NISCAIR Online Periodicals Repository Collection: IJPAP Vol.50(09) [September 2012]

Energy balance method and amplitude frequency formulation based simulation of strongly non-linear oscillators

Title: Energy balance method and amplitude frequency formulation based simulation of strongly non-linear oscillators

Authors: Ganji, Davood D; Azimi, Mohammadreza; Mostofi, Mehdi

Abstract: The Energy Balance Method (EBM) and Amplitude Frequency Formulation (AFF) have been applied to derive the approximate analytical solution for motion of two mechanical oscillators. In first problem both methods yield the same result but in the second problem, the results which are obtained from Amplitude Frequency Formulation and Energy Balance Method are different. In comparison with the forth order Runge-Kutta method, the results show that these methods are very convenient for solving non-linear equations and also can be used for strong non-linear oscillators.

Page(s): 670-675

Effects of grain boundaries on the performance of polycrystalline silicon solar cells

Title: Effects of grain boundaries on the performance of polycrystalline silicon solar cells

Authors: Joshi, D P; Sharma, Kiran

Abstract: A comprehensive carrier recombination model under optical illumination near grain boundaries (GBs) is proposed by considering the asymmetric Gaussian energy distribution of GB interface states model. A new recombination velocity S(L_n) is proposed to study the dependence of effective diffusion length of minority carriers on grain size and GB interface state density. The dependence of GB space charge potential barrier height (qV_g), the recombination velocities, and polycrystalline silicon (PX-Si) solar cell parameters on grain size, illumination level, and GB interface state density have also been studied. It is observed that the efficiency of solar cells is mainly determined by the potential barrier height qV_g. Considering the effect of vertical GBs in the junction depletion region of a solar cell, it is also observed that their effect is smaller in the small grain size range as compared to that in the large grain size range. A reasonably good agreement is obtained between the theoretical predictions and the available experimental data.

Page(s): 661-669

Thickness dependent electrical and optical properties of nanocrystalline copper sulphide thin films grown by simple chemical route

Title: Thickness dependent electrical and optical properties of nanocrystalline copper sulphide thin films grown by simple chemical route

Authors: Shinde, M S; Ahirrao, P B; Patil, I J; Patil, R S

Abstract: A Novel chemical bath deposition (CBD) method has been developed to deposit semiconducting nanocrystalline copper sulphide (Cu₂S) thin films on ordinary glass substrates with different thicknesses. The deposition bath consists of aqueous copper chloride (CuCl₂), ammonia (NH₃) and thiourea [SC(NH₂)₂]. It is found that the deposition parameters significantly influence the quality and the thickness of Cu₂S films. The films were uniform and adherent to glass substrates. The deposited films have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), optical absorption and electrical resistivity. The effect of film thickness on the optical, structural and electrical properties has been studied. The shift of 0.46 eV in the optical band gap energy (E_g) and decrease in electrical resistivity from 6.463 10^-2to 8.973 10^-3 Ω-cm and increase in the grain size of Cu₂S crystallites from 30 to 250 nm were observed when the film thickness was varied from 130 to 250 nm.

Page(s): 657-660

Surface modification of GaAs induced by argon ion implantation

Title: Surface modification of GaAs induced by argon ion implantation

Authors: Hussain, S; Gayen, R N; Dutt, M B; Pal, A K

Abstract: Surface modification of GaAs (100) due to Ar⁺ ion bombardment has been studied by measuring optical, AFM, SEM, Raman and PL measurements. GaAs was bombarded with 250 keV argon ions with three different doses of 1×10¹⁶ cm^-2, 1×10¹⁵ cm^-2and 1×10¹⁴ cm^-2. AFM studies indicated that the surface became rougher with ion bombardment (dose) and the surface roughness increased from 0.706 nm for un-bombarded GaAs to 3.671 nm for bombarded samples. Peaks shifted to lower 2θ values for bombarded samples. The full width at half maxima (FWHM) of the XRD peaks for reflections from (200) and (400) planes of GaAs increased for films bombarded with increased Ar⁺ fluxes and increase in FWHM for (400) plane peak is quite significant. The LO peak at ~290 cm^-1 of the Raman spectra shifted to lower wave number and became broader with the Ar⁺ flux. PL spectra showed a strong luminescence peak at ~ 1.5 eV followed by two smaller peaks located at ~1.40 eV and 1.1 eV. Photoluminescence bands at ~ 1.5 eV band were assigned to annihilation of free and localized excitons by small donors and acceptors. The shoulders at ~1.48 eV and ~1.47 eV represented the transition due to free-to-bound recombination and the defects GaAs.

Page(s): 650-656