Showing 5 results for Band Gap
A. Gaur, D. Sharma, P. Gaur, B.p. Malik, N. Singh,
Volume 4, Issue 2 (6-2010)
Abstract
The Photoexcited carrier lifetime (τ) and peak to valley transmission difference (ΔTp-v) in direct and indirect band gap crystals has been investigated by the use of single beam open and closed aperture z-scan technique using frequency doubled Nd:YAG laser. The peak to valley transmission difference (ΔTp-v) is found to be of the order of 10-2 in case of direct band gap crystals and of the order of 10-3 in case of indirect band gap crystals. The carrier life time (τ) is found to be in nanoseconds range in case of direct band gap crystals and picoseconds range in case of indirect band gap crystals. Lower value of (τ) and (ΔTp-v) in case of indirect band gap crystals can be attributed to the reduction in the value of carrier density (N) and small value of nonlinear phase shift ( Δϕ ),respectively.
F. Rahman, J. Podder, M. Ichimura,
Volume 5, Issue 2 (7-2011)
Abstract
Thin films of indium doped zinc sulfide (ZnS) for different indium (In) concentrations (x=0.0 - 0.8) were deposited onto glass substrate by spray pyrolysis method at 523K temperature. Aqueous solution of zinc acetate, indium chloride and thiorea were used to deposit the In-Zn-S film. The deposited thin films were characterized by Energy dispersive X-ray (EDX), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and by UVvisible spectroscopy. The XRD spectra of In-Zn- S revealed both the amorphous and polycrystalline property for different In concentration. The EDX showed a well stoichiometric result of different compositions of In in ZnS thin films. The granularity of irregular shape is observed in In doped ZnS thin films surface by scanning electron microscope. From the absorbance and transmittance data it is observed that the band gap energy is decreased from 3.75eV to 3.1eV with the increase of In concentration in ZnS.
Mohsen Dehbashi, Mousa Aliahmad,
Volume 6, Issue 2 (10-2012)
Abstract
Sn 0.986 Ni 0.014 O nanoparticles have been synthesized by a simple co-precipitation method. Nanoparticles crystallize in lower temperature (350°C) and shorter time (2h) respect to other methods. The sample characterized by various standard techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Atomic absorption spectroscopy (AAS) and UV–Vis spectroscopy. The X-ray diffraction reveals that sample is pure rutile-type tetragonal phase, the crystalline size Sn0.986Ni0.014O nanoparticles is 27 nm. UV-Vis spectroscopy is revealed the optical band gap to be 3.98 eV for Sn0.986Ni0.014O nanoparticles that is higher than the bulk value of SnO (2.5–3 eV).
Dr. Samad Roshan Entezar, Mrs Arezo Rashidi ,
Volume 8, Issue 2 (7-2014)
Abstract
In this paper, properties of reflection phase in one-dimensional quaternary photonic crystals combining dispersive meta-materials and positive index materials are investigated by transfer matrix method. Two omnidirectional band gaps are located in the band structure of considered structure. However, we limit our studies to the frequency range of the second wide band gap. We observe that the value of the reflection phase difference between TE and TM waves can be controlled by changing the incident angle and frequency. Also, the results show that the reflection phase difference in the second band gap increases by increasing the incident angle, and remains almost unchanged in a broad frequency band. Furthermore, at two points near to the edges of the gap the reflection phase difference keeps almost zero in spite of the change of incident angle. Based on these properties, phase compensators and omni-directionally synchronous reflectors and also polarizers can be designed.
Dr. Savarimuthu Robinson, Dr. Krishnan Vijaya Shanthi,
Volume 10, Issue 2 (11-2016)
Abstract
In this paper, homogeneous, wavelength shift biosensor is designed for sensing the protein concentration using two dimensional Photonic Crystal Ring Resonator (PCRR). The sensor is designed to monitor the protein concentration from 0% to 100%. The proposed sensor is composed of periodic Si rods embedded in an air host with a circular PCRR that is placed between the inline quasi waveguides. It is observed that the resonant wavelength of the sensor is shifted (0.9 nm) to higher wavelength while increasing the protein concentration (5%) as the protein has a unique refractive index for each level. With this underlying principle, the performance of the sensor is analyzed for different protein concentration.
