S. Charar

Postgrowth annealing of (Ga,Mn) As under As capping: An alternative way to increase TC

In situ postgrowth annealing of (Ga,Mn)As layers under As capping is adequate for achieving high Curie temperatures (TC) in a similar way as ex situ annealing in air or in N2 atmosphere practiced earlier. Thus, the first efforts give an increase of TC from 68 to 145 K after 2 h annealing at 180 °C. These data, in combination with lattice parameter determinations and photoemission results, show that the As capping acts as an efficient sink for diffusing Mn interstitials.

Prospective investigations of orthorhombic ZnGeN2: synthesis, lattice dynamics and optical properties

Abstract We have reported the synthesis of orthorhombic ZnGeN2 with extremely intense photoluminescence signal in the visible portion of the spectrum. The first analysis of the lattice dynamics of this crystalline phase has been proposed by using both infra-red and micro-Raman spectroscopy.

Preparation of Bi2Te3 Films by Hot-Wall Epitaxy and Characterization of p–n Junction

The deposition of bismuth telluride thin films, as well as of Bi-Sb-Te and Bi-Te-Se ternary alloys by hot-wall epitaxy, has been optimized on various substrates like Si, SiO 2 and SiO 2 /Si. In order to enhance the thermoelectric power, we investigated the electrical conductivity a, the Hall coefficient R H and the Seebeck coefficient S. The properties of the epitaxial films grown on SiO 2 and on SiO 2 /Si substrates are rather similar whereas for Bi 2 (Te 1-x Se x ) 3 ternary alloys, the n and p doping is close to the optimum value that can be from bona fide expected. Finally, the study of current-voltage characteristics at room temperature, for a p-Bi 2 Te 3 -n-Bi 2 Te 3 junction allowed us to determine various and important parameters (n, R s , J s and Φ B ).

Magnetization steps in Sn1-xEuxTe: Eu-Eu exchange and Eu distribution

The magnetization of Sn1-x Eux Te, with x = 0.011 and 0.042, was measured at 20 mK in magnetic fields up to 90 kOe. Magnetization steps (MSTs) from pairs and triplets were observed. The MSTs give J /kB = -0.311±0.006 K for the dominant Eu-Eu exchange constant. Comparisons of the magnetization curves with numerical simulations indicate that, instead of being distributed randomly, the Eu ions tend to bunch together. A phenomenological approach which uses the concept of a local Eu concentration xL is quite successful in describing the data for these two samples.

Pb/p-PbSe junction: An investigation of current-voltage and capacitance-voltage measurements

Abstract Molecular beam epitaxy has been used to grow p-PbSe/CaF2/Si(111) heterostructures. Using such stuctures, which are fully compatible with standard photolithographic technological procedures, photovoltaic sensors have been realized. The I(V) characteristics of the Pb/p-PbSe contacts have been investigated experimentally and theoretically over a wide temperature range from 4 to 300 K. Evidence of the contribution of bulk and surface impurity concentrations in the space charge region at high temperature is presented. The Schottky barrier height has been derived from a fit to the experimental data. We used the theory of Padovani and Stratton in the context of Fermi-Dirac statistics. In addition the capacitance-voltage characteristics of Pb/p-PbSe diodes have been investigated. The Schottky barrier height has been obtained and the existence of an inversion layer at the surface of p-type PbSe layer has been demonstrated.

Eu-Eu exchange interaction and Eu distribution in Pb 1 − x Eu x Te from magnetization steps

The magnetization of

Experimental determination of the phonon density of states in filled skutterudites: evidence for a localized mode of the filling atom

{\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Eu}}_{x}\mathrm{Te}

Antisymmetric magnetoresistance anomalies and magnetic domain structure in GaMnAs/InGaAs layers

samples with

Mid Infrared Optical Investigations of Pb1—xEuxSe ∥ BaF2 Thin Films Grown by MBE

x=0.019

Planar Hall ring sensor for ultra-low magnetic moment sensing

, 0.026, and 0.060 was measured at 20 mK in fields up to 50 kOe, and at 0.6 K in fields up to 180 kOe. The 20 mK data show the magnetization steps (MSTs) arising from pairs and from triplets. The pair MSTs are used to obtain the dominant Eu-Eu antiferromagnetic exchange constant,