• K ASOKAN

Articles written in Bulletin of Materials Science

• 12C5+ radiation effects in SR-86 track recording polymer

The samples of SR-86 polymer were irradiated with12C5+ ions of energy 5·0 MeV/u using fluences of 1011−1014 ions/cm2 at NSC Pelletron in a high vacuum scattering chamber. The optical studies show an increase in absorption of UV or IR in the shorter wavelength region (250–500 nm). The study also reveals that the increase in radiation dose extends the optical absorption region to longer wavelengths. It is observed that the bulk etch rate of this polymer is enhanced after heavy ion irradiation.

• A study on defect annealing in GaAs nanostructures by ion beam irradiation

In this study, annealing of deep level (EL2) defect in gallium arsenide (GaAs) nanostructures by argon ion beam irradiation has been reported. GaAs nanodots of diameter ranging from 15 to 22 nm were deposited on silicon substratesusing the ions of GaAs generated by hot, dense and extremely non-equilibrium argon plasma in a modified dense plasma focus device. GaAs nanodots thus obtained were irradiated by Ar$^{2+}$ ion beam of energy 200 keV with varying ion fluences from $1 \times 10^{13}$ to $5 \times 10^{15}$ ions cm$^{−2}$ in the low energy ion-beam facility. The ion-beam irradiation transformed the as deposited GaAs nanodots into uniform GaAs nanostructured films of thickness $\sim$30 nm. The obtained nanostructured films are polycrystalline with paucity of arsenic antisite (EL2) deep level defect. The excess arsenic present in the as-deposited GaAs nanodots is the main cause of EL2 defect. Raman and photoluminescence measurements of GaAs nanostructured films indicates removal of excess arsenic, which was present in as-deposited GaAs nanodots, thereby suggesting annealing of EL2 defect from the ion-irradiated GaAs nanostructured films. The change in conductivity type from n- to p-type obtainedfrom Hall measurement further confirms annealing of EL2 defects. The ion-irradiated GaAs nanostructured films have low leakage current due to removal of defects as obtained in current–voltage study, which corroborate the annealing of EL2 defect. The defect-free GaAs nanostructured films thus obtained have potential applications in fabrication of highly efficient optoelectronic and electronic devices.

• Thermal effects on resistive switching in manganite–silicon thin film device

In this article, we report the results of the fabrication and studies of Y$_{0.95}$Ca$_{0.05}$MnO$_3$/Si device (referred hereafter as YCMO/Si) by pulsed laser deposition (PLD) and its temperature-dependent resistive switching (RS) behaviours measured across the YCMO/Si interface. These temperature (100–300 K)-dependent hysteretic current–voltage ($I–V$) characteristics have been understood on the basis of various possible charge conduction mechanisms involving the thermal effects on the charge carriers during four different cycles of the RS behaviours. Variations in the values of barrierheight and the ratio of free to trapped charge carrier densities with temperature have been discussed for reverse bias mode of this YCMO/Si device. Temperature-dependent temperature coefficient of resistance (TCR) under different applied forward voltages shows an interesting variations in TCR with applied forward voltage, which proves this device as a potential candidate for practical applications.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020