نتایج جستجو برای: low band gap
تعداد نتایج: 1423945 فیلتر نتایج به سال:
among the low–dimensional allotropes of carbon, nanotubes and graphene have attracted very much attention from nano–science and nanotechnology specialists. they have been proposed as building blocks in nanometer device engineering. however, these structures are not defect–free. in this thesis, we focused on defective carbon nanotubes and graphene, and studied the effect of couple of very common...
abstract nowadaysphotovoltaic solar cells (pvs) areacknowledged the fastest growing energy technology in the word, however, they only account for only fraction of current global renewable energy capacity. it isrecognized that this incomplete market penetration has been largely a result of the technology’sexcessive cost. so researchers are trying to find innovative, economic way with theaim of ...
Study of the band – gap shift in CdS films : Influence of thermal annealing in different atmospheres
Study of the band–gap shift in CdS films: Influence of thermal annealing in different atmospheres. Abstract We study by photoacoustic spectroscopy the band–gap shift effect of CdS films. The CdS films were grown by chemical bath deposi-tion and exposed to different annealing atmospheres over a range of temperature in which the sample structure is observed to change. We show the band–gap evoluti...
A plate periodically bonded with piezoelectric patches on its surfaces is considered. The differential quadrature element method is used to solve the wave motion equation for the two-dimensional periodic structure. The method is very simple and easy to implement. Based on the method, band structures for in-plane wave propagating in the periodic piezoelectric plate are studied, from which the fr...
Ag2Te simultaneously shows high mobility and low thermal conductivity, however the relatively low band gap of 0.2 eV prevents it from achieving high thermoelectric figure of merit, zT, in the high temperature phase. In this study, the band gap of Ag2Te has been increased enabling a zT of unity by forming alloys and composites with PbTe, thereby demonstrating the importance of exploiting potenti...
This paper presents and compares three analytical methods for calculating low frequency band gap boundaries in doubly periodic arrays of resonating thin elastic shells. It is shown that both Foldy-type equations (derived with lattice sum expansions in the vicinity of its poles) and a self-consistent scheme could be used to predict boundaries of low-frequency (below the first Bragg band gap) ban...
حلقه های قفل شده فاز تمام دیجیتال یکی از مباحث مهم در دنیای امروز الکترونیک هستند. حلقه قفل فازهای (pll ) که به وسیله روشهای آنالوگ طراحی می شدند نسبت به تغییرات دما و ولتاژ و پروسس حساس بودند. این امر موجب سختی طراحی و نیازمندی به طراحی مجدد در تکنولوژی های جدید می شود. این در حالی است که با استفاده از حلقه های قفل فاز تمام دیجیتال این مشکلات برطرف میشوند. حلقه های قفل فاز تمام دیجیتال (adpll...
In this article, we considered the field analysis in photonic crystal Bragg fibers. We apply the method of transmission matrix to calculater the dispersion curves, the longitudinal wave number over wave number versus incident wavelength, and the field distributions of TE and TM modes in the Bragg fiber. Our analysis shows that the field of guided modes is confined in the core and can exist onl...
In this research, we have studied the photonic band structure, optical properties and thermal emission spectrum of 2D Silicon photonic crystal with hexagonal structure. The band structure, band gap map and the gap size versus radius have been calculated by plane wave expansion method. The maximum band gap size of TE (TM) polarization and the complete gap size are 51% (20%) and 17% at air hole r...
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