InSb/CdTe Heterostructures Grown by Molecular Beam Epitaxy

Given the potential for quantum effect device application, the growth, by molecular beam epitaxy, and characterization of InSb-CdTe heterostructures is described. Two procedures for growth of these heterostructures are employed. For the growth of InSb/CdTe double heterostructures, InSb and CdTe layers are grown in separate MBE growth chambers connected via an ultrahigh vacuum transfer module. Here, antimony originating from a compound InSb source oven is used for growth of InSb layers. For the growth of CdTe/InSb multiple quantum well structures, InSb and CdTe layers are grown in a single MBE growth chamber, where antimony is derived from an antimony cracking furnace. To study the optical nature of heteroepitaxially grown InSb, infrared photoluminescence from InSb based double heterostructures has been examined. Despite the transferral of grown layers between III-V and II-VI chambers, luminescence gathered from thick” InSb active layers has shown the existence of recombination features which are similar to bulk InSb. For multilayer structures, grown in a single chamber with the use of an antimony cracker, emphasis has been placed on structural examination by transmission electron microscopy and x-ray diffraction techniques. Examination of multilayer structures by transmission electron microscopy suggests tha t the cracker may be useful for the growth of InSb at low substrate temperatures and low growth rates. Using the cracker, CdTe/InSb superlattice structures have been grown showing multiple satellite peaks in the x-ray diffraction spectrum

Molecular Beam Epitaxy of ZnSe on GaAs Epilayers for Use in MIS Devices

The use of ZnSe on GaAs epilayers (epi) as a pseudo-insulator in field effect device applications is demonstrated. The passivating ZnSe layers are grown on GaAs(epi) by interrupted growth molecular beam epitaxy (MBE) using two separate MBE machines. A thin layer of amorphous arsenic protects the GaAs(epi) during transfer between the MBE systems. When nucleated on the GaAs(epi), the ZnSe grows layer-by-layer as revealed by the reflection high energy electron diffraction pattern generated in the II-VI MBE growth chamber. A study of intensity oscillations in the electron diffraction pattern is further used to understand the initial growth stages of ZnSe on GaAs(epi). The material properties of the ZnSe/GaAs(epi) heterostructure are briefly examined. Even though ZnSe and GaAs have a 0.25% lattice mismatch, transmission electron micrographs show that very thin films (1OOOA) of ZnSe form a coherent and dislocation free interface with the GaAs(epi). In thicker ZnSe films, strain relieving misfit dislocations are observed. Photoluminescence measurements reveal information about the effect of the lattice mismatch on the energy band structure of the ZnSe. For the 1OOOA film, the excitonic features are shifted upwards in energy, and the normally degenerate light and heavy hole valence bands split into two bands. As the 1OOOA of ZnSe is an appropriate thickness for an insulator in a field-effect device, the ZnSe/ GaAs(epi) heterostructure is then used in metal-insulator-semiconductor (MIS) capacitors and transistors. Most prominent, the fabrication of the first depletion-mode field-effect transistors based on the ZnSe/n-GaAs heterointerface are described. The transistors display near ideal characteristics with complete current saturation and cutoff; the channel modulation indicates th a t the Fermi level is not pinned a t the ZnSe/n-GaAs interface. With the success of the depletion-mode transistors, the use of ZnSe and GaAs(epi) in future MIS devices appears promisin

Characteristics of myosin profile in human vastus lateralis muscle in relation to training background.

Twenty-four male volunteers (mean +/- SD: age 25.4+/-5.8 years, height 178.6+/-5.5 cm, body mass 72.1+/-7.7 kg) of different training background were investigated and classified into three groups according to their physical activity and sport discipline: untrained students (group A), national and sub-national level endurance athletes (group B, 7.8+/-2.9 years of specialised training) and sprint-power athletes (group C, 12.8+/-8.7 years of specialised training). Muscle biopsies of vastus lateralis were analysed histochemically for mATPase and SDH activities, immunohistochemically for fast and slow myosin, and electrophoretically followed by Western immunoblotting for myosin heavy chain (MyHC) composition. Significant differences (

In ovo injection of prebiotics and synbiotics affects the digestive potency of the pancreas in growing chickens

Abstract The purpose of the study was to examine the effect of 2 prebiotics and 2 synbiotics on the digestive potency of pancreas in 1-, 3-, 7-, 14-, 21-, and 34-day-old cockerels. Prebiotics (inulin and Bi2 tos) and synbiotics (inulin + Lactococcus lactis subsp. lactis and Bi2 tos + Lactococcus lactis subsp. cremoris) were injected in ovo into the air cell on the 12th d embryonic development. Their application increased the activity of amylase, lipase, and trypsin in the pancreas. The most pronounced changes were observed at the end of the investigated rearing period (d 34). The strongest stimulative effects on amylase were shown by both synbiotics, on lipase synbiotic Bi2 tos + Lactococcus lactis subsp. cremoris, and on trypsin all the used prebiotics and synbiotics. Simultaneously, neither the absolute nor the relative mass of the pancreas in comparison to control group were changed. Also, the injected in ovo compounds did not cause a deterioration in the posthatching condition of the chicken liver, as determined by measurement of the activity of marker enzymes in the blood (alanine aminotransferase and aspartate aminotransferase). Treatment with the prebiotics and synbiotics did not change the feed conversion ratio but Bi2 tos (galacto-oligosaccharide) and inulin (fructan) + Lactococcus lactis subsp. lactis significantly increased final BW

Specific features of the luminescence and conductivity of zinc selenide on exposure to X-ray and optical excitation

The set of experimental data on the X-ray-excited luminescence and X-ray induced conductivity of ZnSe are compared to the data on the photoluminescence and photoconductivity. It is experimentally established that the current-voltage characteristics and the kinetics of phosphorescence and current relaxation depend on the type of excitation. It is found that the external electric field influences the intensity and shape of bands in the luminescence spectra. It is shown that the character of excitation defines the kinetics of recombination, charge carrier trapping, and conductivity in wide-gap semiconductors.Comment: 7 pages, 7 figures, published in Fizika i Tekhnika Poluprovodnikov, 2010, Vol. 44, No. 5, pp. 594-59

Building solids inside nano-space: from confined amorphous through confined solvate to confined ‘metastable’ polymorph

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate – ROY (259.3 g mol1). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical – indomethacin (IMC, 357.8 g mol1), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids

Chemical Beam Epitaxy of Compound Semiconductors

Contains an introduction, reports on three research projects and a list of publications.3M Company Faculty Development GrantDefense Advanced Research Projects Agency Subcontract 216-25013Defense Advanced Research Projects Agency Subcontract 542383Joint Services Electronics Program Contract DAAL03-92-C-0001National Science Foundation Grant ECS 88-46919National Science Foundation Grant ECS 89-05909National Science Foundation Grant DMR 92-0295