http://rulrepository.ru.ac.bd/handle/123456789/77 Tue, 07 Apr 2026 21:40:21 GMT 2026-04-07T21:40:21Z http://rulrepository.ru.ac.bd/handle/123456789/1136 Studies of the Effects of Annealing, Partial Degassing and Light Soaking on Sputtered A-Si:H Films Through Analysis of Infrared and Thermal Effusion Results Hashem, Md. Abul Hydrogenated amorphous silicon, a-Si:H, is a promising material with ideal properties for various types of optoelectronic devices. At the same time, the material suffers from some serious disadvantages including Staebler wronski effect (SWE), in which the efficiency of a solar cell decreases gradually with prolong exposure to light. It is believed that the quality of a-Si:H alloy is closely related to its hydrogen content and to the nature of silicon-hydrogen bonds. On the otherhand, hydrogen has indirect influence on the occurrence of SWE. a-Si:H often contains significant amount of impurities such as oxygen and nitrogen which have sufficient influence on their optoelectronic properties. Hence, the various bonding configurations involving Si, H, O and N has been studied to investigate their role in the light induced structural changes in a-Si network. Infrared spectroscopy (IR) and thermal hydrogen effusion (TE) have been used to characterize the sputtered a-Si:H samples. The results have been analyzed to study the nature of the silicon-hydrogen, silicon-oxygen and silicon-nitrogen bonds and to identify the effects of partial degassing, annealing and light soaking on these bonds. The samples were prepared by reactive radio frequency sputtering under different deposition conditions to produce hydrogen contents ranging from 10 to 35 at.%. Slightly contaminated samples were found to contain oxygen and nitrogen concentrations up to ~3 and 1.5 at.% respectively. Samples were deposited, generally, onto crystalline silicon (100) with few exceptions onto stainless steel substrates at a deposition rate of -4 nm/min. The substrate temperature was controlled at ~120 °C and the thickness of the films were from -0.08 to 6 um. Different sets of samples were subjected to partial degassing (in vacuum), annealing (in hydrogen atmosphere) and light soaking (under sun light AM1). Infrared absorption spectra, from 370 to 5000 cm', were obtained using a fourier transform infrared spectrometer. A quadrupole mass spectrometer was used to monitor the evolution of hydrogen. Several computer softwares were used to analyze the resulting data. Uncontaminated samples show three hydrogen-related distinct features at 650, 850-895 and 2090 cm1 due to wagging, bending and stretching vibrations, respectively, of the various silicon-hydrogen bonds. Nitrogen containing samples show, in addition, a features at 790 cm1. Samples containing oxygen exhibit the distinct features at 940-980 and 1000-1045 cm1 regions due to Si-O-Si and H/Si-SiO2-O-SIO2-Si/H configurations respectively. The evolution of weakly bonded hydrogen occured at different temperatures; more contaminated samples, having evolutions peaks at higher temperatures, indicate better stability to thermal degradation. Incorporation and/or movement of oxygen atoms are also a consequence of partial degassing. Higher hydrides are related to 850-895 cm' doublet and have lesser contribution to feature at 650 cm. The peak at 2000 cm1 has contributions from (Si-H2), and clustered Si-H. The 2090 cm'' peak is a result of Si-H2, (Si-H2), Si-H3 and Si-H groups. In annealed samples, some IR inactive hydrogen become IR active and there is evidence of the movement of oxygen atoms from the bulk of the film towards the film- substrate interface. The peaks at 2000 and 2090 cm moves towards higher wavenumber with increasing annealing temperatures. Oxygen atoms become mobile as a result of prolonged illumination and seem to move through a-Si network. Also the oxygen atoms in the crystalline Si-O form new configurations and /or diffuse into the bulk of a-Si:H film. No evidence of the movement of the nitrogen atoms through a-Si network was observed. Some weak Si-H bonds are broken and the hydrogen atoms become mobile in the a-Si network. Thus it appears that hydrogen atoms move through an a-Si:H network as a result of the breaking of Si-H bonds due to the trapping of free-charge carrier following illumination. This creates dangling bonds in the interior of the material. After prolonged illumination, the overall number of new dangling bonds becomes large enough to cause permanent structural damage or photodegradation in the interior of the film. This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD) Wed, 01 Jul 1998 00:00:00 GMT http://rulrepository.ru.ac.bd/handle/123456789/1136 1998-07-01T00:00:00Z http://rulrepository.ru.ac.bd/handle/123456789/1009 Seismic Surface Wave for Studying the Crustal Structure of the South-Eastern Region of Bangladesh Faruk, Md. Omar Earthquake is one of the catastrophic events of the natural disasters that are prone to cause great damage to life and property. In order to decrease the damages, it is essential to gain knowledge for studying the crustal structure of the earth. In this dissertation crustal structure of the south-eastern region of Bangladesh is estimated by using seismic surface wave data. The parameters of the recorded earthquake data are ideally related to the subsurface geology. Geologic properties beneath a region have a major impact on the ground motion by modifying the amplitude, phase, duration, and shape of seismic waves. The main purpose of our work is to study the crustal structure, particularly major crustal boundaries and thicknesses of the structures…………… This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD) Sat, 01 Jan 2011 00:00:00 GMT http://rulrepository.ru.ac.bd/handle/123456789/1009 2011-01-01T00:00:00Z http://rulrepository.ru.ac.bd/handle/123456789/986 A Study of The Electrical And Optical Properties of Zno Thin Films Spray Pyrol Ysed From Zn(C2H302)2 2H20 Ambia, Md. Ghulam Investigations have been carried out on spray pyrolysed undoped and indium doped ZnO thin films for the thickness range 700-4000 A. The undoped ZnO thin films were found to be nonstoichiometric but homogeneous and polycrystaline in structure as confirmed by the structural studies. The virgin films were highly resistive whereas vacuum annealed films are. good transparent conductors. Aging effect has been observed within the first 15 days of the film fabrication. Size effect has been observed below 1500 A. The doped film (ZnO: In) showed higher carrier concentration and Hall mobility. The effect of successive post-deposition ~eat treatments in air and vacuum has been studied. It has been observed that the heat treatment in different ambients have remarkab 1 e effects on the electrical transport properties. Due to the successive heat treatment operation, the carrier concentratio~ - changes from 1015 - 1018 cm-3 and mobility changes from 4 - 16 cm2/vs·. Oxygen chemisorption-desorption mechanism were found to play an important roie to control the electronic properties. Various grain boundary and energy band parameters have been calculated by using conventional extrinsic semi conductor theory and grain boundary trapping models. The samples were non-degerate at room temperature, and the Ha 11 mobility was found to be modu I ated by the grain boundary potential barrier height via the samples temperature. For ZnO thin films two distinct scattering process viz the grain boundary scattering and the piezoelectric scattering are found to play a predominant role in limiting the Hall mobility.------ This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD) Sat, 01 Jan 1994 00:00:00 GMT http://rulrepository.ru.ac.bd/handle/123456789/986 1994-01-01T00:00:00Z http://rulrepository.ru.ac.bd/handle/123456789/979 Preparation and Properties of the Mn-Oxide Thin Films by Spray Pyrolysis Technique Islam, Abu Kalam Md. Faridul Oxides of manganese in particular undoped manganese dioxide (Mn02) thin films of thickness ranges 85 - 380 run have been prepared onto glass substrate at a deposition· rate of 6.7 nm/min by a simple spray pyrolysis technique under various deposition conditions. The effects of different deposition variables on structural, electrical and optical properties of the films have been studied in detail. These studies show that various deposition parameters have remarkable effects on spray deposited Mn02 thin films. X-ray diffraction and Transmission Electron Microscopy studies show that Mn02 thin films are homogeneous and polycrystalline in structure. The virgin films are shown highly resistive whereas annealed films exhibit a reasonable conduction. Electrical conductivity has been measured as a function of temperature ranging from 303 to 413K and its conductivity exhibits an anomaly at a temperature 323K. The decrease in resistivity with increasing temperature indicates that the samples are semiconducting in nature. The heat-treatment of the Mn02 samples at different ambient have remarkable effects on the electrical transport properties. The annealing was carried out in vacuum for 2 hours at a constant temperature of 473K. During annealing oxygen chemisorption-desorption mechanism is found to play an important role in controlling the electronic properties of the films. A thickness effect of activation energy is observed in Mn02 films. The effect shows that the activation energy above anomaly is inversely proportional to the thickness whereas its value is directly proportional below the anomaly temperature. This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD) Sat, 01 Jan 2005 00:00:00 GMT http://rulrepository.ru.ac.bd/handle/123456789/979 2005-01-01T00:00:00Z