Dr. 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 joined as an Assistant Professor in the Department of Physics, BUET on 2 April 2016. She completed her for Ph. D Thesis from Department of Physics, BUET on 7 December 2019. She joined as an Associate Professor in the Department of Physics, BUET on 8 September 2020. Her research interest is in the field of Materials Science, especially on synthesis and characterization of semiconducting and polymer thin films. She is currently working on the investigation of gas sensing and humidity sensing properties of metal oxide thin films and nanomaterials. She is also involved in the research related to crystal growth and characterization.
M. S. Thesis: Study of Electrical and Optical Properties of p-Type Single Crystal Gallium Arsenide and p-Type Silicon
M. Phil. Thesis: Characterization of Boron Doped Zinc Oxide Thin Films Prepared by Spray Pyrolysis Deposition Technique
Ph. D. Thesis: SYNTHESIS AND CHARACTERIZATION OF Mg AND Al DOPED Fe2O3 THIN FILMS FOR GAS SENSING APPLICATION
Bangladesh University of Engineering and Technology
Bangladesh University of Engineering and Technology
University of Dhaka
University of Dhaka
Centre for Nano Science and Engineering, IISc, Bengaluru, India
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.
International conference on Physics-2016 organized by Bangladesh Physical Society
4th International Conference on STRUCTURE, PROCESSING AND PROPERTIES OF MATERIALS 2018
7th Conference of Bangladesh Crystallographic Association organized by Bangladesh Crystallographic Association
National Conference on Physics – 2019 organized by Bangladesh Physical Society
International Conference on Physics - 2020 organized by Bangladesh Physical Society
Influence of substrate temperature on the morphological, structural, optical and electrical properties of nanostructured CuO thin films synthesized by spray pyrolysis technique
Nanostructured copper oxide (CuO) thin films have been synthesized onto the glass substrates from aqueous solutions of copper (II) acetate monohydrate precursor salt by a cost effective spray pyrolysis technique at various substrate temperatures between 473 and 673 K. The effects of varying substrate temperature on the structure, surface morphology, optical and electrical properties of the synthesized CuO thin films were studied. Scanning Electron Microscopic (SEM) images revealed agglomerated nanoparticles on the surface of CuO thin films. X-Ray Diffraction (XRD) analysis revealed monoclinic structure with the predominant (̅111) orientation of the synthesized films. Crystallite size increased (9.15 to 10.29 nm) with the increase of substrate temperature. In UV-vis-NIR spectroscopy, CuO thin films showed higher transparency in the NIR region. An optical band gap of CuO thin film was found in the range of 2.04 - 2.49 eV. Transmittance and band gap decreased with the increase of substrate temperature up to 573 K and found to increase at 673 K. On the other hand, extinction coefficient and refractive index increased with the increase of substrate temperature up to 573 K and decreased afterwards. Electrical resistivity of CuO thin films was found in the range 1.16 ×103 - 4.61 ×103 Ω-m and decreased with the increment of the substrate temperature up to 573 K. Activation energies of CuO thin film were found in the range 0.08 - 0.57 eV. Hence, we report the influence of substrate temperature for the synthesis of nanostructured CuO thin films, best fit for optoelectronic applications.
Effect of M (Ni, Cu, Zn) doping on the structural, electronic, optical, and thermal properties of CdI2: DFT based theoretical studies
Structural, electronic, optical, and thermal properties of undoped and metal,M(Ni, Cu, and Zn), doped cadmium iodide (CdI2) were studied using a generalized gradient approximation of density functional theory. Lattice constants found from the theoretical studies of the structure of the undoped and doped CdI2 are in good agreement with those found in the available experimental and theoretical investigations. A strong mixing of I 5p and M 3d states is found after the doping of 3d M in CdI2, which alters the bandgap from positive to negative. Among all M (Ni, Cu, and Zn), Ni doped CdI2 with a narrow negative bandgap evolve the quantum dot level. Due to interactions between the Cd 4d and M 3d states, the measured optical and thermal properties of the doped system assessed with pure CdI2 indicate unusual behaviors, which suggest that the material can be used in different nano-electronic and electrochemical applications and in biological levels such as detection
of COVID-19 pathogens.
Undoped and manganese (Mn)-doped zinc oxide (ZnO) thin films have been deposited onto glass substrates at 300 ∘C using a low cost spray pyrolysis technique. Structural, optical and electrical properties of the as-deposited films have been investigated. Scanning electron microscopy images show the existence of clusters with well-defined nucleation centers consisting of highly dense ganglia-like fibers over a large area around the nucleation center. Chemical compositions of the ZnO and Mn-doped ZnO thin films are studied by using energy dispersive X-ray (EDX) analysis. X-ray diffraction spectra depict that the films have polycrystalline wurtzite structure. The average crystallite sizes are calculated in the range of 8 -16 nm by Williamson–Hall method and found in good agreement with Scherer method. Optical transmittance of the films is about 80% in the visible region. Bandgap energy is tuned to 2.83 eV from 3.10 eV with increasing Mn doping. Electrical resistivity at room-temperature decreases significantly with increasing Mn doping as well as increasing temperature from 300–440 K. The activation energies in the temperature ranges 300–350 K and 350 - 440 K are found to be in the range of 0.25–0.16 eV and 0.35–0.59 eV, respectively. Hall Effect measurements show that the thin films have negative Hall co-efficient indicating nn-type conductivity at room-temperature. Carrier concentration is found to be of the order of 1018 cm−3.
Influence of Ni doping on the morphological, structural, optical and electrical properties of CuO thin films deposited via a spray pyrolysis
Nanostructured copper oxide (CuO) and Nickel (Ni)-doped CuO thin films with different concentrations of Ni ranging from 2 to 8 at.% were synthesized onto a plain glass substrate at the substrate temperature, 350 ◦C by a thermal spray pyrolysis technique. Field emission scanning electron microscopy (FESEM) analysis of CuO and Nidoped CuO thin films detected the closely spaced rock-like nanostructures, evenly distributed on the film surfaces. The average particle sizes of CuO and Ni-doped CuO thin films were calculated from the FESEM and found between 260 and 63 nm. Energy-dispersive X-ray analysis revealed that CuO and Ni-doped CuO thin films were stoichiometric and typically comprised of Cu, O, and Ni. X-ray diffraction analysis showed the monoclinic
structure of the films with the most preferred orientation plane (111) along with the (111), (202) and (022) crystalline planes. The maximum crystallite size was found at about 81 nm for 6 at% Ni-doped CuO thin film. CuO film showed an optical transmittance of about 33% in the visible-NIR region. Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. With the rise of Ni content in CuO thin films, the optical bandgap gradually increased from 2.28 to 2.78 eV. Resistivity raised from 9.28 × 103 to 49.01 × 103 Ω-cm with the increase of the amount of Ni.
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 technique. As-deposited film surfaces comprised of agglomerated spherical nanoparticles and a semi-spongy porous structure for 4 at% Mn doping. Energy dispersive analysis of X-rays confirmed the chemical composition of the films. X-ray diffraction spectra showed a polycrystalline monoclinic structure with the predominance of the ( 11) peak. Optical 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, respectively. Refractive index and static dielectric constants were computed from the optical spectra. Electrical resistivity of CuO and Mn-doped CuO (Mn:CuO) thin films was found in the range from 10.5 to 28.6 Ω·cm. The 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 films. Carrier concentration and mobility were found in the orders of 1017 cm–3 and 10–1 cm2 /(V·s), respectively. The Hall coefficient was found to be between 9.9 and 29.8 cm3 /C. The above results suggest the suitability of Mn:CuO thin films in optoelectronic applications.
CuO thin film has a wide variety of potential applications due to distinctive optical properties and native p-type electrical conductivity. The weak p-type electrical conductivity of CuO thin film can be modified via doping suitable elements into it. In this work, we acquired n-type electrical conductivity in the CuO thin film by cadmium (Cd) doping for the first time. Pristine and Cd doped CuO thin films are fabricated at 325 ºC using a simple spray pyrolysis technique with different doping concentrations (i.e x = 0.00, 0.02, 0.04, 0.06 and 0.08). X-ray diffraction (XRD) spectra of Cd doped CuO thin films match to the polycrystalline with a monoclinic structure and no peak corresponding to Cd impurity or non-stoichiometric phases are found in the XRD pattern. Based on the XRD patterns, the average crystallite size is obtained from 15.12 to 30.53 nm. Furthermore, a closely-spaced nanoparticle is confirmed by the field emission scanning electron microscopes (FESEM). The energy dispersive analysis X-ray spectra (EDAX) demonstrate the effect of substitutions of Cu2+ ions by Cd2+ ions in the pristine CuO lattice network. Hall Effect measurements reveal that the p-type conductivity of CuO thin films alters to n-type as a result of Cd doping. The electrical resistivity of Cd doped CuO thin films upraise with the reduction of carrier concentration and increment of carrier mobility with the increase of Cd concentration in the films. An increment of transmittance and broadening of the blue shift optical band gap is possessed in CuO thin films via Cd doping and found as a promising material for a wide range of optoelectronic device applications.
Role of Zn dopants on the surface morphology, chemical structure and DC electrical transport properties of nanostructured p-type CuO thin films
This paper is based on the studies of surface morphology, chemical structure and DC electrical transport properties of zinc (Zn) doped copper oxide (CuO:Zn) thin films synthesized by spray pyrolysis technique. CuO and CuO:Zn thin films were deposited onto ultrasonically cleaned microscope glass substrates at the substrate temperature 423 K. Zn concentration (conc.) in CuO:Zn thin films was varied from 1 to 6 at%. In field emission scanning electron microscopic images of CuO:Zn thin films nanostructures are observed around the nucleation center. The maximum average particle size is found about 18 nm for 5 at% Zn doped CuO:Zn thin film. X-ray photoelectron spectroscopy confirms the chemical structure and composition of the films. Activation energy of CuO:Zn thin films in the temperature range 350 - 423 K increases from 0.17 - 0.39 eV with the rise of Zn conc. in the range of 2 - 6 at%. DC electrical resistivity of CuO:Zn thin films is found in the order of 104 Ω-cm. Hall effect measurements confirms the p-type conductivity of CuO:Zn thin films with the carrier conc. in the order of 1018 cm-3. Carrier mobility of 5 at% CuO:Zn thin film is as high as 84.83 cm2 V-1 s-1.
Structural, optical and electronic properties of CuO and Zn doped CuO: DFT based First-principles calculations
Density functional theory based First-principles calculations have been performed to investigate the structural, optical and electronic properties of CuO and Zn doped CuO and compared with experimental results. Calculations are demonstrated by Cambridge Serial Total Energy Package. Calculated values of lattice parameters matched 80% with experimental data of CuO and for Zn doped CuO, there was a 55% match. Figures of electronic band structure, TDOS and PDOS have been computed from the electronic structure of CuO and Zn doped CuO. Significant transition occurs in band gap after Zn doping. Optical properties showed that CuO and Zn doped CuO were transparent, having a small energy gap and maximum reflectivity at infrared region. The real part of refractive index was higher at lower energy region and imaginary part of refractive index was zero at 28 eV photon energy. The calculated value of band gap was in good agreement with the experimental value.
Band Gap Tuning, n-type to p-type Transition and Ferrimagnetic Properties of Mg Doped α-Fe2O3 Nanostructured Thin Films
Fe2O3 thin films have a wide range of applications in gas sensing, biosensing, optoelectronics, spintronics, etc. In this paper, pure and Mg doped Fe2O3 thin films are prepared onto glass substrates by a simple chemical spray pyrolysis technique. Cubic and rectangular cuboid shaped nanocrystals are observed in the FESEM images of the films up to 6 at% Mg concentration. XRD patterns of Mg doped Fe2O3 thin films match with the corundum structure showing the predominance of (104) orientation. Crystallite size increases from 29 to 87 nm with the increase of Mg concentration in the films. Raman spectroscopy indicates that Mg doped Fe2O3 thin films consist of only pure hematite or α-Fe2O3 phases. Chemical composition of the films are confirmed by energy dispersive X-ray analysis. Optical transmittance and band gap rise with the uplift of Mg concentrations. The maximum transmittance is found to be 83% for 10 at% Mg doped Fe2O3 thin film. In the photoluminescence spectroscopy, green emission is dominant up to 6 at% Mg doping and dominance of blue emission is observed in the 8 and 10 at% Mg doped Fe2O3 thin films. The n-type electrical conductivity of Fe2O3 changed into p-type for 6, 8 and 10 at% Mg doping. Electrical resistivity is found in the order of 105 Ω-cm which rises with Mg concentration. Pure Fe2O3 thin film shows ferromagnetic nature, whereas Mg doped Fe2O3 thin films show ferrimagnetic nature at room temperature. Mg doped Fe2O3 thin films may be suitable for sensing purposes and high power devices.
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 Al Doping on the Structure and Properties of Fe2O3 Thin Films: High Transparency, Wide Band Gap, Ferromagnetic Behavior
This paper is based on detailed study of structural, morphological, optical, transport and magnetic properties of aluminum (Al) doped ferric oxide (Fe2O3) thin films deposited onto glass substrates at 350 ºC by spray pyrolysis technique. Al concentration was varied from 0 to 10 atomic percentages (at%). The X-ray diffraction patterns of Al doped Fe2O3 thin films showed the corundum structure with the predominant (104) peak. In scanning electron micrographs, the surfaces of the Al doped Fe2O3 thin films were observed to be formed of nanoparticles. Al doped Fe2O3 thin films were transparent in visible to near infrared region. Transmittance and optical band gap of Al doped Fe2O3 thin films increased with the rise of Al concentration up to 6 at% and then decreased for the 8 and 10 at% Al concentrations. Al doped Fe2O3 thin films showed n-type electrical conductivity with high mobility and Hall coefficient. Electrical resistivity of Al doped Fe2O3 thin films varied from 5.67 105 to 8.92 105 Ω-cm and carrier concentration was found between 1.56 1017 and 8.64 1017 cm-3. Hysteresis loops of Al doped Fe2O3 thin films recorded at room temperature matched the nature of soft ferromagnetic materials and the saturation magnetization decreased with Al concentration in Fe2O3 thin films.
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).
Investigation of structural, optical and electrical properties of calcium substituted barium titanate thin films for various optoelectronic applications
Thin films of Ba1-xCaxTiO3 with various calcium (Ca) contents (x = 0, 2, 4, 6, and 8 at.%) were successfully synthesized onto the glass substrate by a thermal spray pyrolysis technique. Field emission scanning electron microscopy images revealed that the average grain size varies from 1.38 to 4.95 μm. The presence of all the elements was confirmed by energy dispersive X-ray analysis. The X-ray diffraction analysis confirmed the formation of the hexagonal phase of as-deposited samples. The crystallite sizes were found to reduce from 189 to 116 nm as a result of Ca doping. Atomic force microscopy indicated surface roughness varies from 86 to 187 nm. The 2 at.% Ca doped thin films exhibited transparency of about 47%. From the UV-visible spectra, an increment of optical conductivity is calculated from 2.9 to 7.3 s-1. The optical band gap varies from 3.90 to 3.80 eV with the increase of Ca substitution. The electrical resistivity of the films decreased from 11.95×103 to 7.54×103 Ωm with increasing Ca content. Nanostructured thin films with uniform surfaces and well-distributed grains are grown in the present research. The results obtained from Ba1-xCaxTiO3 thin films could be useful for various optoelectronic applications.
Structural and optical properties of manganese doped nickel oxide thin films
Nickel oxide (NiO) is a p-type metal oxide semiconductor with a band gap in the range of 3.60 – 4.00 eV. In this work, a simple and low-cost spray pyrolysis technique was used for the deposition of NiO thin films with 0, 1, 2, 3, and 4 at% manganese (Mn) concentrations. In the X-ray diffraction (XRD) analysis of the films, peaks correspond to (002), (111), (200), (220), (311) and (222) crystalline planes appeared. The films exhibited face-centered cubic (fcc) structure with the predominance of (111) peak. The intensity of (111) peak maximized for 1 at% Mn doping in NiO indicating improvement in crystallinity in comparison with NiO film. No other peaks corresponding to Mn impurities were found in the XRD analysis. No further improvement was found in crystalline structure upon 4 at% Mn doping. The optical properties of the deposited films were studied in the spectral range 300 – 1100 nm using a UV-vis spectrophotometer. NiO and Mn-doped NiO films were transparent in the visible and near infrared region. The transmittance of the film increased significantly with Mn doping. The transmittance of 2 at% Mn doped NiO film reached a maximum of about 87%, which is much higher than the maximum transmittance of NiO film. The optical band gap of the films was in the range of 3.17- 4.03 eV. The maximum band gap was found for 2 at% Mn doped NiO thin film. The increase of transparency and optical band gap indicates the applicability of this material in the field of optoelectronics devices.
Modifications in structure and optical-electrical properties of cupric oxide thin films doped with manganese
Cupric oxide (CuO), an environment friendly p-type transition metal oxide was studied in undoped and doped nanostructured forms by researchers for several potential applications such as solar cells, transistors, gas sensors, etc. In this work, manganese (Mn) doped CuO thin films were prepared onto glass substrates at the substrate temperature of 523 K using spray pyrolysis technique. The amount of Mn concentration was varied from 0 to 6 at% in CuO thin films. The prepared samples were annealed at 723 K in the air for 1 hour. The film surface was observed to be comprised of aggregations of nanoparticles in the Scanning Electron Microscopic images. Elemental composition of the films was confirmed by Energy Dispersive X-ray analysis. The as-deposited films showed amorphous structure, whereas the annealed films showed monoclinic structure with the preferential orientation along (
Zinc oxide (ZnO) and boron (B) doped ZnO thin films were deposited onto microscope glass slides by spray pyrolysis technique. The amount of B doping was varied between 1 and 5 at% in ZnO thin films. An evolution in surface morphology from nanofibrous to nanoflakes pattern has been observed in B doped ZnO thin films by field emission scanning electron and atomic force microscopies images. The chemical structure and composition of the films are confirmed by Energy dispersive X-ray and X-ray photoelectron spectroscopy analyses. The films show a polycrystalline wurtzite structure with the preferential (002) orientation in X-ray diffraction analysis. Crystallite size is found in the range of 18 to 32 nm. The films are transparent in the Vis-NIR region and the optical band gap is found between 3.20 and 3.29 eV. Direct current electrical resistivity and carrier concentration of B doped ZnO thin films are found in the order 10-2 Ω-cm and 1020 cm-3, respectively. The films show a change of majority charge carriers from n-type to p-type for 5 at% B doping. The highest carrier mobility is found to be 1.44 cm2V-1s-1 for 1 at% B doped ZnO thin film. The results of various investigations presented in the paper suggest the suitability of B doped ZnO thin films in optoelectronic applications.
Studies on the Topographical and Photoluminescence Properties of Mg Doped Fe2O3 Thin Films
Magnesium (Mg) doped Ferric oxide (Fe2O3) thin films were synthesized onto soda lime glass substrates at the temperature of 350 ℃ by the thermal spray pyrolysis technique. Mg doped Fe2O3 thin films were prepared with 0, 2, 4, 6, 8 and 10 at% Mg concentrations. Mg doped Fe2O3 thin films are found to have porous surface with uniform distribution of peaks and valleys in atomic force microscopy images. The average roughness of Mg doped Fe2O3 thin films increases in the range 11 to 66 nm with Mg concentration. X-ray diffraction spectra of Mg doped Fe2O3 thin films show that the films have corundum structure with preferential (104) peak. Mg doping causes shifting and splitting of (104) peak due to the generation of lattice asymmetry in Fe2O3 structure. Raman spectroscopy of Mg doped Fe2O3 thin films shows the presence of hematite phases in the range of wavenumber 200 - 1320 cm-1. The optical band gap widens from 2.11 - 2.75 eV with the increase of Mg concentration. Refractive index and extinction coefficient at the wavelength 750 nm decreases with Mg concentration. Photoluminescence (PL) property of Fe2O3 thin film is enhanced via Mg doping and that promotes the blue emission in Fe2O3 thin films. Band gap widening is also evident from the PL spectra. The exclusive topographical features, improved crystalline structure, broadened band gap and enriched PL behavior of Mg doped Fe2O3 thin films suggest its suitability in the fabrication of optoelectronic devices.
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).
Lecture plan of PHY 153
Lecture plan of PHY 171
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 and Sol-gel spin coating technique. She works on binary, ternary and multilayered metal oxide thin films. She is recently working on gas sensing material. She has constructed a gas sensitivity testing unit for investigating the gas sensitivity of metal oxide thin films and nanomaterials. She is also involved in the research related to Crystal growth, charaterization and optical crystallography. She has a keen interest to work for environment safety applications.
Synthesis of Nanostructured Metal Oxide Thin Films and Construction of a Cost Effective Gas Sensitivity Testing Unit for Environmental Applications