Optical Properties Of Thin Layers Research Articles

Comparison of energy transfer between Terbium and Ytterbium ions in glass and glass ceramic: Application in photovoltaic

The structural and optical properties of thin layers based on 70%SiO2–30%HfO2 doped with different concentration of rare earth ions (terbium and ytterbium) have been studied with a view to integrating them in a photovoltaic cell as a spectral conversion layer in order to improve its efficiency, by using down-conversion process. These thin films were synthesized by using sol gel technique and deposited on the pure silica substrate by dip-coating method. The DC layer can be placed on the front side of a solar cell and can enhance the current by converting ultraviolet (UV) photons into a large number of visible photons.In present study two series of samples are compared, the first series corresponds to samples treated at 900 °C (glass- S) while the second series concerns samples treated at 1000 °C (glass-ceramic- SC). These series are based on 70SiO2–30HfO2 activated by different molar concentrations of rare earths [Tb + Yb]/[Si + Hf] = 7%, 9%, 12%, 15%, 17%, 19% and 21%.Photoluminescence results of reference samples (without Yb3+) showed an emission from 5D4 to 7FJ (J = 3, 4, 5, 6) level characteristic transitions of Tb3+, with a maximum peak in the green centered at 543.5 nm corresponding to the 5D4→7F5 transition. For the co-doped samples a clear NIR PL emission around 980 nm was detected, due to the 2F5/2→2F7/2 transition of Yb3+ ions. From luminescence decay curves of Tb3+ maximum emission peak (7F5→5D4 transition at 543.5 nm) we have identified the energy transfer efficiency. The quantum efficiency increases by increasing the total [Tb + Yb] concentration. The most significant yield was achieved with [Tb + Yb]=19%, the maximum quantum transfer efficiency obtained was 190% for glass-ceramic samples and 161% for glassy one.

Effect of Photoconductivity Precursor Volume on Structural, Physical, Electrical and Optical Properties of Thin Layers of Cadmium Oxide (CdO) Nanostructures Produced Using Spray Pyrolysis Technique

Thin layers of Cadmium Oxide (CdO) are produced over glassy substrate by spray pyrolysis technique with precursor volumes of 50, 75 and 100 (ml). FESEM images of samples show the formation of nanometric structures and structural characterization of them resulted from XRD spectroscopy indicate the formation of cubic polycrystalline structure in growing layers with preferred direction of (111). Evaluating the optical properties of samples show that optical band gap of layers is reduced from 3.6 to 3.4 (eV) by increasing the precursor volume and the optical absorption coefficient of samples is in UV region at about 105 (cm-1). Data analysis indicates that the produced sample in volume of 100 mL has the smallest penetration depth (smaller than 200 nm) in UV region. On the other hand, thin layers of Cadmium Oxide (CdO) with various volumes of Cadmium acetate solution (40, 50 and 70 ml) were deposited using spray pyrolysis technique over a glassy substrate. Samples were investigated using FESEM images, XRD and UV-Vis spectra as well as I-V characteristic. It was found that all samples were grew up with polycrystalline nanostructures along the preferred direction of (002). In addition, it was found that grew up sample in the volume of 50 (ml) are of optimum photoconductivity condition in visible range regarding optimum structural (largest crystallite size and lowest crystallite defect density) and optical (smallest band gap and highest light absorption) conditions.

The Effect of Temperature Variations on the Optical Properties of Tin Oxide Film with Doping Aluminum, Fluorine and Indium for Semiconductor Electronic Devices

The manufacture of a thin layer of SnO2: (Al + F + In) was carried out by using the sol-gel spin coating method on a glass substrate with various temperatures (25, 50, 100, 150, and 200 °C).The purpose of this study is to determine the optical properties of thin layers which include transmittance, absorbance, band gap energy and activation energy. The optical properties of the coating were characterized using a UV-Vis spectrophotometer with a wavelength of 200-1100 nm. The results showed that the absorbance value increased with increasing temperature at a wavelength of 300 nm. The absorbance values ​​obtained for temperature variations were in the percentages of 95: 5% and 75: 25%, respectively 3.46-4.50 and 3.96-5.76. The transmittance value obtained increased, namely 73.00-86.30% and 74.20-99.30%. In addition, the energy band gap decreased from 3.60-3.41 eV and 3.57-3.31 eV for direct allowed, while 3.69-3.58 eV and 3.65-3.54 eV for indirect allowed. Activation energy decreased from 2.00-1.18 eV and 1.60-1.12 eV. In general, the absorbance and transmittance values ​​increase with increasing ripening temperature and the addition of doping aluminum, fluorine, and indium, while the bandgap energy and activation energy values ​​obtained decrease with increasing ripening temperature and increasing the doping percentage of aluminum, fluorine, and indium. The decrease in the value of the bandgap energy and the activation energy can make it easier for electrons to move from the valence band to the conduction band so that the material is slightly conductive and acts as a semiconductor.

The optical signature of few-layer ReSe2

Optical properties of thin layers of rhenium diselenide (ReSe2) with thicknesses ranging from mono- (1 ML) to nona-layer (9 MLs) are demonstrated. The photoluminescence (PL) and Raman scattering were measured at low (T=5K) and room (T=300K) temperature, respectively. The PL spectra of ReSe2 layers display two well-resolved emission lines, which blueshift by about 120 meV when the layer thickness decreases from 9 MLs to a monolayer. A rich structure of the observed low-energy Raman scattering modes can be explained within a linear chain model. The two phonon modes of intralayer vibrations, observed in Raman scattering spectra at about 120cm−1, exhibit very sensitive and opposite evolution as a function of layer thickness. It is shown that their energy difference can serve as a convenient and reliable tool to determine the thickness of ReSe2 flakes in the few-layer limit.

The thickness effect to optical properties of SnO2 thin film with doping fluorine

Synthesis of SnO2:F thin layer was grown using the sol-gel spin coating method on a glass substrate with various layers (one to four layers). The purpose of the synthesis was to determine the optical properties of thin layers including transmittance, absorbance, energy bandgap, and activation energy. The optical properties of the layers were characterized using UV-Vis spectrophotometers with a wavelength of 200-1100 nm. The results showed that at a wavelength of 300 nm the absorbance value decreased with an increasing number of layers. Absorbance values obtained for variations in layers (one to four layers) for the percentage of 95:5% and 75:25%, respectively 3.59-2.85 and 4.30-3.42, while the transmittance value decreased, namely 96.8-79.6% and 98.3-81.1%. Besides, the energy bandgap obtained decreases with an increasing number of layers. The energy bandgap decreased from 3.69-3.56 eV and 3.59-3.42 eV for direct allowed, while 4.00-3.91 eV and 3.96-3.83 eV for indirect allowed. Activation energy decreased from 0.23-0.07 eV and 4.35-1.43 eV.

Silver Nanorods Layer Based on Polyvinyl Alcohol on Glass Substrates by Dip-Coating Method

This research reports the investigation of the performance of a thin layer based on silver nanorods using the dip-coating method. The synthesis was conducted by polyol method at an oil bath temperature of 140 °C. In the synthesis of silver nanorods, materials used were silver nitrate (AgNO3) as the main raw material, ethylene glycol (EG) as the solvent, and a small amount of sodium chloride (NaCl) as a mediated-agent (precursor). Polyvinyl alcohol (PVA) used as a capping agent and stabilizer in this process. Diameter and length of silver nanorods were 800 nm and 15 µm, respectively. Furthermore, the silver nanorods suspension was deposition onto a glass substrate with a variety of dipping cycles. The result showed the thickness of the thin layer is linear with a number of dipping cycles. Electrical and optical properties of thin layer show that sheet resistance about of 30 Ω sq-1 by transmittance above of 80%. The silver nanorods thin film can be used as a conductive and transparent electrode for various optoelectronic applications.

Microstructural & Optical Properties of Thin Layers in the Fabrication of Field Effect Transistors

Microstructural & Optical Properties of Thin Layers in the Fabrication of Field Effect Transistors

Mechanism of a microwave-assisted polyol synthesis of nanosize CuInSe2 particles and their optical and photoelectric properties

Mechanism of the reaction in which CuInSe2 nanoparticles are formed in synthesis by the microwaveassisted polyol method was studied. The morphology and optical properties of thin layers (films) produced from the synthesized CuInSe2 nanoparticles and the morphology and photoelectric properties of composite films based on CuInSe2 and [6,6]phenyl C61 butyric acid methyl ester were examined. It is shown that CuInSe2 nanoparticles can be used to form a photo-absorbing layer in composite organo-inorganic solar cells.

The Study of the Influence of Deposition Method on Electrical and Optical Properties of PPV Polymer with High Glass Temperature

The paper is focused on comparison of electrical and optical properties of thin layers of copolymer with high glass transition temperature Tg-PPV (poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene], poly{2-[4'-(3'',7''-dimethyloctyloxy)-1',4'-phenyl]-1,4-phenylenevinylene} and poly{2-[3'-(3'',7''-dimethyloctyloxy)-1',4'-phenyl]-1,4-phenylenevinylene)}) prepared by two different deposition methods: by spin-coating and by electrophoretic deposition. We found several differences in absorption and emission spectra using those two preparation techniques. On the other hand, the photoelectrical properties were similar.

Structural and optical properties of a-SiCN thin film synthesised in a microwave plasma at constant temperature and different flow of CH4 added to HMDSN/N2/Ar mixture

Amorphous SiCN (a-SiCN) thin films were deposited by microwave plasma assisted chemical vapour deposition (MPACVD) using N2, Ar, CH4 and vaporised hexamethyldisilazane (HMDSN) gases. The CH4 ratio (0 to 12%) effect on composition, structural and optical properties of thin layers synthesised at a constant growth temperature of 550°C has been studied. It was found that layers are mainly composed of silicon nitride like compound and that CH4 addition leads to denser and smoother films. An augmentation of the refractive index from 1.72 to 2.05 and Tauc gap from 4.3 to 4.7eV has also been measured with CH4 ratio increase from 0 to 12%. These results show that CH4 addition to the feed gas allows varying the composition, morphology and the optical properties of HMDSN a-SiCN based films.

Spectral and concentration dependences of the optical properties of thin layers of oxidized amorphous copper and nickel nanoparticles in the infrared spectral region

The optical properties of thin layers of nanostructures based on oxidized amorphous copper and nickel granules are studied in the IR spectral region. The absorption spectra of layers are calculated taking into account luminescence. It is noted that the spectral features of the absorption coefficients of these nanostructures are determined by the enhanced absorption and luminescence of oxides in the vicinity of metal nanoparticles. A nonmonotonic concentration dependence of the absorption and transmission coefficients of oxidized copper nanoparticles on a silicon substrate in the IR region is found. The absorption maximum corresponds to the oxide shell layer that is half-filled with nanostructured metal. The concentration dependences of absorption coefficients of nanostructures based on oxidized nickel particles exhibit features at different wavelengths in the IR spectral region.

Second and third order optical processes in anisotropic polymer waveguides

Second harmonic generation and linear optical properties of thin layers and optical wave-guides prepared by Langmuir-Blodgett-technique or spin-coating/corona poling from new maleic acid anhydride (MAA) polymers carrying NLO chromophores in the side chain, from polymethylmethacrylate/disperse red host-guest systems and from 2-docosylamino-5-nitropyridine (DCANP) amphiphiles have been studied. We found that high-quality wave-guides with high non-linear optical coefficients can be prepared from all of these materials either by LB or by spin-coating/corona poling. We reached phase matching for special wave guide structures. By computer simulation we evaluated the intensity distribution within wave-guide for the fundamental, second and third harmonic wave based on coupled amplitude equations.

The electrical and optical properties of thin layers of nano-sized antimony doped tinoxide particles

For the use in anti-static films on glass or polymeric substrates, transparent conductive layers can be prepared by spinning an aqueous suspension of nano-sized antimony-doped tinoxide (ATO) particles. These layers have a resistivity which is substantially higher than that of homogeneous ATO layers which are deposited by physical vapour deposition techniques. By curing the films to temperatures up to 700 °C, the resistivity of the particle layer can be decreased by two or three decades. Because the nano-sized particles are prepared by a low-temperature process a different mechanism can contribute to this decrease in resistivity. Possible effects which may influence the conductivity are sintering of the particles, change of the bulk material and the presence of an insulating layer at the outside of the particles. This decrease can be explained by the presence of an insulating antimony-rich layer on the outside of the particles, the thickness of which is reduced when the layer is cured. At temperatures above 350 °C, sintering of the particles also highly influences the decrease in resistivity. At temperatures above 700 °C, the resistivity is increased due to segregation of the antimony to the surface of the particle.

Optical properties of thin layers of GaAs strained to InP

Single-strained layers of GaAs grown between InP barriers have been studied by photoluminescence with temperature and applied hydrostatic pressure as external perturbations. A type II band alignment at atmospheric pressure was found.

Structure and optical properties of polycarbonate films with microcrystallites of BEDT-TTF polyiodides

The morphology, structure and optical properties of thin layers of crystalline bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) polyiodides formed within the surface layer of polycarbonate film were investigated. The samples were obtained by exposing the polymer films containing 2 wt.% of molecularly dispersed ET to vapors of I 2/CH 2Cl 2 solutions of different I 2 concentration. X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that, depending on the preparation conditions, ET polyiodides form plate-like crystals, flakes and some less organized layer covering microcrystallites. In all cases only (001) reflexes attributed to the α-ET 2I 3 phase were registered in the X-ray diffraction (XRD) experiments. Reaction of iodine with already formed crystals leads to new morphological structures. Using saturated iodine solutions the nonconducting polyiodides are formed which, under ambient conditions, undergo transformation into a stable conducting salt.

Electronic properties and microstructure of undoped, and B- or P-doped polysilicon deposited by LPCVD

In this paper, we present some results on the electrical and optical properties of thin layers of polysilicon obtained by LPCVD in a sector reactor [1]. This reactor is representative of annular reactor, in which a large batch can be processed (total area up to 150 m 2). The layers are either undoped, or in situ doped with boron or phosphorus. The optical constants were determined by the analysis of absorption and transmission spectra. We show that the absorption coefficient of the layers (doped or undoped) enable a total absorption in the visible range with a thickness of 10 μm. We then show that uniform growth rate can be obtained on 100 cm 2 substrates, with a value of 200 A ̊ mn at 660°C for undoped or P-doped silicon, and 700 A ̊ mn for B-doped silicon. The carrier concentrations ranges between 1 × 10 17 and 1 × 10 20cm −3, which allows the realization of doping gradient during the process and potentially good solar cells with a high productivity.

Reaction kinetics and optical properties of semiconducting MnSi1.73 grown on ?001? oriented silicon

The growth kinetics and optical properties of thin layers of MnSi1.73 have been studied. MnSi1.73 was formed by thermal reaction (485–570°C) of Mn-Si thin-film couples, through a nucleation-controlled process. MnSi1.73 is semiconducting and the band-gap energy was optically determined using a spectrophotometer and a sample with a single MnSi1.73 layer on a silicon substrate. The value was between 0.78 and 0.83 eV.

Easy axis orientation mapping of soft magnetic films using a magneto-optic Kerr BH imager

A novel method of easy-axis orientation (EAO) mapping for thin magnetic films is described. The method employs a magnetooptic Kerr sensor to detect the discrete switches in film magnetization direction that occur when a rotating magnetic field mod H mod <H/sub k/ is applied to a magnetically anisotropic thin film. An instrument implementing this method has been constructed and is capable of generating easy-axis maps at a rate of 3 locations/s with 1 degrees accuracy. Experimental measurements show that the EAO determination is only slightly sensitive to stray fields, such as the Earth's field. The optical properties of thin layers covering the magnetic film have been observed to lead to distortions in the Kerr signal, although these distortions do not affect the accuracy of the EAO measurements.<<ETX>>

Optical properties of thin layers of SiOx

Obliquely evaporated films of silicon oxide, SiOx, widely used to align the nematic liquid crystals in electro-optics devices, were investigated optically by attenuated total reflection on a pyramid with a rectangular base covered with a thin layer of gold. This configuration allowed us to make measurements in two perpendicular directions and to determine any in-plane anisotropy. Reflectivity measurements versus angles of incidence exhibited minima associated with both resonant guided modes and surface plasmon oscillations (SPO). Analyses revealed that the obliquely deposited SiOx layers were slightly birefringent and porous, the porosity being determined by the SPO shift when air was replaced by a liquid, hexane. Here the voids surrounding the columnar deposits of SiOx became filled with either air or hexane and, in spite of the heterogeneous structure of the films, effective indices of refraction for the SiOx layer could be determined. Applying the Maxwell–Garnett theory for spherical particles embedded in a host medium (air and hexane), we found that the dielectric constant of our SiOx layers were close to that of stoichiometric SiO2 with a slight optical anisotropy.

Analysis method for optical properties of thin layers on thick transparent substrates

General formulas for optical reflectance, transmittance, and ellipsometry for an inhomogeneous thin layer on a thick transparent substrate are derived. In the formulas, substrate interference effects that negatively affect information concerning the optical properties of the thin layer are removed. These formulas have already been applied in the analysis of infrared transmittance of a heavily doped semiconductor.