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Reddy, P.R. Sekhar,Janardhanam, V.,Jyothi, I.,Chang, Han-Soo,Lee, Sung-Nam,Lee, Myung Sun,Reddy, V. Rajagopal,Choi, Chel-Jong Elsevier 2017 Superlattices and microstructures Vol.111 No.-
<P><B>Abstract</B></P> <P>Au-CuPc nanocomposite films were prepared by simultaneous evaporation of Au and CuPc with various Au and CuPc concentrations. Microstructural analysis of Au-CuPc films revealed elongated Au cluster formation from isolated Au nanoclusters with increasing Au concentration associated with coalescence of Au clusters. Au-CuPc films with different compositions were employed as interlayer in Al/n-Si Schottky diode. Barrier height and series resistance of the Al/n-Si Schottky diode with Au-CuPc interlayer decreased with increasing Au concentration. This could be associated with the enhancement of electron tunneling between neighboring clusters due to decrease in spacing of Au clusters and formation of conducting paths through the composite material. Interface state density of the Al/n-Si Schottky diode with Au-CuPc interlayer increased with increasing Au concentration. This might be because the inclusion of metal decreases the crystallinity and crystal size of the polymer matrix accompanied by the formation of local defect sites at the places of metal nucleation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Au-CuPc nanocomposite films with varying Au and CuPc content were formed by co-evaporation. </LI> <LI> Au-CuPc nanocomposite films were employed as interlayer in Schottky diode. </LI> <LI> Elongated Au clusters were formed from isolated Au nanoclusters with increasing Au content. </LI> <LI> Au-CuPc interlayer with higher CuPc content showed higher barrier and series resistance. </LI> <LI> Electron tunneling increased due to formation of conducting paths between clusters. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Reddy, M. Siva Pratap,Kwon, Mi-Kyung,Kang, Hee-Sung,Kim, Dong-Seok,Lee, Jung-Hee,Reddy, V. Rajagopal,Jang, Ja-Soon The Institute of Electronics and Information Engin 2013 Journal of semiconductor technology and science Vol.13 No.5
We have investigated the electrical properties of Ru/Ni/n-GaN Schottky structure using current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The barrier height (${\Phi}_{bo}$) and ideality factor (n) of Ru/Ni/n-GaN Schottky structure are found to be 0.66 eV and 1.44, respectively. The ${\Phi}_{bo}$ and the series resistance ($R_S$) obtained from Cheung's method are compared with modified Norde's method, and it is seen that there is a good agreement with each other. The energy distribution of interface state density ($N_{SS}$) is determined from the I-V measurements by taking into account the bias dependence of the effective barrier height. Further, the interface state density $N_{SS}$ as determined by Terman's method is found to be $2.14{\times}10^{12}\;cm^{-2}\;eV^{-1}$ for the Ru/Ni/n-GaN diode. Results show that the interface state density and series resistance has a significant effect on the electrical characteristics of studied diode.
Rajagopal Reddy, V.,Sri Silpa, D.,Yun, H.J.,Choi, C.J. Academic Press 2014 Superlattices and microstructures Vol.71 No.-
The electrical and structural properties of a fabricated W/p-InP Schottky barrier diode (SBD) have been investigated as a function of annealing temperature. The W/p-InP SBD exhibits good rectification behavior. The barrier height (BH) and ideality factor of the W/p-InP SBD are determined to be 0.82eV (I-V)/0.98eV (C-V) and 1.34, respectively. However, the BH is increases to 0.87eV (I-V)/1.08eV (C-V) after annealing at 300<SUP>o</SUP>C. When the SBD is annealed at 400<SUP>o</SUP>C, the BH decreases to 0.74eV (I-V)/0.86eV (C-V) and the ideality factor increases to 1.45. Results indicate that a maximum BH is obtained on the W/p-InP SBD at 300<SUP>o</SUP>C. Norde method is also employed to determine BHs of W/p-InP SBD which are in good agreement with those estimated by the I-V method. Further, Cheung method is used to estimate the series resistance of the W/p-InP SBD, and the consistency is checked using the Norde method. Besides, the energy distribution of interface state density is determined from the forward bias I-V data at different annealing temperatures. Auger electron spectroscopy and X-ray diffraction studies revealed that the formation of W-P interfacial phases at the W/p-InP interface may be the cause for the increase of BH upon annealing at 300<SUP>o</SUP>C. AFM results indicated that the overall surface morphology of the W/p-InP SBD did not change significantly at elevated temperatures.
Rajagopal Reddy, V.,Janardhanam, V.,Leem, C.H.,Choi, C.J. Academic Press 2014 Superlattices and microstructures Vol.67 No.-
The temperature dependent electrical characteristics of Se/n-GaN Schottky barrier diode have been investigated in the temperature range of 130-400K in the steps of 30K. The estimated barrier height (φ<SUB>bo</SUB>) and ideality factor n are found to be 0.46eV and 3.83 at 130K, 0.92eV and 1.29 at 400K. The φ<SUB>bo</SUB> and n are found to be strongly temperature dependent and while the φ<SUB>bo</SUB> decreases and the n increase with decreasing temperature. Such behavior of φ<SUB>bo</SUB> and n is attributed to Schottky barrier inhomogeneities, explained by the assumption of Gaussian distribution of barrier heights at the metal/semiconductor interface. Experimental results revealed the existence of a double Gaussian distribution with mean barrier height values of 1.33 and 0.90eV and standard deviations (σ<SUB>o</SUB>) of 0.0289 and 0.010V, respectively. The modified ln(I<SUB>o</SUB>/T<SUP>2</SUP>)-(q<SUP>2</SUP>σ<SUB>o</SUB><SUP>2</SUP>/2k<SUP>2</SUP>T<SUP>2</SUP>) versus 10<SUP>3</SUP>/T plot gives φ<SUB>bo</SUB> and Richardson constant (A<SUP>*</SUP>) values as 1.30 and 0.88eV, 23.6 and 19.2 A/cm<SUP>2</SUP> K<SUP>2</SUP> at 400 and 130K, respectively without using the temperature coefficient of the barrier height. Further, the barrier height obtained from C-V method decreases with an increase in temperature. It is also noted that the barrier height value estimated from the C-V method is higher than that estimated from the I-V method at various temperatures. Possible explanations for this discrepancy are presented. The interface state density (N<SUB>ss</SUB>) is found to be decreased with an increasing temperature. The reverse-bias leakage current mechanism of Se/n-GaN Schottky diode is investigated. Both Poole-Frenkel and Schottky emissions are described and discussed.
Sooty Mould Infection on Mulberry-Management
Reddy, C.Rajagopal,Reddy, P.Lakshmi,Misra, Sunil,Reddy, K.Dharma,Sujathamma, P. Korean Society of Sericultural Science 2003 International Journal of Industrial Entomology Vol.6 No.2
Black sooty mould fungus was observed on the upper side of the mulberry leaves caused by the Capnodium sp. This fungus develops with the utilization of the honeydew dropped by the whiteflies. Few selected insecticides like Monocrotophos, Chloropyriphos and Nuvan were tried to control the whitefly incidence and followed by the application of Maida (wheat flour paste) and Starch solution separately to control the incidence of the Capnodium on mulberry. It is found that a significant control of the whitefly incidence with the application of Nuvan (2 $m\ell$/L) and followed by Chloropyriphos (2 $m\ell$/L) and Monocrotophos (1.6 $m\ell$/L) and also a significant control of sooty mould infection were recorded with Starch and Maida application.
Rajagopal Reddy, V.,Janardhanam, V.,Won, Jonghan,Choi, Chel-Jong Elsevier 2017 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.499 No.-
<P><B>Abstract</B></P> <P>An Au/Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB> (CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, <I>I</I>-<I>V</I> and <I>C</I>-<I>V</I> measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82eV) compared to the Au/n-GaN SJ (0.69eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by <I>I</I>-<I>V</I>, Cheung’s and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density (<I>N<SUB>SS</SUB> </I>) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of <I>N<SUB>SS</SUB> </I>. Moreover, the capacitance-frequency (<I>C</I>-<I>f</I>) and conductance-frequency (<I>G</I>-f) characteristics of SJ and HJ are measured in the range of 1kHz–1MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the <I>N<SUB>SS</SUB> </I> estimated from <I>C</I>-<I>f</I> and <I>G</I>-<I>f</I> characteristics is lower compared to those estimated from <I>I</I>-<I>V</I> characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>