T (+98) 23 352 20220
Email: international@du.ac.ir
Damghan University
University Blvd, Damghan, IR
Mehdi Adelifard
Assistant Professor of Condensed Matter Physics
Biography
Mehdi Adelifard obtained his Ph.D. in solid state physics from Shahrood University of technology on
Septemer 2012, based on ”An investigation on physical properties of thin films and
nanostructures in chalcogenide compound semiconductors”. Here, he was involved in the
characterization of CuS, CuS-ZnS (CZS) binary and Cu2SnS3 (CTS) ternary semiconductors by means
of XRD, FESEM, UV.Vis-NIR spectrophotometer, Hall effect setup and solar cell analyzer.
Mehdi Adelifard has authored or co-authored over 20 publications in national and international journals
or conference proceedings.
Education
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Ph.D. 2012
Solid State Physics
Shahrood University of Technology, Shahrood, Iran
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M.Sc. 2008
Solid States Physics
Ferdowsi University of Mashhad, Mashhad, Iran
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B.Sc. 2005
Atomic Physics
Shiraz University, Shiraz, Iran
Teaching
- Nanophysics and nanotechnology devices (Graduate courses)
- Fundamental Physics
- Optics & Wave
- Analytical Mechanics
- Geometric Optics
Selected Publications
DOI: 10.1016/j.jaap.2016.09.022
The Cu2FeSnS4 (CFTS) nanostructured thin films have been spray deposited onto glass substrates without any post-sulfurization in toxic atmosphere such as H2S or ‘S’ vapor. The influence of substrate temperatures on the structural, morphological, compositional, optical, electrical and photoconductivity properties of the CFTS thin films have been studied. These properties are found to be strongly dependent on the substrate temperature. XRD spectra analysis revealed that all CFTS thin films showing pure stannite structure. The improved crystallinity of the CFTS with a (112) orientation was observed with increasing the substrate temperature. The spray synthesized CFTS films exhibit a smooth, uniform and dense topography. EDS study reveals that the deposited thin films are nearly stoichiometric. The direct band gap energy for the CFTS thin films is found to be about 1.50 eV, which is close to the ideal band gap for the highest theoretical conversion efficiency of solar cell. Electrical conductivity and hole mobility of the CFTS films increases with increasing substrate temperatures. The films were p-type and shows photoconductivity. Electrical measurements (I–V curves) were registered in dark and under light exposure and were correlated with the films composition and structure, as obtained from the EDS analysis and XRD patterns. © 2016 Elsevier B.V.
AUTHOR KEYWORDS: CFTS; Electrical properties; Optical properties; Spray pyrolysis; Thin film
INDEX KEYWORDS: Copper; Electric properties; Energy gap; Hole mobility; Optical properties; Photoconductivity; Pyrolysis; Solar cells; Spray pyrolysis; Substrates; Topography, CFTS; Electrical conductivity; Electrical measurement; Nanostructured thin film; Photovoltaic applications; Quaternary semiconductors; Spray-pyrolysis techniques; Substrate temperature, Thin films
PUBLISHER: Elsevier B.V.
DOI: 10.1007/s00339-016-0216-3
There is a great interest in the use of graphene sheets in thin film solar cells with low-cost and good-optoelectronic properties. Here, the production of absorbent conductive reduced graphene oxide (RGO) thin films was investigated. RGO thin films were prepared from spray-coated graphene oxide (GO) layers at various substrate temperature followed by a simple hydrazine-reducing method. The structural, morphological, optical, and electrical characterizations of graphene oxide (GO) and RGO thin films were investigated. X-ray diffraction analysis showed a phase shift from GO to RGO due to hydrazine treatment, in agreement with the FTIR spectra of the layers. FESEM images clearly exhibited continuous films resulting from the overlap of graphene nanosheets. The produced low-cost thin films had high absorption coefficient up to 1.0 × 105 cm−1, electrical resistance as low as 0.9 kΩ/sq, and effective optical band gap of about 1.50 eV, close to the optimum value for solar conversion. The conductive absorbent properties of the reduced graphene oxide thin films would be useful to develop photovoltaic cells. © 2016, Springer-Verlag Berlin Heidelberg.
INDEX KEYWORDS: Absorption; Conductive films; Energy gap; Fourier transform infrared spectroscopy; Graphene; Hydrazine; Nanostructured materials; Oxide films; Photoelectrochemical cells; Photovoltaic cells; Solar absorbers; Solar cells; Thin film solar cells; X ray diffraction analysis, Absorption co-efficient; Chemically converted graphene; Electrical characterization; Electrical resistances; Graphene nanosheets; Optoelectronic properties; Reduced graphene oxides; Reduced graphene oxides (RGO), Thin films
PUBLISHER: Springer Verlag
DOI: 10.1007/s10854-016-4445-1
We have investigated the effect of sulfur concentration ([S]/[Mo] = 0–10 at.%) on nanostructural, optical and electrical properties of MoO3 thin films grown on glass substrate by spray pyrolysis technique. X-ray diffraction analysis showed that the films were crystallized with mixed structures of MoO3 orthorhombic and MoS2 hexagonal structure. According to FESEM images, the studied films have a sponge-type structure on the order of nanometers. Optical measurements revealed that two distinct inflexions indicative two transitions correspond to MoO3/MoS2 phases in agreement with the XRD analysis. The Hall effect and thermoelectric measurements have shown p-type conductivity, and the free hole density increases with increasing sulfur to molybdenum ratio, in agreement with reflectance spectra of the layers. The obtained value of Seebeck coefficient for MoO3 film with [S]/[Mo] ratio of 8 at.% was as high as 169 μV/K. © 2016, Springer Science+Business Media New York.
INDEX KEYWORDS: Layered semiconductors; Molybdenum oxide; Optical data processing; Semiconducting films; Spray pyrolysis; Substrates; Sulfur; X ray diffraction analysis, Hexagonal structures; Optical and electrical properties; Optical measurement; P type conductivity; Reflectance spectrum; Spray-pyrolysis techniques; Sulfur concentrations; Thermoelectric measurements, Thin films
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10854-016-4420-x
We have investigated the impact of sulfurization and changing the metal salt ratio ([s]/[w] = 6–24 at.%) in the precursor solution on the structural, morphological, optical, electrical and photoconductivity properties of WS2/WO3 binary thin films grown on glass substrate by the spray pyrolysis technique. X–ray diffraction analysis showed that while the as-deposited samples present an amorphous nature, annealing these films in sulfur atmosphere generate a mix phase of WS2/WO3. FESEM study revealed the changes in surface morphology with increase in sulfur concentration in the spray solution. UV–Vis optical measurements analysis showed that these binary films have a relatively high absorption coefficient ~2 × 104–8 × 104 cm−1 in the visible spectrum with two distinct inflexions indicative of two transitions correspond to WS2/WO3 phases in agreement with the XRD analysis. The electrical studies showed that all these samples have a p-type conductivity; and the resistivity and photoconductivity decreases with increasing the sulfur to tungsten molar ratio. © 2016, Springer Science+Business Media New York.
INDEX KEYWORDS: Absorption spectroscopy; Amorphous films; Optical data processing; Photoconductivity; Semiconducting films; Spray pyrolysis; Substrates; Tungsten compounds, Absorption co-efficient; Diffraction analysis; Fabrication and characterizations; Optical measurement; P type conductivity; Precursor solutions; Spray-pyrolysis techniques; Sulfur concentrations, Thin films
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10854-015-3392-6
Silver sulfide (Ag2S) thin films have been deposited onto glass substrates using spray pyrolysis technique. The substrate temperature (260–310 °C) and also Ag to S molar ratio (0.33 and 0.43) dependent structural, morphological, optical, electrical and thermoelectrical properties of samples have been studied. The X-ray diffraction studies showed that the samples have single acanthite (α-Ag2S) phase with monoclinic structure and preferred orientation change from $$(bar{1}12)$$(1¯12) to $$(bar{1}03)$$(1¯03) plan with increasing sulfur content. SEM and AFM analyses revealed a compact surface morphology with slightly rough surface. Optical measurements showed a relatively high absorption coefficient (∼5 × 104–6 × 105 cm−1) in the visible range, with an effective optical band gap of ∼2.01–2.23 eV. The electrical studies showed that all these samples have an n-type conductivity and the free electron density increases with increasing the substrate temperature, in agreement with the reflectance spectra of the layers. The thermoelectric measurements revealed that the maximum Seebeck coefficient of −198 μV/K (at T = 400 K) was obtained for Ag2S (Ag:S = 0.33 at.%) film at substrate temperature of 310 °C. © 2015, Springer Science+Business Media New York.
INDEX KEYWORDS: Electrons; Energy gap; Optical data processing; Spray pyrolysis; Substrates; Sulfide minerals; Sulfur; Sulfur compounds; Thin films; X ray diffraction, Absorption co-efficient; Free-electron density; Monoclinic structures; Preferred orientations; Spray-pyrolysis techniques; Substrate temperature; Thermoelectric measurements; X-ray diffraction studies, Silver compounds
PUBLISHER: Springer New York LLC
DOI: 10.1007/s00339-015-9389-4
Photovoltaic Cu2ZnSnS4 (CZTS) thin films have been deposited on the glass substrate by a simple and low-cost spray pyrolysis technique without sulfurization treatment in a toxic atmosphere. The influence of the substrate temperatures on the structural, compositional, morphological, optical and electrical properties of the CZTS films was investigated. The formation of kesterite structure in the films was confirmed using X-ray diffraction measurements. The improved crystallinity of the CZTS with a (112) orientation was observed with increasing the substrate temperature. The band gap of all films was found to be in the range from 1.44 to 1.56 eV which is close to the ideal band gap for the highest theoretical conversion efficiency of solar cell. AFM analysis revealed a smooth, compact and crack-free morphology. The electrical studies showed that all these samples had a p-type conductivity, and the free hole density and mobility increased with increasing the substrate temperature. © 2015, Springer-Verlag Berlin Heidelberg.
INDEX KEYWORDS: Copper; Energy gap; Hole mobility; Semiconducting films; Spray pyrolysis; Substrates; X ray diffraction, Electrical studies; Free hole density; Nanostructured Cu; Optical and electrical properties; P type conductivity; Spray-pyrolysis techniques; Substrate temperature; X-ray diffraction measurements, Thin films
PUBLISHER: Springer Verlag
DOI: 10.1007/s10854-015-2888-4
Cu2ZnSnS4 (CZTS) absorber layers have been deposited via a spray pyrolysis technique without sulfurization process. Spray precursor solutions were prepared with different zinc to tin ratios, and the effects on film growth, structural, compositional, morphological, optical and electrical properties were investigated. The formation of kesterite structure with (112), (220) and (116) planes in the films was confirmed using X-ray diffraction measurements. AFM analysis revealed a smooth, compact and crack-free morphology. The estimated absorption coefficient was close to 105 cm−1 in the visible region for all CZTS films, and the values obtained for the optical band gap energy of the films were between 1.30 and 1.46 eV. The electrical studies showed that all these samples had a p-type conductivity, and the free hole density and mobility reduced with increasing the Zn/Sn molar ratio compatible with the shifts in the transmittance and reflectance spectra. © 2015, Springer Science+Business Media New York.
INDEX KEYWORDS: Energy gap; Hole mobility; Semiconducting films; Solar cells; Spray pyrolysis; X ray diffraction; Zinc, Absorption co-efficient; Optical and electrical properties; Optical band gap energy; Precursor solutions; Solar-cell applications; Spray-pyrolysis techniques; Transmittance and reflectances; X-ray diffraction measurements, Film growth
PUBLISHER: Springer New York LLC
DOI: 10.3139/146.111120
We have established the effect of copper dopant concentration (Cu/Sn = 0 - 30 at.%) on the structural, morphological and optical properties of SnO2 : S films grown on glass substrate using a spray pyrolysis technique. According to the experimental evidence and data analysis, we found that the polycrystalline layers in undoped condition mainly consist of mixed phases such as SnS2 and SnO2, whilst in doped ones, Cu2SnS3 and Cu4SnS4 phases are dominant. With increasing Cu concentration, a decrease in the grain size with a change in the shape of the grains is observed. Optical measurement analysis showed that these films have a direct band gap energy of about 2.98 - 3.59 eV. © Carl Hanser Verlag GmbH & Co. KG.
AUTHOR KEYWORDS: Copper and sulfide doping; Nanostructures; Spray pyrolysis; Thin films; Tin oxide
INDEX KEYWORDS: Copper; Doping (additives); Nanostructures; Optical data processing; Optical properties; Oxide films; Semiconductor doping; Substrates; Thin films; Tin oxides, Cu concentrations; Dopant concentrations; Effect of coppers; Experimental evidence; Nanostructured thin film; Optical measurement; Polycrystalline layers; Spray-pyrolysis techniques, Spray pyrolysis
PUBLISHER: Carl Hanser Verlag
DOI: 10.1007/s12034-012-0363-x
CuxS thin films with different Cu to S molar ratios (0·33 and 0·43) have been deposited by spray pyrolysis method on glass and FTO coated glass substrates using an aqueous solution of copper (II) acetate and thiourea at a substrate temperature of 285°C. The structural, surface morphological, optical and electrical characterizations of the samples were carried out using XRD, FESEM, UV-Vis and PL spectrophotometer and four-probe apparatus, respectively. X-ray diffraction analysis showed that while the layer/glass sample has an individual CuS (covellite) crystalline phase, the layer/FTO sample includes two additional phases of Cu2S (chalcocite) and Cu1·8S (digenite) as well. Optical measurements showed that all these materials have a relatively high absorption coefficient (∼5 × 104-2·3 ×105 cm-1) in the visible region and direct bandgap of the layers was confirmed with the corresponding room temperature PL spectra. With the resistivity measurements at room and higher temperatures (up to 100°C) confirm that all samples are degenerate in nature with high electrical conductivities of ∼103 (Ω.cm) -1. © Indian Academy of Sciences.
AUTHOR KEYWORDS: Electrical properties; Nanostructures; Optical properties; Semiconductors; Spray pyrolysis
INDEX KEYWORDS: Absorption coefficients; Coated glass; Coated glass substrates; Comparative studies; Copper sulfides; Covellite; Crystalline phase; Four-probe; High electrical conductivity; Molar ratio; Nanostructural thin films; Optical and electrical characterization; Optical measurement; PL spectra; Resistivity measurement; Room temperature; S thin films; Spray pyrolysis method; Substrate temperature; Visible region; XRD, Copper; Deposits; Electric conductivity; Electric properties; Nanostructures; Optical data processing; Optical properties; Semiconductor materials; Spray pyrolysis; Substrates; Sulfide minerals; Thin films; Thioureas; X ray diffraction analysis, Glass
DOI: 10.1016/j.optcom.2012.06.030
We have investigated the effect of zinc concentration ([Zn]/[Cu]=0-100 at%) on nanostructural, optical and electrical properties of CuS-ZnS binary thin films grown on glass substrate by the spray pyrolysis technique. X-ray diffraction analysis showed that the films were crystallized with mixed structures of CuS hexagonal and ZnS cubic structure. UV-vis optical measurements analysis showed that these binary films have a relatively high absorption coefficient (∼10 5 cm -1) in the visible spectrum with a direct band gap in the range of 2.57-2.45 eV in agreement with the corresponding room temperature PL spectra. The electrical studies showed that all these samples have a p-type conductivity and the free hole density decreases with increasing [Zn]/[Cu] molar ratio, in agreement with the reflectance spectra of the layers, originating from plasma oscillations. © 2012 Elsevier B.V. All rights reserved.
AUTHOR KEYWORDS: CuS-ZnS compound semiconductor; Electrical properties; Nanostructures; Optical properties; Spray pyrolysis
INDEX KEYWORDS: Absorption coefficients; Binary compounds; Binary films; Compound semiconductors; Cubic structure; Direct band gap; Effect of zincs; Electrical studies; Free hole density; Glass substrates; Mixed structure; Molar ratio; Nanostructural; Optical and electrical properties; Optical measurement; P-type conductivity; PL spectra; Reflectance spectrum; Room temperature; Spray-pyrolysis techniques; Visible spectra, Absorption spectroscopy; Nanostructures; Optical data processing; Optical properties; Plasma oscillations; Spray pyrolysis; Substrates; Thin films; X ray diffraction analysis; Zinc; Zinc sulfide, Electric properties
DOI: 10.1016/j.apsusc.2012.02.079
Copper sulphide (CuS) thin films have been deposited on glass substrates by spray pyrolysis method using an aqueous solutions of copper (II) acetate and thiourea with different Cu to S molar ratios (0.33 and 0.43) at various substrate temperatures of 260, 285 and 310°C. The structural, optical and electrical characterizations have been carried out using XRD, UV-Vis. transmittance/reflectance, PL spectra and Hall effect measurements. These characterizations indicated the formation of a CuS single phase (covellite) with polycrystalline nature with preferred orientation along (1 0 2) plane, except one with amorphous nature. Optical studies showed that the deposited layers have a relatively high absorption coefficient (5 × 10 4 to 1 × 10 5 cm -1) in the visible range, with an effective optical band gap of ∼2.4-2.6 eV. The Hall effect data showed that all the grown samples have a degenerate p-type conductivity with a hole concentration of ∼1.8 × 10 20 to 1.7 × 10 21 cm -3. © 2012 Elsevier B.V. All rights reserved.
AUTHOR KEYWORDS: Electrical properties; Nanostructures; Optical properties; Semiconductors; Spray pyrolysis
INDEX KEYWORDS: Absorption coefficients; Copper sulphides; Covellite; Deposited layer; Glass substrates; Hall effect measurement; Molar ratio; Nanostructural; Optical and electrical characterization; Optical and electrical properties; Optical study; P-type conductivity; PL spectra; Polycrystalline; Preferred orientations; Single phase; Spray pyrolysis method; Substrate temperature; Various substrates; Visible range; XRD, Amorphous materials; Copper; Hall effect; Optical properties; Semiconductor materials; Spray pyrolysis; Substrates; Sulfide minerals; Sulfur; Thin films; Thioureas, Electric properties
DOI: 10.1088/0031-8949/85/03/035603
Thin films of Cu 2SnS 3 have been deposited by the spray pyrolysis technique. Various Sn/Cu molar ratios (from 0.0 to 1.0) were applied, which allowed the study of the copper tin sulfide phase. Structural, morphological and compositional analyses have been carried out using x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The pure CuS thin film showed the covellite phase with hexagonal crystal structure, and with increasing the Sn/Cu molar ratio, the films grown were crystallized with triclinic Cu 2SnS 3 ternary phase. Optical measurement analysis showed that the deposited layers have a relatively high absorption coefficient (∼10 5 cm -1) in the visible spectrum, about one order of magnitude higher than in other published reports. Also these layers presented a reduction of about 1 eV in the values of band gap from 2.57 to 1.58 eV with an increment in the Sn/Cu molar ratio from 0.0 to 1.0. The electrical properties studies showed that all these samples are p-type semiconductors and the resistivity decreases with increasing the Sn/Cu molar ratio. © 2012 The Royal Swedish Academy of Sciences.
INDEX KEYWORDS: Absorption coefficients; Compositional analysis; Covellite; Deposited layer; Field emission scanning electron microscopy; Hexagonal crystal structure; Molar ratio; Optical measurement; P type semiconductor; Photovoltaic applications; Spray-pyrolysis techniques; Ternary phase; Ternary semiconductors; Tin sulfide; Visible spectra, Electric properties; Energy dispersive spectroscopy; Field emission microscopes; Optical data processing; Spray pyrolysis; Sulfide minerals; Thin films; Tin; X ray diffraction, Copper
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