UV Vis NIR Spectrometer Research Articles

Enhancement of nonlinear optical susceptibility of CuPc films by ITO layer

In the present study, the Copper Phthalocyanine (CuPc)/ITO thin film was fabricated using thermal evaporation method. The structural property was analyzed by X-ray diffraction study and confirms that the thin film has been preferentially grown along (200) plane. The atomic force microscope study was carried out on deposited film and quality of thin films is assessed by calculating the roughness of the films. The direct and indirect band gap, linear and nonlinear optical characteristics of grown films were calculated by using UV–Vis–NIR spectrometer studies. The calculated values of the first direct and indirect band gaps (Eg1(d) &Eg1(ind)) are 1.879 and 1.644 eV as a fundamental gap, while the values of second direct and indirect band gap (Eg2(d) &Eg2(ind)) are 1.660 and 1.498 eV as an onset gap for CuPc. The values of nonlinear refractive index (n2) and third order nonlinear optical susceptibility (χ3) are found to be 5 × 10−8 and 8 × 10−9 (theoretical) and 5.2 × 10−8 and 1.56 × 10−7 (experimental) respectively. The optical band and third order nonlinear properties suggest that the as-prepared films are may be applied in optoelectronic and nonlinear applications.

Effect of Argon Gas Flow Rate on the Optical and Mechanical Properties of Sputtered Tungsten Thin Film Coatings

Tungsten thin film coatings were deposited on SS304 substrates by DC magnetron sputtering process. Optical and mechanical properties changes have been studied as a function of varying argon gas flow rate during magnetron sputtering process. The effect of argon flow rate on depositionrate, mechanical and optical properties of the tungsten films prepared at Different power rate was investigated by surface profilometer, nanoindenter, FESEM and UV Vis NIR spectrometer. With increasing argon gas flow rate increases deposition rate and hence higher IR reflectance in IR region and at lower argon gas flow rate the absorptance is higher. The optimized results allows us to select the deposition condition for solar absorptance and thermal emittance for solar thermal applications. The XRD analysis shows that the deposited tungsten thin film coatings were in polycrystalline in nature and surface roughness increases with increase in argon gas flow rate. Nanoindentation test result yields that hardness of DC magnetronsputtered tungsten thin film increases with argon gas flow rate from 200sccm to 500sccm.

Influence of power density on high purity 63 mm diameter polycrystalline diamond deposition inside a 2.45 GHz MPCVD reactor

63 mm diameter polycrystalline diamond (PCD) films were synthesized via a microwave plasma chemical vapor deposition (MPCVD) reactor in 99% H2–1% CH4 atmosphere. Two different conditions, i.e. the typical condition (input power of 5 kW and gas pressure of 13 kPa) and the high power density condition (input power of 10 kW and gas pressure of 18 kPa), were employed for diamond depositions. The color changes of the plasma under the two proposed conditions with and without methane were observed by photographs. Likewise, the concentrations of hydrogen atoms and carbon active chemical species in plasma were analyzed by optical emission spectroscopy (OES). The morphologies and purity of the PCD films were investigated by scanning electron microscopy (SEM) and Raman spectroscopy, respectively. Finally, the transmission spectrum of the polished PCD plates was characterized by a UV–Vis–NIR spectrometer. Experimental results showed that both the concentrations of hydrogen atoms and carbon radicals increased obviously, with the boost input power and higher pressure. The films synthesized under the high power density condition displayed higher purity and more uniform thickness. The growth rates in 10 kW and 18 kPa reached ~7.7 µm h−1, approximately 6.5 times as much as that occurred in the typical process. Moreover, the polished plates synthesized under the high power density condition possessed a relatively high optical transmittance (~69%), approaching the theoretical values of approximately 71.4% in IR. These results indicate that the purity and growth rate of big-area PCD films could be simultaneously increased with power density.

Color tuning of Lu3Al5O12:Dy3+ ceramic-based white light-emitting phosphors via Yb incorporation

Transparent Lu3Al5O12:Dy3+ ceramics were fabricated for UV-pumped white light-emitting diodes (WLEDs) via solid-state sintering under vacuum. The color chromaticity of the ceramic-based phosphors were tuned by tailoring the Dy3+ concentration and incorporating Yb into the crystal lattice to form (Lu, Yb)3Al5O12:Dy3+ solid solutions. Phase composition, microstructure, optical and photoluminescence properties of the ceramics were investigated in detail by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV–vis-NIR spectrometer and fluorescence spectrophotometer, respectively. White light can be obtained by combining the UV-chip and the structure/property-optimized ceramic phosphors. The color hue was tuned from (0.4107, 0.4037) to (0.3647, 0.3299) with the increasing Yb content from 0 to 0.5 substituting Lu sites in the garnet structure. The (Lu0.5Yb0.5)3Al5O12: 0.01Dy3+ ceramic-based phosphor showed a relative low correlated color temperature of 4137K. The decrease in PL intensities with Yb incorporation was also discussed via microstructure and fluorescence lifetime characterizations.

Growth and characterization of DAST crystal with large-thickness

Highly nonlinear optical 4-N, N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystals with large surface and thickness was grown by the slope nucleation technology with slow-cooling in a high concentration solution. The structure and composition of the crystal were confirmed by X-ray diffraction (XRD). The surface morphology of the crystal was characterized by optical microscope. Growth layers were observed on the (001) surface and several isolated “island layers” were also found. The mechanism of crystal growth was analyzed. Etching behavior of the (001) and (001¯) faces of the crystal was studied with methanol, respectively. Optical properties of the crystal were also characterized by UV–vis–NIR spectrometer. The dielectric constants and the dielectric loss were tested by impedance analyzer.

Investigation on crystalline perfection, optical transmittance, birefringence, temperature-dependent refractive index, laser damage threshold and pyroelectric characteristics of inversely soluble lithium sulfate monohydrate single crystals

Bulk prismatic lithium sulfate monohydrate (LSMH) single crystals were grown by seed rotation with slow heating method from aqueous solution. Small FWHM obtained from high-resolution X-ray diffraction spectrum shows that the crystals grown by this method have less defects and absence of low-angle grain boundaries. The high transmittance and low reflectance nature of the grown crystal was observed using UV–Vis–NIR spectrometer. The principal refractive indices of a LSMH crystal have been measured by a prism coupling method for the wavelengths of 0.407, 0.532, 0.828, 1.064 and 1.551 µm at room temperature, and Sellmeier equations are determined from the fitting of the data point. The refractive index data confirm that LSMH crystal is negative biaxial and the optic axis lies in YZ plane with an angle (2Vy) of 51.74° with respect to y axis at 532 nm wavelength. The thermo-optic coefficients were determined from the temperature-dependent refractive indices measured in the range of 30–125 °C for the wavelengths of 532 and 1064 nm. The surface laser damage threshold studies reveal the higher optical radiation stability against 532-nm laser. The pyroelectric coefficients and pyroelectric figure of merit were determined from the pyroelectric current measurement by the Byer and Roundy method.

Effect of substrate temperature on the physical properties of co-evaporated Sn2S3 thin films

We report the deposition of tin sulfide (Sn2S3) thin films by co-evaporation technique at different substrate temperatures. The influence of substrate temperature on the structural and optical properties of the thin films is investigated. X- ray diffraction (XRD) analysis and Micro-Raman studies confirm the formation of Sn2S3 phase. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to examine the surface morphology. The transmission spectra of the deposited Sn2S3 thin films have been recorded in the wavelength range of 200–3000nm using UV–vis-NIR spectrometer. Film thickness (d) and optical constants such as refractive index (n), extinction coefficient (k), real (ε1) and imaginary (ε2) parts of the dielectric constants of thin films are estimated from the optical transmittance. The optical band gaps of the deposited films at different substrate temperatures are in the range of 1.46–1.64eV. Hall effect measurements confirm the n-type nature of the as-prepared Sn2S3 thin films.

Growth, structural, optical, thermal and mechanical properties of cytosinium hydrogen selenite: A novel nonlinear optical single crystal

A novel nonlinear optical single crystal of cytosinium hydrogen selenite was grown from aqueous solution of cytosinium hydrogen selenite by slow solvent evaporation method at room temperature. The structural properties of grown crystal have been studied by single crystal and powder X-ray diffraction analysis. Presence of various functional groups was identified from Fourier transform infrared spectroscopy. The optical transmittance and absorbance spectra were recorded by UV–vis-NIR spectrometer and the grown crystal possesses good transparency in the entire visible region. The dielectric constant and dielectric loss of the crystal were calculated as a function of frequency at different temperatures. The mechanical strength of the cytosinium hydrogen selenite crystal was estimated using Vicker’s microhardness tester. Etch patterns of the cytosinium hydrogen selenite crystal were obtained using distilled water as etchant for different etching time. Second harmonic generation efficiency tested using Nd:YAG laser is about 1.5 times that of KDP.

Effect of annealing temperature on the structural, morphological, optical and electrical properties of Co3O4 thin film by nebulizer spray pyrolysis technique

In this investigation, spray pyrolysis using nebulizer technique is employed to fabricate cobalt oxide (Co3O4) thin films onto glass substrate at 250 °C. The deposited homogeneous Co3O4 thin films were thermally treated under different annealing temperatures. The influences of annealing temperature on the properties of the coated thin films are examined by XRD, SEM, EDAX, UV–Vis–NIR spectrometer and four probe techniques. XRD analysis confirmed the growth of polycrystalline cubic Co3O4 thin films. SEM analysis showed that the size of the spherical grains is increased with the increase of annealing temperature. The EDAX spectra have indicated that the grown film is in the composition of Co and O. The optical spectra has shown a decrease in transmittance for the increase of annealing temperature, and consequently the band-gap energy values are reduced as 2.26, 2.05 and 1.73 eV for as-deposited, annealed at 300 and 400 °C respectively. The optical constants like refractive index, extinction coefficient have also been determined from the optical measurements. Current versus voltage studies showed the ohmic nature of the films.

Metal-Organic Frameworks as Promising Photosensitizers for Photoelectrochemical Water Splitting.

Ti-based metal-organic frameworks (MOFs) are demonstrated as promising photosensitizers for photoelectrochemical (PEC) water splitting. Photocurrents of TiO2 nano wire photoelectrodes can be improved under visible light through sensitization with aminated Ti-based MOFs. As a host, other sensitizers or catalysts such as Au nanoparticles can be incorporated into the MOF layer thus further improving the PEC water splitting efficiency.

Synthesis and characterization of silicon-doped polycrystalline GaN films by r.f. sputtering

Silicon-doped polycrystalline GaN films were successfully deposited at temperatures ranging from 300 to 623 K on fused silica and silicon substrates by radio frequency (r.f.) magnetron sputtering at a system pressure of ∼5 Pa. The films were characterized by optical as well as microstructural measurements. The optical properties were studied by UV–vis–NIR spectrometer and photoluminicence (PL) measurements. The microstructural information was obtained from scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD) studies. PL measurement at 80 K exhibited two strong transitions located at ∼2.1 and ∼2.7 eV along with lower intensity peaks for luminescence at the higher energy side at ∼3.45 and ∼3.3 eV for all the films deposited here, and the peaks at ∼3.45 and ∼3.3 eV could be ascribed to transitions related to excitons bound to a neutral donor for h-GaN and c-GaN, respectively. A broad peak at ∼2.1 eV indicated the presence of yellow luminescence in all the films. The SEM and AFM images revealed that the films are compact with well-dispersed polycrystalline constituting the films. The XRD traces contained the signature of both the hexagonal and cubic phases of GaN.

Role of immersion time on the properties of SILAR deposited CuO thin films

CuO thin films were synthesized at relatively low temperature by employing an inexpensive SILAR method. Effect of immersion time on the properties of grown film was studied using structural, morphological and optical characterizations. Structural, morphological, optical and electrical studies of the prepared CuO films were done using X-ray diffraction, field emission scanning electron microscope, and UV–Vis–NIR spectrometer and Hall probe, respectively. The films were found show different nanostructures depending on immersion time. The calculated crystalline size of the films is found increase with the increase of immersion time, and it is found to be 19 nm for 30 s immersion time. Vibration peaks of Cu–O and O–Cu–O bonds have been identified using Fourier transformation infrared spectroscopy. Optical band gap energy of the grown CuO films is calculated and it is found vary from 1.8 to 1.6 eV depending on the immersion time and annealing temperature. Hall effect measurements have shown a p-type conductivity of the grown films.

Preparation of rod shaped nickel oxide thin films by a novel and cost effective nebulizer technique

Nickel oxide thin films have been deposited from 0.3M aqueous solution of nickel chloride onto microscopic glass substrates, which were chemically and ultrasonically cleaned before coating. The film depositions are carried out with 1ml, 2ml, 5ml and 10ml. The substrate temperature, spray rate, distance between substrate and nozzle and air flow rate were fixed at 400°C, 0.5ml per min, ~7cm and 1.2kg/cm2 respectively after optimization of these deposition parameters. The effect of the volume of sprayed solution on structural, optical properties and surface morphology of the films was investigated using X-ray diffractrometer, UV–vis–NIR spectrometer, photoluminescence spectrometer, Raman spectrometer, scanning electron microscope and liner four probe resistivity set-up respectively. The diffraction peak along (111) plane at 2θ=37.2° for all the films was observed. Besides this other low intensity peaks were observed along (200) and (220) Miller planes. The peaks indicated that this corresponds to cubic structure of NiO thin films. Optical transmittance and absorption spectra are recorded using a UV–vis–NIR spectrometer. When the quantity of sprayed volume increased, the transmittance decreased, consequently the band-gap energy wanes from 3.64 to 3.21eV. From PL spectra, the samples show sharp and strong UV emission around 376nm corresponding to the near band-edge emission of NiO under excitation of 275nm. The surface morphology of the films was carried out using SEM to find the smooth, uniform and pin hole free surface. The composition of the films was estimated using EDAX spectrum of the films. The resistivity results show that the activation energy decreases with increase in the sprayed volume solution.

Effect of titanium dioxide (TiO2) on largely improving solar reflectance and cooling property of high density polyethylene (HDPE) by influencing its crystallization behavior

In this study, the different crystal forms of titanium dioxide (TiO2) were added into high density polyethylene (HDPE) to fabricate cool material. Crystal structure, crystallization behavior, crystal morphology were investigated by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and polarized optical microscope (POM). Scanning electron microscope (SEM) was applied to observe dispersion of TiO2 particles in the HDPE matrix and the cross section morphology. The solar reflectance and actual cooling property were evaluated by UV–Vis–NIR spectrometer and a self-designed device. By adding TiO2 particles into HDPE matrix, the polymer chain could crystallize into more perfect and thermal stable lamella. The presence of TiO2 particles dramatically increased the number of nucleation site therefore decreased the crystal size. The subsequent solar reflectance was related to the degree of crystallinity, the spherulite size of HDPE, refractive index, and distribution of TiO2 particles in HDPE matrix. It was found the rutile TiO2 could largely improve the total solar reflectance from 28.2% to 51.1%. Finally, the temperature test showed that the composites had excellent cooling property, which was in accordance with solar reflectance result.

Structural and optical studies on nickel oxide thin film prepared by nebulizer spray technique

In the present work, nickel oxide thin film has been deposited on glass substrates at temperature 400°C by simple and inexpensive nebulizer spray technique. The effect of the volume of sprayed solution on structural and optical properties of the films were investigated using X-ray diffractometer, UV–Vis–NIR spectrometer, photoluminescence, Raman spectrum and linear four probe resistivity measurement, respectively. It is found that increase in the sprayed volume of solution with 0.3M leads to increase in the film thickness. XRD studies indicated cubic structure and the crystallites are preferentially oriented along the [111] direction. It is also found that as the sprayed volume of the solution increases the transmittance decreases, consequently the band edge shifted from lower wavelength to higher wavelength and the band-gap energy wanes from 3.64eV to 3.13eV. From PL spectra, the sample shows sharp and strong UV emission around 376nm corresponding to the near bandedge emission of NiO under excitation of 275nm.

The influence of deposition temperature in the photovoltaic properties of spray deposited CZTS thin films

Thin films of Cu2ZnSnS4 (CZTS) is one of the most promising kesterite semiconductor materials for absorption layer in thin film solar cells because of its suitable optical band gap (1.5eV), cost-effective and eco-friendly nature. CZTS thin films were successfully deposited on soda lime glass substrates using spray pyrolysis and the effect of variation of substrate temperature on the structural and optoelectronic properties was investigated. The powder X-Ray diffraction of the deposited thin films showed that the crystallinity was improved with increasing substrate temperature and it has a polycrystalline nature with (112), (220) and (116) phases. Surface morphology of the films was studied employing Atomic Force Microscopy which reveals that the average roughness and grain size increases when the substrate temperature increases. Optical band gap of the films had been studied using UV–Vis–NIR spectrometer and was found to be 1.40–1.60eV which is close to the ideal band gap for highest theoretical conversion efficiency of solar cell. Hall measurements revealed that the films are p-type, with a carrier concentration between 1.524×1017cm−3 and 4.218×1017cm−3 and also the microstructure of these CZTS thin films were studied using Raman spectroscopic measurements.

Effect of nucleating agent on the crystallization behavior, crystal form and solar reflectance of polypropylene

Nucleating agents of polypropylene (PP) have a function in accelerating the crystallization rate, decreasing the spherulite size and transforming the crystal form. Materials with high solar reflectance are widely used in the field for cooling purpose. In this work, three types of nucleating agents were applied to improve the optical properties: malonic acid, sorbitol, and carboxylate nucleating agent (NTC). Differential scanning calorimetry (DSC) measurement was conducted to investigate the crystallization behavior. Wide angle X-ray diffraction (WAXD) was used to study the crystal structure and the crystal form. Polarized optical morphology (POM) was chosen to observe the crystal morphology. UV–vis-NIR spectrometer was performed to record the solar reflectance from 280 to 2500nm. It was found that nucleating agents could increase the crystallinity, decrease the spherulie size and transform the crystal form of PP, which in turn improved the solar reflectance considerably. Especially, β crystal form with high birefringence exhibited more excellent solar reflectance in comparison with neat PP, PP/malonic acid and PP/sorbitol. The order of solar reflectance is as follow: spherulites of β crystal form>small spherulites of α crystal form>large spherulites of α crystal form>disordered polymeric chain. All these types of PP have high thermal emittance more than 0.85, 1wt% NTC even improves this value of PP to 0.90.

Influence of Fe-doping on the optical and electrical properties of ZnO films

We have prepared Fe doped ZnO films, by spin coating, and investigated their structure, morphology, optical and electrical properties by means of the X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, UV–vis–NIR spectrometer and the temperature dependence of electrical conductivity measurements, respectively. XRD results indicates that the films under study posses a polycrystalline structure. A deterioration of the crystallite preferentially orientation, with the increase of Fe doping concentration, was observed. The optical transmittance measurements reveal that the transparency of studied films decreases with the increase of Fe concentration in ZnO. The electrical behavior was analyzed during a heat treatment. The experimental results indicate that the introduction of Fe impurities decreases the conductivity of ZnO with two orders of magnitude. Mott variable range hopping model was proposed to analyze the mechanisms of electronic transport, in low temperature ranges.

Improved optical absorption and photocurrent of GaAs solar cells with hexagonal micro-hole array surface texturing

We demonstrate an improvement in power conversion efficiency of single-junction GaAs solar cells incorporated with micro-hole arrays. The GaAs solar cells are grown by low-pressure metalorganic chemical vapor deposition on (100) GaAs substrates. The micro-hole arrays were formed on the surface of the GaAs solar cells, and the measurement on the reflectance and photocurrent generation are performed using an UV–Vis–NIR spectrometer and an external quantum efficiency measurement system, respectively. It is shown that the micro-hole arrays have the effect of scattering the incident light away from the original direction resulting in the reduction of reflectance over 350–873nm spectrum regime. The micro-hole arrays formed on the surface of the solar cells enhanced the photocurrent generation which was increased with the extended optical path length in the absorption layer. As a result, an enhancement in power conversion efficiency of up to 12.3% compared to that of reference solar cell was obtained under 1sun AM 1.5G illumination at room temperature.

Synthesis of polyhedral Ag nanostructures by a PVP-assisted hydrothermal method

Silver nanocrystals, including single-crystalline cubic nanostructures and multiply twined polyhedrons, have been synthesized by a hydrothermal method with the presence of poly(vinyl pyrrolidone) (PVP). Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and UV–Vis–NIR spectrometer have been employed to investigate the morphology and optical properties of the products. The results show that the shapes of Ag nanostructures are mainly correlated to the molar ratio between PVP and AgNO3. Anisotropic Ag nanostructures with shapes of cube, truncated octahedron, decahedrons, and icosahedrons were obtained when the molar ratio changed in the range of 4–20. It’s quite possible that Fullerene-structured Ag nanocrystal can be formed through this method. The plausible growth mechanisms for the Ag nanostructures of various shapes were present, in which PVP serves as both reducing and surfactant agent for the reduction of Ag+ and growth modifier of the nanocrystals.