Electric properties of chemically deposited lithium doped cadmium sulphide films

Electrical properties of chemically deposited CdS and lithium doped CdS films have been investigated by using techniques of Photo-thermoelectric and Photo-Hall effects. Dark electron densities are independent of temperature between 100 and 330°K because of shallow donors and quasi-intrinsic behaviour is apparent above 330°K. Electron density and mobility in these films have been measured as a function of temperature under strong photoexcitation. The electron mobility is found to be thermally activated with energies 0.2 and 0.22 eV for CdS:Li and CdS films respectively. The Hall mobility and electron density in these films have also been measured as a function of temperature under strong photoexcitation and found that both the free carrier density and mobility are reduced by the adsorption of oxygen, former by larger factor than the latter. The resulting very high electron density and very low electron mobility in the temperature region studied also indicate that most of the photoconductivity in chemically deposited films is caused by an increase in electron density due to photoexcitation.     

Photoconductive properties of some chemically deposited (Cd-Pb)S films

Films of (Cd-Pb)S have been prepared using chemical deposition in aqueous alkaline bath and their subsequent condensation on substrates. Important achievements in terms of electrical response, optical absorption and photoconductivity (PC) excitation spectra, SEM, XRD and photoluminescence (PL) studies are presented and discussed. From the photocurrent curves, the ratio I _PC (saturated photocurrent)/I _DC (dark current) was observed to be of the order of 10⁶ for the systems prepared with CdCl₂, and to be 10⁷ when doped with samarium nitrate. Values of trap depth E, lifetime and mobility are evaluated from the PC decay. Band gaps are determined from the two spectra. Diffraction lines in XRD studies are associated with CdS and PbS, and according to SEM studies, layered growth of the films takes place. PL of samarium-doped (Cd-Pb)S films shows an emission peak in the green-yellow region under 365-nm excitation. The PL brightness decreases with temperature.     

Optical fiber refractometers based on indium tin oxide coatings fabricated by sputtering

This Letter presents the fabrication of optical fiber refractometers based on indium tin oxide (ITO) coatings deposited by sputtering with response in the visible region. ITO thin films have been sputtered by means of a rotating mechanism that enables the fabrication of smooth and homogeneous coatings onto the optical fiber core. The ITO coating acts as a resonance supporting layer. This permits us to couple light from the waveguide to the ITO-coating/external medium region at specific wavelength ranges. The device is sensitive to external medium refractive index, which allows its utilization as a refractometer. The sensitivity is dependent on the coating thickness, ranging from 523.21 to 1221 nm/refractive index unit in the explored sensors. The sensor development process is time effective compared to other techniques such as dip coating or layer-by-layer self-assembly, which is interesting in terms of mass production.     

溅射制备非晶氮化镓薄膜的光学性能

采用直流磁控溅射方法在不同的氩气-氮气（Ar-N₂）气氛中制备了非晶氮化镓（a-GaN）薄膜. X射线衍射分析（XRD）和拉曼光谱（Raman）表明薄膜具有非晶结构. 通过椭偏光谱（SE）得到薄膜的折射率和厚度都随着氩气分量的增多而增大. 紫外—可见光谱（UV-Vis）的测量得到,当氩气分量R,即Ar/（Ar+N₂）,为0%时,薄膜的光学带隙为3.90eV,比晶体GaN （c-GaN） 的较大,这主要是由非晶结构中原子无序性造成的;而当R关键词： 非晶氮化镓 溅射 光学带隙 带尾态     

Optical properties of GaAs films deposited via pulsed ion ablation

Optical reflectance and absorbance of gallium arsenide films formed on polycrystalline corundum, quartz glass, and copper foil are investigated in the energy interval of 1.1–6.2 eV. The films have been deposited from ablation plasma induced by a high-power ion beam. The exponential and interband absorbance spectra of the material of films are determined by defects in the GaAs crystalline lattice and the intricate composition of the material with predominance of nanocrystalline inclusions in the amorphous phase. Films deposited on polycor at the plasma flame center with the use of a low-resistance target have optimal properties for application in devices of optoelectronics and solar power engineering. Thermal vacuum treatment at 300–850 K modifies the optical properties of films owing to annealing of defects and changing of the structural-phase composition of a material.     

Structure and optical properties of chemically synthesized titanium oxide deposited by evaporation technique

Titanium oxide inorganic ion exchange material was synthesized by hydrolysis with water and ammonia solution. Structural feature of the synthesized titanium oxide was analyzed using X-ray diffraction, X-ray fluorescence and infrared spectrometer technique. Tentative formula of titanium oxide was determined and written as TiO₂·0.58H₂O. Titanium oxide films were deposited on glass substrates by means of an electron beam evaporation technique at room temperature from bulk sample. The films were annealed at 250, 350, 450, and 550 °C temperatures. Transmittance, reflectance, optical energy gap, refractive index and extinction coefficient were investigated. The transmittance values of 85% in the visible region and 88% in the near infrared region have been obtained for titanium oxide film annealed at 550 °C. Kubelka-Munk function was used to evaluate the absorption coefficient which was used to determine the optical band gap. It was found that the optical band gap increases with increasing annealing temperature whereas the refractive index and extinction coefficient decreases.     

Optical properties of Ag@cicada wing substrate deposited by Ag nanoparticles

In this paper, Ag nanoparticles were deposited on Ag@cicada wing array by using the cicada wings as templates to study its optical properties, including surface enhanced Raman scattering (SERS), polarization and surface enhanced fluorescence (SEF). The nanogaps between adjacent conical protrusion can be well dominated by adjusting the sputtering time and the optimal substrate AgNPs@Ag@cicada wing arrays have a noteworthy enhancement of SERS signal. Characterization of the prepared optimal substrate certified that it possesses the excellent SERS performances. Basically consistent SERS signal strength at the different polarization angles of the optimal substrate indicates that its polarization-independence. The SEF spectra shows that the optimal substrate has a slightly lower and unstable enhancement at this initial stage of repeated examination due to the weak adhesion between the Ag@cicada wing arrays and Ag nanoparticles. The outstanding optical properties indicate that it has enormous potential in the label-free detection and biological analytes determination.     

Electrical and optical properties of chemically deposited conducting glass for SIS solar cells

Thin layers of conducting glass (SnO₂:F) of 3 ohm per square sheet resistance were chemically deposited on borosilicate glass for potential applications in SIS solar cells. The layers exhibit 90% optical transmission at the solar maximum (0.5 μm). In an optical investigation of the conducting glass at room temperature, a direct allowed transition at 4.1 eV was observed. Indirect allowed transition was also observed with an energy gap of 2.65 eV and an assisting phonon of 0.05 eV. These observations were supported by reflectance data obtained by an integrating sphere. A technique of making ohmic contacts with SnO₂:F layers is also described.     

Phase conversion of chemically exfoliated molybdenum disulfide

Multilayer MoS₂ is exfoliated by Li treatment. A thin film of Li-treated MoS₂ contains a large portion of 1T phases. This is attributed to the atomic structural change caused by Li insertion, which is investigated using X-ray photoelectron spectroscopy (XPS). In a phase recovery via thermal annealing at 523 K in air, we observe another phase, referred to as the relaxed 1T phase, with a slightly larger binding energy than the 1T phase. After annealing at 523 K in air, the peak intensity of the relaxed 1T phase is reduced, accompanying a strong MoO_x peak and weak S 2s peak, according to XPS. This indicates that the annealing of Li-treated MoS₂ in air yields sulfur vacancies that induce the oxidation of Mo. However, after annealing at 523 K in vacuum, no MoO_x is observed, and the considerable peak intensity of the relaxed 1T phase remains, which starkly contrasts Raman-spectroscopy results supporting a full recovery from the 1T phase to the 2H phase. The absence of a gating effect of the Li-treated MoS₂ device supports the possibility of an incomplete phase change of Li-treated MoS₂ annealed in a vacuum.     

Structure and properties of Co-Ni-Fe coatings deposited electrolytically in the X-Ray irradiation

The main processes governing the formation of Co-Ni-Fe alloys electrolytically deposited in the X-ray irradiation have been discussed. It has been found that the electrical and magnetic properties depend on the deposition and irradiation regimes. The factors responsible for the variation in the electrical resistivity and specific magnetization of the films prepared by electrolytic deposition, which are caused by variations in the surface morphology, elemental composition, decrease in the porosity, and increase in the electrolytical deposition rate under X-ray irradiation, have been considered.     

Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar⁺ ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar⁺ ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.     

Optical and structural properties of polycrystalline CdSe deposited on titanium substrates

We report studies of photoluminescence, Raman scattering and x-ray diffraction performed on CdSe polycrystalline films deposited on titanium substrates by two different methods: chemical deposition and electroplating. We discuss the changes observed in these films as they are subjected to heat treatments. The differences observed in the energy gap of both types of film and their evolution as a function of annealing temperature are tentatively explained in terms of quantum confinement produced by the small grain size of the films.     

Optical properties of pigmented coatings taking into account particle interactions

A T-matrix approach is used to obtain the orientation-averaged scattering and absorption cross sections of randomly oriented particle clusters, and the average angular distribution of the radiation scattered by them. The coefficients involved in the expansion of the phase function are obtained from this T-matrix approach, and used in a multiple scattering formalism to characterize the angular distribution of the diffuse radiation propagating through a particulate coating perpendicularly illuminated with collimated visible radiation. Asymmetry between forward and backward propagating diffuse radiation intensities is taken into account by means of this multiple scattering approach, which is based on solving the radiative transfer equation for successive scattering order contributions. A four-flux model is applied to compute the reflectance in terms of wavelength of the incident radiation and particle concentration. An application of the formalism is carried out to predict the optical properties of titanium dioxide pigmented polymer coatings, in terms of the pigment volume fraction and the degree of aggregation.     

Optical properties of thallium indium disulfide (TlInS2) single crystals

Transmission, photoluminescence, and reflectance spectra of TlInS2 single crystals grown by the Bridgman–Stockbarger method were measured at 4.2 K near the fundamental absorption edge. Narrow lines at ~2.5535 and ~2.5694 eV were observed in the transmission spectrum and assigned to ground and excited free-exciton states, respectively. The free-exciton binding energy and band-gap energy Eg were found to be ~21.2 meV and ~2.5747 eV, respectively. A recombination mechanism was proposed for the TlInS2 near-band-edge and deep luminescence.     

Structural and optoelectronic properties of antimony tin sulphide thin films deposited by thermal evaporation techniques

Thin films of SnSb₂S₄ have been prepared on glass substrate by using thermal evaporation techniques. The films were annealed in argon gas at low pressure in sealed glass ampoules at 85 °C, 150 °C, 275 °C and 325 °C. XRD of the films reveal that the low temperature annealed films are poly crystalline while the as deposited films and high annealed films are in amorphous states. There is no adequate variation in the photoconductivity response of the amorphous and crystalline phases. The transmittance of the films is low and having no transmittance below 740 nm. The band gap calculated by ellipsometry technique is in the range of 1.82–3.1 eV. The films have n-type conductivity but the film annealed at 325 °C show p-type conductivity.     

Structural, optical and electrical properties of tin oxide thin film deposited by APCVD method

Tin oxide (SnO₂) thin films have been grown on glass substrates using atmospheric pressure chemical vapour deposition (APCVD) method. During the deposition, the substrate temperature was kept at 400°C–500°C. The structural properties, surface morphology and chemical composition of the deposited film were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and Rutherford back scattering (RBS) spectrum. XRD pattern showed that the preferred orientation was (110) having tetragonal structure. The optical properties of the films were studied by measuring the transmittance, absorbance and reflectance spectra between λ = 254 nm to 1400 nm and the optical constants were calculated. Typical SnO₂ film transmits ∼ 94% of visible light. The electrical properties of the films were studied using four-probe method and Hall-voltage measurement experiment. The films showed room temperature conductivity in the range 1.08 × 10² to 1.69 × 10² Ω⁻¹cm⁻¹.     

Optical and transport properties of chemical bath deposited CdS: Al films

Aluminium doped and undoped CdS films are deposited on the glass substrates by chemical bath deposition technique. Their optical and transport properties are studied and the effect of dopant concentration on these properties is discussed at length.     

Optical and structural properties of pulsed laser ablation deposited ZnO thin film

A limited number of reports exists in the literature concerning the systematic study of the structural and optical properties of ZnO thin films, produced by pulsed laser ablation, in correlation with the deposition parameters adopted. In this paper we present a characterization of a sample prepared by this technique and studied by photoelectron spectroscopy and X-ray diffraction. The dielectric function of both target and films has been deduced by reflection electron energy loss spectroscopy.