فهرست مطالب maryam gholizadeh arashti

In this paper, Al films were deposited on glass and steel substrates by using thermal evaporation technique. X-ray diffraction (XRD) analysis was used for structural characterization of Al thin films. It was found that the growth process mechanism of Al film on two substrates was different. The difference in the growth mechanism and microstructures affects the surface properties. Atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) have been used to describe the surface morphology and fractal properties of Al films. The fractal properties obtained by autocorrelation function (ACF), height-height correlation function (H(r)) and Minkowski function are described and compared with each other. The results of 2D AFM images show that the Al film on the steel substrate has higher surface roughness, roughness exponent, and lateral correlation length compared to the glass substrate. However, the Al film on the glass substrate has a higher spatial complexity with a fractal dimension of Df = 2.88.

Cadmium telluride nanoparticles (CdTe NPs) were deposited by the thermal evaporation method on glass substrates at a temperature of 373 K and a vacuum pressure of 2.7 mPa, and thin films with the thickness of 100 nm were fabricated. The prepared films were subjected to ultraviolet-visible (UV-Vis) spectroscopy to study the optical properties of thin films. To investigate the effect of annealing temperature on the optical properties of cadmium telluride thin films, these films were annealed at temperatures (323-373) K. The light absorption spectra of films before and after annealing were recorded using UV-Vis spectroscopy at a wavelength range of 600-1600 nm shows that the value of light absorption by films  increased with the increased annealing temperature. The optical energy bandgap of the grown films has a decrement process from 1.519 eV after annealing. The results of the Tauc plot show the decrease in energy bandgap with annealing. Extinction and refractive indices increase with increment of photon energy and annealing temperature. The relative density and electronic polarizability of grown films increase after annealing. Other optical parameters obtained in this work, including the real and imaginary parts of the dielectric constant, increase, while the surface and volume energy loss functions decrease with increase of the annealing temperature. The results of this work indicate that the deposited cadmium telluride thin films annealed at 373 K have better optical properties for photoelectronic applications.

The Al zig-zag sculptured thin film consists of two identical columns, the first nanocolumns (zig) are oriented at the angle χ, and the second nanocolumns (zag) are oriented at the angle (π- χ). The optical properties of these nanostructures were obtained using the transfer matrix method for linear s- and p- polarized incident lights in the wavelength range of 300-1000 nm. The reflection and transmission spectra of the zigzag nanostructures with different arm numbers and lengths were obtained at different incident angles. The Bragg peaks begin to appear for zig-zag nanostructures of morethan 4 arms for s- polarized light at angles greater than 30. For zig-zag structures of 4, 8, and 16 arms, one, two, and three Bragg peaks were observed, respectively. However, for p- polarized light, no Bragg peak was observed at any of the incident angles. Also, for the zig-zag structure of 8 arms for s-polarized light at 60 incident angles, the number of Bragg peaks increases with increasing arm length. In addition, the peaks created in the wavelengths below 550 nm showed a red shift while the peaks that appeared in the wavelengths above 550 nm showed a blue shift.

Cadmium telluride (CdTe) nanoparticles were deposited on glass substrates coated by indium tin oxide (ITO) and fluorine doped tin oxide (FTO) as transparent conducting films at 200 °C under pressure of 2×10-5 mbar. The thickness of the prepared films prepared was about 200 nm. The structure, optical, electrical, and morphological properties of the layers were analyzed by x-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, current-voltage (IV) characterization, and scanning electron microscopy (SEM), respectively. XRD patterns show the cubic structure of the deposited CdTe thin film on both ITO and FTO substrates. The preferred orientation of deposited films also changed from (111) for ITO substrate to (220) for FTO substrate. The crystallite size of films on ITO and FTO in these orientations were about 23.41 and 34.84 nm, respectively. The thin-film transmittance spectra were determined using UV-Vis spectroscopy in the wavelength range of 200-1200 nm. The optical energy bandgap of thin films on ITO and FTO substrates was calculated to be 1.60 and 1.63 eV, respectively. The I-V curve shows more electrical conductivity of the CdTe thin film on the FTO compared to the ITO. The surface morphology images show homogeneity and uniformity of the surface.

In this work, cadmium telluride nanoparticles were synthesized by sonochemical method and then thin films with the thicknesses about of 100 nm were deposited on glass substrates using thermal evaporation technique at a substrate temperature of 200 °C and vacuum pressure of 2×10-5 mbar. Sonochemical method is one of the best methods for synthesizing nanomaterials with very small particle sizes. After synthesis and deposition, the prepared films were subjected to x-ray diffraction, ultraviolet-visible spectroscopy and scanning electron microscopy to study the structure, optical properties and morphology of the films. XRD patterns indicated that the grown films were polycrystalline with a cubic structure on the preferred orientation (200).The size of the synthesized nanoparticles and crystallite size of the thin film grown on glass in the preferred orientation (200) were 16 nm &10.65 nm, respectively. Light absorbance spectra of nanoparticle and thin film obtained by UV-Vis spectroscopy at the wavelength range 600-1600 nm showed the increase of light absorption after deposition. The optical energy band gap was increased from 1.48 for nanoparticles to 1.51 for the deposited films. The SEM taken on the scale of 500 nm from nanoparticles and thin films showed the homogeneity and uniformity of both of them

Zig-zag Al nanostructures were fabricated on the glass and steel using thermal evaporation technique. The structural, morphology and electrical properties of Al thin films were studied by using AFM, FESEM and four-point probe instrument. FESEM analysis showed that the grains are distributed on the zig-zag Al-glass and their shape is polygonal while the grains on the zig-zag Al-steel surface have a non-uniform distribution and the shape of the grains is oval. AFM analysis indicated the surface roughness of zig-zag Al-steel nanostructures is more than the zig-zag Al-glass. Moreover, the wrinkles on the zig-zag Al-steel and the small protuberances on the zig-zag Al-glass observed. The anisotropy of electrical was performed in two perpendicular directions x and y of the samples surface. The average electrical resistivity of the zig-zag Al films on glass and steel produced were obtained about 4.69×10-8 and 5.85×10-8 Ω.m, respectively. Simulation results by the perturbation method agree with the experimental results.

Today there is a heightened interest in the field of theoretical study of thermoelectric properties due to widespread application of thermoelectric materials. In this research, the Seebeck coefficient (S) and Merit Factor (Z) are calculated for C20-nGen and C20-nSin (n=1-5) bowl structures and the most suitable thermoelectric systems are selected. The quantum calculations are done at the level of LSDA/6-31G of Density Functional Theory (DFT). As the temperature increases from 200k to 400k, the seebeck coefficients of these structures decrease for p-type semiconductors and increase for n-type semiconductors. The maximum values of merit factor are achieved for C19Ge1   equal to 1.78at 278k and for C17Si3 equal to 1.03 at 400k. Therefore, the structures of p-type of C19Ge1 and n-type of C17Si3 with more temperature difference are selected as the best thermoelectric systems. The structures of C20-nGen with n=1,2,5 as the both n-type and p-type semiconductors and C20-nSin with n=3 for n-type and also n=1,3 for p-type have Z>1 and are suitable for thermoelectric systems.

In this research, IR and frontier molecular orbital (FMO) computations were employed for investigating the performance of B12N12 as a novel recognition element for fabrication of quetiapine thermal and electrochemical sensors. All of the computations were done by density functional theory method in the B3LYP/6-31G(d) level of theory and in the aqueous phase. The obtained enthalpy changes (ΔHad), Gibbs free energy variations (ΔGad) and thermodynamic equilibrium constants (Kth) indicated that quetiapine interaction with boron nitride nanocage is exothermic, spontaneous, irreversible and experimentally feasible. The bond lengths between the adsorbent and the adsorbate and adsorption energy values showed quetiapine interaction with B12N12 is a chemisorption. The temperature was also optimized and the findings revealed 298.15 K is the best temperature for quetiapine adsorption on the B12N12 surface. The DOS spectrums showed B12N12 is an appropriate electroactive recognition for fabrication of new quetiapine electrochemical sensors. The specific heat capacity values (CV) proved the thermal conductivity of quetiapine has improved after its interaction with the nanostructure. Some structural parameters including energy gap, chemical hardness, chemical potential, electrophilicity, maximum transferred charge, zero-point energy and dipole moment were also calculated and discussed in details.

In this research, the thermodynamic stability, Energy of Gap and Electrical conductivity of nano structures of C20 bowl, C20-nSin (n=1-5) and C20-nGen (n=1-5) were investigated at the level of Quantum calculations of LSDA/6-31G of Density Functional Theory (DFT) at the room temperature. We have studied the application of these structures in solar cells. The most stable structures are C15Ge5 and C17Si3 at 300 K. The results show that the substitutes decrease gap of energy and increase the electrical conductivity, but the number of Silicon or Germanium substitute does not have the regular effect on the gap of energy. The C17Ge3 and C16Si4 have the lowest gap of energy and also have more conductivity. The gap of HOMO and LUMO energy levels of the electron donor and electron acceptor components is the most important factor for the electron transfer with photovoltaic application potential. The two structures of C17Si3 as electron acceptor and C15Ge5 as electron donor with the maximum voltage of 1.93 volt can be used in producing solar cell.