Mehnaz Sharmin was born in Rajshahi, Bangladesh on 26 May 1985. She finished her S.S.C. and H.S.C. level studies under Rajshahi Education Board and obtained B. Sc.(Hons) in 2006 (held in 2008) and M. Sc. in Physics in 2007 (held in 2009) securing First class in both the examination from the Department of Physics, University of Dhaka, Bangladesh. She performed her thesis work on p-type GaAs and p-type Si. She worked as a Lecturer in Physics at Primeasia University from 6 Feb 2011 to 1 Oct 2011 and joined as a Lecturer in the Department of Physics, Bangladesh University of Engineering and Technology (BUET), Dhaka, on 2 October 2011. She completed her M. Phil. in Physics on 29 July 2015 from the Department of Physics, BUET. She enrolled for Ph. D. in Physics program at Department of Physics, BUET in October-2015 postgraduate session and is currently doing her thesis work. She joined as an Assistant Professor in the Department of Physics, BUET on 2 April 2016. Her research interest is in the field of Materials Science, especially on synthesis and characterization of semiconducting and polymer thin films.
University of Dhaka
University of Dhaka
Bangladesh University of Engineering and Technology
Centre for Nano Science and Engineering, IISc, Bengaluru
Awarded by Bangabandhu Science and Technology Fellowship Trust.
Awarded by University of Dhaka.
General grade scholarship awarded by Board of Intermediate and Secondary Education, Rajshahi.
General grade scholarship awarded by Board of Intermediate and Secondary Education, Rajshahi.
Talent pool scholarship, Santahar Harvey Girls' High School, Thana: Adamdighi, District: Bogra, Division: Rajshahi
Talent pool scholarship, S.M. I Academy, Thana: Adamdighi, District: Bogra, Divsion: Rajshahi.
Modifications in structure, surface morphology, optical and electrical properties of ZnO thin films with low boron doping
Boron doped zinc oxide (ZnO:B) thin films with low B concentration, varied between 0.50 and 1.50 atomic percentages (at%) are prepared at substrate temperatures (TS) between 300 and 450 °C using spray pyrolysis technique. Polycrystalline wurtzite structure is observed in the X-ray diffraction patterns of ZnO:B thin films, where (002) is the predominant peak. Texture coefficient corresponding to (002) peak increases with B concentration from 0.50 to 1.00 at%. Crystallite size is found between 22 and 64 nm. Nanofibrous surface morphology is observed in the field emission scanning electron microscopic images of ZnO:B thin films. The average nanofiber thickness value varies from 198 to 498 nm. Atomic force microscopic images show the nanotip-like topology of ZnO:B thin films. The average surface roughnesses of the films are found in the range of 2.99–12.45 nm. ZnO:B thin films are found to be highly transparent between visible to near infrared region of the electromagnetic spectrum. The highest transmittance of 87% is noticed for the 1.00 at% ZnO:B thin film prepared at the TS of 450 °C. Optical band gaps of ZnO:B thin films vary between 3.15 and 3.31 eV. 1.00 at% ZnO:B thin films prepared at various TS show lower values of the band gap, refractive index and extinction coefficient at the photon wavelength of 750 nm. Electrical resistivity of ZnO:B thin films are found to be between 0.25 × 104 and 1.39 × 104 Ω m. 1.00 at% ZnO:B thin films prepared at various TS show less electrical resistivity. Arrhenius plots of ZnO:B thin films prepared at various TS show two conduction regions and activation energies of ZnO:B thin films are higher for the films deposited at lower TS. ZnO:B thin films show n-type conductivity and carrier concentration increases with the increase of B concentration.
Influence of Substrate Temperature on the Properties of Spray Deposited Nanofibrous Zinc Oxide Thin Films
Zinc oxide (ZnO) thin films were deposited onto glass substrates by a spray pyrolysis technique at the substrate temperatures (T S) between 250 and 500 °C. T S was observed to be one of the key parameters to influence the structural, surface morphological, optical and transport properties of ZnO thin films. X-ray diffraction patterns of the ZnO thin films showed polycrystalline hexagonal wurtzite structure and the preferred orientation was along (002) plane which got more prominent with the increase of T S. Field emission scanning electron microscopy of ZnO thin films showed the existence of nanofibers in the films with the average thickness ranging from 308 to 540 nm. Atomic force microscopy revealed that roughness of the ZnO thin film increased at higher T S. ZnO thin films were highly transparent in the visible to near infrared region with the maximum transmittance of 89% and the optical band gap was found from 3.23 to 3.31 eV. ZnO thin films showed n-type conductivity with the carrier concentrations ranging between 1019 and 1020 cm− 3. ZnO thin film deposited at the T S of 400 °C showed the highest mobility, highest carrier concentration and less resistivity.
Structural, Morphological, Optical and Electrical Properties of Spray Deposited Zinc Doped Copper Oxide Thin Films
Nanostructured spray deposited zinc (Zn) doped copper oxide (CuO) thin films were characterized by employing X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy. XRD patterns of CuO and Zn doped CuO thin films indicated monoclinic structure with the preferred orientation along (1¯11)(1¯11) plane. Maximum value of crystallite size is found about 28.24 nm for 5 at% Zn doped CuO thin film. In FESEM images, nanoparticles were observed around the nucleation center. EDX analysis confirms the presence of all component elements in CuO and Zn doped CuO thin films. Analysis by AFM of CuO and Zn doped CuO thin films figured out decrease of surface roughness due to Zn doping. UV–Vis–NIR spectroscopy showed that CuO and Zn doped CuO thin films are highly transparent in the NIR region. Optical band gap of CuO thin films decreased with substrate temperature and that of Zn doped CuO thin films increased with Zn concentration. Refractive index of CuO and Zn doped CuO thin films raised with photon wavelength and became constant in the NIR region. 5 at% Zn doped CuO thin film showed the highest optical conductivity and the lowest electrical resistivity at room temperature.
Structural and Optical Characterization of Magnesium Doped Zinc Oxide Thin Films Deposited by Spray Pyrolysis
Pure and magnesium (Mg) doped zinc oxide (ZnO) thin films were prepared onto clean glass substrate by spray pyrolysis (SP) technique at the
substrate temperature of 300°C. Various optical parameters such as absorption co-efficient, band gap energy, refractive index, extinction coefficient
of the thin films were studied using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300-2500 nm. Optical band
gap increased from 3.24 to 3.46 eV with the increase of Mg concentration from 0 to 40%. Transmittance and refractive index of the Mg doped
ZnO thin films decreased due to the increase of Mg concentration. The EDX spectra confirmed the increase of Mg and consequent reduction in
Zn content in the Mg doped ZnO thin films. Pure and Mg- doped ZnO films were annealed at 425°C for 1 hour. X-ray diffraction (XRD) study
of the annealed films showed hexagonal type of polycry-stalline structure with the preferred orientation along (101) plane with some other
peaks (100), (002), (102), (110), (103) and (112). From the XRD patterns it was found that grain size decreased from 63.45 to 36.56 nm, lattice
constant and c remained almost constant with Mg doping concentration.
Structure, Morphology and Opto-Electrical Properties of Nanostructured Indium Doped SnO2 Thin Films Deposited by Thermal Evaporation
Indium doped Tin oxide (SnO2: In) thin films of various thicknesses (200-600 nm) with fixed 2% indium (In) concentration were prepared by thermal evaporation method onto glass substrates under high vacuum (10-6 Torr). As deposited films were vacuum annealed at 200o C for 60 minutes. The structure, optical, electrical and morphology properties of SnO2: In thin films were investigated as a function of film thickness. The XRD analysis revealed that films were polycrystalline in nature with a tetragonal structure having (110) plane as the preferred orientation. The average crystalline size increased from 34.8 to 51.25 nm with increase of film thicknesses. The surface morphology of the doped films was obtained by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM). Optical transmittance was obtained from a double beam UV-Vis- NIR spectrophotometer. Maximum transmittance varied from 65-76% in the visible range of the spectrum. Optical band gap (Eg) varied between 2.89 and 3.20 eV. The resistivity of SnO2: In thin films was as high as 105 Ω-cm. Activation energy of the films were found to be 0.18 to 0.47 eV for 300-600 nm film thicknesses. Due to high optical band gap and high electrical resistivity, these nanostructured films can be used in optoelectronic devices especially as opto-insulator.
Effect of Doping Concentration on the Optical Properties of Indium-Doped Gallium Arsenide Thin Films
Effects of indium doping (concentration 0.2, 0.3 and 0.4%) on the optical properties of GaAs thin films were studied. Thin films of 600 nm were grown onto chemically and ultrasonically cleaned glass substrate by thermal evaporation method in high vacuum (~10-4 Pa) at 50°C fixed substrate temperature. The samples were annealed for 15 minutes at a fixed temperature of 200°C. The thicknesses of films were being measured in situ by a quartz crystal thickness monitor during deposition. The transmittance and reflectance data were found using UV-VIS-NIR spectrophotometer in the photon wavelength range of 310 ~ 2500 nm. These data were utilized to compute the absorption coefficient, refractive index, extinction co-efficient and band gap energy of the studied films. Here transmittance was found 78 for 0.2% indium doping concentration. The band gap energy decreased with the increase of doping concentration.
Optical and Structural Properties of p-Type Silicon
Electrical, optical and structural properties of p-type single crystal silicon were investigated in this work. Electrical conductivity of p-type silicon was measured in the temperature ranges 190 - 300 K. The acceptor ionization energy (E A) was between 0.047 - 0.051 eV.
Photoconductivity of the material was investigated by varying sample current, light intensity and temperature at a constant chopping frequency of 45.60 Hz. Absorption co-efficient () of the material was calculated from optical transmittance and reflectance measurements
at room temperature (300 K) in the wavelength range of 300 -2500 nm. The direct optical band gap energy was found between 2.10 - 2.20 eV and the indirect optical band gap energy was found between 0.95 – 1.0 eV. The lattice parameter (a) was found to be 5.419Å from X-ray diffraction method (XRD).
STRUCTURAL AND OPTICAL CHARACTERIZATION OF VACUUM EVAPORATED ZINC SELENIDE THIN FILMS
Optical and structural characterization of Zinc Selenide (ZnSe) thin films (thickness ranging between 200 - 500 nm) prepared by vacuum (~10-6 Torr) evaporation method were investigated. The thin films were deposited with varying substrate temperature in the range 373 - 573K. Optical measurements were carried out with UV-VIS-NIR spectrophotometer with photon wavelength ranging between 300-2500 nm. The absorption coefficient, energy band gap, refractive index and extinction coefficient were determined using transmission and reflection spectra at the same wavelength range. The dependence of absorption coefficient in the photon energy had been determined. Analysis showed that direct transition occured with band gap energies ranges from 2.6 eV to 2.9 eV. Refractive indices and extinction coefficients were evaluated in the above spectral range. For structural properties, 300nm films were deposited with varying substrate temperatures and were vacuum annealed in situ at 373 K for one hour. The X- ray diffraction (XRD) patterns showed polycrystalline nature of films having cubic (Zinc blende) structure. The most preferential orientation is along  direction for all deposited films together with other abundant planes  and . Structural parameters such as lattice constant, grain size, internal stress, microstrain, dislocation density were calculated. The value of lattice constant was estimated to be5.660 Å to 5.761 Å.. The grain sizes were calculated to be which ranges between 266 Å to 384 Å. With the increase of substrate temperature the average grain size of the ZnSe films increases, asrevealed from the XRD studies.
OPTICAL AND TRANSPORT PROPERTIES OF p-TYPE GaAs
Electrical properties such as electrical resistivity, Hall coefficient, Hall mobility, carrier concentration of p-type GaAs samples were studied at room temperature (300 K). Resistivity was found to be of the order of 5.6 × 10-3Ω-cm. The Hall coefficient (RH) was calculated to be 7.69 × 10-1cm3/C and Hall mobility (μH) was found to be 131cm2/V-s at room temperature from Hall effect measurements. Carrier concentration was estimated to be 8.12 × 1018/cm3 and the Fermi level was calculated directly from carrier density data which was 0.33 eV. Photoconductivity measurements were carried on by varying sample current, light intensity and temperature at constant chopping frequency 45.60 Hz in all the cases mentioned above. It was observed that within the range of sample current 0.1 - 0.25mA photoconductivity remains almost constant at room temperature 300K and it was found to be varying non-linearly with light intensity within the range 37 - 12780 lux. Photoconductivity was observed to be increasing linearly with temperature between 308 and 428 K. Absorption coefficient (α) of the samples has been studied with variation of wavelength (300 - 2500 nm). The value of optical band gap energy was calculated between 1.34 and 1.41eV for the material from the graph of (αhν) 2 plotted against photon energy. The value of lattice parameter (a) was found to be 5.651Å by implying X-ray diffraction method (XRD).
The Effect of Al on the Structural, Morphological, Topological, Optical, Transport and Magnetic Properties of Fe2O3 Thin Films
Ferric oxide (Fe2O3) is a large band gap material having the versatility of applications in various devices. Aluminum (Al) is a popular dopant used for Fe2O3 to modify the structure and properties of the material. In this work, Al doped Fe2O3 thin films were prepared onto clean glass substrates at the substrate temperature of 350 °C with 0, 2, 4, 6, 8 and 10 at% Al concentration by spray pyrolysis technique. Field emission scanning electron microscopy and atomic force microscopy images showed the presence of nanoparticle agglomerates and regular distribution of pores covering the scanned areas of Al doped Fe2O3 thin films. X-ray diffraction patterns of Al doped Fe2O3 thin films showed polycrystalline Corundum structure with a predominant orientation along (104) plane, which disappeared at 10 at% Al doping. Raman spectroscopy of Fe2O3 thin films suggested the presence of pure α-Fe2O3 or hematite phases in the film. Optical transmittance of Al doped Fe2O3 thin films increased with the rise of Al concentration up to 6 at% and the maximum transmittance was found to be 87 %. The optical band gap increased from 2.19 to 2.98 eV with the increment of Al concentration up to 6 at%. The room temperature electrical resistivity of Al doped Fe2O3 thin films was found between 5.90 x 105 and 8.92 x 105 Ω-cm. Al doped Fe2O3 thin films showed n-type electrical conductivity and carrier concentration in the order of ~ 1017 cm-3 in Hall effect measurements. Ferromagnetic properties of Fe2O3 thin films were softened upon Al doping. Homogeneous surface, regular distribution of pores, better crystalline structure, high transparency, wide band gap, n-type conductivity and ferromagnetic behavior of Al doped Fe2O3 thin films recommends its suitability in optoelectronic devices.
Influence of Mg doping on The Electrical Transport Mechanism, Optical and Magnetic Properties of Fe2O3 Thin Films
Ferric oxide (Fe2O3) is an intrinsic n-type semiconductor having a wide band gap and environment friendly nature. Magnesium (Mg) is one of the p-type dopants used to enhance electrical conductivity of Fe2O3. In this work, Mg doped Fe2O3 thin films were synthesized with 0, 2, 4, 6, 8 and 10 at% Mg concentrations by a simple spray pyrolysis technique. The surface of the films comprised of uniformly distributed nanoparticles along with some cubic shaped nanocrystals, which were found up to 6 at% Mg doping. Corundum structure with the favored orientation along (104) plane is found in the X-ray diffraction patterns of Mg doped Fe2O3 thin films. Raman spectra of Fe2O3 thin films showed the existence of pure α-Fe2O3 or hematite phases in the film, which mostly disappeared after 10 at% Mg doping. Transmittance of Mg doped Fe2O3 thin films increased with the rise of Mg concentration. The maximum transmittance was about 83 %, found in 10 at% Mg doped Fe2O3 thin films. The optical band gap widened from 2.14 to 2.75 eV with the increment of Mg concentration up to 8 at%. The room temperature electrical resistivity of Mg doped Fe2O3 thin films increased from 4.9 × 105 - 12.2 × 105 Ω-cm with the increase of Mg concentration. The n-type conductivity of Fe2O3 thin film is changed to p-type above 6 at% Mg doping and carrier mobility decreased with the raise of Mg concentration. The hysteresis loop of Mg doped Fe2O3 thin films recommended that Mg doping softened the ferromagnetic properties of Fe2O3. The unique surface morphology, better crystallinity, high transparency, wide band gap, p-type conductivity and ferromagnetic behavior of Mg doped Fe2O3 thin films recommended its versatile use in manufacturing optoelectronic devices.
Structural, Morphological, Optical and Electrical Properties of ZnO/SnO2 Thin Films Synthesized by Thermal Spray Pyrolysis Technique for Optoelectronic Applications
Effect of Al Doping on Physical Properties of Sprayed α-Fe2O3 Nanoparticle Thin Films Synthesized for Optoelectronic Applications
Investigation of Structural, Morphological, Optical and Electrical Properties of Spray Synthesized Fe2O3 Thin Films for Optoelectronic Applications
The Influence of Al Doping on the Physical Properties of Fe2O3 Nanoparticle Synthesized by Chemical Spray Pyrolysis for Optoelectronic Applications
Structural, Morphological, Optical and Electrical Properties of Al:Fe2O3 Nanoparticle Thin Films Synthesized for Gas Sensing Applications,
Nanostructure and Opto-electrical Properties of Temperature Dependent Indium Doped Tin Oxide Thin Films
Sol-gel Spin Coating: A Promising Technique for Preparation of Multilayer Metal Oxide Thin Films for Optoelectronic Applications
Versatility of Spray Pyrolysis Technique for Synthesis of Multilayer Metal Oxide Thin Films
Wide Band Gap and High Optical Transparency in Mg Doped Fe2O3 Thin Films: A Suitable Candidate for Optoelectronic Devices
Effect of Mg Incorporation on the Structural, Morphological, Optical, Electrical and Magnetic Properties of Ferric Oxide Nanoparticle Thin Films
Role of Substrate Temperature on the Opto-electrical Properties of Indium Doped Tin Oxide Thin Films
Characterization of Spray Pyrolized CuO Thin Films Depostied at Various Substrate Temperatures
Investigation of Structure, Morphology, Optical and Electrical Properties of Sprayed ZnO Thin Films Deposited at Various Substrate Temperatures
Effect of Zinc Doping on Structure and Properties of CuO Thin Films Synthesized by Spray Pyrolysis Technique
Effect of Substrate Temperature on Structural, Optical and Electrical Properties of Vacuum Evaporated Indium Doped Tin Oxide Thin Films
Opto-Electrical Properties of Nanostructured Indium Doped Tin Oxide Vacuum Evaporated Thin Films
Structural and Surface Morphological Properties of Spray Deposited CuO and Zinc Doped CuO Thin Films
Influence of Boron Doping on The Structural Properties of ZnO Thin Films Deposited by Spray Pyrolysis Technique
Electrical, Optical and Structural Properties of p-Type Silicon
Effect of Substrate Temperature on the Optical Properties of Vacuum Evaporated CdTe Thin Films
Substrate Temperature Dependent Structural Properties of Thermal Evaporated ZnSe Thin Films
Electrical and Optical Properties of p-Type GaAs
Electrical conductivity of p-type single crystal Gallium Arsenide was measured in the temperature ranges 170K-300K. It was found that electrical conductivity decreases with the increase of temperature. The logarithmic graph of conductivity (lnσ) versus the inverse of temperature (in K-1) was found to be almost linear in ranges 185K-195K (below room temperature). The acceptor ionization energy (ΔEA) obtained from the graphs was 0.0308 eV. Photoconductivity of the same samples was also measured under different conditions. The effect of varying sample current (I), light intensity (IL) and temperature (T in K) on photoconductivity at a constant chopping frequency 45.60 Hz were investigated. It has been seen that photoconductivity increases nonlinearly with light intensity and it increases linearly with temperature. Absorption coefficient (α) of the same samples was also measured at the room temperature within the wavelength range 300 nm-2500 nm and the optical band gap energy was calculated to be 1.425 eV from the plot of (αhν) 2 versus photon energy (E).
Mehnaz does her research in Experimental Physics, Solid State Physics and Materials Science. Her current project is 'Synthesis of Oxide thin films for Biomedical and Optoelectronic Applications by Spray Pyrolysis Technique' She is recently working on gas sensing material.