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Acta Metallurgica Sinica(English Letters) 2013年第6期26卷 699-706页

作者： Muhammad Arslan Riaz Muhammad arshad mahmood Rashad Rasheed Department of Applied Physics Federal Urdu University of ArtsSciences and Technology National Institute of Lasers and Optronics

Thin films of Zn1-xCuxSe （x= 0.00, 0.05, 0.10, 0.15, 0.20） were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 ~C and 400 ~C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy （RBS）, X-ray diffraction （XRD）, spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characteriza- tion including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 ℃ annealed samples at 745 cm-1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.

关键词： Closed space sublimation Annealing effect Structural Transmission Band gap Spectroscopic ellipsometer Raman spectroscopy

Structural and spectroscopic analysis of wurtzite（ZnO）1-x（Sb2O3）x composite semiconductor

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Progress in Natural Science:Materials International 2015年第2期25卷 131-136页

作者： Hafeez ullah Amjid Iqbal M. Zakria arshad mahmood University of Trento Department of Physics Via Sommarive 14 Povo 38123 Trento Italy Center for Materials and Microsystems Fondazione Bruno Kessler Via Sommarive 18 Povo 38123 Trento Italy National Institute of Lasers and Optronics (NILOP) Nilore Islamabad Pakistan

The structural, vibrational and impedance analysis for(Zn O)1 x(Sb2O3)xcomposite synthesized by solid state reaction technique were carried out in the present investigation. X-ray diffraction(XRD) study showed that(Zn O)1 x(Sb2O3)xcomposite has hexagonal(wurtzite) crystal structure. Variation in lattice constants with Sb-doping indicated the proper incorporation of Sb dopant in Zn O host matrix. The results of Raman spectroscopy test suggested the signature of E2(high) and E1(TO) Raman modes, and verified the wurtzite structure of(Zn O)1 x(Sb2O3)x composite. Two additional phonon bands(671, 712) cm 1appeared in Raman spectra of composite samples due to the existence of the lattice defects caused by Sb doping or may be other intrinsic lattice defects formed during the synthesis of(Zn O)1 x(Sb2O3)xcomposite. The frequency dependent on the electrical characteristics, such as, impedance(Z), dielectric constant(ε) and AC conductivity(σ) have been studied in a range of frequencies for different Sb concentration at room temperature. The electrical measurement results showed that the impedance increased with Sb dopant concentration, while dielectric constant and AC conductivity decreased with Sb dopant concentration.

关键词： (Zn O)1 x(Sb2O3)x Semiconductors XRD Raman spectroscopy Impedance spectroscopy

Structural and optical properties of Cr doped ZnO crystalline thin films deposited by reactive electron beam evaporation technique

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Progress in Natural Science:Materials International 2013年第1期23卷 64-69页

作者： Amjid Iqbal arshad mahmood Taj Muhammad Khan Ejaz Ahmed National Institute of Laser and Optronics(NILOP) P.O.NiloreIslamabad 45650Pakistan Physics Division PINSTECH P.O.NiloreIslamabad 45650Pakistan

ZnO and Cr-doped ZnO thin films are grown on to glass substrates using reactive electron beam(e-beam) evaporation *** of structural,morphological,and optical properties with Cr doping is investigated.X-ray diffraction(XRD) studies show that the films are polycrystalline in nature with single *** dispersive spectroscopy(EDS) results demonstrate that Cr ions are substitutionally incorporated into *** force microscopy(AFM) reveals that the films present a compact surface and root mean squared(RMS) roughness increased with Cr *** optical band gap energy Eg of the films has been determined using Transmission data by spectrophotometer and *** band gap energy found to be decreased with increasing Cr doping *** optical constants(refractive index,extinction coefficient) are calculated using ellipsometry and found to increase with Cr doping concentration.

关键词： Cr doping Thin film ZnO thin films Roughness Ellipsometry Optical constants

Hydrothermal synthesis and characterization of carbon-doped TiO2 nanoparticles

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Chinese Physics B 2020年第11期29卷 516-521页

作者： Zafar Ali Javaid Ismail Rafaqat Hussain AShah arshad mahmood Arbab Mohammad Toufiq Shams ur Rahman Department of Physics COMSATS University IslamabadPark RoadIslamabad 45550Pakistan Department of Chemistry COMSATS University IslamabadPark RoadIslamabad 45550Pakistan National Institute of Lasers and Optronics College Pakistan Institute of Engineering and Applied Sciences(NILOP-CPIEAS)Nilore 45650IslamabadPakistan Department of Physics Hazara University MansehraMansehra 21300Pakistan

We report the hydrothermal growth of pure and doped TiO2 nanoparticles with different concentrations of *** microstructure of the as-synthesized samples is characterized by x-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),energy dispersive x-ray spectroscopy(EDX),and Raman spectroscopy to understand the structure and *** XRD patterns confirm the formation of anatase phase of TiO2 with the average crystallite size is calculated to be in the range of 13 nm to 14.7 *** functional groups of these nanostructures are characterized by Fourier transformed infrared(FT-IR)spectroscopy,which further confirms the single anatase phase of the synthesized ***-visible absorption spectroscopy is used to understand the absorption behavior,which shows modification in the optical bandgap from 3.13 eV(pure TiO2)to 3.74 eV(1.2 mol%C-doped TiO2).Furthermore,the Ti^3+centers associated with oxygen vacancies are identified using electron paramagnetic resonance spectroscopy(EPR).

关键词： titanium dioxide hydrothermal synthesis defect states bandgap

Facile Synthesis as well as Structural, Raman, Dielectric and Antibacterial Characteristics of Cu Doped ZnO Nanoparticles

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Journal of Materials Science & Technology 2015年第3期31卷 300-304页

作者： Javed Iqbal Nauman Safdar Tariq Jan Muhammad Ismail S.S.Hussain arshad mahmood Shaheen Shahzad Qaisar Mansoor Laboratory of Nanoscience and Technology Department of Physics International Islamic University Institute of Biomedical and Genetic Engineering (IBGE) Nano Devices Labs National Institute of Lasers and Optronics (NILOP) Department of Bioinformatics and Biotechnology International Islamic University

Here, undoped and Cu doped ZnO nanoparticles(NPs) have been prepared by chemical co-precipitation technique. X-ray diffraction(XRD) results reveal that Cu ions are successfully doped into ZnO matrix without altering its wurtzite phase. The single wurtzite phase of ZnO is retained even for 10 wt% Cu doped ZnO sample. It is observed from the electron microscopy results that higher level of Cu doping varies the morphology of ZnO NPs from spherical to flat NPs. Moreover, the particle size is found to increase with the increase in Cu doping level. Raman spectroscopy results further confirm that Cu dopant has not altered the wurtzite structure of ZnO. Impedance spectroscopy results reveal that the dielectric constant and dielectric loss have increasing trend with Cu doping. Cu doping has been found to slightly decrease the bactericidal potency of ZnO nanoparticles.

关键词： Cu doped ZnO Nanoparticles Co-precipitation method

Structural and optical properties of Zn1-xNixTe thin films prepared by electron beam evaporation technique

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Progress in Natural Science:Materials International 2015年第1期25卷 22-28页

作者： arshad mahmood R. Rashid U. Aziz A. Shah Zahid Ali Qaiser Raza Tanveer Ashraf Nano Devices Laboratories National Institute of Lasers and Optronics (NILOP) P.O. Nilore Islamabad Pakistan

Zn1-xNixTe thin films with different composition(x=0.0, 0.05, 0.10, 0.15 and 0.20) were deposited on glass substrate by electron beam evaporation technique followed by its characterization using advanced structural and optical analysis techniques. Structural properties of the prepared thin films were studied by X-ray diffraction(XRD). The XRD patterns revealed that the binary compounds transformed into a ternary compound with cubic structure having preferred orientation along the c-direction with(111) planes. Composition analysis of the films was determined by energy dispersive analysis of X-rays(EDAX) and found to be in agreement with the precursor composition. Optical properties such as extinction coefficient(k) and band gap energy of these films were examined by using a spectroscopic ellipsometer. It was found that the extinction coefficient(k) increased with the addition of Ni content in the alloy. In comparison, the band gap energy was also determined by using transmission spectra and found to be agreed with that of the ellipsometric results. These analyses confirm that the band gap energy decreases with the increase of Ni content in the alloy.

关键词： E-beam evaporation Solar cells,Zn1-xNixTe Ellipsometry Extinction coefficient Band gap energy

PRETTA：A COMPUTER PROGRAM FOR PWR PRESSURIZER’S TRANSIENT THERMODYNAMICS

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Journal of Shanghai Jiaotong university(Science) 2001年第2期6卷 181-186页

作者： arshad mahmood( School of Power and Eng. Shanghai Jiaotong Univ.

A computer program PRETTA “Pressurizer Transient Thermodynamics Analysis” was developed for the prediction of pressurizer under transient conditions. It is based on the solution of the conservation laws of heat and mass applied to the three separate and non equilibrium thermodynamic regions. In the program all of the important thermal-hydraulics phenomena occurring in the pressurizer: stratification of the hot water and incoming cold water, bulk flashing and condensation, wall condensation, and interfacial heat and mass transfer have been considered. The bubble rising and rain-out models are developed to describe bulk flashing and condensation, respectively. To obtain the wall condensation rate, a one-dimensional heat conduction equation is solved by the pivoting method. The presented computer program will predict the pressure-time behavior of a PWR pressurizer during a variety of transients. The results obtained from the proposed mathematical model are in good agreement with available data on the CHASHMA nuclear power plant's pressurizer performance.

关键词： computer program pressurizer pressure transient prediction

Tunability of physical properties of (Cd:Zn)S thin film by Close Space Sublimation Process (CSSP)

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Progress in Natural Science:Materials International 2012年第4期22卷 281-287页

作者： M.Zakria arshad mahmood A.Shah Q.Raza Taj Muhammad khan E.Ahmed National Institute of Lasers and Optronics (NILOP) P.O.NiloreIslamabadPakistan Pakistan Institute of Nuclear Science and Technology (PINSTECH) P.O.NiloreIslamabadPakistan

The present paper reports on a systematic study of the influence of Zn alloying on the structural and optical properties of Cd1-xZnxS thin films. X-ray diffraction study for structural analysis reveals that the two binary compounds have been completely transformed into ternary compound with hexagonal (wurtzite) structure with preferred orientation along c-direction with (002) planes. The optical properties such as optical constants and band gap energy of the films were examined by using spectroscopic ellipsometer and Photospectrometery. It was found that the optical constants (n and k) decrease with the addition of Zn content in the alloy. It was also confirmed that the band gap increases with increasing Zn amount in the alloy and is attributed to quantum size effect in the grain size. Raman spectroscopy analysis shows one dominant phonon band at 326cm-1 , the so-called longitudinal optical (LO) mode for all the alloy composition (x). The appearance of a single phonon band in the Raman spectra established the formation of single phase hexagonal structured Cd1-xZnxS thin film. The LO band is asymmetrically broaden and high frequency shifted due to potential fluctuation caused by the dopant material. The AFM results showed that the surface roughness was decreased with increasing Zn content.

关键词： Cd1-xZnxS Ellipsometry Raman spectroscopy AFM

Photoluminescence and structural analysis of wurtzite(ZnO)1-x(V2O5)x composite

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Journal of Semiconductors 2018年第8期39卷 6-9页

作者： Amjid Iqbal arshad mahmood Q. Raza A. Shah Rashad Rashid Zahid Ali A. Malik U. Aziz National Institute of Laser and Optronics (NILOP) P.O. Nilore-45650 Islamabad Pakistan

This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction(XRD) studies show that(ZnO)(VO)composites have the poly crystalline wurtzite structure of hexagonal Zn O. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E1(TO) and E2(high) Raman modes show that the Zn O still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence(PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of VOup to a certain concentration(x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission.

关键词： Raman modes dislocation density band edge emission (ZnO)_(1-x)(V_2O_5)_x luminescence

EXTENDED SYSTEMS FOR MULTIPLE S-BREAKING TURNING POINTS IN Z_2×Z_2-SYMMETRIC NONLINEAR PROBLEMS

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Numerical Mathematics A Journal of Chinese Universities(English Series) 1995年第2期4卷 119-132页

作者：叶瑞松杨忠华 arshad mahmood Institute of Mathematics Shantou UniversityShantouGuang dOng Department of Mathematics Shanghai University of Science and Department of Mathematics Allama Iqbal Open UniversityH-8ISLAMABADPAKISTAN

Making use of the Z2×Z2 symmetry,we could study the structure near multiple S-treaking turning *** particular,we show that there exist two kinds of singular point path through double S breaking turning points and triple S bieaking turning points,one ts quadratic turning pornt path and one is quadratic pitch fork bifurcation point *** simple regular extended systems to corn pute double and triple S-breaking turning points are *** examples are also

关键词： Z2×Z2 symmetry double S-breaking turning points triple S-breaking turning points tetended systems