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Singh A.,Bhabha Atomic Research Center | Samanta S.,Bhabha Atomic Research Center | Kumar A.,Bhabha Atomic Research Center | Debnath A.K.,Bhabha Atomic Research Center | And 5 more authors.
Organic Electronics: physics, materials, applications | Year: 2010

The charge transport properties of 100 nm thick cobalt phthalocyanine (CoPc) films grown on single crystal Al2O3 (0 0 0 1 oriented) and quartz substrates using molecular-beam epitaxy, have been investigated as a function of applied bias (±50 V) and temperature (300-75 K). Films grown on Al2O3 are highly ordered and exhibited non-hysteretic current-voltage (J-V) characteristics. The J-V characteristics in this case are well described by space-charge-limited conduction (SCLC) mechanism. On the other hand, films grown on quartz substrates are highly disordered and exhibited hysteretic J-V characteristics. Analyses of complex hysteretic J-V's in disordered films indicated a transition from trap-controlled SCLC mechanism to Poole-Frankel emission with lowering temperature. Various parameters, such as, hole density, trap concentration and space charge limited motilities have been estimated. X-ray photoelectron spectroscopy data show that charge trapping centers in the films grown on quartz substrates are created by chemisorbed oxygen. © 2010 Elsevier B.V. All rights reserved.

Seredin P.V.,Voronezh State University | Goloshchapov D.L.,Voronezh State University | Lenshin A.S.,Voronezh State University | Ternovaya V.E.,Voronezh State University | And 5 more authors.
Semiconductors | Year: 2015

Structural and spectroscopic methods are used to study the epitaxial layers of n-type AlxGa1 − xAs solid solutions produced by the metal-organic chemical vapor deposition method. It is shown that, when AlxGa1 − xAs solid solutions are doped with carbon to a level of (1.2–6.7) × 1017 cm−3, the electron mobility is anomalously high for the given impurity concentration and twice exceeds the calculated value. It is assumed that the ordered arrangement of carbon in the metal sublattice of the solid solution leads to a change in the average distance between impurity ions, i.e., to an increase in the mean free path of the carriers and, consequently, in the carrier mobility. The observed effect has immediate practical importance in the search for various technological ways of increasing the operating speed of functional elements of modern optoelectronic devices. The effect of the anomalously high carrier mobility in the epitaxial layer of a heteropair opens up new opportunities for the development of new structures on the basis of AlxGa1 − xAs compounds. © 2015, Pleiades Publishing, Ltd.

Oka T.,Research Institute of Electronics | Hojo H.,University of Shizuoka
Langmuir | Year: 2014

We report a simple method to produce a single crystal region of an inverse bicontinuous cubic (QII) phase of a lipid, 1-monoolein. By starting with the lipid of the sponge (L3) phase in the presence of 1,4-butanediol, we can obtain a single crystal region of the double-diamond QII phase in 1 week by controlled dilution of 1,4-butanediol. The length of the single crystal region in a 0.5 mm diameter capillary was on the order of millimeters. X-ray diffraction images of the region showed diffraction "spots", but not "rings" as in powder diffraction. The diffraction images also changed rotation angle dependently. We could assign Miller indices to all of the distinguishable diffraction spots from the region. This method would bring benefits to the basic and applied research areas of the Q phases. © 2014 American Chemical Society.

Zenin V.V.,Voronezh State Technical University | Stoyanov A.A.,Research Institute of Electronics | Petrov S.V.,OAO Voronezh Plant of Semiconductor Devices Assembly | Chistyakov S.Yu.,OAO Voronezh Plant of Semiconductor Devices Assembly
Russian Microelectronics | Year: 2014

Some methods of the formation of microwelds, which are most acceptable for the assembly of 3D-wares with the use of wire leadouts, have been analyzed. Some peculiarities of the bonding of inner wirings on a die and a package by different welding methods, such as pressure welding with indirect pulsed heating and thermosonic, ultrasonic, and split-tip welding, have been considered. The effect of structural and technological factors on the quality of microwelds made by ultrasonic welding with the use of aluminum wire, aluminum metallization on a die, and gold, nickel, and nickel alloy coatings has been studied. Some information on microwelds made with the use of copper wire and copper metallization has been represented. © 2014 Pleiades Publishing, Ltd.

Samanta S.,Bhabha Atomic Research Center | Aswal D.K.,Research Institute of Electronics | Singh A.,Bhabha Atomic Research Center | Debnath A.K.,Bhabha Atomic Research Center | And 4 more authors.
Applied Physics Letters | Year: 2010

The temperature dependent current-voltage (J-V) characteristics of highly-oriented cobalt phthalocyanine films (rocking-curve width=0.11°) deposited on (001) LaAlO3 substrates are investigated. In the temperature range 300-100 K, charge transport is governed by bulk-limited processes with a bias dependent crossover from Ohmic (J∼V) to trap-free space-charge-limited conduction (J∼ V2). The mobility (μ) at 300 K has a value of ∼7 cm2 V-1 s-1 and obeys Arrhenius-type (ln μ∼1/T) behavior. However, at temperatures <100 K, the charge transport is electrode-limited, which undergoes a bias dependent transition from Schottky (ln J∼ V1/2) to multistep-tunneling (conductivity varying exponentially on the inverse of the square-root of electric field). © 2010 American Institute of Physics.

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