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Siva Pratap Reddy, M.,Rajagopal Reddy, V.,Jyothi, I.,Choi, Chel‐,Jong John Wiley Sons, Ltd. 2011 Surface and interface analysis Vol.43 No.9
<P><B>Abstract</B></P><P>Schottky rectifiers are fabricated on <I>n</I>‐type GaN using Ni/Pd metallization scheme and its characteristics have been investigated by current‐voltage (I‐V), Capacitance‐Voltage (C‐V), X‐Ray Diffraction (XRD) and SIMS measurements as a function of annealing temperature. The calculated Schottky barrier height of the as‐deposited contact was found to be 0.60 eV (I‐V), 0.71 eV (C‐V) with an ideality factor of 1.44. However, the barrier height slightly increases after annealing at 300, 400 and 500 °C. On the basis of the experimental results, a high‐quality Schottky contact with barrier height and ideality factor of 0.81 eV (I‐V), 0.88 eV (C‐V) and 1.13 respectively, can be obtained after annealing at 600 °C for 1 min in a nitrogen atmosphere. Further, after annealing at 700 °C, it is found that the barrier height slightly decreased to 0.74 eV (I‐V) and 0.85 eV (C‐V). From the above observations, one can note that Ni/Pd Schottky contact exhibits excellent electrical properties after a rapid thermal annealing at 600 °C. According to the SIMS and XRD analysis, the formation of gallide phases at the Ni/Pd/<I>n</I>‐GaN interface could be the reason of the barrier height increase at elevated annealing temperatures. The Atomic Force Microscopy (AFM) results show that the overall surface morphology of Ni/Pd Schottky contacts on <I>n</I>‐GaN is fairly smooth. The above observations reveal that Ni/Pd Schottky metallization scheme was a good choice for the fabrication of high‐temperature and high‐power device applications. Copyright © 2010 John Wiley & Sons, Ltd.</P>
Pearce, J V,Edler, F,Elliott, C J,Greenen, A,Harris, P M,Izquierdo, C Garcia,Kim, Y-G,Martin, M J,Smith, I M,Tucker, D,Veltcheva, R I BUREAU INTERNATIONAL DES POIDS ET MESURES 2018 METROLOGIA -BERLIN- Vol.55 No.4
<P>By using a simple model to relate the electromotive force drift rate of Pt–Rh thermoelements to d<I>S</I>/d<I>c</I>, i.e. the sensitivity of the Seebeck coefficient, <I>S</I>, to rhodium mass fraction, <I>c</I>, the composition of the optimal pair of Pt–Rh wires that minimizes thermoelectric drift can be determined. The model has been applied to four multi-wire thermocouples each comprising 5 or 7 Pt–Rh wires of different composition. Two thermocouples were exposed to a temperature of around 1324 °C, one thermocouple to around 1492 °C, i.e. the melting points of the Co–C and Pd–C high temperature fixed points, respectively, and one thermocouple to a series of temperatures between 1315 °C and 1450 °C. The duration of exposure at each temperature was several thousand hours. By performing repeated calibrations <I>in situ</I> with the appropriate fixed point during the high temperature exposure, the drift performance has been quantified with high accuracy, entirely free from errors associated with thermoelectric homogeneity. By combining these results it is concluded that the Pt-40%Rh versus Pt-6%Rh is the most stable at the temperatures investigated. A preliminary reference function was determined and is presented.</P>
Non-Ohmic conduction in polydiacetylene thin films
Aleshin, A.N.,Chu, S.W.,Kozub, V.I.,Lee, S.W.,Lee, J.Y.,Lee, S.H.,Kim, D.W.,Park, Y.W. Elsevier 2005 CURRENT APPLIED PHYSICS Vol.5 No.1
<P><B>Abstract</B></P><P>We have studied the current–voltage (<I>I</I>–<I>V</I>) characteristics of polydiacetylene (PDA) thin films in the temperature region 300–1.7 K. It was found that at electric fields higher than 2×10<SUP>4</SUP> V/cm, the <I>I</I>–<I>V</I> characteristics are strongly super-linear with negative temperature coefficient of starting voltage. Negative gate voltage increases the source-drain current (the effect is more pronounced at low temperature), whereas the magnetic field up to 7 T does not affect it. The results demonstrate that at low temperature the charge transport is mainly supported due to a charge injection and tunneling from the metallic banks, whereas at higher temperatures the activation energy is related to the band gap mismatch between the different polymer chains or granules.</P>
Janardhanam, V.,Jyothi, I.,Lee, J.-H.,Kim, J.-Y.,Reddy, V.R.,Choi, C.-J. JAPAN INSTITUTE OF METALS 2014 MATERIALS TRANSACTIONS Vol.55 No.5
We investigated the electrical characteristics of Au/n-GaN Schottky rectifier incorporating a copper pthalocyanine (CuPc) interlayer using current voltage (I-V), capacitance voltage (C-V) and conductance voltage (G-V) measurements. The barrier height of the Au/CuPc/n-GaN Schottky contact was higher than that of the Au/n-GaN Schottky diode, indicating that the CuPc interlayer influenced the space charge region of the n-GaN layer. The series resistance of Au/CuPc/n-GaN Schottky contact extracted from the C-V and G-V methods was dependent on the frequency. In addition, the series resistance obtained from C V and G V characteristics was comparable to that from Cheung's method at sufficiently high frequencies and in strong accumulation regions. The forward log / log V plot of Au/CuPc/n-GaN Schottky contact exhibited four distinct regions having different slopes, indicating different conduction mechanisms in each region. In particular, at higher forward bias, the trap-filled space-charge-limited current was the dominant conduction mechanism of Au/CuPc/n-GaN Schottky contact, implying that the most of traps were occupied by injected carriers at high injection level.
K. V. Smyrnova,A. D. Pogrebnjak,V. M. Beresnev,S. V. Litovchenko,S. O. Borba‑Pogrebnjak,A. S. Manokhin,S. A. Klimenko,B. Zhollybekov,A. I. Kupchishin,Ya. O. Kravchenko,O. V. Bondar 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5
Nanostructured multicomponent (TiAlSiY)N coatings were fabricated by the cathodic-arc physical vapor deposition (CAPVD). In this study, a bias potential applied to the substrate was − 200 and − 500 V, and changes in structure and propertiesof coatings were investigated. Samples had a single-phase state with a face-centered cubic (FCC) lattice. Small crystallitesof about 7.5 nm and texture with [110] axis were observed at − 500 V. However, lower bias potential resulted in the formationof crystallites of about 41.6 nm with [111] preferred orientation. Moreover, coatings were characterized by superhardstate and demonstrated low wear, high abrasion and crack resistance. The testing of the polycrystalline cubic boron nitride(PCBN) cutting inserts covered with (TiAlSiY)N revealed an increase in the tool life coeffi cient during cutting by 1.66times in comparison with the base tool material. Therefore, (TiAlSiY)N coating is a perspective material for application asa protective layer in cutting tools.
Jyothi, I.,Lee, Hoon-Ki,Janardhanam, V.,Lee, Sung-Nam,Choi, Chel-Jong American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.10
<P>The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of a Ti/p-type strained Si-on-insulator (sSOI) Schottky diode were measured as a function of temperature in the range, 175-375 K. The Schottky barrier parameters of the Ti/p-type sSOI diode, which were interpreted using thermionic emission theory, indicated a strong temperature dependence of the barrier height and ideality factor. The barrier height and ideality factor decreased and increased, respectively, with decreasing temperature, which was attributed to the distribution of barrier heights due to the inhomogeneity at the metal-semiconductor interface. In addition, the discrepancy in the barrier heights obtained from the I-V and C-V techniques confirmed the inhomogeneities in the Schottky barrier. The inhomogeneities in the barrier characterized under the assumption of a Gaussian distribution revealed the existence of a double barrier distribution with a transition occurring at 275 K. The Richardson plot interpreted with the Gaussian distribution approach yielded a Richardson constant of 21.4 Acm(-2)K(-2) in the high temperature region close to the theoretical value of 31.6 Acm(-2)K(-2) for p-type sSOI. The low frequency noise measurements of the Ti/p-type sSOI Schottky diodes in the forward bias exhibited a 1/f(gamma) dependence with gamma ranging from 0.67 to 1.30, indicating the origin of noise due to the fluctuations in the carrier number caused by trapping-detrapping processes in the traps of the depletion region. Furthermore, the current-noise-power spectral density indicated the presence of defect states or traps existing in the depletion region or in the forbidden gap of the sample.</P>
Seo, I.-T.,Park, H.-Y.,Dung, N.V.,Choi, M.-K.,Nahm, S.,Lee, H.-G.,Choi, B.-H. IEEE 2009 and Frequency Control Vol.56 No.11
<P>Various amounts of Nb<SUB>2</SUB>O<SUB>5</SUB> in the (Na<SUB>0.5</SUB>K<SUB>0.5</SUB>) NbO<SUB>3</SUB> (NKN) ceramic were replaced by V<SUB>2</SUB>O<SUB>5</SUB> to decrease its sintering temperature to below 950°C. A small V<SUB>2</SUB>O<SUB>5</SUB> content resulted in a dense microstructure with an increased grain size for the specimen sintered at 900°C due to the presence of a liquid phase. When V<SUB>2</SUB>O<SUB>5</SUB> was added to the NKN ceramics, their orthorhombic-to-tetragonal transition temperature increased from 178°C to around 200°C. However, their Curie temperature decreased from 402°C to around 330°C. The k<SUB>p</SUB>, <SUB>ε3</SUB> <SUP>T</SUP>/<SUB>ε0</SUB>, and Q<SUB>m</SUB> values increased with V<SUB>2</SUB>O<SUB>5</SUB> addition, probably due to the increased density and poling state, which was identified by the phase angle. The specimen with x = 0.05, sintered at 900°C for 8 h, exhibited the following piezoelectric properties: k<SUB>p</SUB> = 0.32, <SUB>ε3</SUB> <SUP>T</SUP>/<SUB>ε0</SUB> = 245, d<SUB>33</SUB> = 120 (pC/N), and Q<SUB>m</SUB> = 232.</P>
Janardhanam, V.,Jyothi, I.,Lee, J.H.,Yun, H.J.,Won, J.,Lee, Y.B.,Lee, S.N.,Choi, C.J. Elsevier Sequoia 2017 THIN SOLID FILMS - Vol.632 No.-
The electrical properties of Cu-germanide(Cu<SUB>3</SUB>Ge)/n-type Ge Schottky contacts formed as a result of a solid state reaction between Cu and n-type Ge were investigated as a function of the rapid thermal annealing (RTA) temperature and correlated with its microstructural evolution driven by the RTA process. The variations of the barrier height of Cu<SUB>3</SUB>Ge/n-type Ge Schottky rectifiers caused by the RTA process were determined using current-voltage (I-V) and capacitance-voltage (C-V) methods. The Cu<SUB>3</SUB>Ge film formed after annealing at 400<SUP>o</SUP>C exhibited a relatively uniform surface and interface morphology. This led to the formation of a laterally homogenous Schottky barrier in the Cu<SUB>3</SUB>Ge/n-type Ge Schottky diode, resulting in an improvement of its rectifying I-V behavior. On the other hand, after annealing above 500<SUP>o</SUP>C, the Cu<SUB>3</SUB>Ge film was severely agglomerated without film continuity and eventually evolved into isolated islands at 600<SUP>o</SUP>C. Such structural degradation of Cu<SUB>3</SUB>Ge led to a rapid decrease in the barrier height and an increase in the reverse leakage current of the Cu<SUB>3</SUB>Ge/n-type Ge Schottky diode. The electric field dependence of the reverse current showed that the reverse leakage current in the Cu<SUB>3</SUB>Ge/n-type Ge Schottky diodes was dominated by a Poole-Frenkel emission mechanism, regardless of the RTA temperatures.
Kartavtseva, I.V.,Ginatulina, L.K.,Nemkova, G.A.,Shedko, S.V. The National Institute of Biological Resources 2013 Journal of species research Vol.2 No.1
An investigation of the karyotypes of two species of the genus Brachymystax (B. lenok and B. tumensis) has been done for the Russia Primorye rivers running to the East Sea basin, and others belonging to Amur basin. Based on the analysis of two species chromosome characteristics, combined with original and literary data, four cytotypes have been described. One of these cytotypes (Cytotype I: 2n=90, NF=110-118) was the most common. This common cytotype belongs to B. tumensis from the rivers of the East Sea basin and B. lenok from the rivers of the Amur basin, i.e. extends to the zones of allopatry. In the rivers of the Amur river basin, in the zone of the sympatric habitat of two species, each taxon has karyotypes with different chromosome numbers, B. tumensis (2n=92) and B. lenok (2n=90). Because of the ability to determine a number of the chromosome arms for these two species, additional cytotype have been identified for B. tumensis: Cytotype II with 2n=92, NF=110-124 in the rivers basins of the Yellow sea and Amur river and for B. lenok three cytotypes: Cytotype I: 2n=90, NF=110 in the Amur river basin; Cytotype III with 2n=90, NF=106-126 in the Amur river basin and Cytotypes IV with 2n=92, NF=102 in the Baikal lake.