Physics

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Shiv Nadar University

We exploit the hidden symmetry structure of a recently proposed non-Hermitian Hamiltonian and of its Hermitian equivalent one. This sheds new light on the pseudo-Hermitian character of the former and allows access to a generalized quantum condition. Special cases lead to hyperbolic and Morse-like potentials in the framework of a coordinate-dependent mass model. © 2005 IOP Publishing Ltd.

(SoNS) School of Natural Sciences

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Journal of Physics A: Mathematical and General

Pseudo-Hermiticity and some consequences of a generalized quantum condition

Synthetic metals

Photoinduced absorption and nonlinear optical properties of disubstituted polyacetylenes: Theory

We demonstrate white organic light-emitting diodes (OLEDs) having spectral width of approximately 260 nm in electroluminescence (EL) in a simple bilayer structure, consisting of TPD and zinc benzothiazole, without taking recourse to complex strategies such as blending and doping. The EL is broader than the corresponding photoluminescence (PL) of both component materials and their structures. A deconvolution of PL and EL spectra shows that as large as 60% of the broad EL emission originates from multiple exciplexes formed at the interface during electrical excitation. © 2005 American Institute of Physics.

Applied Physics Letters

White organic light-emitting diodes based on spectral broadening electroluminescence due to formation of interfacial exciplexes

We discuss the distribution of size and aerial density of Ge nanocrystals in a metal-oxide-semiconductor (MOS) memory structure fabricated by molecular beam epitaxy combined with rapid thermal processing; the size and aerial density of Ge nanocrystals are controlled by varying the thickness of the deposited Ge layer and the processing time. Variation of tunnel oxide thickness is demonstrated with the extension of the processing time. The effect of processing time and tunnel oxide thickness on the electrical properties of the MOS structures is investigated by high frequency capacitance-voltage measurements. © Springer-Verlag 2004.

Applied Physics A: Materials Science and Processing

Size and aerial density distributions of Ge nanocrystals in a SiO 2 layer produced by molecular beam epitaxy and rapid thermal processing

2005 International Semiconductor Device Research Symposium

Homo and heteroepitaxial growth of hexagonal and cubic Mg xZn1-xO alloys

Physical Review Letters

{Condensed Matter: Electronic Properties, etc.-Spin-Flop Ordering from Frustrated Ferro-and Antiferromagnetic Interactions: A Combined Theoretical and Experimental Study of a Mn {\ldots}}

In this paper effects of lead doping on the lattice response and phase transitions of bismuth-layered structure Sr 1-xPb xBi 2Nb 2O 9 (x = 0.0 to 0.5 in steps of 0.1) ferroelectric ceramic are reported. It is observed that structure attains more tetragonality with doping of lead up to 40%. Increased orthorhombic distortion is also observed. Curie temperatures of all samples were measured and the phase transition is explained in terms of lattice response of these ceramics. Sample with x = 0.5 shows decreased tetragonal strain and Curie temperature. Also, relationship of polarization with lattice response is discussed.

Ferroelectrics

Structural distortions and behavioural changes in phase transition of aurivillius type Sr 1-xPb xBi 2Nb 2O 9 ferroelectric

Inside a box of size L we contemplate the simplest PT -symmetric piece-wise constant potential of size ℓ < L and purely imaginary strength ig and describe all its bound states in closed form.

Czechoslovak Journal of Physics

Weakly non-Hermitian square well

The luminescent properties of quartz and silica doped with photoactive ions depend on the structural and chemical properties of the matrix and doping elements. The dynamic solid phase epitaxy of α -quartz during Ba+ -ion implantation at 300-1170 K and its relationship to cathodoluminescence emission are investigated in this work. Rutherford backscattering channeling analysis revealed that the amorphous layer created by 1× 1015 175 keV Ba ions cm2 at 300 K almost disappeared when the implantation temperature was raised to 1120 K. Between 770 and 1100 K the cathodoluminescence spectra taken at room temperature exhibit dramatic changes with the implantation temperature and allow to distinguish between color centers related to quartz, ion-irradiated silica, and implanted Ba ions. After achieving almost complete epitaxial recovery, only a violet band at 3.4 eV remained, which we attribute to Ba -related luminescence centers. Samples first implanted with Ba ions and then postannealed in air or O 2 18 atmosphere up to 1320 K did not show full epitaxy of the amorphized layer. © 2005 American Institute of Physics.

Journal of Applied Physics

Cathodoluminescence and solid phase epitaxy in Ba -irradiated α -quartz

Epitaxial thin films of optimally doped, underdoped, and Zn-doped YBa2Cu3O7-δ (YBCO) were grown on single crystal (001) Nb:SrTiO3 substrates by pulsed laser deposition (PLD) and the electrical properties of the corresponding interface junctions were examined. The growth conditions were optimized in each case to get the appropriate crystalline quality of the films as well as the desired normal state and superconducting properties. The films or heterointerfaces were characterized by x-ray diffraction, Rutherford backscattering (RBS) ion channeling spectrometry in normal and oxygen resonance modes, magnetic susceptibility, four probe in-plane resistivity, and the temperature dependent current-voltage (I-V) characteristics. Nonlinear I-V curves (forward and reverse) were obtained in all the cases, revealing some characteristic differences and interesting temperature evolution. These data, when analyzed within the framework of a standard description of transport across the metal-semiconductor (Schottky) interface, suggest lateral intrinsic nanoscale electrical inhomogeneity in the system. Also as compared to the case of optimally doped YBCO a small but definitive lowering of the effective Schottky barrier height ΦB is observed for junctions based on oxygen underdoped and Zn-doped YBCO. © 2005 The American Physical Society.