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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.

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 Ni-doped 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 ( 1 ‾ 11) along with the (111), ( 2 ‾ 02) and (02 2 ‾ ) 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.

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 $$\left( {\bar 111} \right)$$ 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, 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[Formula: see text]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 [Formula: see text]-type conductivity at room-temperature. Carrier concentration is found to be of the order of 10[Formula: see text] cm[Formula: see text].

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.Dhaka Univ. J. Sci. 64(1): 1-6, 2016 (January)

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.

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.

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.

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 (?EA) 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). DOI: http://dx.doi.org/10.3329/dujs.v63i1.21766 Dhaka Univ. J. Sci. 63(1): 37-41, 2015 (January)

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.

This paper presents a 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 °C 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 the 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 with the nature of soft ferromagnetic materials and the saturation magnetization decreased with Al concentration in Fe2O3 thin films.

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 -3 Ω-cm. The Hall coefficient (RH) was calculated to be 7.69 × 10 -1 cm 3 /C and Hall mobility (μ H ) was found to be 131cm 2 /V-s at room temperature from Hall effect measurements. Carrier concentration was estimated to be 8.12 × 10 18 /cm 3 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 (αhυ) 2 plotted against photon energy. The value of lattice parameter (a) was found to be 5.651 by implying X-ray diffraction method (XRD). DOI: http://dx.doi.org/10.3329/jbas.v36i1.10926 Journal of Bangladesh Academy of Sciences, Vol. 36, No. 1, 97-107, 2012

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.