V. Kumar; R. Singhal; R. Vishnoi; M. Gupta; P. Sharma; M. K. Banerjee; K. Asokan; H. Sharma; A. Gupta; D. Kanjilal
Abstract
In the present work, the effects of 120 MeV Au ion irradiation at different fluences ranging from 1×10 12 to 3×10 13 ions/cm 2 on structural and electrical properties of thin films of Nickel-titanium (Ni-Ti) shape memory alloys (SMAs) grown on Si substrate using DC magnetron co-sputtering ...
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In the present work, the effects of 120 MeV Au ion irradiation at different fluences ranging from 1×10 12 to 3×10 13 ions/cm 2 on structural and electrical properties of thin films of Nickel-titanium (Ni-Ti) shape memory alloys (SMAs) grown on Si substrate using DC magnetron co-sputtering is studied. The surface morphology, crystallization and phase transformation behaviour of these films were investigated using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Four-terminal resistivity measurement method. XRD pattern reveals that both the phases-martensite as well as austenite exist in the pristine film. Resistivity measurements revealed a two way transformation from cubic to rhombohedral and from rhombohedral to monoclinic phase in pristine film and decrease in its transformation temperature with increased fluence. At higher fluences 5×10 12 and 1×10 13 ions/cm 2 , films showed non-metallic behaviour which could be due to the disorder occurring in these films due to ion impact and precipitate formation. The elemental composition of pristine film is determined by Rutherford backscattering spectroscopy.
Ranjana S. Varma; D.C. Kothari; A.K. Mallik; A. Bhatnagar; D. Kanjilal; S. Santra; R.G. Thomas; R. Tewari; S. Neogy; G.K. Dey
Abstract
Silver ion exchanges on silicate glasses were carried out at different temperatures 320 °C, 400 °C, and 500 °C for 60 min. The exchanged glasses were either annealed at 500 °C for 60 min or swift heavy ion (SHI) irradiated using 120 MeV Ag 9+ ions at a fluence of 5 x 10 12 ions/cm 2 . ...
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Silver ion exchanges on silicate glasses were carried out at different temperatures 320 °C, 400 °C, and 500 °C for 60 min. The exchanged glasses were either annealed at 500 °C for 60 min or swift heavy ion (SHI) irradiated using 120 MeV Ag 9+ ions at a fluence of 5 x 10 12 ions/cm 2 . Silver nanoparticles were formed in the samples ion exchanged at 500 °C without any post-exchange treatments. Post-exchange annealing treatment resulted in silver nanoparticle formation for samples ion exchanged at temperature of 320 °C and 400 °C. Whereas post irradiation treatment for ion exchanged sample at 320 °C resulted in Ag4 nanocluster formation. After post-irradiation, the density of Ag nanoparticles increases for the sample ion exchanged at temperature of 500 °C. RBS was used to obtain silver depth profiles in the ion exchanged samples. Near surface accumulation of Ag atoms is observed in the RBS spectra for the samples prepared at high ion exchange temperature of 500 °C or SHI irradiated samples, in which Ag nanoparticle formation was also observed. UV-vis absorption spectroscopy and Transmission Electron Microscopy (TEM) were used to obtain signatures of nano-particles and to estimate their size. The ion exchanged glasses without nanoparticles were characterized for their possible use in multimode planar waveguides. The post-exchange treated glasses lost their waveguide property, but exhibited nonlinear optical property indicating their potential use for optical switching. Open aperture z-scan measurements for the sample prepared at high ion exchange temperature of 500 °C shows optical limiting behavior, whereas the samples prepared at low ion exchange temperature followed by annealing or irradiation show saturation behavior.
Ranjana S. Varma; D.C. Kothari; S. Santra; R.G. Thomas; R. Tewari; S. Neogy; C.S. Suchand Sandeep; Reji Philip; D. Kanjilal
Abstract
In the present work, we have used swift heavy ions (SHI) irradiation and post irradiation annealing to synthesize Ag nanoparticles in fused silica. Fused silica samples deposited with 15 nm of Ag film were irradiated using SHI beam of 120 MeV Ag 9+ ions at different fluences and post irradiation annealing ...
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In the present work, we have used swift heavy ions (SHI) irradiation and post irradiation annealing to synthesize Ag nanoparticles in fused silica. Fused silica samples deposited with 15 nm of Ag film were irradiated using SHI beam of 120 MeV Ag 9+ ions at different fluences and post irradiation annealing was done at 500 °C in air for 30 min. The samples were characterized using UV-vis absorption spectroscopy, Rutherford Backscattering Spectrometry (RBS), GAXRD, Transmission Electron Microscopy (TEM), and open aperture z-scan measurements. The signature of Ag nanoparticles was observed in optical absorption spectra and the average size of the Ag nanoparticles was estimated using Mie’s theory. The size of the nanoparticles (~3 nm) was also confirmed from the GAXRD and TEM measurements. RBS results for Ag/SiO2 irradiated with the fluence of 5 x10 13 ions/cm 2 shows the decrease in slope at the interface of the Ag profile, indicating a partial mixing at a fluence of 5 x10 13 ions/cm 2 . Open aperture z-scan measurement of Ag/SiO2 SHI irradiated sample after annealing shows a saturation behavior, indicating that the sample is optically non-linear. The sample shows saturation behavior but does not show optical limiting behavior, which indicates that the size and number density of nanoparticles are low. The ability to control the particle size using ion beam technique as a function of fluence and observed nonlinearity results provide concrete evidence that Ag nano composite glasses can be used in nonlinear and optical limiting application.
S. Pal; A. Sarkar; D. Sanyal; T. Rakshit; D. Kanjilal; P. Kumar; S. K. Ray; D. Jana
Abstract
1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 14 ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get ...
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1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 14 ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get insight on the defects in the irradiated samples Ultraviolet-visible (UV-vis) absorption, Raman, and photoluminescence (PL) spectroscopy and Glancing Angle X-Ray Diffraction (GAXRD) measurements have been carried out. Enhancement of overall disorder in the irradiated samples is reflected from the GAXRD peak broadening. UV-vis absorption spectra of the samples shows new absorption bands due to irradiation. Complete absorption in the blue region of the spectrum and partial absorption in the green and red region changes the sample colour from white to reddish brown. The Raman peak representing wurtzite structure of the ZnO material (~ 437 cm -1 ) has decreased monotonically with the increase of irradiation fluence. At the same time, evolution of the 575 cm -1 Raman mode in the irradiated samples shows the increase of oxygen deficient disorder like zinc interstitials (IZn) and/or oxygen vacancies (VO) in ZnO. PL spectrum of the yellow coloured sample shows large reduction of overall luminescence compared to the unirradiated one. Further increase of fluence causes an increase of luminescence in the blue region of the spectrum. The blue-violet emission can be associated with the interstitial Zn (IZn) related optical transition. The results altogether indicates IZn type defects in the highest fluence irradiated sample. Large changes in the electrical resistance and luminescent features of ZnO using Ar ion beam provides a purposeful way to tune the optoelectronic properties of ZnO based devices.
Jitendra Pal Singh; Sanjeev Gautam; Braj Bhusan Singh; Sujeet Chaudhary; D. Kabiraj; D. Kanjilal; K. H. Chae; R. Kotnala; Jenn-Min Lee; Jin-Ming Chen; K. Asokan
Abstract
MgO based magnetic tunnel junctions (MTJs) exhibit high tunneling magnetoresistance (TMR) and have potential applications in magnetic random access memories. This study addresses the role of interface in the Fe/MgO/Fe based MTJs. For present investigation, Fe/MgO/Fe multilayer stack on Si substrates ...
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MgO based magnetic tunnel junctions (MTJs) exhibit high tunneling magnetoresistance (TMR) and have potential applications in magnetic random access memories. This study addresses the role of interface in the Fe/MgO/Fe based MTJs. For present investigation, Fe/MgO/Fe multilayer stack on Si substrates is grown by electron beam evaporation method and has been investigated for structural, magnetic and electronic properties. All the layers in the stack were of polycrystalline in nature as evidenced from X-ray diffraction studies, and the magnetic measurements show the attributes perpendicular magnetic anisotropy. Results from near edge X-ray absorption spectra at Fe L-edges measured by total electron yield mode and X-ray reflectometry indicate the formation of FeOx at the Fe/MgO interface. These are associated with hybridization of Fe (3d)-O(2p) levels at Fe/MgO interface in the stack and thickness of layers in the stacks. Absence of magnetic de-coupling between top and bottom ferromagnetic layers has been attributed to interface roughness and oxidation at Fe/MgO interface. This study highlights the role of interface and oxidation that need to be considered for improving the TMR for devices.
V. Sarath Chandra; K. Elayaraja; R. V. Suganthi; M. I. Ahymah Joshy; I. Sulania; P.K. Kulriya; K. Asokan; D. Kanjilal; S. Narayana Kalkura
Abstract
Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is the main inorganic component of hard tissues like bone and teeth. HAp incorporated with magnetic ions, play an important role in cell separation, magnetic resonance imaging (MRI), targeted drug delivery and in hyperthermia treatment of cancer. In this study, the ...
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Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is the main inorganic component of hard tissues like bone and teeth. HAp incorporated with magnetic ions, play an important role in cell separation, magnetic resonance imaging (MRI), targeted drug delivery and in hyperthermia treatment of cancer. In this study, the effect of 60 MeV Si 5+ ion on the hydrothermally synthesized Fe 3+ doped hydroxyapatite (Fe-HAp, 33 nm) was investigated. At higher fluences, partial amorphization with an increase in the cluster size and surface roughness was observed. Depending on the ion fluence, pores ranging from 300 to 360 nm in size were produced. Irradiated Fe-HAp samples showed enhanced haemocompatibility and bioactivity. The drug (amoxycillin, AMX) loaded irradiated samples exhibited high antimicrobial activity.
Jitendra Pal Singh; I. Sulania; Jai Prakash; S. Gautam; K. H. Chae; D. Kanjilal; K. Asokan
Abstract
Present work reports 200 MeV Ag 15+ irradiation induced effects on the surface morphology, grain size and local electronic structure in MgO thin films deposited by e-beam evaporation under ultra High vacuum. The grain size was found to decrease from 37 nm (pristine film) to 23 nm for the sample irradiated ...
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Present work reports 200 MeV Ag 15+ irradiation induced effects on the surface morphology, grain size and local electronic structure in MgO thin films deposited by e-beam evaporation under ultra High vacuum. The grain size was found to decrease from 37 nm (pristine film) to 23 nm for the sample irradiated with fluence of 1×10 12 ions/cm 2 and thereafter it increases upto fluence of 5×10 12 ions/cm 2 . Similar changes with ion fluence were also observed for surface roughness. Shifting and disappearance of peaks in X-ray absorption spectra with irradiation shows the electronic structure modification after irradiation. The detailed analysis of observed results has been done on the basis of existing theories.
