[en] An electron cyclotron resonance (ECR) based medium energy ion beam facility, known as High Fluence Ion Beam Facility (HFIBF), is commissioned at Nanotechnology Application Centre, University of Allahabad. The facility is a user facility for ion beam driven materials synthesis, properties modification and their characterizations. The source can be operated up to maximum of 25 kV extraction and 300 kV platform potential and it includes RF plasma, oven and sputter ion sources for gases, low melting point metals and high melting points metal ions generations, respectively. The main advantages of the facility is the high flux and large area scanning. (author)

[en] We have demonstrated the possibility of doing Rutherford Backscattering Spectrometry (RBS) with 12 MeV C at NSC. Usage of heavy ions in RBS offers advantages over conventional RBS like better depth resolution, mass resolution and sensitivity. In spite of poor energy resolution of SSBD for heavy ions, we obtained depth resolution of about 10 nm, comparable with conventional RBS, due to high stopping power of C and the chosen scattering geometry. (author)

[en] We present an experimental study on evolution of dumbbell-shaped ZnO microstructures. Structure, shape, size and optical properties were monitored by means of scanning electron microscopy, x-ray diffraction, and photoluminescence spectroscopy, respectively. Our results show that a crystalline phase of ZnO is formed. A uniform distribution of randomly oriented dumbbell-shaped ZnO microstructures is observed. Near band edge as well as deep level visible emissions confirmed that there are intrinsic defects present in the system. Emissions extending from UV region to visible region show that these microstructures are good quality optical material which can be used in photocatalytic field. - Highlights: • Dumbbell-shaped ZnO micro-rods were synthesized by starch assisted hydrothermal process. • Micro-rods were of crystalline nature, confirmed by x-ray diffraction. • UV-emission as well as deep level visible emissions were observed. • Broad absorption band is observed which can be utilized in photocatalytic field

[en] Thermally grown thin films of LiF were irradiated with 150 MeV Ag ions at various fluences. The quality of films was studied using GAXRD, which shows that films are c-axis oriented. It also shows that grain size decreases and the intensity of (200) orientation enhances with fluence, which is the preferential orientation. These results are further confirmed by photoluminescence studies, which shows that the concentration of F₃⁺ and F₂ color centers decreases with ion fluence due to increase in surface to volume ratio under Swift Heavy Ion (SHI) irradiation. (author)

[en] The electrical characteristics of Au/n-Si (1 0 0) Schottky rectifier have been studied in a wide irradiation fluence range using conventional current-voltage (I-V) and capacitance-voltage (C-V) measurements. The I-V characteristics showed an abnormal increase in forward current at low voltage. The device shows a bend in forward I-V and reverses bias C-V characteristics due to extra current, suggesting that there are two independent contributions to thermionic current, corresponding to two levels of the Schottky barrier. It is shown that the excess current at low voltage can be explained by taking into account the role of heavy ion irradiation induced defects at the metal semiconductor interface

[en] Thin epitaxial GaN films grown on 6H-SiC(0001) substrates were implanted with 180 keV Co ions at three different fluences. As-implanted samples were characterized with secondary ion mass spectrometry and Rutherford backscattering spectrometry to obtain the Co depth profiles and the maximum Co concentrations. As-implanted samples were annealed applying two different techniques: rapid thermal annealing and annealing by swift heavy ion irradiation. Rapid thermal annealing was done at two temperatures: 1150 deg. C for 20 s and 700 deg. C for 5 min. 200 MeV Ag ions at two fluences were used for annealing by irradiation. Crystalline structure of the pristine, as-implanted, and annealed samples was investigated using x-ray diffraction, and the results were compared. Improvement of the crystalline quality was observed for rapid thermal annealed samples at the higher annealing temperature as confirmed with rocking curve measurements. The results indicate the presence of Co clusters in these annealed samples. Swift heavy ion irradiation with the parameters chosen for this study did not lead to a significant annealing

[en] The effect of 50 MeV Ni ion irradiation on Au/n-GaN Schottky diode has been studied by in situ current voltage characterization. The variation of Schottky parameters with ion irradiation is discussed by varying the irradiation fluence from 5 x 10⁹ to 5 x 10¹¹ ions cm^-2. These results are interpreted on the basis of energy loss mechanisms of swift heavy ion (SHI) irradiation at the metal-semiconductor interface.

[en] 200 nm thick SiO_2 layers grown on Si substrates were implanted with 150 keV Ge ions at three different fluences. As-implanted samples were characterized with time-of-flight secondary ion mass spectrometry and Rutherford backscattering spectrometry to obtain depth profiles and concentration of Ge ions. As-implanted samples were annealed at 950 °C for 30 min. Crystalline quality of pristine, as-implanted, and annealed samples was investigated using Raman scattering measurements and the results were compared. Crystalline structure of as-implanted and annealed samples of embedded Ge into SiO_2 matrix was studied using x-ray diffraction. No secondary phase or alloy formation of Ge was detected with x-ray diffraction or Raman measurements. Scanning transmission electron microscope measurements were done to get the nanocrystal size and localized information. The results confirmed that fluence dependent Ge nanocrystals of different sizes are formed in the annealed samples. It is also observed that Ge is slowly diffusing deeper into the substrate with annealing

[en] The highly oriented pyrolytic graphite (HOPG) samples (Grade ZYB with grain size ∼1 mm) are irradiated with 150 MeV Au beam with fluences varying from 1 x 10¹¹ ions/cm² to 2 x 10¹³ ions/cm². The surface topography and the I-V characteristics are studied using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) at Nuclear Science Centre, New Delhi. The formation of hillocks is observed for the samples irradiated with fluences of 1 x 10¹¹ ions/cm², 1 x 10¹² ions/cm² and 1 x 10¹³ ions/cm² with typical diameters of 6.2, 2.2 and 1.5 nm, respectively. No hillocks are observed for the sample irradiated with fluence of 2 x 10¹³ ions/cm², though the formation of small craters at some places are observed. The formation of hillocks is attributed to nuclear energy loss induced collision cascades near the surface. The reduction in hillocks size and formation of craters at higher fluence is attributed to the electronic sputtering from the surface. The STS studies of I-V characteristics show an increasing ohmic behavior with fluence which is attributed to increasing metallic state for HOPG surface due to irradiation induced increase of carbon bond lengths

[en] One hundred and twenty mega electron volts [120 MeV] of Au ion irradiation induced increase in conductivity at ion impact sites in C₆, has been observed using conducting atomic force microscope (C-AFM). The current image shows the formation of ion tracks having much larger conductivity as compared to surroundings in C₆ films on Si substrate. The increase in conductivity is attributed to the electronic energy loss induced polymerization and transformation from insulating C₆ to conducting graphite like carbon around ion path. The unirradiated sample has a semiconducting nature of I-V characteristic, which shows an increased ohmic behavior with increasing fluence. This effect has been attributed to simultaneous imaging of more than one track at sites where very close/overlapping ion impacts take place