V. Thiruvengadam; Braj Bhusan Singh; Palash Kumar Manna; Subhankar Bedanta
Abstract
Molybdenum disulfide (MoS2) is one among the transition-metal dichalcogenide (TMD) family which exhibits exotic physical properties at their mono-layer limit. We report a facile way to fabricate stoichiometric, crystalline and star shaped MoS2 film. In this work, ultra-thin MoS2 films were fabricated ...
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Molybdenum disulfide (MoS2) is one among the transition-metal dichalcogenide (TMD) family which exhibits exotic physical properties at their mono-layer limit. We report a facile way to fabricate stoichiometric, crystalline and star shaped MoS2 film. In this work, ultra-thin MoS2 films were fabricated by two step process (i) RF sputtering of MoS2 target followed by (ii) sulfurization to improve stoichiometry and crystallinity. In order to study the effect of sulfurization temperature on sputtered MoS2, sulfurization has been performed at five different temperatures - 700, 750, 775, 800 and 825°C. Surface morphology of as sputtered and sulfurized MoS2 films were characterized using optical and scanning electron microscopes. Crystallinity and layer thickness of the fabricated MoS2 films were estimated by using Laser Raman spectroscopy. These results confirm that as sputtered MoS2 films are discontinuous, amorphous in nature and it crystalizes into a layered structure during sulfurization at temperature ≥ 750°C. It was observed that at sulfurization temperature of 800°C, the nucleated crystallites well grown into a star shaped crystalline MoS2 with their thickness vary between 2 and 3 mono-layers. These star shapes can provide more surface area/edges that can be exploited to enhance the efficiency of gas sensors.
K. S. Gour; A. K. Yadav; Rahul Kumar; J. S. Tawale; V. N. Singh
Abstract
Zinc oxysulfide or Zn(O,S) is emerging as an alternate n-type buffer layer for kesterite, chalcogenides and CdTe based thin film solar cell due to it is being made from non-toxic elements and tunable bandgap, its suitable optical and electrical properties required for a buffer layer. Generally, buffer ...
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Zinc oxysulfide or Zn(O,S) is emerging as an alternate n-type buffer layer for kesterite, chalcogenides and CdTe based thin film solar cell due to it is being made from non-toxic elements and tunable bandgap, its suitable optical and electrical properties required for a buffer layer. Generally, buffer layers of these solar cells are deposited using chemical bath deposition (CBD) techniques, but these require breaking of vacuum and again inserting the sample in vacuum during solar cell fabrication, which is not economical and is cumbersome. Sputtering is considered to be industrial process and therefore, here we have deposited Zn(O,S) thin film by sputtering technique and effect of sulfurization temperature on bandgap and composition of Zn(O,S) films have been studied. The bandgap of deposited films changed from 3.36 eV to 3.15 eV by changing the sulfurization temperatures. By changing the sulfurization temperature, the composition of films also changed. Crystallite size (D) of Zn(O,S) films increased from 12.1 nm to 22.3 nm by varying the sulfur content for samples S1-S4, respectively. Optical, morphological, compositional and structural properties have been studied using UV-Vis-NIR spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffractometer (XRD), respectively.
Kartik H. Patel; Sushant K. Rawal
Abstract
This paper is aimed to explore structural, optical and wettability aspects of zinc oxide (ZnO) nanostructured thin films prepared by radio frequency (RF) magnetron sputtering from a zinc target using gas mixtures of helium and oxygen. The increase of deposition time from 40 to 110 minutes improves evolution ...
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This paper is aimed to explore structural, optical and wettability aspects of zinc oxide (ZnO) nanostructured thin films prepared by radio frequency (RF) magnetron sputtering from a zinc target using gas mixtures of helium and oxygen. The increase of deposition time from 40 to 110 minutes improves evolution of (100), (002) and (110) peaks for ZnO films whereas its (101) peak is evident at deposition time of 110 minutes. At sputtering pressure of 0.5Pa only (100) and (110) peaks are observed. The crystallinity of ZnO films decreases as the sputtering pressure is increased from 0.5 to 8.0Pa. The average crystallite size of films increases from 14nm to 18nm when deposition time is increased from 40 to 110 minutes and from 11nm to 17nm when deposition pressure is raised from 0.5Pa to 8.0Pa. We have studied wettability of water and ethylene glycol for deposited nanostructured ZnO films. The maximum value of contact angle; transmission and energy band gap were 106˚, 87% and 3.27eV respectively for deposited nanostructured thin films.
Jaspal Singh; Kavita Sahu; Sini Kuriakose; Nishant Tripathi; D. K. Avasthi; Satyabrata Mohapatra
Abstract
Nanostructured TiO2 thin films with highly enhanced photocatalytic activity were prepared by atom beam sputtering technique. The effects of thermal annealing on the structural, morphological and photocatalytic properties of TiO2 thin films were investigated using X-ray diffraction, atomic force microscopy, ...
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Nanostructured TiO2 thin films with highly enhanced photocatalytic activity were prepared by atom beam sputtering technique. The effects of thermal annealing on the structural, morphological and photocatalytic properties of TiO2 thin films were investigated using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, Raman spectroscopy and UV-visible absorption spectroscopy. X-ray diffraction studies showed that the as-deposited TiO2 thin films made up of anatase TiO2 nanoparticles transformed into anatase/ rutile mixed-phase TiO2 nanoparticles upon annealing. Field emission scanning electron microscopy and atomic force microscopy studies revealed growth of TiO2 nanoparticles from 16 nm to 29 nm upon annealing at 600 o C. The photocatalytic activities of the nanostructured TiO2 thin films were studied by monitoring photocatalytic degradation of methylene blue in water. Our results showed that the as-deposited nanostructured TiO2 thin films exhibited highly enhanced photocatalytic efficiency as compared to the annealed samples. The mechanism underlying the enhanced photocatalytic activity of nanostructured TiO2 thin film is tentatively proposed.
R. Siddheswaran; Petr Nov
Abstract
Thin films of BaTiO3 and Co, Nb co-doped BaTiO3 on glass and Si (100) substrates were deposited by RF sputtering (at 350 ºC), and annealed. The amorphous and crystalline phases were observed for the as-deposited and annealed samples, respectively from the X-ray diffraction (XRD) studies. The magnetic ...
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Thin films of BaTiO3 and Co, Nb co-doped BaTiO3 on glass and Si (100) substrates were deposited by RF sputtering (at 350 ºC), and annealed. The amorphous and crystalline phases were observed for the as-deposited and annealed samples, respectively from the X-ray diffraction (XRD) studies. The magnetic behaviour of the pure and doped BaTiO3 films was studied by vibrating sample magnetometry (VSM). In this study, the ferromagnetic behaviour at room temperature was observed in the Co, Nb co-doped BaTiO3 of both amorphous and crystalline films. The annealed polycrystalline Co, Nb co-doped BaTiO3 films have the larger saturation magnetization and coercivity than the amorphous films. The room temperature ferromagnetic responses were also observed by the Magneto-optical Kerr effect (MOKE) measurements for both as-deposited and annealed samples.
Jyoti Jaiswal; Manpreet Singh;Ramesh Chandra; Amit Sanger; Ashwani Kumar; Satyendra Mourya; Samta Chauhan; Ritu Daipuriya
Abstract
In the present work, structural, morphological, optical and wettability properties of DC magnetron sputtered titanium (Ti) thin films have been investigated. The nanostructured Ti thin films were deposited on glass and silicon substrates at various deposition angles, θD = 0°, 30°, 45° ...
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In the present work, structural, morphological, optical and wettability properties of DC magnetron sputtered titanium (Ti) thin films have been investigated. The nanostructured Ti thin films were deposited on glass and silicon substrates at various deposition angles, θD = 0°, 30°, 45° and 60°. HCP structure of Ti thin films with preferred peak orientations (100) and (002) were revealed from XRD. It was observed that as the deposition angle increases, film thickness (~260 - 100 nm) as well as average crystallite size (~27 - 11 nm) of Ti thin films decrease. Significant changes in topography of the films, with change in deposition angle, have been observed. The optical and wettability results suggested that transmission, reflection, absorption and water contact angle of Ti thin films are strongly influenced by deposition angle due to change in its surface roughness. The large near infrared (NIR) absorbance (~ 66 - 75%) was found for the sample deposited at θD = 30°, which exhibited hydrophobic (~ 94.6°) nature with high surface roughness (~ 28 nm).
R. Subba Reddy; K. Radhamma; A. Sivasankar Reddy; S. Uthanna
Abstract
Thin films of molybdenum doped (2.7 at.%) zinc oxide (MZO) were deposited on glass substrates held at room temperature by RF magnetron sputtering of mosaic target of Mo-Zn at different substrate bias voltages. The influence of substrate bias voltage on the structural, electrical and optical properties ...
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Thin films of molybdenum doped (2.7 at.%) zinc oxide (MZO) were deposited on glass substrates held at room temperature by RF magnetron sputtering of mosaic target of Mo-Zn at different substrate bias voltages. The influence of substrate bias voltage on the structural, electrical and optical properties was investigated. The MZO films deposited on unbiased substrate were of amorphous, while those formed at substrate bias voltage of -40 V and above were of nanocrystalline. The crystallite size of the films improved with the applied bias voltage. At higher substrate bias voltage of -120 V the ion bombardment induced the high defect density in the films hence decrease in the crystallinity. The films formed at substrate bias voltage of -80 V exhibited low electrical resistivity of 1.2x10 -2 Ωcm and optical transmittance of about 79 %. These films showed optical band gap of 3.29 eV and figure of merit of 19 Ω -1 cm -1 .
Nadarajah Muhunthan; Om P. Singh; Vidya N. Singh; Kedar N. Sood
Abstract
Copper zinc tin sulfide (CZTS) thin film was deposited by co-sputtering metal targets and post-deposition sulfurization in H2S. Temperature-dependent electrical conductivity and photoconductivity effects in CZTS are studied. The low temperature electrical conductivity measurement shows acceptor level ...
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Copper zinc tin sulfide (CZTS) thin film was deposited by co-sputtering metal targets and post-deposition sulfurization in H2S. Temperature-dependent electrical conductivity and photoconductivity effects in CZTS are studied. The low temperature electrical conductivity measurement shows acceptor level energy value as 36.85 meV. A large decay time of 108 s at 300K, 99 s at 200K and 94 s at 100K after switching off the light source was observed. The decay behavior of this persistent photoconductivity (PPC) in CZTS follows the double exponential function. The results show that defects are responsible for the observed PPC in CZTS. The combined measurements of low temperature electrical conductivity and photoconductivity give account of the defect level. Control of these defects can improve the quality of material and thus the resulting device.
Priyadarshini Dash; Haripriya Rath; Udai B. Singh; Sunil Ojha; Devesh K. Avasthi; Naresh C. Mishra
Abstract
Two sets of gold thin films of thickness of about 20 and 50 nm, grown by thermal evaporation method on (100) silicon wafers were irradiated by 197 MeV Au ions. Grazing incidence X-Ray diffraction (GIXRD) study has been revealed lattice expansion on decreasing the film thickness. 197 MeV Au ion irradiation ...
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Two sets of gold thin films of thickness of about 20 and 50 nm, grown by thermal evaporation method on (100) silicon wafers were irradiated by 197 MeV Au ions. Grazing incidence X-Ray diffraction (GIXRD) study has been revealed lattice expansion on decreasing the film thickness. 197 MeV Au ion irradiation was not affect either the cubic crystal structure of gold or its lattice parameter. Atomic force microscopy (AFM) study indicated that the evolution of the surface morphology with ion fluence crucially depended on the film thickness, the thinner film being more sensitive than the thicker one. Irradiation led to nanoparticles formation on the surface of the films. This observation is in contrast to the generally perceived damaging role of swift heavy ion (SHI) irradiation. Power spectral density analysis of the roughness along both the lateral and vertical directions demonstrated dominance of surface diffusion over volume diffusion induced by SHI irradiation. A comparison of the sputtering yield obtained from Rutherford back scattering (RBS) spectra of the irradiated films and transmission electron microscopy (TEM) of the particles sputtered from the films and collected by a catcher grid during irradiation indicated that more than the surface and volume diffusion processes, it is the irradiation induced sputtering that controls the overall surface morphology of the films. The surface roughness increase with ion fluence and the irradiation induced sputtering yield was found to be larger in thinner films. Film thickness dependence of the evolution of surface morphology and sputtering yield with 197 MeV Au ion irradiation clearly indicates the dominance of the electronic energy loss over the nuclear energy loss of the projectiles ions in the target medium and opens up the ways for examining the applicability of different models of ion-matter interaction in systems with reduced dimensions.
Om P. Singh; N. Muhunthan; Vidya N. Singh; Bhanu P. Singh
Abstract
In this study, CZTS thin films were deposited by co-sputtering Cu, ZnS and SnS targets and sulfurizing it in H2S atmosphere at 550 °C. It has been observed that by varying the sulfurization time from 5 to 40 min, the secondary phases got eliminated and stoichiometric film is obtained. This leads ...
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In this study, CZTS thin films were deposited by co-sputtering Cu, ZnS and SnS targets and sulfurizing it in H2S atmosphere at 550 °C. It has been observed that by varying the sulfurization time from 5 to 40 min, the secondary phases got eliminated and stoichiometric film is obtained. This leads to change in the optical band gap from 1.67 to 1.51 eV. The crystallite size calculated using the broadening in the (112) peak of the X-ray diffraction spectra also changed with the sulfurization time from 15.0 to 21.7 nm. Broadening and shift in the Raman peaks have also been observed. Changes in grain size have been observed in scanning electron microscopic studies. In short, the increased band gap reported in literatures may be due to the presence of impurities (except for particles where quantum confinement is applicable; with size less than ~ 7 nm). The above conclusion is based on careful analysis of XRD and Raman data. This study shall help in characterizing CZTS thin film properly, growing high quality CZTS thin films for the realization of high efficiency and durable CZTS based solar cell.
R. Subba Reddy; A. Sreedhar; A. Sivasankar Reddy; S. Uthanna
Abstract
Zinc oxide (ZnO) thin films were formed by RF reactive magnetron sputtering onto p-type silicon and glass substrates held at room temperature. The thickness of the films deposited was in the range 160 – 398 nm. The thickness dependence structural, morphological and optical properties of ZnO films ...
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Zinc oxide (ZnO) thin films were formed by RF reactive magnetron sputtering onto p-type silicon and glass substrates held at room temperature. The thickness of the films deposited was in the range 160 – 398 nm. The thickness dependence structural, morphological and optical properties of ZnO films were systematically investigated. The maximum crystallite size of 21 nm observed at films thickness of 231 nm by X- ray diffraction. Scanning electron microscopic analysis revealed that the growth of nanowires in all the films. The root mean square roughness of the films increased from 7.3 to 53 nm in the thickness range of investigation. Fourier transform infrared analysis confirmed the Zn-O bonding located at wavenumber of 413 cm -1 . The average optical transmittance of the films was about 89 % in the visible region. The optical band gap of the ZnO films decreased from 3.14 to 3.02 eV with increase of film thickness from 160 to 398 nm respectively.
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