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Band gap tuning and p to n-type transition in Mn-doped CuO nanostructured thin films

journal of Semiconductors 2022年第1期43卷 59-68页

作者： R.Rahaman M.Sharmin j.podder Department of Physics Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh

Here we discuss the synthesis of copper(II)oxide(CuO)and manganese(Mn)-doped CuO thin films varying with 0 to 8 at%Mn using the spray pyrolysis ***-deposited film surfaces comprised of agglomerated spherical nanoparticles and a semi-spongy porous structure for 4 at%Mn *** dispersive analysis of X-rays confirmed the chemical composi-tion of the films.X-ray diffraction spectra showed a polycrystalline monoclinic structure with the predominance of the(11)*** band gap energy for direct and indirect transitions was estimated in the ranges from 2.67-2.90 eV and 0.11-1.73 eV,*** index and static dielectric constants were computed from the optical *** resistivity of CuO and Mn-doped CuO(Mn:CuO)thin films was found in the range from 10.5 to 28.6Ω·*** tiniest electron effective mass was calculated for 4 at%Mn:CuO thin films.P to n-type transition was observed for 4 at%Mn doping in CuO *** con-centration and mobility were found in the orders of 10^(17)cm^(-3)and 10^(-1)cm^(2)/(V·s),*** Hall coefficient was found to be between 9.9 and 29.8 cm^(3)/*** above results suggest the suitability of Mn:CuO thin films in optoelectronic applications.

关键词： Mn:CuO spray pyrolysis FESEM XRD band gap Hall effect

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Effect of Fe-doping on the structural and optical properties of ZnO thin films prepared by spray pyrolysis

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journal of Semiconductors 2013年第7期34卷 31-36页

作者： S.M.Salaken E.Farzana j.podder Department of Electrical and Electronic Engineering Bangladesh University of Engineering and TechnologyDhaka-1000Bangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhaka-1000Bangladesh

Fe-doped ZnO thin films have been prepared by spray pyrolysis on glass substrates and the influence of Fe-doping concentration on the structural and optical properties of the films has been *** X-ray diffraction （XRD） analysis shows that Fe doping has a significant effect on crystalline quality,grain size and strain in the thin *** best crystalline structure is obtained for 3 at%Fe doping as observed from scanning electron microscopy （SEM） and ***,lower or higher Fe-doping degrades the crystalline quality in ***,UV spectroscopy demonstrates the influence of Fe-incorporation on visible range transmittance of ZnO where the best transmittance is obtained for 3 at%*** results have been illustrated simultaneously focusing previous results obtained from literature.

关键词： ZnO spray pyrolysis thin films

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Effect of Annealing Temperature on Structural, Optical and Electrical Properties of Pure CdS Thin Films Deposited by Spray Pyrolysis Technique

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Advances in Materials Physics and Chemistry 2012年第4期2卷 226-231页

作者： A. Hasnat j. podder Department of Physics Bangladesh University of Engineering and Technology Dhaka Bangladesh Department of Physics Jagannath University Dhaka Bangladesh

Effect of annealing temperature on the properties of CdS thin films are carried out in this work. Nanocrystalline cadmium sulphide (CdS) thin films were prepared using spray pyrolysis deposition (SPD) technique and the structural, optical and electrical properties were investigated for different annealing temperature (as deposited, 300, 400 & 500 C). The surface morphology and compositional properties studied by SEM and EDX respectively. The crystal structure of CdS thin film was studied by X-ray diffraction. The crystallite size and lattice constant of SPD CdS thin films were investigated. The optical parameters such as transmittance, absorption coefficient and energy band gap of the films with thermal annealing temperature was investigated by UV/VIS spectrophotometer. The variation of band gap values of CdS thin film samples were found to be in the range of 2.51 to 2.8 eV. Electrical resistivity measurements were carried out in fourprobe Vander Pauw method at different temperature. So CdS films may be a good candidate for suitable application in various optoelectronic devices.

关键词： Spray Pyrolysis CdS Annealing Temperature Structural Optical Band Gap

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Dynamics of novel COVID-19 in the presence of Co-morbidity

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Infectious Disease Modelling 2022年第2期7卷 138-160页

作者： Amit Kumar Saha Chandra Nath podder Ashrafi Meher Niger Department of Mathematics University of DhakaDhaka1000Bangladesh

A novel coronavirus(COVID-19)has emerged as a global serious public health issue from December *** having a weak immune system are more susceptible to coronavirus *** is a double challenge for people of any age with certain underlying medical conditions including cardiovascular disease,diabetes,high blood pressure and cancer ***-morbidity increases the probability of COVID-19 *** this paper a deterministic compartmental model is formulated to understand the transmission dynamics of *** mathematical analysis of the model shows that it exhibits backward bifurcation phenomenon when the basic reproduction number is less than *** the case of no re-infection it is shown that having the reproduction number less than one is necessary and sufficient for the effective control of COVID-19,that is,the disease free equilibrium is globally asymptotically stable when the reproduction threshold is less than ***,in the absence of reinfection,a unique endemic equilibrium of the model exists which is globally asymptotically stable whenever the reproduction number is greater than *** simulations of the model,using data relevant to COVID-19 transmission dynamics,show that the use of efficacious face masks publicly could lead to the elimination of COVID-19 up to a satisfactory *** study also shows that in the presence of co-morbidity,the disease increases significantly.

关键词： COVID-19 Co-morbidity Face-mask

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Effect of awareness,quarantine and vaccination as control strategies on COVID-19 with Co-morbidity and Re-infection

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Infectious Disease Modelling 2022年第4期7卷 660-689页

作者： Amit Kumar Saha Shikha Saha Chandra Nath podder Department of Mathematics University of DhakaDhaka1000Bangladesh Department of Mathematics Bangladesh University of Engineering and Technology(BUET)Dhaka1000Bangladesh

In this paper,a deterministic compartmental model is presented to assess the impact of vaccination and non-pharmaceutical interventions(social distance,awareness,face mask,and quarantine)on the transmission dynamics of COVID-19 with co-morbidity and *** expression for the basic reproduction number is then derived for this *** analysis shows that the model exhibits backward bifurcation phenomenon when the basic reproduction number is less than *** for the case of no reinfection,the model has a globally asymptotically stable disease-free equilibrium(DFE)when the basic reproduction number is less than ***,it is shown that in the case of no re-infection,a unique endemic equilibrium point(EEP)of the model exists which is globally asymptotically stable whenever the reproduction number is greater than *** the global sensitivity and uncertainty analysis,we have identified mask coverage,mask efficacy,vaccine coverage,vaccine efficacy,and contact rate as the most influential parameters influencing the spread of *** simulation results show that the use of effective vaccines with proper implementation of non-pharmaceutical interventions could lead to the elimination of COVID-19 from the *** simulations also suggest that the control strategy that ensures a continuous and effective mass vaccination program is the most cost-effective control *** study also shows that in the presence of any co-morbidity and with the occurrence of re-infection,the disease burden may increase.

关键词： COVID-19 Co-morbidity Face-mask Quarantine Vaccination Optimal control Re-infection

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