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ION IRRADLATION STUDIES OC CARGON FILMS PREPARED BY PLASMA ASSISTED CVD METHOD
Bhattacharyya, Bhattacharyya, Somnath-,Sayeed, Ahmed,Kanjilal, Kanjilal, D.,Subramanyam, S.V 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.1 No.3
Amorphous hydrogeneted carbon films were prepared by plasma assisted cvd metnod and their dc conductivity as studied as a function of temperature in the range of 300K to 10K. Films were then subjected to high energy(170MeV)$I^{+13}$ ion irradiation. After irradiation an marked change was observed in the conductivity and its temperature dependenc. The conductivity decreased by 2 to 3 orders of magnitude, room temperature activation energy increased and a gap appeared in the electronic structure. Photo-emission spectropic study on the material show a decrease in the $\pi$ states of the electronic density of states spectrum from UPS and a noticible change in the Cls peak shape in XPS.
Study on the ferromagnetism in Co and N doped ZnO thin films
S. Ramasubramanian,R. Thangavel,M. Rajagopalan,A. Thamizhavel,K. Asokan,D. Kanjilal,J. Kumar 한국물리학회 2013 Current Applied Physics Vol.13 No.8
Present investigation reports the structural, optical and magnetic properties of co-doping of Co and N ions in ZnO samples, prepared by two distinct methods. In the first method, samples are synthesized by Solegel technique in which the Co and N are co-doped simultaneously during the growth process itself. In the second case, N ions are implanted in the Co doped ZnO thin films grown by Pulsed Laser Deposition (PLD). Structural studies showed that the nitrogen implantation on Co doped ZnO samples developed compressive stress in the films. X-ray photoelectron spectroscopy confirmed the doping of Co and N in ZnO matrix. In the Resonant Raman scattering multiple LO phonons up to fifth order are observed in the (Co, N) co-doped ZnO. Photoluminescence spectra showed that there is reduction in the bandgap due to the presence of Co in the lattice and also the presence of Zn vacancies in the films. All samples showed ferromagnetic behavior at room temperature. The magnetic moment observed in the implanted films is found to be varied with the different dosages of the implanted N ions. First principle calculations have been carried out to study the possible magnetic interaction in the co-doped system. Present study shows that the ferromagnetic interaction is due to the hybridization between N 2p and Co 3d states in the (Co, N) co-doped ZnO and is very sensitive to the geometrical configurations of dopants and the vacancy in the ZnO host lattice.
High-energy ion induced physical and surface modifications in antimony sulphide thin films
S. Subramanian,M. Balaji,P. Chithra Lekha,K. Asokan,D. Kanjilal,Indra Sulania,Jai Prakash,D. Pathinettam Padiyan 한국물리학회 2010 Current Applied Physics Vol.10 No.4
Sb2S3 thin films prepared by electrodeposition on indium tin oxide coated glass substrate were irradiated with 150 MeV Ni11+ ions for various fluence in the range of 1011–1013 ions/㎠. The modifications in the structure, surface morphology and optical properties have been studied as a function of ion fluence. X-ray diffraction (XRD) analysis indicates a shift in the (2 4 0) peak position towards lower diffraction angle and a decrease in grain size with increase in ion fluence. Presence of microcracks due to irradiation induced grain splitting effect has been observed from the SEM micrograph at higher ion fluence. The optical absorbance spectrum revealed a shift in the fundamental absorption edge and the band gap energy increased from a value of 1.63 eV for as-deposited films to 1.80 eV for the films irradiated with 1013 ions/㎠.
Defects mediated diffusion in Pt/Co/Pt multilayers induced by dense electronic excitations
Neeru Sehdev,Rohit Medwal,Zener Sukra Lie,Dinesh Chandra Agarwal,K. Asokan,D. Kanjilal,S.Annapoorni 한국물리학회 2014 Current Applied Physics Vol.14 No.3
Present study compares the effects of 200 MeV Ag15þ and 100 MeV O7þ ion irradiations on the structural, interfacial mixing and magnetic properties of annealed Pt/Co/Pt layers fabricated by DC magnetron sputtering. X-ray diffraction analysis shows that ion irradiations coupled with post annealing results in the formation of the face centred tetragonal L10 CoPt phase. Irradiation using 200 MeV Ag15þ ions having higher ionizing energy transfer to the film was found to be more efficient in causing structural phase transition as compared with that using 100 MeV energy O7þ ions having lower ionizing energy transfer at similar fluence. Rutherford back scattering analysis reveals the role of defect mediated inter-atomic diffusion in tailoring the alloy composition of the film irradiated by different energetic ions. A broad magnetic switching field distribution for O7þ ion irradiated films compared to Ag15þ ion irradiation was evident from the magnetic measurements. The contribution of alloy composition to switching field distribution has been discussed in details. Above results showed that the electronic energy loss and fluence dependent defects, generated by irradiation, played an important role in tuning the structural, atomic diffusion and magnetic reversal properties of Pt/Co/Pt.
Singh, J.P.,Gautam, S.,Srivastava, R.C.,Asokan, K.,Kanjilal, D.,Chae, K.H. Academic Press 2015 Superlattices and microstructures Vol.86 No.-
Present work investigates the crossover from paramagnetism to superparamagnetism as a function of crystallite size in zinc ferrite nanoparticles using near edge X-ray absorption spectroscopy. Synthesized paramagnetic and superparamagnetic nanoparticles exhibit presence of Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP> ions with dominant concentration of Fe<SUP>3+</SUP> ions. Fe L- and O K-edges spectra of paramagnetic nanoparticles consist of more intense spectral features compared to that of superparamagnetic nanoparticles. This reflects enhanced t<SUB>2g</SUB> and e<SUB>g</SUB> symmetry states of Fe-O hybridized states in paramagnetic nanoparticles induced by increased degree of crystallization.
Tuning of ripple patterns and wetting dynamics of Si (100) surface using ion beam irradiation
Tanuj Kumar,U.B. Singh,Manish Kumar,Sunil Ojha,D. Kanjilal 한국물리학회 2014 Current Applied Physics Vol.14 No.3
Ripple patterns on Si (100) surface have been fabricated using 200 keV Arþ oblique ion beam irradiation. Dynamical evolution of patterns is studied for the fluences ranging from 3 1017 ions/cm2 to 3 1018 ions/cm2. AFM study reveals that the exponential growth of roughness with stable wavelength of ripples up to higher fluence values is lying in the linear regime of Continuum models. Stylus Profilometer measurement was carried out to emphasize the role of sputtering induced surface etching in ripple formation. Rutherford Backscattering Spectroscopy shows the incorporation of Ar in the near surface region. Observed growth of ripples is discussed in the framework of existing models of surface patterning. Role of ion beam sputtering induced surface etching is emphasized in formation of ripples. In addition, the wetting study is performed to demonstrate the possibility of engineering the hydrophilicity of ripple patterned Si (100) surface.
Kumar, Parmod,Malik, Hitendra K.,Gautam, S.,Chae, K.H.,Asokan, K.,Kanjilal, D. Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.710 No.-
<P><B>Abstract</B></P> <P>Present study shows that dense electronic excitations caused by ion beam irradiation in Zn<SUB>0.9</SUB>Mg<SUB>0.1</SUB>O films lead to significant changes in room temperature ferromagnetism. It is found that defects are playing dominant role in the modification of various physical properties including ferromagnetic behaviour. Presence of defects were investigated through photoluminescence spectroscopy along with local electronic structure study using X-ray absorption spectroscopy. This novel observation is relevant to get further insight into ferromagnetic origin and maybe applied to tune magnetic properties for spintronic applications. A strong correlation exists between the ferromagnetic properties and defects produced during high energy irradiation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> RF sputtered Zn<SUB>0.9</SUB>Mg<SUB>0.1</SUB>O thin films. </LI> <LI> Investigation on magnetic properties of Zn<SUB>0.9</SUB>Mg<SUB>0.1</SUB>O films caused by SHI irradiation. </LI> <LI> Presence of defects were confirmed through PL and XAS. </LI> </UL> </P>
Manna Ashis K.,Joshi Shalik R.,Satpati B.,Dash P.,Chattaraj Ananya,Srivastava S.K.,Kanjilal A.,Kanjilal D.,Varma Shikha 한국물리학회 2022 Current Applied Physics Vol.43 No.-
The present study explores the role of Ti ion implantation in structural phase transition in TiO2 thin films. Raman and TEM results reveal that after implantation Rutile phase in films increases at the expense of Anatase nanostructures. Though the as-deposited films display the presence of bigger anatase nanoparticles, after implantation, predominantly phonon confined smaller (~ 8 nm in size) anatase nanostructures are observed. GIXRD and Raman results further reflect presence of a critical fluence, 1 × 1013 ions/cm2, where the initial transformation from anatase to Rutile phase is observed. The role of Oxygen vacancies, in this transformation, has been explored here by XPS. Modifications in UV–Vis and Bandgap results show rich behavior which also reflects phase transformation at the critical fluence. Results further indicate that the phase transition gets first initiated deeper in the film and later on the surface. Interestingly, aggregation of larger Anatase nano-particles appears to be responsible for the structural transformation as observed here.
Kumar, Parmod,Sharma, Vikas,Singh, Jitendra P.,Kumar, Ashish,Chahal, Surjeet,Sachdev, K.,Chae, K.H.,Kumar, Ashok,Asokan, K.,Kanjilal, D. Elsevier 2019 Journal of magnetism and magnetic materials Vol.489 No.-
<P><B>Abstract</B></P> <P>Present work aims at investigating the structural, magnetic and dielectric properties of zinc doped Fe<SUB>2</SUB>O<SUB>3</SUB> nanoparticles (pure, 10%, 20% & 30%) and correlated with their local electronic structures using X-ray absorption near-edge structure (XANES) spectroscopy. X-ray diffraction and Raman measurements infer that doping of Zn cations lead to the formation of secondary phases corresponding to ZnFe<SUB>2</SUB>O<SUB>4</SUB> along with the hematite phase of Fe<SUB>2</SUB>O<SUB>3</SUB>. Magnetic measurements show that magnetization vs magnetic field curve for 10% Zn doping exhibit maximum saturation magnetization (~2.93 × 10<SUP>−3</SUP> emu/g) as well as the coercivity (~956 Oe). The values of these parameters decrease for higher content of Zn. The temperature dependence of dielectric behaviour follows the same trend as that of the lattice parameter and magnetic measurements. The XANES spectra at Fe L- and Fe K-edges indicate partial reduction of Fe<SUP>3+</SUP> ions into Fe<SUP>2+</SUP> upon Zn doping in the Fe<SUB>2</SUB>O<SUB>3</SUB> lattice. However, divalent state is favourable for Zn (i.e. Zn<SUP>2+</SUP>) within the doping range reported in this study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Zn doped Fe<SUB>2</SUB>O<SUB>3</SUB> nanoparticles. </LI> <LI> Study of magnetic and electrical properties. </LI> <LI> Correlation of magnetic and electrical properties with local electronic structure. </LI> </UL> </P>