T (+98) 23 352 20220
Email: international@du.ac.ir
Damghan University
University Blvd, Damghan, IR
Mohammad Reza Fadavieslam
Assistant Professor of Condensed Matter Physics
TEL: +98-2335220090
Selected Publications
DOI: 10.1007/s00339-018-2019-1
Silver-doped tin-sulfide thin films were deposited on glass substrates at 400 °C through spray pyrolysis. Afterward, the effects of Ag doping on the structural, optical, and electrical properties of thin films were investigated. The precursor solution was prepared by dissolving tin chloride (SnCl4∙5H2O) and thiourea (CS(NH3)2) in deionized water and subsequently adding silver acetate (AgC2H3O2). SnS2:Ag thin film was prepared with [Ag][Sn] % of 1, 2, and 3 at.%. X-ray diffraction analysis showed that the thin film exhibited a preferred (001) orientation in the SnS2 phase, and the intensity of the (001) peak increased with increased Ag-doping concentration. In addition, scanning electron microscopy indicated that the thin films presented spherical grains. Increased doping concentration also resulted in a decrease in the single-crystal grain size from 14–6 nm, with an average grain size of 80–123 nm. Moreover, the optical bandgap decreased from 2.75 to 2.56 eV, and the carrier concentration decreased from 95.48 × 1015 cm−3 to 2.48 × 1015 cm−3. On the contrary, the Hall mobility increased from 59.725 to 183.28 cm2/v s. The electrical resistance also increased from 1.096 to 13.75 Ω cm. Hall effect studies revealed that the films exhibited n-type conductivity. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
INDEX KEYWORDS: Ammonia; Carrier concentration; Chlorine compounds; Deionized water; Film preparation; Grain size and shape; Hall mobility; IV-VI semiconductors; Layered semiconductors; Scanning electron microscopy; Semiconducting tin compounds; Semiconductor doping; Silver compounds; Single crystals; Spray pyrolysis; Substrates; Sulfur compounds; Tin compounds; X ray powder diffraction, Average grain size; Doping concentration; Electrical resistances; Glass substrates; N-type conductivity; Optoelectronic applications; Precursor solutions; Single-crystal grains, Thin films
PUBLISHER: Springer Verlag
DOI: 10.1007/s00339-018-1591-8
This paper reports the effects of substrate temperature on the structural, optical, and electrical properties of Cu2ZnSnS4 (CZTS) thin films deposited on soda lime glass through spray pyrolysis without sulfurization. Substrate temperatures ranged from 250 to 500 °C at a step of 50 °C, and a precursor solution was prepared by dissolving copper chloride, zinc acetate, zinc chloride, and thiourea in ethanol and di-ionized water. The films were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy, ultraviolet–visible spectroscopy, and electrical resistance and Hall effect measurements, respectively, obtained by two-point probe and van der Pauw techniques. XRD revealed the formation of polycrystalline CZTS thin films and the appearance of relatively intense and sharp diffraction peaks at (112), (200), (220), and (312) of a kesterite phase with (112) preferential orientation, in which the crystalline degree increased as substrate temperature increased. Surface morphological analysis demonstrated the formation of a smooth, compact, and uniform CZTS surface. When substrate temperature increased from 250 to 500 °C, single-crystal grains increased from 6.38 to 28 nm, carrier concentration increased from 3.4 × 1017 to 2.36 × 1019 cm−3, Hall mobility increased from 30.96 to 68.52 cm2/V.S, optical band gap decreased from 1.74 to 1.14 eV, and resistivity decreased from 0.59 to 3.87 × 10−3 Ωcm. Hall effect analysis indicated that the films exhibited p-type conductivity. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
INDEX KEYWORDS: Carrier concentration; Chlorine compounds; Copper compounds; Energy gap; Field emission microscopes; Hall effect; Hall mobility; Pyrolysis; Scanning electron microscopy; Semiconducting films; Single crystals; Solar cells; Spray pyrolysis; Tin compounds; X ray diffraction; Zinc; Zinc chloride; Zinc compounds, Electrical resistances; Field emission scanning electron microscopy; Hall effect measurement; Morphological analysis; Preferential orientation; Single-crystal grains; Solar-cell applications; Van der Pauw technique, Thin films
PUBLISHER: Springer Verlag
DOI: 10.1007/s00339-017-1229-2
Antimony-doped tin oxide SnO2:Sb thin films were fabricated through atmospheric pressure chemical vapor deposition at T = 350 °C on soda lime glass substrates. After preparing the thin films, the effects of oxygen and argon flow rates on the structural, optical, and electrical properties were investigated. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, optical absorption (UV-Vis), and electrical resistance measurements using the two-point probe technique and the Hall effect. The results showed that the films contained uniform polycrystalline structures. Accordingly, the structural, morphological, optical, and electrical properties of the samples indicated the following effects: (a) Increasing the oxygen flow rate from 60 to 160 cc/min decreased the intensity of XRD peaks, the average roughness from 48.5 to 47.9 nm, the average transmission from 44 to 40 (in the visible region), the optical band gap from 3.74 to 3.66 eV, and the carrier mobility from 239.52 to 21.08 cm2/V.S; moreover, it increased the average grain size from 74 to 79 nm, the thickness from 320 to 560 nm, the specific resistance from 3.38 × 10−2 to 14.9 × 10−2 Ω cm, the carrier concentration from 7.72 × 1017 to 1.99 × 1018 cm−3, and the Seebeck coefficient from 47.2 to 57.85 μVk−1 (at 400 K). (b) Increasing the argon flow rate of 40 cc/min to 120 cc/min decreased the intensity of XRD peaks, the average size of grains from 88 nm to 61 nm, the optical band gap from 3.66 to 2.73 eV, the carrier concentration from 1.99 × 1018 to 1.73 × 1017 cm−3, and the Seebeck coefficient from 57.85 to 36.59 μVk−1 (at 400 k); moreover, this increased the average roughness from 47.9 to 50.8 nm, the average transmission from 40 to 64 (in the visible region), thickness from 560 to 620 nm, specific resistance from 14.9 × 10−2 to 39.87 × 10−2 Ω cm, and carrier mobility from 21.08 to 90.61 μv/vs. (c) All thin films had degenerate n-type conductivity. © 2017, Springer-Verlag GmbH Germany.
INDEX KEYWORDS: Antimony; Atmospheric chemistry; Atmospheric pressure; Atomic force microscopy; Carrier concentration; Carrier mobility; Chemical vapor deposition; Deposition; Electromagnetic wave absorption; Energy gap; Flow rate; Light absorption; Nanocomposites; Optical band gaps; Oxide films; Scanning electron microscopy; Seebeck coefficient; Substrates; Thin films; Tin oxides; X ray diffraction, Antimony-doped tin oxide; Atmospheric pressure chemical vapor deposition; Average grain size; Electrical resistance measurement; N-type conductivity; Polycrystalline structure; Soda lime glass substrate; Specific resistances, Vapor deposition
PUBLISHER: Springer Verlag
DOI: 10.1007/s10854-017-6475-8
The effect of ZnO nanoparticles as an electron transport layer (ETL) on the electronic properties of organic light-emitting diodes (OLEDs) was experimentally investigated in this study. OLED was fabricated with the structure of ITO/PEDOT:PSS/PVK/Eu/ZnO nanoparticle/PBD/Al, and then loaded with different amounts on ZnO nanoparticles. The scanning electron microscope field effect, optical absorption, luminescence, and current density–voltage of the OLEDs were characterized. Results showed that using ZnO nanoparticles as an ETL enhanced the performance and efficiency of the OLEDs. Moreover, increasing the loading amount of the ZnO nanoparticles increased luminescence and transparency and decreased work voltage. The characterization results showed that adding layers of ZnO nanoparticles changed the work voltage from 12.2 to 10 V, maximum luminescence from 0.19 to 0.23, and transparency from 60 to 86%. © 2017, Springer Science+Business Media New York.
INDEX KEYWORDS: Electromagnetic wave absorption; Electron transport properties; Electronic equipment; Electronic properties; Light; Light absorption; Light emitting diodes; Luminescence; Metal nanoparticles; Nanoparticles; Scanning electron microscopy; Transparency; Zinc oxide, Electron transport layers; Loading amount; Organic light emitting diodes(OLEDs); ZnO nanoparticles, Organic light emitting diodes (OLED)
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10854-016-6009-9
Ag-doped tin-sulfide thin films were deposited with in spray pyrolysis method at T = 425 °C on soda lime glass substrates. The effects of Ag doping were investigated on the structural, optical, and electrical properties of thin films. Double deionized water was used as a precursor solution in which tin chloride (SnCl45H2O) and thiourea (CS(NH3)2) in addition to silver acetate (AgC2H3O2) were dissolved. All in all resulted to preparation of SnS2:Ag thin films with [Ag]/[Sn]%=0,1,2,3and4at.%. The (001) plane is the preferred orientation of the SnS2 phase which is analyzed by X-ray diffraction (XRD). The intensity of mentioned peak has an increasing trend, generally, with increasing Ag doping concentration. Thin films have spherical grains as is shown in SEM images. Increasing doping concentration from 1 to 4%, causes decrease in: single-crystal grains from 14.68 to 6.31 nm, optical band gap from 2.75 to 2.62 eV, carrier concentration from 3.11 × 1017 to 2.58 × 1017 cm−3, and Hall mobility from 1.81 to 0.13 cm2/v s, as well as increase in: average grain size, generally, from 70 to 79 nm and electrical resistance from 11.11 to 181.26 Ω cm, respectively. The majority carriers are electrons for these films as is concluded from Hall Effect measurements. © 2016, Springer Science+Business Media New York.
INDEX KEYWORDS: Carrier concentration; Chlorine compounds; Deionized water; Deposition; Energy gap; Film preparation; Hall mobility; IV-VI semiconductors; Layered semiconductors; Lime; Semiconducting tin compounds; Semiconductor doping; Single crystals; Spray pyrolysis; Substrates; Sulfur compounds; Thin films; Tin compounds; X ray diffraction, Electrical resistances; Hall effect measurement; Optical and electrical properties; Preferred orientations; Single-crystal grains; Soda lime glass substrate; Spray pyrolysis deposition; Spray pyrolysis method, Silver compounds
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10854-016-5809-2
Cu-doped tin-sulfide thin films were deposited onto glass substrates at T = 400 °C through spray pyrolysis. The effects of Cu doping on the structural, optical, and electrical properties of the thin films were investigated. The precursor solution was prepared by dissolving tin chloride (SnCl4·5H2O) and thiourea (CS(NH3)2) in deionized water and then adding copper chloride (Cl2Cu2H2O). SnS2:Cu thin films were prepared with [Cu]/[Sn]%=0,1,2,3,4at.%. X-ray diffraction analysis showed that the thin films had a preferred (001) orientation of the SnS2 phase and that the intensity of the (001) peak decreased with increased doping concentration from 1–4 at.%. Scanning electron microscopy studies indicated that the thin films had spherical grains. Characterization results of thin films showed that single-crystal grains, average grain size, optical band gap, carrier concentration, Hall mobility, and electrical resistance varied within 5–14 nm, 46–104 nm, 2.81–2.99 eV, 2.42 × 1016–26.73 × 1016 cm−3, 2.41 × 10−3–20.04 × 10−3 cm2/v.s, and 9.05–12.89 Ω cm, respectively. Hall effect studies further revealed that the films exhibited n-type conductivity. © 2016, Springer Science+Business Media New York.
INDEX KEYWORDS: Carrier concentration; Chlorine compounds; Copper compounds; Deionized water; Energy gap; Film preparation; Hall mobility; IV-VI semiconductors; Layered semiconductors; Scanning electron microscopy; Semiconducting tin compounds; Semiconductor doping; Single crystals; Spray pyrolysis; Substrates; Sulfur compounds; Thin films; Tin compounds; X ray diffraction analysis, Average grain size; Doping concentration; Electrical resistances; N-type conductivity; Precursor solutions; Semiconductor thin films; Single-crystal grains; Spray-pyrolysis techniques, Optical films
PUBLISHER: Springer New York LLC
DOI: 10.1007/s12043-016-1237-3
This report investigated the structural, optical and electrical properties of V-doped SnO2 thin films deposited using spray pyrolysis technique. The SnO2:V films, with different V-content, were deposited on glass substrates at a substrate temperature of 550°C using an aqueous ethanol solution consisting of tin and vanadium chloride. X-ray diffraction studies showed that the SnO2:V films were polycrystalline only with tin oxide phases and the preferred orientations are along (1 1 0), (1 0 1), (2 1 1) and (3 0 1) planes. Using Scherrer formula, the grain sizes were estimated to be within the range of 25-36 nm. The variation in sheet resistance and optical direct band gap are functions of vanadium doping concentration. Field emission scanning electron microscopy (FESEM) revealed the surface morphology to be very smooth, yet grainy in nature. Optical transmittance spectra of the films showed high transparency of about ∼69-90% in the visible region, decreasing with increase in V-doping. The direct band gap for undoped SnO2 films was found to be 3.53 eV, while for higher V-doped films it shifted toward lower energies in the range of 3.27-3.53 eV and then increased again to 3.5 eV. The Hall effect and Seebeck studies revealed that the films exhibit n-type conductivity. The thermal activation energy, Seebeck coefficient and maximum of photosensitivity in the films were found to be in the range of 0.02-0.82 eV (in the low-temperature range), 0.15-0.18 mV K-1 (at T = 350 K) and 0.96-2.84, respectively. © Indian Academy of Sciences.
AUTHOR KEYWORDS: SnO2:V; Spray pyrolysis; Thin film
INDEX KEYWORDS: Activation energy; Chlorine compounds; Conductive films; Energy gap; Field emission microscopes; Oxide films; Scanning electron microscopy; Semiconductor doping; Spray pyrolysis; Substrates; Temperature; Tin oxides; Vanadium compounds; X ray diffraction, Aqueous ethanol solutions; Field emission scanning electron microscopy; Optical and electrical properties; Optical transmittance spectrum; Preferred orientations; Spray-pyrolysis techniques; Thermal activation energies; X-ray diffraction studies, Thin films
PUBLISHER: Indian Academy of Sciences
DOI: 10.1007/s10854-016-4379-7
In this research, antimony-doped tin dioxide (ATO) films were deposited on glass substrates at T = 550 °C through spray pyrolysis. The effects of antimony doping on the structural, optical, and electrical properties of the thin films were investigated. Tin chloride (SnCl4·5H2O) and antimony chloride (SbCl3) were used as a host and a dopant precursor, respectively. X-ray diffraction (XRD) analysis indicated that the undoped SnO2 thin film exhibited a preferred (211) orientation. As the Sb doping concentration increased, a different preferred (200) orientation was observed. Field emission scanning electron microscopy analysis revealed polyhedron-like grains of the thin films. Atomic force microscopy analysis demonstrated that the minimum and maximum amounts of roughness were within the (Formula presented.) molar ratio of 10 and 7.5 at.% concentrations, respectively. As the doping concentration increased, the average grain size initially increased and then decreased; electrical resistance initially decreased and subsequently increased; the carrier concentration and Hall mobility initially increased and then decreased; and Seebeck coefficient decreased. The optical band gap of the thin films ranged from 3.16 to 3.8 eV. Hall effect and thermoelectric studies revealed that the films exhibited an n-type conductivity. © 2016, Springer Science+Business Media New York.
INDEX KEYWORDS: Antimony compounds; Atomic force microscopy; Carrier concentration; Chlorine compounds; Energy gap; Field emission microscopes; Hall mobility; Optical properties; Scanning electron microscopy; Semiconductor doping; Spray pyrolysis; Substrates; Tin dioxide; X ray diffraction analysis, Antimony chlorides; Average grain size; Dopant precursors; Doping concentration; Electrical resistances; Field emission scanning electron microscopy; Glass substrates; N-type conductivity, Thin films
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10854-015-3835-0
In this research, SnO2 films were prepared by atmospheric pressure chemical vapor deposition technique on a glass substrate. Then, the effects of oxygen and nitrogen flow rates and deposition time on the structural, optical and electrical properties of the thin films were studied. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy, electrical resistance measurements using two-point probe technique, Hall Effect, photo-conductivity effect and optical absorption (UV–Vis). The films had uniform polycrystalline structure. The average optical band gap of the films was 3.8 eV. The results of Hall Effect showed that majority carriers were n-type and carrier concentration varies in the range of 5.84 × 1018–1.89 × 1019 cm−3. Increasing oxygen flow rate led to increasing the specific resistance, photosensitivity and Seebeck coefficient (at 350 K), and also decreasing optical band gap, mean grain size and surface roughness plus higher XRD peaks. Increasing nitrogen flow rate led to decreasing optical band gap, specific resistance, and photosensitivity and Seebeck coefficient (at 350 K). Increasing the deposition time led to an increase–decrease trend in the optical band gap, a decrease–increase trend in specific resistance and an increase in photosensitivity and Seebeck coefficient (at 350 K). The average transmittance and optical band gap of films were 82 % and 3.8 eV, respectively. Hall Effect studies revealed that the films exhibit n-type conductivity. © 2015, Springer Science+Business Media New York.
INDEX KEYWORDS: Atmospheric chemistry; Atmospheric pressure; Atomic force microscopy; Carrier concentration; Chemical vapor deposition; Energy gap; Field emission microscopes; Flow rate; Hall effect; Light absorption; Light sensitive materials; Nitrogen; Optical band gaps; Oxygen; Photosensitivity; Scanning electron microscopy; Seebeck coefficient; Substrates; Surface roughness; Thin films; X ray diffraction, Atmospheric pressure chemical vapor deposition; Electrical and optical properties; Electrical resistance measurement; Field emission scanning electron microscopy; Optical and electrical properties; Oxygen and nitrogens; Polycrystalline structure; Specific resistances, Optical films
PUBLISHER: Springer New York LLC
DOI: 10.1088/1674-4926/34/8/082001
Thin films of tin selenide (SnxSey) with an atomic ratio of r=[y/x] = 0.5, 1 and 1.5 were prepared on a glass substrate at T = 470°C using a spray pyrolysis technique. The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride (SnCl4· 5H2O) and selenide acide (H 2SeO3). The prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy, scanning tunneling microscopy, scanning helium ion microscopy, and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of the SnxSey thin films were then studied. The SnxSey thin films had a polycrystalline structure with an almost uniform surface and cluster type growth. The increasing atomic ratio of r in the films, the optical gap, photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV, 0.01 to 0.31 and -26.2 to -42.7 mV/K (at T = 350 K), respectively. In addition, the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe2 phases. © 2013 Chinese Institute of Electronics.
AUTHOR KEYWORDS: optical band gap; spray pyrolysis; thin film; tin selenide
INDEX KEYWORDS: Alcoholic solutions; Helium ion microscopies; Polycrystalline structure; Scanning electrons; Selenium concentrations; Spray-pyrolysis techniques; Tin selenides; UV-vis spectroscopy, Chlorine compounds; Optical band gaps; Scanning electron microscopy; Scanning tunneling microscopy; Semiconducting selenium compounds; Spray pyrolysis; Substrates; Thin films; Tin; Ultraviolet visible spectroscopy; X ray diffraction, Film preparation
DOI: 10.1088/1674-4926/32/11/113002
Tin sulfide thin films (SnxSy) with an atomic ratio of y/x = 0.5 have been deposited on a glass substrate by spray pyrolysis. The effects of deposition parameters, such as spray solution rate (R), substrate temperature (Ts) and film thickness (t), on the structural, optical, thermo-electrical and photoconductivity related properties of the films have been studied. The precursor solution was prepared by dissolving tin chloride (SnCl4, 5H2O) and thiourea in propanol, and Sn xSy thin film was prepared with a mole ratio of y/x = 0.5. The prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. It is indicated that the XRD patterns of SnxSy films have amorphous and polycrystalline structures and the size of the grains has been changed from 7 to 16 nm. The optical gap of SnxSy thin films is determined to be about 2.41 to 3.08 eV by a plot of the variation of (αhν)2 versus hν related to the change of deposition conditions. The thermoelectric and photo-conductivity measurement results for the films show that these properties are depend considerably on the deposition parameters. © 2011 Chinese Institute of Electronics.
AUTHOR KEYWORDS: photoconductivity; spray pyrolysis; thin film; tin sulfide
INDEX KEYWORDS: Atomic ratio; Deposition conditions; Deposition Parameters; Glass substrates; Measurement results; Mole ratio; Optical gap; Polycrystalline structure; Precursor solutions; Spray solutions; Spray-pyrolysis techniques; Substrate temperature; Tin chlorides; tin sulfide; UV-vis spectroscopy; XRD patterns, Amorphous films; Amorphous materials; Chlorine compounds; Electric properties; Film preparation; Photoconductivity; Scanning electron microscopy; Substrates; Thin films; Thioureas; Tin; Tinning; Ultraviolet spectroscopy; Ultraviolet visible spectroscopy; Vapor deposition; X ray diffraction, Spray pyrolysis
DOI: 10.1088/0031-8949/84/03/035705
In this paper, thin films of tin sulfide (SnxSy) with atomic ratios of y/x=0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 have been prepared on a glass substrate at T=420°C using the spray pyrolysis technique. The initial materials for the preparation of thin films were an alcoholic solution consisting of tin chloride (SnCl4.5H2O) and thiourea (CS(NH3)2). The prepared thin films were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray analysis, scanning helium ion microscopy and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of SnxSy thin films have been studied. The SnxSy thin films had a polycrystalline structure with a nearly uniform surface and cluster-type growth. With increasing the atomic ratio of (y/x) in films, the optical gap, photosensitivity, thermal activation energy and Seebeck coefficient changed from 2.72 to 2.37 eV, from 0.05 to 0.78, from 0.07 to 0.48 eV (in the high temperature range) and from +0.17 to -0.22 mV K-1 (at T=350 K), respectively. In addition, the structure of tin sulfide thin films tends to a nearly single-crystal state in (001) preferred orientation corresponding to SnS2 phase with increasing (y/x) ratio. These structure situations considerably influence the photosensitivity and thermoelectric properties of thin films. © 2011 The Royal Swedish Academy of Sciences.
INDEX KEYWORDS: Alcoholic solutions; Atomic ratio; Energy dispersive x-ray; Glass substrates; Helium ion; High temperature range; Optical gap; Polycrystalline structure; Preferred orientations; Semiconductor thin films; Spray-pyrolysis techniques; Thermal activation energies; Thermoelectric properties; Tin chlorides; Tin sulfide; UV-vis spectroscopy, Activation energy; Chlorine compounds; Crystal orientation; Helium; Light sensitive materials; Optical films; Photoconductivity; Photoelectricity; Photosensitivity; Scanning electron microscopy; Spray pyrolysis; Substrates; Thermoelectric equipment; Thermoelectricity; Thin films; Thioureas; Tin; Ultraviolet spectroscopy; Urea; X ray diffraction; X ray diffraction analysis, Film preparation
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