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Shiv Nadar University

(SoNS) School of Natural Sciences

There has been a keen interest in metal benzothiazoles, and specifically for zinc benzothiazole for applications involving broad emission such as white light organic light emitting diodes. The broad emission characteristic is normally attributed to occurrence of exciplexes and is believed to further broaden in electroluminescence from a bilayer device. In order to understand possible role of molecular level interaction in photoluminescence (PL), we study PL decay dynamics of zinc benzothiazole powder, thin film and a virtual alloy with a hole transport material TPD (prepared by stacking very thin alternate layers of the two materials). We observe significant hastening of the PL decay from powder and 'effective alloy' to the thin film. To unravel the nature of changes in decay dynamics, we employ both least square fitting, and time domain spectroscopy known as time analyzed transient spectroscopy (TATS). The efficacy of the later procedure in obtaining insights is demonstrated. Our results indicate that inter molecular interaction in the condensed phase significantly influence the life time of the radiative species in this material. © 2005 Elsevier B.V. All rights reserved.

Physics

World University root node

Synthetic Metals

Time domain spectroscopic study of PL decay in zinc benzothiazole suitable for white light emitting OLEDs

2005 International Semiconductor Device Research Symposium

Surface and interface analysis of MgxZn1-xO cubic and hexagonal phases by X-ray photoelectron and rutherford back scattering spectroscopies

Ion implantation and recrystallization of quartz may be a very important process for photonic applications. We have investigated how laser irradiation can be used to epitaxially recrystallize layers of α-quartz, which were amorphized by 175 keV Rb + or 250 keV Cs + ion implantation at a fluence of 2.5 × 10 16 cm -2 . The samples were irradiated with pulses of a XeCl excimer laser (wavelength 308 nm, pulse length 55 ns, energy density 3.2-5 J/cm 2 ). The thickness of the amorphous layer and the quality of the recrystallized layer were analyzed by Rutherford Backscattering Channeling Spectroscopy. Partial epitaxial recrystallization was found for all laser-irradiated samples that proceeded faster for higher laser energy density, however no full epitaxy was achieved up to the maximum laser energy of 5 J/cm 2 . The degree of epitaxy was more or less the same for 20 or 200 laser shots. © 2005 Elsevier B.V. All rights reserved.

Applied Surface Science

Laser-induced epitaxial recrystallization after alkali-ion implantion into α-quartz

A method of forming a sheet of Ge nanocrystals in a SiO2 layer based on molecular beam epitaxy (MBE) and rapid thermal processing (RTF) is presented. The method takes advantage of the very high precision by which a very thin Ge layer can be deposited by MBE. With proper choice of process parameters the nanocrystal size can be varied between ∼3 and ∼8 nm and the area-density between ∼1×1011 and ∼1×10 12 dots/cm2. The tunneling oxide thickness is determined by the thickness of a thermally grown SiO2 layer, and is typically 4 nm. C-V measurements of MOS capacitors reveal hole and electron injection from the substrate into the nanocrystals. Memory windows of about 0.2 and 0.5 V for gate-voltage sweeps of 3 and 6 V, respectively, are achieved. © 2005 Materials Research Society.

Materials Research Society Symposium Proceedings

Ge nanocrystals in MOS-memory structures produced by molecular-beam epitaxy and rapid-thermal processing

Synthetic metals

A correlated study of linear optical absorption in tetracene and pentacene

Physical Review B

Photoinduced absorption in disubstituted polyacetylenes: Comparison of theory with experiments

We report on the growth of highly oriented Hf O2 thin films of monoclinic phase stabilized by 5% Co doping on (001) yttrium-stabilized zirconia (YSZ) using pulsed-laser deposition at 700 °C at an oxygen partial pressure of 10-4 Torr. On the other hand, pure Hf O2 of such quality did not grow on YSZ in wide range of growth parameters. Rutherford backscattering-ion channeling in this film showed a 24% minimum yield (χmin) indicating highly oriented film growth, while hardly any ion channeling was observed in the undoped sample. High-resolution transmission electron microscopy revealed a sharp interface, and no signature of Co clusters. Electron energy loss spectroscopy showed that Co is in the 2+ state. Attempts were also made to grow films on a (001) Si substrate, and the results showed a very low ion channeling yield (∼8%). © 2005 American Institute of Physics.

Fulltext

Applied Physics Letters

Growth of highly oriented Hf O2 thin films of monoclinic phase on yttrium-stabilized Zr O2 and Si substrates by pulsed-laser deposition

In this article we present the growth of hexagonal phase MgZnO on nonconventional substrates such as quartz and on sapphire for comparison of the device property. We are reporting the realization of MgZnO-based UV detector on quartz by the pulsed laser deposition technique. MgZnO films are characterized by x-ray diffraction, UV-visible spectroscopy, and Rutherford backscattering-channeling techniques. The morphology of the films is studied by atomic force microscopy. The metal-semiconductor-metal device was fabricated on the MgZnO film to study the device photoresponse under proper UV irradiation. © 2005 American Vacuum Society.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

Realization of Mg (x=0.15)Zn (1-x=0.85)O -based metal-semiconductor-metal UV detector on quartz and sapphire

A brief overview is given of recent developments and fresh ideas at the intersection of PT-and/or CPT-symmetric quantum mechanics with supersymmetric quantum mechanics (SUSY QM). Within the framework of the resulting supersymmetric version of CPT-symmetric quantum mechanics we study the consequences of the assumption that the "charge" operator C is represented in a, differential-operator form of the second or higher order. Besides the freedom allowed by the Hermiticity constraint for the operator CP, encouraging results are obtained in the second-order case. In particular, the integrability of intertwining relations proves to match the closure of our nonlinear (viz., polynomial) SUSY algebra. In a particular illustration, our form of CPT-symmetric SUSY QM leads to a new class of non-Hermitian polynomial oscillators with real spectrum which turn out to be PT-asymmetric. © World Scientific Publishing Company.

International Journal of Modern Physics A

CPT-conserving Hamiltonians and their nonlinear supersymmetrization using differential charge-operators C

Known shape-invariant potentials for the constant-mass Schrödinger equation are taken as effective potentials in a position-dependent effective mass (PDEM) one. The corresponding shape-invariance condition turns out to be deformed. Its solvability imposes the form of both the deformed superpotential and the PDEM. A lot of new exactly solvable potentials associated with a PDEM background are generated in this way. A novel and important condition restricting the existence of bound states whenever the PDEM vanishes at an end point of the interval is identified. In some cases, the bound-state spectrum results from a smooth deformation of that of the conventional shape-invariant potential used in the construction. In others, one observes a generation or suppression of bound states, depending on the mass-parameter values. The corresponding wavefunctions are given in terms of some deformed classical orthogonal polynomials. © 2005 IOP Publishing Ltd.