Structural and optical properties of vanadium doped SnO₂ nanoparticles with high photocatalytic activities

Reddy, Ch.V.,Babu, B.,Vattikuti, S.V.P.,Ravikumar, R.V.S.S.N.,Shim, J. Elsevier [etc.] 2016 Journal of luminescence Vol.179 No.-

Vanadium (0.01, 0.03 and 0.05mol%) doped SnO<SUB>2</SUB> nanoparticles have been synthesized using combustion synthesis method. The as-prepared nanoparticles were characterized using various measurements such as XRD, SEM with EDS, HRTEM, Raman spectroscopy, optical, PL, XPS and FT-IR techniques. The crystal structure and average particle sizes of the prepared nanoparticles were confirmed from the XRD. The average crystalline particle sizes were decreased by increasing the vanadium dopant concentration. The presence of vanadium as V<SUP>4+</SUP> species in the host lattice was confirmed by X-ray photoelectron spectroscopy. The band gap energies were decreased by increasing dopant concentration. The 0.05mol% doped sample showed higher photocatalytic activity than undoped, V-1 and V-3 in decomposing rhodamine B (RhB) under UV light irradiation. The Raman and IR spectra confirm the fundamental vibration of SnO<SUB>2</SUB> host molecules.

Effect of annealing temperature on the electrical and structural properties of V/p-GaN Schottky structures

Padma, R.,Nagaraju, G.,Rajagopal Reddy, V.,Choi, Chel-Jong Elsevier 2016 THIN SOLID FILMS - Vol.598 No.-

<P><B>Abstract</B></P> <P>The electrical and structural properties of V/p-GaN Schottky barrier diode (SBD) have been investigated as a function of annealing temperature. The Schottky barrier height (SBH) of the as-deposited contact is found to be 0.82eV (<I>I–V</I>) and 1.10eV (<I>C–V</I>). However, it is noted that the SBH increases for the contact annealed at 400°C and the values are 0.94eV (<I>I–V</I>) and 1.21eV (<I>C–V</I>). Further, with increasing annealing temperature up to 500°C, the SBH decreases to 0.92eV (<I>I–V</I>) and 1.19eV (<I>C–V</I>). Also, the rectification ratio of the V/p-GaN SBD is evaluated for as-deposited and annealed contacts. The electrical parameters of the V/p-GaN SBD are also discussed with Cheung's and Norde functions. It is noted that the interface state density decreases upon annealing at 400°C and then slightly increases after annealing at 500°C. Results reveal that the superior electrical characteristics are obtained for the contact annealed at 400°C. The electrical results are also correlated with the interfacial microstructure of the contacts. The AES and XRD results reveal that the formation of nitride phases at the interface may be the reason for the increase of SBH after annealing at 400°C. The formation of gallide phases at the interface may be reason for the decrease in the SBH.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annealing effects on electrical and structural properties of V/p-GaN SBD are studied. </LI> <LI> Maximum barrier height is obtained on V/p-GaN SBD upon annealing at 400°C. </LI> <LI> Interface state density decreases with increasing annealing temperature up to 400°C. </LI> <LI> Electrical results are correlated with the interfacial microstructure of the contacts. </LI> <LI> Nitride interfacial phases are responsible for increase in BH after annealing at 400°C. </LI> </UL> </P>

Microstructural, chemical states and electrical properties of Au/CuO/n-InP heterojunction with a cupric oxide interlayer

Balaram, N.,Rajagopal Reddy, V.,Sekhar Reddy, P.R.,Janardhanam, V.,Choi, Chel-Jong Elsevier 2018 Vacuum Vol.152 No.-

<P><B>Abstract</B></P> <P>Cupric oxide (CuO) is synthesized by simple chemical bath deposition method and deposited on n-type InP substrate using e-beam evaporation technique. First, the structural and chemical compositional analysis of CuO/n-InP are analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD and XPS results confirmed that the formation of CuO on n-type InP substrate. Then, Au/CuO/n-InP heterojunction is fabricated with a CuO interlayer and correlated its results with the Au/n-InP Schottky junction (SJ). The barrier height (Φ<SUB>b</SUB>) and ideality factor (n) are extracted through I-V and C-V methods and the respective values are 0.66 eV (I-V)/0.80 eV (C-V) and 1.24, and 0.78 eV (I-V)/0.94 eV (C-V) and 1.62 for the SJ and HJ diodes, respectively. By applying Cheung's and Norde functions, the Φ<SUB>b</SUB>, ideality factor and series resistance (R<SUB>S</SUB>) are derived for the SJ and HJ diodes. The derived interface state density (N<SUB>SS</SUB>) of HJ is lower than the SJ; results demonstrated that the CuO interlayer plays an important role in the decreased N<SUB>SS</SUB>. The Poole-Frenkel emission is the dominant current conduction mechanism in reverse bias of both SJ and HJ diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural and chemical properties of CuO films are analysed by XRD and XPS. </LI> <LI> Barrier height of Au/n-InP SJ was modified by CuO interlayer. </LI> <LI> Heterojunction has a good rectification ratio compared to the Schottky junction. </LI> <LI> The interface state density of HJ is lower as compared to the SJ. </LI> <LI> Poole-Frenkel mechanism is found to dominate in both SJ and HJs. </LI> </UL> </P>

Synthesis of VO2 (B) nanorods for Li battery application

Ch.V. Subba Reddy,Edwin H. Walker Jr.,S.A. Wicker Sr.,Quinton L. Williams,Rajamohan R. Kalluru 한국물리학회 2009 Current Applied Physics Vol.9 No.6

Vanadium dioxide nanorods were synthesized through a hydrothermal reaction from V2O5 xerogel, poly (vinyl pyrrolidone) (PVP) and lithium perchlorate (LiClO4). The prepared samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical discharge–charge cycling in lithium battery. SEM images reveal the nanorods to have dimensions on the order of 1–3 ㎛ in length and 10–50 nm in diameter. The measured initial discharge capacity of the lithium battery with a cathode made of VO2 (B) nanorods was 152 mA h/g. Vanadium dioxide nanorods were synthesized through a hydrothermal reaction from V2O5 xerogel, poly (vinyl pyrrolidone) (PVP) and lithium perchlorate (LiClO4). The prepared samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical discharge–charge cycling in lithium battery. SEM images reveal the nanorods to have dimensions on the order of 1–3 ㎛ in length and 10–50 nm in diameter. The measured initial discharge capacity of the lithium battery with a cathode made of VO2 (B) nanorods was 152 mA h/g.

Analgesic and Anti-inflammatory Activity of Carissa carandasLinn fruits and Microstylis wallichii Lindl Tubers

Alok Sharma,G.D. Reddy,Atul Kaushik,K.Shanker,R.K. Tiwari,Alok Mukherjee,Ch.V. Rao 한국생약학회 2007 Natural Product Sciences Vol.13 No.1

ethanolic (50% v/v) extracts of Carissa carandas (fruits) (Apocynaceae) and Microstylis wallichii(tubers) (Orchidaceae) were examined for anti-inflamatory and analgesic activities in experimental animals.Carissa carandas and Microstylis wallichii (50 - 200 mg/kg) caused a dose dependent inhibition of swellingcaused by carrageenin significantly in cotton pellet induced granuloma in rats (P < 0.05 to P < 0.001). There was asignificant increase in the analgesy meter induced pain in rats. The extracts of Carissa carandas and Microstyliswallichii resulted in an inhibition of stretching episodes and percentage protection was 16.05 - 17.58%respectively in acetic acid induced writhing.KeywordsCarissa carandas, Microstylis wallichii, pain, inflamation

Temperature Dependent Current-Voltage and Capacitance-Voltage Characteristics of an Au/n-Type Si Schottky Barrier Diode Modified Using a PEDOT:PSS Interlayer

Khurelbaatar, Z.,Shim, K.-H.,Cho, J.,Hong, H.,Reddy, V.R.,Choi, C.-J. JAPAN INSTITUTE OF METALS 2015 MATERIALS TRANSACTIONS Vol.56 No.1

<P>The temperature dependence of the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of an Au/n-type Si Schottky barrier diode (SBD) with a PEDOT:PSS interlayer was investigated. The SBD parameters, such as Schottky barrier height (Phi(B)), ideality factor (n), saturation current (I-o), doping concentration (N-D), and series resistance (R-s), were obtained as a function of temperature. The Richardson constant (A**) obtained from the In(I-o/T-2) versus 1000/T plot was much less than the theoretical value for n-Si. The mean Schottky barrier height ((Phi) over bar (bo)) and standard deviation (sigma(0)) calculated using the apparent Schottky barrier height (Phi(ap)) versus 1/2kT plot were 1.26 eV and 0.15 eV, respectively. From a fit of the modified Richardson plot of In(I-0/T-2) - (q sigma)(2)/2(kT)(2) versus 1000/T, the A** was extracted as 134 A/cm(2)K(2), which was close to the theoretical value of the n-Si. The interface state densities obtained from the Au/PEDOT:PSS/n-Si SBD decreased with increasing temperature. Furthermore, the conduction mechanism dominating the reverse-bias leakage current in Au/PEDOT:PSS/n-Si SBD was described and discussed.</P>

Modification of Schottky Barrier Properties of Ti/p-type InP Schottky Diode by Polyaniline (PANI) Organic Interlayer

Reddy, P.R. Sekhar,Janardhanam, V.,Jyothi, I.,Yuk, Shim-Hoon,Reddy, V. Rajagopal,Jeong, Jae-Chan,Lee, Sung-Nam,Choi, Chel-Jong The Institute of Electronics and Information Engin 2016 Journal of semiconductor technology and science Vol.16 No.5

The electrical properties of Ti/p-type InP Schottky diodes with and without polyaniline (PANI) interlayer was investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements. The barrier height of Ti/p-type InP Schottky diode with PANI interlayer was higher than that of the conventional Ti/p-type InP Schottky diode, implying that the organic interlayer influenced the space-charge region of the Ti/p-type InP Schottky junction. At higher voltages, the current transport was dominated by the trap free space-charge-limited current and trap-filled space-charge-limited current in Ti/p-type InP Schottky diode without and with PANI interlayer, respectively. The domination of trap filled space-charge-limited current in Ti/p-type InP Schottky diode with PANI interlayer could be associated with the traps originated from structural defects prevailing in organic PANI interlayer.

Temperature-Dependent Electrical Properties and Carrier Transport Mechanisms of TMAH-Treated Ni/Au/Al2O3/GaN MIS Diode

Reddy, M. S.,Puneetha, P.,Reddy, V. R.,Lee, J. H.,Jeong, S. H.,Park, C. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.11

<P>The temperature-dependent electrical properties and carrier transport mechanisms of tetramethylammonium hydroxide (TMAH)-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The experimental results reveal that the barrier height (I-V) increases whereas the ideality factor decreases with increasing temperature. The TMAH-treated Ni/Au/Al2O3/GaN MIS diode showed nonideal behaviors which indicate the presence of a nonuniform distribution of interface states (N (SS)) and effect of series resistance (R (S)). The obtained R (S) and N (SS) were found to decrease with increasing temperature. Furthermore, it was found that different transport mechanisms dominated in the TMAH-treated Ni/Au/Al2O3/GaN MIS diode. At 150 K to 250 K, Poole-Frenkel emission (PFE) was found to be responsible for the reverse leakage, while Schottky emission (SE) was the dominant mechanism at high electric fields in the temperature range from 300 K to 400 K. Feasible energy band diagrams and possible carrier transport mechanisms for the TMAH-treated Ni/Au/Al2O3/GaN MIS diode are discussed based on PFE and SE.</P>

Electrical and frequency-dependent properties of Au/Sm2O3/n-GaN MIS junction with a high-k rare-earth Sm2O3 as interlayer

V. Manjunath,V. Rajagopal Reddy,P.R. Sekhar Reddy,V. Janardhanam,최철종 한국물리학회 2017 Current Applied Physics Vol.17 No.7

High-k rare-earth samarium oxide (Sm2O3) films are formed on n-GaN surface and analyzed its compositional properties by XPS measurements. XPS results specify that the Sm2O3 films are formed at the interface. Then, the Au/Sm2O3/n-GaN MIS junction is prepared with a Sm2O3 as insulating layer and correlated its electrical properties with the Au/n-GaN MS junction. The MIS junction shows highest barrier height ((0.81 eV (I-V)/1.0 eV (C-V)) for MIS junction than the MS junction (0.68 eV (I-V)/0.90 eV (C-V)). Excellent rectifying property is observed with lowest reverse leakage current and higher barrier height for the MIS junction than the MS junction, implying that the Sm2O3 insulating layer effectively modified the barrier height. The barrier heights determined from I-V, Cheung's, Norde and JS eV plot closely matched with each other, suggesting that these techniques are reliable and valid. The estimated interface state density of the MIS junction (1.990 1011 cm2eV1 (EC-0.82 eV)) is lower than the MS junction (9.204 1012 cm2eV1 (EC-0.70 eV)), which demonstrates that the Sm2O3 insulating layer performs an important role in lowering the interface state density. The frequency-dependent characteristics of the MS and MIS junctions are discussed in the frequency range of 10 kHz to 1 MHz and found that the determined capacitance values decrease with increasing frequency. The forward I-V characteristic of the MS and MIS junctions reveals the ohmic behavior at low voltage regions and space-chargelimited conduction at higher voltage regions. Results reveal that the reverse leakage current in the studied MS and MIS junctions is controlled by a Poole-Frenkel emission.

Effects of Annealing on Electrical Characteristics and Current Transport Mechanisms of the Y/p-GaN Schottky Diode

Reddy, V. R.,Asha, B.,Choi, C. J. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.7

<P>This study investigates the effects of annealing on the electrical properties and current transport mechanism of Y/p-GaN Schottky barrier diodes (SBDs). We found no significant change in the surface morphology of the Y Schottky contacts during the annealing process. The Schottky barrier height (SBH) of the as-deposited Y/p-GaN SBD was estimated to be 0.95 eV (I-V)/1.19 eV (C-V). The SBH increased upon annealing at 400A degrees C and 500A degrees C, and then decreased slightly with annealing at 600A degrees C. Thus the maximum SBH of the Y/p-GaN SBD was achieved at 500A degrees C, with values of 1.01 eV (I-V)/1.29 eV (C-V). In addition, the SBH values were estimated by Cheung's, Norde, and I-s-V plots and were found to be in good agreement with one another. Series resistance (R (S)) values were also calculated by I-V, Cheung's, and Norde functions at different annealing temperatures, with results showing a decrease in the interface state density of the SBD with annealing at 500A degrees C, followed by a slight increase upon annealing at 600A degrees C. The forward-bias current transport mechanism of SBD was investigated by the logI-logV plot at different annealing temperatures. Our investigations revealed that the Poole-Frenkel emission mechanism dominated the reverse leakage current in Y/p-GaN SBD at all annealing temperatures.</P>