Study on the Effect of Nitrogen-Ion Implantation in Semi-Insulating InP by Using Scanning Tunneling Microscopy

Jayavel P,Cheul-Ro LEE,아소칸,Haris M,Hayakawa Y,santhakumar k,Tetsuo soga 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I

The effects of low-energy (110 keV) nitrogen ion (N$^+$) implantation at fluences of 1 $\times$ 10$^{13}$ and 1 $\times$ 10$^{14}$ cm$^{-2}$ in semi-insulating InP samples have been studied using cross sectional scanning tunneling microscopy. The atomically resolved images of the implanted samples reveal lattice disordering and point defects, which are attributed to implantation-induced effects. At fluence of 1 $\times$ 10$^{14}$ cm$^{-2}$, deformation of the atomic structures is observed. Cleaved-edge tunneling spectroscopy of the implanted samples has been carried out under dark conditions. The observed results demonstrate that two components of current are associated with the tunneling characteristics. Furthermore, the N$^+$ implantation is observed to induce extended states in the conduction band in which the tunneling of electrons occur. Our results suggest that low-energy N$^+$ implantation influences the atomic structures and the tunneling spectra of low-conductivity InP.

Study on the Effect of Nitrogen-Ion Implantation in Semi-Insulating InP by Using Scanning Tunneling Microscopy

Jayavel, P.,Haris, M.,Hayakawa, Y.,Santhakumar, K.,Lee, C. R.,Soga, T.,Asokan, K. Korean Physical Society 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2

Synthesis and application of graphene-αMoO₃ nanocomposite for improving visible light irradiated photocatalytic decolorization of methylene blue dye

Mahalingam, Shanmugam,Ramasamy, Jayavel,Ahn, Young-Ho Elsevier 2017 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.80 No.-

<P><B>Abstract</B></P> <P>Graphene-alpha-molybdenum trioxide (α-MoO<SUB>3</SUB>) nanocomposites were synthesized using a facile hydrothermal method. The synthesized material was characterized by various physico-chemical techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), ultra-violet–visible diffuse reflectance spectroscopy (DRS) and Raman spectroscopy. Raman spectroscopy revealed a D to G band intensity ratio of approximately one, which confirmed the good graphitization of the synthesized graphene and graphene-MoO<SUB>3</SUB> nanocomposite. The I<SUB>D</SUB>/I<SUB>G</SUB> ratio of the G-αMoO<SUB>3</SUB> nanocomposite was calculated to be 1.2. HRTEM revealed graphene sheets decorated with MoO<SUB>3</SUB> nanoparticles. The size of the MoO<SUB>3</SUB> nanoparticles dispersed over the wrinkled graphene sheets layers was 10 ± 5 nm. The chemical state functionality and composition (carbon, oxygen and molybdenum) of the G-αMoO<SUB>3</SUB> nanocomposite was examined by XPS. TGA was performed to examine the thermal stability and decomposition of the nanomaterials and nanocomposite. The photocatalytic performance of the bare synthesized MoO<SUB>3</SUB> nanoparticles and graphene-αMoO<SUB>3</SUB> nanocomposite was analyzed by the degradation of MB dye under ultra-violet and visible light irradiation. The G-αMoO<SUB>3</SUB> nanocomposite showed an extraordinarily higher photocatalytic activity than the bare MoO<SUB>3</SUB> nanoparticles. Up to 97% and 96% of the MB dye was removed under UV and visible light irradiation, respectively. A comparison of the photocatalytic effect of the bare MoO<SUB>3</SUB> and G-MoO<SUB>3</SUB> nanocomposite showed that the bare MoO<SUB>3</SUB> induced less photocatalytic degradation than the G-MoO<SUB>3</SUB> nanocomposite. The photocatalytic result suggested that graphene plays an important role in enhancing the photocatalytic activity. These results show that the G-αMoO<SUB>3</SUB> nanocomposite is an efficient catalyst for the degradation of MB dye and has potential in industrial wastewater treatment. The mechanism of the degradation process was examined by calculating the rate constant and half-life of the degradation process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of G-αMoO<SUB>3</SUB> nanocomposites by a surfactant free hydrothermal method. </LI> <LI> The G-αMoO<SUB>3</SUB> nanocomposite possess improved visible light photocatalytic activity. </LI> <LI> The highest degradation efficiency of 97% and 96% was achieved for the G-αMoO<SUB>3</SUB> catalyst. </LI> <LI> G-αMoO<SUB>3</SUB> can be used as an efficient catalyst for industrial waste water treatment. </LI> </UL> </P> <P><B>Graphic abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of in-phase type waviness in the walls of a confined Savonius rotor placed in a long channel

J. Ramarajan,S. Jayavel 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

Wind energy is one form of renewable energy that emits zero CO 2 to the environment. Wind power has enormous potential to access and produce energy from it. Savonius turbine is a vertical axis wind turbine (VAWT). The power coefficient (C p ) of the Savonius turbine is lesser than horizontal axis wind turbine (HAWT), but the Savonius turbine can extract energy from even low wind regions. However, HAWTs can produce wind energy only from higher wind velocities. Researchers have already reported improvement in the C p of the Savonius turbine due to confinement. In the present work, the waviness is introduced and the distance of waviness from the rotor has been studied. Two-dimensional numerical simulations were carried out using ANSYS Fluent 2019R3 solver with SST k-ω turbulence model. In the confined channel, compared to base case, an improvement of 27.22 % in C p has been attained for the proposed channel configuration with local waviness.

Enhanced Photocatalytic Degradation of Synthetic Dyes and Industrial Dye Wastewater by Hydrothermally Synthesized G-CuO-Co3O4 Hybrid Nanocomposites Under Visible Light Irradiation

Mahalingam, Shanmugam,Ramasamy, Jayavel,Ahn, Young-Ho Springer-Verlag 2018 Journal of cluster science Vol.29 No.2

<P>To enhance the degradation of colour and chemical oxygen demand using photocatalytic activity, Graphene-CuO-Co3O4 hybrid nanocomposites were synthesized using an in situ surfactant free facile hydrothermal method. The photocatalytic degradation of synthetic anionic dyes, methyl orange (MO) and Congo red (CR), and industrial textile wastewater dyes under visible light irradiation was evaluated. The synthesized nanocomposite was characterized structurally and morphologically using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscope, and Fourier transform infrared spectroscopy. Evaluation of the colour indicated complete removal at 15 min of irradiation for the MO and CR dyes, with 99% degradation efficiency. The reaction time for the primary effluent wastewater dye was 60 min for 81% dye removal. In contrast, a longer reaction time was required to meet the national discharge regulation for the raw wastewater dye, 300 min for 60% dye removal. The mechanism for dye degradation using the Graphene-CuO-Co3O4 hybrid nanocomposite was elucidated using the Langmuir-Hinshelwood model, and the rate constant and half-life of the degradation process were calculated. The results demonstrate that photocatalytic degradation using a hybrid nanocomposite and visible light irradiation is a sustainable alternative technology for removing colour from wastewater dye.</P>

Studies on the structural, optical, dielectric and mechanical properties of non-linear optical manganese mercury Tetrathiocyanate glycol mono methyl ether (MMTG) single crystal

A. Bhaskaran,라그하반,R. MohanKumar,R. Jayavel 한국물리학회 2010 Current Applied Physics Vol.10 No.5

Non-linear optical manganese mercury teterathiocyanate glycol monomethyl ether [MnHg(SCN)4(C3H8O2)] compound was synthesized and single crystals were grown from water-glycol monomethyl ether (1:1) mixed solvent by slow cooling method. Structure and crystallinity of the grown crystal were confirmed by both single crystal and powder X-ray diffraction analysis. Presence of functional groups and coordination of glycol monomethyl ether and thiocyanate in MMTG were confirmed by FT-IR analysis. Optical transmittance and second harmonic generation of the grown crystal were studied by UV–Vis spectrum and Kurtz powder technique. A dielectric study was performed on the MMTG single crystal to study the power dissipation of the material in the presence of alternating electric field. Mechanical behaviour was analysed using Vicker’s microhardness test. Optical surface damage measurement was carried out to confirm the suitability of MMTG crystal for NLO applications.

Studies on the growth, structural, optical, thermal and electrical properties of nonlinear optical cadmium mercury thiocyanate glycol monomethyl ether single crystal

라그하반,A. Bhaskaran,R. Sankar,R. Jayavel 한국물리학회 2010 Current Applied Physics Vol.10 No.2

Single crystals of cadmium mercury thiocyanate glycol monomethyl ether (CMTG) were grown from a mixed solvent of glycol monomethyl ether (GME):water (1:1) by slow evaporation method. The crystal structure and morphology were confirmed by single crystal X-ray diffraction analysis. Presence of functional groups and the coordination of glycol monomethyl ether (GME) and thiocyanate (SCN-) in the CMTG compound were confirmed by FT-IR analysis. Optical transparency of the grown crystal was studied by UV–Vis spectroscopy. Thermal stability and decomposition process were studied by means of TGA and DTA analysis. Dielectric measurement on CMTG single crystal was carried out for various frequency and temperatures. The surface studies by scanning electron microscopy reveals the formation of layer growth pattern indicative of 2D nucleation mechanism. From the second harmonic output power measurement by Kurtz powder method, it is observed that CMTG is a potential material for nonlinear optical applications among the bimetallic thiocyanate adducts series.

On the Study of the Atomic Structures of Nitrogen-Ion-Implanted InP

santhakumar K,이철로,아소칸,Hayakawa Y,Jayavel p,Tetsuo soga 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I

Nitrogen ions at doses of 1 $\times$ 10$^{13}$ -- 1 $\times$ 10$^{15}$ cm$^{-2}$ have been implanted in semi-insulating (SI) InP (100) single-crystal substrates. The surface topography of as-grown and implanted samples has been investigated using atomic force microscopy (AFM). The as-grown InP surface has minimum roughness and appears to be smooth. Angstrom-level pits-type defects are seen on the InP surface after the implantation. Root-mean-square roughness values measured for the as-grown and the implanted InP samples. The surface roughness increased with increasing the nitrogen-ion dose monotonically up to 5 $\times$ 10$^{14}$ cm$^{-2}$ and decreased at a dose of 1 $\times$ 10$^{15}$ cm$^{-2}$ the increase in the roughness was due to implantation-induced damages, and the decrease at higher dose 10$^{15}$ cm$^{-2}$ might have been be due to plastic deformation on the surface associated with a surface amorphisation. Post-implantation annealing smoothened the surface. Roughness values decreased relative to the implanted samples up to a dose 5 $\times$ 10$^{14}$ cm$^{-2}$, which indicates that the defects were partially annealed. At a higher dose of 10$^{15}$ cm$^{-2}$, there was no change in roughness value in spite of annealing. This indicates that the InP surface had been plastically deformed leading to amorphization at higher dose. Further, Raman characterization of these implanted samples clearly supports the surface amorphization at higher doses.

Study on the Effects of H+ and He+ Implantation in Semi-Insulating GaAs by Using Raman Spectroscopy

santhakumar kannappan,Cheul-Ro LEE,Hayakawa Y,Jayavel P,Jin soo Kim,Kesavamoorthy R,Muraleedaran Nair,Tetsuo soga 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I

Fifty-keV hydrogen-ion (H$^+$) and 70-keV helium-ion (He$^+$) implantation with doses from 10$^{13}$ to 10$^{16}$ cm$^{-2}$ in semi-insulating (100) gallium-arsenide (GaAs) single- crystal substrates have been carried out. Raman spectra of as-grown, implanted, and post-implantation-annealed GaAs samples are analyzed. Two LO phonon modes have been observed for all the samples. The lower wavenumber peak is attributed to the strained surface layer whereas the higher wavenumber peak is due to bulk GaAs crystal. For H$^+$ implantation, the peak positions of both peaks shift towards lower wavenumber up to a dose of 10$^{14}$ cm$^{-2}$ due to passivation of charge carriers. For higher doses, the peak positions shift towards higher wavenumber due to hydrogen-filled vacancy loops. On the other hand, for He$^+$-implanted samples, the peak positions increase for doses up to 10$^{13}$ cm$^{-2}$ and then decrease at higher doses. The immiscible nature of helium at low doses causes the increase in the peak positions. In contrast, implantation-induced damage is dominant at higher doses. Implantation-induced defects are partially annealed by post-implantation annealing, causing a blueshift of the peak positions for the H$^+$-implanted samples. In He$^+$-implanted samples, the peak positions redshift due to annealing of He interstitials at low doses and blueshift due to annealing of implantation-induced defects at high doses.

Electronic Structure of Mn-Doped ZnO Studied by Using X-ray Absorption Spectroscopy

P. Thakur,K. H. Chae,M. Subramanain,R. Jayavel,K. Asokan 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

Mn-doped ZnO thin films that showed ferromagnetism at room temperature were synthesized with nominal compositions Zn1-xMnxO (x = 0.03, 0.05, 0.07, 0.10 and 0.15) by using a spray pyrolysis technique. High-resolution X-ray diffraction studies suggested that the doped Mn ions occupied Zn sites and that all the samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The near-edge X-ray absorption fine structure (NEXAFS) measurements at the O K-edge clearly exhibited a pre-edge spectral feature, which evolved with Mn doping, similar to one observed in hole-doped cuprates and manganites. The Mn L3;2-edge NEXAFS spectra exhibited divalent Mn apart from mixed valent Mn3+ / Mn4+ states, which were well supported by Mn K-edge spectra.