Determination Of Energy Band Gap Research Articles

Determination of energy band gap of α-LiIO3 doped with L-Arginine and L-Nitroarginine amino acids using diffuse reflectance spectroscopy

An accurate determination of the band gap energy is crucial for predicting the photophysical and photochemical properties of investigated materials. In the present work, the dependence of the energy band gap (Eg ) of α-LiIO3 crystals doped with L-arginine and L-nitroarginine amino acids was obtained. The method, based on the simultaneous fitting of many absorption mechanisms to the spectral dependence of the Kubelka-Munk function estimated from diffuse reflection data, as well as Tauc's method, has been applied to determine the energy band gap. In the case of a small dopant concentration, additional electron states appear within the band gap of the crystals. As a result, a broad absorption band appears in the material spectrum. The optical transmittance spectra were recorded using an Agilent Cary 60 spectrophotometer in the spectral range 190–1100 nm.

X-ray/gamma radiation shielding properties of Aluminium-Barium[sbnd]Zinc Oxide nanoparticles synthesized via low temperature solution combustion method

For the first time Aluminium-BariumZinc oxide nanocomposite (ZABONC) was synthesized by solution combustion method where calcination was carried out at low temperatures (6000C) to study the electromagnetic (EM) (X/γ) radiation shielding properties. Further for characterization purpose standard techniques like PXRD, SEM, UV-VISIBLE, FTIR were used to find phase purity, functional groups, surface morphology, and to do structural analysis and energy band gap determination. The PXRD pattern shows (hkl) planes corresponding to spinel cubic phase of ZnAl2O4, cubic Ba(NO3)2, α and γ phase of Al2O3 which clearly confirms the formation of complex nano composite. From SEM histogram mean size of nano particles was calculated and is in the order of 17 nm. Wood and Tauc’s relation direct energy band gap calculation gives energy gap of 2.9 eV. In addition, EM (X/γ) shielding properties were measured and compared with the theoretical ones using standard procedures (NaI (Tl) detector and multi channel analyzer MCA). For energy above 356 keV the measured shielding parameters agree well with the theory, while below this value slight deviation is observed, due to the influence of atomic/crystallite size of the ZABONC. Hence synthesized ZABONC can be used as a shielding material in EM (X/γ) radiation shielding.

Investigation the optical band gap of self-assembled monolayer of tin selenide synthesized by chemical solution deposition

In this study, the fabrication and characterization of the thin layer of SnSe self-assembled were investigated by control of the preparation parameters. SnSe binary nanoparticles semiconductor were prepared using chemical solution deposition technique. The deposition time and temperature and the solution concentration that govern the evolution of the configuration films and optical band gap in chemical deposition processes was explored. We benefited from Rutherford Backscattering Spectrometry with 2 MeV 4He ions to determine the depth profile of the elements in tin selenide. UV–visible spectroscopy was used for energy band gap determination. Also, the nanostructured and the morphologies of the thin films were analyzed by scanning electron microscopy. We were able to achieve a broad optical band gap ranging from 5.82 to 3.06 eV of SnSe thin films appropriate for solar cell and photovoltaic applications.

Optical, Dielectric and Ferroelectric Characteristics of Gel Grown Erbium Tartrate Hexahydrate Crystals

With an aim of finding a material suitable for microelectronic applications, experiments were performed to grow erbium tartrate crystals by gel encapsulation. The crystals grow with very well-developed and remarkably flat habit faces as revealed by micro-structural studies, using optical and scanning electron microscopy. The study reveals that the most prominent faces include {001}, {100} and {010}. The crystallographic data analysis of x-ray diffraction results, supplemented by trial-and-error software, shows that the compound crystallizes in a tetragonal crystal system with non-centrosymmetric space group. The high resolution x-ray diffraction results indicating the perfection of the grown crystals are presented. Results of ultraviolet–visible near infra-red (UV–Vis–NIR) spectra leading to determination of energy band gap of 5. 56 eV are described and discussed. The refractive index of the grown material comes out to be 1.40. Comparative analysis of dielectric characteristics of the grown material is made, both for the single crystal and powder form. The material is shown to be ferroelectric with low value of dielectric constant. Behaviour of dielectric constant, dielectric loss and alternating current (ac) conductivity on frequency of the applied ac field at different temperatures is described and discussed. The results are correlated with those of optical and high resolution x-ray diffraction. The material characteristics as revealed by the study suggest that the compound has the basic qualities of a promising material for microelectronic device applications.

Characterization of Tb-doped hydroxyapatite for biomedical applications: optical properties and energy band gap determination

In the present work, the synthesis, by means of the sol–gel method, of calcium-deficient hydroxyapatite and Tb-doped calcium-deficient hydroxyapatite with dopant content of 10 and 12 wt% is reported. The synthesized samples exhibit diffraction patterns and structural characteristics consistent with those reported in the literature for synthetic hydroxyapatite. The results of the chemical characterization show that the synthesized samples are suitable for biomedical applications, and the incorporation of Tb3+ in the host structure occurs both substitutional and by dopant insertion in calcium vacancy sites. In addition, using spectroscopic techniques, the values of the valence band, optical band gap energies, and luminescent response were determined for all samples, concluding that the increase in dopant has the consequence of decreasing the value of the optical band gap, as it was expected; However, it is also observed that the maximum luminescent emission is obtained for the sample synthesized with 10 wt% of terbium.

ZnSe and copper-doped ZnSe nanocrystals (NCs): Optical absorbance and precise determination of energy band gap beside their exact optical transition type and Urbach energy

The using of a reliable and accurate new method (called in literature as derivation of absorption spectrum fitting (DASF)) for evaluation of the optical band gap (Eg) and also the exact nature of charge carriers optical transitions, is investigated in ZnSe and ZnSe:Cu nanocrystals (NCs) synthesized by rapid microwave irradiation. This method can be performed by using the output of UV–Visible spectroscopy. The obtained Eg values are within the range of 2.985–3.261 eV, depending to the microwave irradiation time and Cu dopant percentage (decreasing trend with increasing of irradiation time and Cu content). The DASF-based obtained results for ZnSe and ZnSe:Cu nanoparticles, showed the more precise values of band gap, with the same trend of previously qualitative reported data on the same samples. Also, the direct gap nature of their optical transitions was justified. To perform the method, there is no any need to the concentration of solutions and merely one need the direct absorption or transmission spectra. In other word, DASF technique was employed on ZnSe NCs to confirm its validity and to avoid non-precise reports on optical band gap which can affect on the device optimizations based on these samples. Moreover, using the values of Eg, refractive index and dielectric constant of each sample were obtained at the absorption edge. Also, the width of the tailing states in the gap (Urbach energy: ETail) was estimated and were within the range of 0.049–0.122 eV, which their very small values in compare with Eg imply to the sharp valence and conduction band edges; it means the good crystallinity nature of the produced samples.

Shapes alteration and optical band gap controlling in NiSe nanostructure thin films with deposition temperature changing

We investigate the deposition temperature that govern evolution of the nanoparticle shape NiSe nanoparticle arrays. NiSe semiconductor nanostructure thin films have been synthesized through a simple chemical bath deposition approach. X-ray diffraction characterization suggested that the product consists of hexagonal phase pure NiSe. The samples were also characterized by absorbance spectra for energy band gap determination, scanning electron microscopy (SEM) and EDAX technique for elemental analysis. The results showed that the deposition temperature plays a crucial role in the process and show a ‘red shift’ of ‘1.5eV’ in their optical band gap. In comparison to other similar works, our method is simple, low cost and can be easily controlled.

Shape, size and configuration tuning in ZnSe nanostructure thin films through deposition temperature, pH controlling and deposition time

We investigate the deposition temperature, pH and deposition time that govern evolution of the nanoparticle shape, size and density of ZnSe nanoparticle arrays. The nanoparticle arrays were grown on glass substrate using a facile chemical bath deposition method. The samples were also characterized by absorbance spectra for energy band gap determination and scanning electron microscopy. In comparison to other similar works, our method is simple, low cost and can be easily controlled. We find that temperature helps to tailoring the nanoparticle shape and has a critical role in comparison with other parameters such as pH and deposition time.

Band gap energy determination by photoacoustic absorption and optical analysis of Cd 1−xZn xTe for low zinc concentrations

In this paper we present a study of the optical properties of CdZnTe single crystal for low Zn concentrations at room temperature using photoacoustic spectroscopy and photoreflectance (PR) measurements. The photoreflectance measurements were carried out in order to determine the E g value at room temperature of the CdTe sample to validate the criterion for the photoacoustic absorption measurements. The closed photoacoustic cell configuration (CPC) was used for the absorption measurements and, we use the knee method in the spectra for the energy band gap determination of CdZnTe as a function of the Zn concentration. The samples under study are commercial samples grown by the Bridgmann technique. X-ray diffraction was carried out in order to determine the Zn concentration of the samples and the FWHM of the diffraction peaks. The correlation between FWHM of the diffractograms and the photoacoustic absorption slopes shows that the absorption slopes could be associated with the crystalline quality of samples.

Photoacoustic determination of energy band gap of semiconductors

Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors namely CdS, CdSe, CdTe, ZnS, ZnO, Se and Si in the powder form. Values obtained have been compared with those reported by conventional methods.