Search results for "Allium"
showing 10 items of 385 documents
Mixed-type circuits with distributed and lumped parameters as correct models for integrated structures
1991
The technology of integrated circuits imposes upon their designers the need to deal with structures with distributed parameters. Figure 4.1 shows a schematic diagram of part of a digital integrated chip, consisting of an n MOS transistor with gate (G), drain (D) and source (S) as terminals, and its thin-film connection with the rest of the chip. This on-chip connection can be made by metals (Al, W), polycristaline silicon (polysilicon) or metal suicides (WSi 2 ). Alternative materials to oxide-passivated silicon substrates are saphire and gallium arsenide (Saraswat and Mohammadi [1982], Yuan et al. [1982], Passlack et al. [1990]).
CCDC 171405: Experimental Crystal Structure Determination
2002
Related Article: F.Thomas, S.Schulz, M.Nieger, K.Nattinen|2002|Chem.-Eur.J.|8|1915|doi:10.1002/1521-3765(20020415)8:8<1915::AID-CHEM1915>3.0.CO;2-Z
Karyological data of four geophytes native to Tunisia
2021
Chromosome numbers were studied in four geophytes collected in Tunisia. Allium pallens was collected from Zembra island, N of Tunisia, while Drimia purpurascens, Oncostema peruvianum and Pancratium foetidum from continental Tunisia. The chromosome numbers found for Allium pallens, Drimia purpurascens, and Oncostema peruvianum coincides with the previous reports obtained from other Mediterranean populations. The chromosome number 2n = 22, found on material from Toujane is the first reported for Pancratium foetidum.
Taxonomic investigation on Allium hirtovaginum group (Amaryllidaceae) from East Mediterranean area
2021
Within taxonomic studies on Allium sect. Codonoprasum from Mediterranean flora, populations belonging to A. hirtovaginum Candargy group were examined. Based on field investigation and herbarium surveyes, this group is represented by very critical and not well known taxa, distributed in the East Mediterranean, showing a marked morphological variability. Currently, the species referable to this group in addition to A. hirtovaginum are also A. pilosum Sibth. & Sm., A. aeginiense Brullo, Giusso & Terrasi and A. nerimaniae Koçyiğit & Kaya. Besides, other 13 species are here described as new to science, they are A. pythagoricum, A. pignattii, A. hippocraticum, A. abanticum, A. velutin…
Residual strain effects on the two-dimensional electron gas concentration of AlGaN/GaN heterostructures
2001
Ga-face AlGaN/GaN heterostructures with different sheet carrier concentrations have been studied by photoluminescence and Raman spectroscopy. Compared to bulk GaN, an energy shift of the excitonic emission lines towards higher energies was observed, indicating the presence of residual compressive strain in the GaN layer. This strain was confirmed by the shift of the E2 Raman line, from which biaxial compressive stresses ranging between 0.34 and 1.7 GPa were deduced. The spontaneous and piezoelectric polarizations for each layer of the heterostructures have been also calculated. The analysis of these quantities clarified the influence of the residual stress on the sheet electron concentratio…
Tin-related double acceptors in gallium selenide single crystals
1998
Gallium selenide single crystals doped with different amounts of tin are studied through resistivity and Hall effect measurements in the temperature range from 30 to 700 K. At low doping concentration tin is shown to behave as a double acceptor impurity in gallium selenide with ionization energies of 155 and 310 meV. At higher doping concentration tin also introduces deep donor levels, but the material remains p-type in the whole studied range of tin doping concentrations. The deep character of donors in gallium selenide is discussed by comparison of its conduction band structure to that of indium selenide under pressure. The double acceptor center is proposed to be a tin atom in interlayer…
Cathodoluminescence study of undoped GaN films: Experiment and calculation
2009
Abstract In this paper, we report the theoretical and experimental results of cathodoluminescence (CL) from GaN layers grown at 800 °C by metal organic vapor phase epitaxy (MOVPE) on silicon substrate. The CL spectra recorded at room temperature reveal the near band-edge emission at 3.35–3.42 eV and a broad yellow luminescence at 2.2 eV. The CL depth analysis at constant power excitation shows inhomogeneous CL distribution in depth of these emissions as the electron beam increases from 3 to 25 keV. There appears a blue shift of the CL band-edge peaks with increasing sample depth. This behavior is explained by a change of the fundamental band gap due to residual strain and the local temperat…
Acoustic manipulation of electron-hole pairs in GaAs at room temperature
2004
We demonstrate the optically detected long-range (>100 μm) ambipolar transport of photogenerated electrons and holes at room temperature by surface acoustic waves (SAWs) in (In,Ga)As-based quantum well structures coupled to an optical microcavity. We also show the control of the propagation direction of the carriers by a switch composed of orthogonal SAW beams, which can be used as a basic control gate for information processing based on ambipolar transport.
Transport properties of nitrogen doped p‐gallium selenide single crystals
1996
Nitrogen doped gallium selenide single crystals are studied through Hall effect and photoluminescence measurements in the temperature ranges from 150 to 700 K and from 30 to 45 K, respectively. The doping effect of nitrogen is established and room temperature resistivities as low as 20 Ω cm are measured. The temperature dependence of the hole concentration can be explained through a single acceptor‐single donor model, the acceptor ionization energy being 210 meV, with a very low compensation rate. The high quality of nitrogen doped GaSe single crystals is confirmed by photoluminescence spectra exhibiting only exciton related peaks. Two phonon scattering mechanisms must be considered in orde…
Electric control of the spin Hall effect by intervalley transitions
2013
Controlling spin-related material properties by electronic means is a key step towards future spintronic technologies. The spin Hall effect (SHE) has become increasingly important for generating, detecting and using spin currents, but its strength-quantified in terms of the SHE angle-is ultimately fixed by the magnitude of the spin-orbit coupling (SOC) present for any given material system. However, if the electrons generating the SHE can be controlled by populating different areas (valleys) of the electronic structure with different SOC characteristic the SHE angle can be tuned directly within a single sample. Here we report the manipulation of the SHE in bulk GaAs at room temperature by m…