-shift of the optical absorption edge indicating quantum confinement effects which may be of interest for photovoltaic applications. [ABSTRACT FROM AUTHOR]

In this work we examine the influence of film thickness and annealing temperature in the growth of Mg2Si thin films. Films were grown by dual cathode magnetron sputtering (DCMS) at room temperature. Two series of films were grown, one with thickness about 0.96μm (films-A) and another with (1.99μm) (films-B). Sputtered films were subsequently annealed in Ar gas atmosphere at temperatures 250°C, 300°C (films-B) and 380°C, 500°C (films-A). Results indicate that growth in films-A proceeds with the formation of two phases, a cubic (Fm-3m) and a strained (compressed) cubic with smaller lattice constant. When film thickness is doubled (films-B) material transforms into unstrained cubic phase. Annealing films-B at 300°C transforms them into the same compressed cubic phase that was observed in films-A. Further annealing of films-A causes a strain relief and at 500°C films are single phase. [ABSTRACT FROM AUTHOR]

This paper reports the electrodeposition of BiTe by potential control electrolysis using a ionic liquid based on choline chloride and malonic acid mixture (1:1 moles) in the 25-60°C temperature range. From cyclic voltammetry and impedance experiments carried out in order to characterize the cathodic process on Pt electrode it was found that the deposition of BiTe from electrolytes occurs on a Te-covered Pt substrate at less negative potentials than for deposition of singular Bi or Te films. Nyquist and Bode impedance spectra showed differences in Pt behavior due to its polarization at various cathodic potentials. The morphology and chemical composition of BiTe films deposited on Cu were determined by AFM, SEM and TEM microscopy. [ABSTRACT FROM AUTHOR]

The doping mechanisms of InN, a promising material for novel optoelectronic and electronic devices, are still not well understood. Unintentional hydrogen doping is one possibility that could explain the unintentional n-type conductivity in high-quality nominally undoped InN films. We measured a series of state-of-the-art InN samples grown by molecular beam epitaxy with 2 MeV 4He-ERDA and RBS, showing the presence of relatively high amounts of hydrogen not only at the surface, but also in a deeper layer. Strong depletion of hydrogen due to the analysing beam was observed and taken into account in the analysis. Here, we report on the details of the analysis and show how the results correlate with the free-electron concentrations of the samples. [ABSTRACT FROM AUTHOR]

A problem of increasing interest in the last years, both for mass-spectrometry and for deposition of organic semiconductor films, is to increase and control the flux of large organic molecules seeded in a carrier gas expanding towards a skimmer. This paper deals with experimental and numerical investigations on the dependence of kinetic energy of Pentacene molecules from the gas flow rate. Pentacene is a very important molecule in the field of organic semiconductors where it plays the role of a prototypical system for molecular electronics. The numerical results concerning the flow rate of helium through an optimized capillary as well as the kinetic energy of Pentacene molecules in the beam are in qualitative agreement with the results of measurements paving the way to the optimization of the device. [ABSTRACT FROM AUTHOR]

Useful optical parameters of thin semiconducting films can be determined by electrochemical and electrical techniques. This work is an attempt to characterize cathodically electrodeposited binary cadmium chalcogenide (CdSe, CdTe) and ternary Cu-chalcopyrite (CuInSe2) films by photoelectrochemical techniques. Namely, photovoltammetry, photocurrent spectroscopy and onset potential method. Some fundamentals, regarding the estimation of band gap energy and flat band potential values of these semiconductors, are briefly discussed. [ABSTRACT FROM AUTHOR]

We investigate domain patterns in a ferromagnetic thin film under an oscillating field. Using a simple two-dimensional Ising-like model, we simulate various kinds of domain patterns and discuss the mechanism of the appearance of those patterns. The simulations of several kinds of lattice patterns shows that the type of a lattice (e.g., square or hexagonal) depends on the amplitude and frequency of the field. Under some conditions, we observe traveling stripe patterns that moves very slowly compared with the frequency of the field. In the case of a high-frequency field, a concentric-ring pattern can appear around a strong defect. Those patterns are explained theoretically by two different methods. [ABSTRACT FROM AUTHOR]

The increasing use of thin film semiconductors in device applications has forced the change to new deposition and processing technologies, compared to the familiar wafer semiconductor technologies. In spite of the lower performance, the process flexibility allowed with low temperature processing has opened the way to quite new products, based on thin film semiconductors. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Since the last two decades, in the area of electronics, group II-VI compounds have drawn considerable interest due to their various applications. Cadmium selenide (CdSe), a member of this group, is one of the promising semiconducting material from its application point of view. The n-type Cd1-XSeX and CdSe films have been deposited onto ultra cleaned glass substrates by electron bean evaporated technique under 10-5 torr vacuum. The n-type Cd1-XSeX thin films has confirmed by Hall effect data. The resistivity of the film has been determined by I-V measurement using four probe setup. It is observed that the resistivity decreases with increases Cd/Se ratio and we found that n-type Cd1-XSeX thin films is more better than CdSe thin films. [ABSTRACT FROM AUTHOR]

This paper reports on the X-ray studies of GaN thin films deposited on Si (111) substrate at different current density using electrochemical deposition technique. The structural properties of GaN films were studied by X-ray diffraction (XRD). XRD analysis showed that hexagonal wurtzite and cubic zinc blende GaN phases were both deposited on Si (111). The lattice constants, the average size of h-GaN crystals and the in-plane (along a-axis) and out of plane (along c-axis) strains were calculated from XRD analysis. [ABSTRACT FROM AUTHOR]

Nanosecond lasers with ultra-violet, visible and infrared wavelengths: KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) were used to ablate polycrystalline Ge target and deposit Ge films in vacuum (<10-6 Torr). Time-integrated optical emission spectra were obtained for laser fluence from 0.5-10 J/cm2. Neutrals and ionized Ge species in the plasma plume were detected by optical emission spectroscopy. Ge neutrals dominated the plasma plume at low laser fluence while Ge+ ions above some threshold fluence. The deposited amorphous thin-film samples consisted of particulates of size from nano to micron. The relation of the film properties and plume species at different laser fluence and wavelengths were discussed. [ABSTRACT FROM AUTHOR]

Colossal electroresistance effects upon application of electric field in perovskite oxide Pr0.7Ca0.3MnO3 (PCMO) thin films, which is a promising candidate for resistance random access memory (RRAM) device have been investigated. Nanocrystalline PCMO films were grown on SiO2 substrates by chemical solution deposition and crystallized at 700° C under different gas atmospheres. Four terminal current voltage characteristics of Ag/PCMO/Ag planar geometry exhibited a sharp transition from a low resistance state (LRS) to a high resistance state (HRS) with a resistance switching ratio of as high as 1100% at room temperature. Nonvolatility and high retention was confirmed by electric pulse induced resistive switching measurements. The resistance switching ratios were found to depend on the annealing conditions, suggesting an interaction between the nonlattice oxygen and oxygen vacancies and/or the cationic vacancy. [ABSTRACT FROM AUTHOR]

We present a numerical calculation for the intra- and inter layer local-field correction factors, GII,(q,0), with unequal density, of coupled electron-electron quantum bilayer system. The are calculated within the framework of quantum self-consistent mean-field approximation of Singwi, Tosi, Land and Sjölander (qSTLS) as a function of layer parameters. We found that intra layer local-field correction factor yields pronounced oscillatory behavior with different layer parameters. The results are compared with GII,(q,0) of recent findings of the equal density effects in electron-electron quantum bilayer systems and G(q,0) of isolated single quantum layer. [ABSTRACT FROM AUTHOR]

ZnO is a wide band gap semiconductor which is used as transparent electrode in solar cells, chemical and gas sensors and light emitting diode etc. This paper reports the sol gel preparation and characterization of ZnO thin film. ZnO thin film was prepared by sol-gel process using zinc acetate dehydrate as a precursor, 2-methoxy ethanol as a solvent and monoethanolamine (MEA) as a stabilizer. The solution was deposited on n-type silicon (111) substrate by spin coating at 3000 rpm. Hydrolysis and condensation process produced a complex solution. After drying at 300° C, samples were annealed at 575° C in nitrogen ambient. Precise control of concentration of precursor, solvent used, spinning speed of the substrate and heat treatment conditions, are the factors which strongly affect the crystallographic orientation and morphology of the resultant ZnO films. The crystalinity of the film as found from X-ray diffraction (XRD) had different orientations, with (002) orientation as most intense having a grain size of 44 nm. [ABSTRACT FROM AUTHOR]

© 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We propose a model of slow surface plasmon polariton distributed feedback laser (spaser) with pump by drift currents in graphene. This model is a kind of hybrid of a distributed feedback laser and a well-known in microwave technology travelling-wave tube. The amplification of SPP wave is created by drift currents in the graphene, and the feedback is realized due to a periodic change of the semiconductor film thickness. [ABSTRACT FROM AUTHOR]

Chalcopyrite semiconductors such as CuIn1-xAlxSe2 have been currently investigated as a promising material for photovoltaic applications since their band gap energy matches with the solar spectrum. The absorber layers as thin as 2μm are sufficient for the absorption of the visible part of sun light, because they are characterized by a high absorption coefficient. The absorber layers are grown by the multi-source evaporation technique. From the X-ray analysis it is found that the films had a preferred oriented along the (112) direction, which confirmed the chalcopyrite phase. The optical studies revealed that replacing 50% of In by Al, will bring the band gap energy to 1.5eV, which will match the solar spectrum. Photo-response of the heterostructure is presented. [ABSTRACT FROM AUTHOR]

Bio polymer like chitosan is dissolved in acids like formic and acetic acid and CdS nano particle prepared by chemical methods has been embedded in the salts of chitosan matrix. The viscous solution is cast into film on the glass substrate using spin coating method and their ionic conductivity has been studied for various frequencies and temperatures. [ABSTRACT FROM AUTHOR]

Copper tin sulphide (Cu3SnS4), a promising solar cell absorber layer, was successfully grown onto soda-lime glass substrates by sulfurization of spray deposited films at a substrate temperature of 400 °C. The sulfurization was carried out at a temperature of 550 °C for 1 hour in 1 mbar pressure. The films were analyzed by studying their structural, morphological, optical and electrical properties. XRD studies revealed that the sulfurized films are polycrystalline Cu3SnS4 with orthorhombic structure. The films are slightly Cu-poor and Sn-rich. The direct optical band gap was found to be 1.80 eV. The room temperature electrical resistivity of the films was found to be 3.50 × 10-4 Ω-cm. [ABSTRACT FROM AUTHOR]

The properties of pure Cu2SnS3 thin films synthesized by direct liquid coating method have been studied for application in TFSCs. The films have band gap of 1.12 eV and an absorption coefficient of ∼105 cm-1. They are p-type with electrical conductivity of 0.5 S/cm and show photoconductivity. TFSCs made of these p-CTS films and n-CdS have been analyzed. The maximum efficiency of CTS solar cells is 33% with VOC and ISC of 0.75 V and 40 mA/cm. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) thin films were deposited onto indium doped tin oxide coated (ITO) glass substrates by electro deposition technique. The deposition bath contains a solution mixture consisting SnCl2 and Na2SeO3. X-ray diffraction studies revealed orthorhombic structure of SnSe films and various micro structural parameters such as crystallite size, dislocation density and strain were calculated. Optical properties were determined by UV-vis-NIR double beam spectrophotometer and direct transition energy band gap was estimated as 1.1 eV. Morphological studies reveal nano rod shaped grains covering the surface of the film and the results are discussed. [ABSTRACT FROM AUTHOR]

A new technique has been developed to measure the carrier mobility and lifetime based on current transients produced by a sub-picosecond laser pulse. The theoretical model we proposed agrees well with the experimental data. This technique has been applied to the material libraries fabricated by the combinatorial growth technique. [ABSTRACT FROM AUTHOR]

Conventional semiconductor material growth technique is costly and time-consuming. Here we developed a new method to growth semiconductor thin films using high through-put combinatorial technique. In this way, we have successfully fabricated tens of semiconductor libraries with high crystallinity and high product of μτ for the purpose of radiation detection. [ABSTRACT FROM AUTHOR]

Imaging of buried epitaxial InAs QDs as well as thin films of PbS QDs was carried out by means of local photocurrent measurements using a conductive atomic force microscope. InAs dots appear as dark areas in the photocurrent map and PbS:PCBM thin films form domain-like structures showing enhanced photoactivity. [ABSTRACT FROM AUTHOR]

ZnO doped with Cu thin films were deposited on indium tin oxide coated glass substrates by electrodeposition using an electrolyte consisting of Cu and Zn perchlorates dissolved in dimethylsulfoxide. The Cu/Zn ratio measured in the thin films is about twice the Cu/Zn ratio present in the starting electrolyte. Irrespective of the Cu content, all the ZnO:Cu films exhibit a hexagonal wurtzite structure typical of ZnO with a preferential orientation along (002) direction. The p-type behaviour of ZnO:Cu films is inferred from the change in the sign of the photocurrent observed for Cu concentrations greater than 2%. Furthermore, a p-n homojunction with a rectifying factor ∼22 were prepared by electrodepositing of ZnO/ZnO:Cu layers. [ABSTRACT FROM AUTHOR]

The effect of Ne+ ion sputtering on amorphous Ga-In-Zn-O (a-GIZO) thin films was investigated by using surface-sensitive, synchrotron-radiation-based, high-resolution X-ray photoelectron spectroscopy (XPS). a-GIZO thin films having different compositions (Ga2O3:In2O3:ZnO = 1:1:1, 2:2:1, 3:2:1, 4:2:1) were investigated. It was found out that the amounts of the In and Zn contents relative to that of Ga decreased noticeably after sufficient sputtering, and that there occurred a subgap state above the valence band maximum and metallic states at the In 3d and 4d core levels as well as at the Fermi edge. [ABSTRACT FROM AUTHOR]

High cubic-phase purity InN films were grown on MgO (001) substrates by molecular beam epitaxy with a cubic-phase GaN buffer layer. The cubic phase purity of the InN grown layers has been analyzed by high resolution X-ray diffraction, μ-Raman scattering and transmission electron microscopy. It is evidenced that the hexagonal-phase content in the InN overlayer much depends on hexagonal-phase content in the cubic-phase GaN buffer layer and increases with increasing the hexagonal-phase GaN content. From Raman scattering measurements, in addition, the InN layer with lowest hexagonal component (6%), only Raman characteristics of cubic TOInN and LOInN modes were observed, indicating a formation of a small amount of stacking faults, which does not affect on vibrational property. [ABSTRACT FROM AUTHOR]

Raman scattering and photoluminescence on Cu2ZnSnSe4 thin films grown by thermal co-evaporation were performed. The photoluminescence spectrum shows a peak below 1.0 eV. The Raman spectra of Cu2ZnSnSe4 show two main peaks at 170, 192-195 cm-1 and additional Raman mode at 260 cm-1, which is ascribed to the Cu2-xSe phase. The lateral distribution of the Cu2-xSe phase in Cu2ZnSnSe4 thin films is investigated by scanning micro-Raman scattering. In Cu-rich samples, the distribution of the Cu2-xSe phase is found to be uneven. [ABSTRACT FROM AUTHOR]

We investigated the structural anisotropy of a-plane GaN films grown by using multi-buffer layer technique on (1-102) r-plane sapphire substrates. For high quality a-plane GaN films, multi-buffer layers with various growth conditions were grown by metal-organic chemical vapor deposition, and analyzed by using several measurement systems such as optical microscopy, scanning electron microscopy, high resolution x-ray diffraction. The experimental results showed that the nucleation-layer thickness and the growth temperature of three-dimensional (3D) growth layer affect significantly the crystal quality of subsequently grown a-plane GaN films. When the nucleation-layer thickness was 150 nm, nuclei were fully coalesced. From the x-ray diffraction results, it appeared that the growth temperature during 3D islands growth affects the full-width at half maximum (FWHM) values of x-ray rocking curves along c- or m-directions. At optimized growth conditions, the omega FWHM values of (11-20) x-ray rocking curve along c- and m-axis were 0.137° and 0.163°, respectively. [ABSTRACT FROM AUTHOR]

Through both the control of oxygen partial pressure during the initial growth stage before As+ implantation and the H2O2 treatment after As doping, ferromagnetic properties for p-ZnMnO:As were effectively improved because of the enhanced long-range ferromagnetic exchange couplings due to the decrease in negatively-charged residual defects. [ABSTRACT FROM AUTHOR]

The ZnO:(Cr,Ti) thin films grown by cosputtering of ZnCrO (Cr∼1at.%) and Ti exhibited the multiferroic indications. This result is considered as originating from the increased magnetic moments supplied from two spins of the incorporated Ti2+(3d24s0) additives and the increased symmetrical molecular-field due to the increased local lattice displacements resulting from the incorporation of Ti codopants. [ABSTRACT FROM AUTHOR]

ZnO thin films were grown on p-type Si (100) by plasma-assisted molecular beam epitaxy (PA-MBE). Before the growth of the ZnO thin films, the initial Zn layers were deposited on the Si substrates. In order to investigate the effects of thermal annealing, the initial Zn layers were annealed at the temperature range from 500 to 700 °C for 30 min under oxygen ambient. The properties of the ZnO thin films with annealed initial Zn layers have been investigated by X-ray diffraction (XRD), room temperature (RT) photoluminescence (PL), and scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]