Research Highlights Archive
Local-structure origins of the sustained Curie temperature in (Ba,Ca)TiO3 ferroelectrics
Igor Levin, Victor Krayzman, and Joseph C. Woicik
While the lattice volume in the solid-solution Ba1−xCaxTiO3 decreases with increasing x, the Curie temperature remains unaffected, in contrast to Ba1−xSrxTiO3. We have determined the origin of this phenomenon by comparing the local structures in (Ba,Ca)TiO3 and (Ba,Sr)TiO3.
Tunable giant magnetic anisotropy in amorphous SmCo thin films
F. Magnus, R. Moubah, A. H. Roos, A. Kruk, V. Kapaklis, T. Hase, B. Hjörvarsson, and G. Andersson
SmCo thin films have been grown by magnetron sputtering at room temperature with a composition of 2–35 at. % Sm. Films with 5 at. % or higher Sm are amorphous and smooth
Improving the intrinsic cut-off frequency of gate-all-around quantum-wire transistors without channel length scaling
A. Benali, F. L. Traversa, G. Albareda, M. Aghoutane, and X. Oriols
Progress in high-frequency transistors is based on reducing electron transit time, either by scaling their lengths or by introducing materials with higher electron mobility. For gate-all-around quantum-wire transistors with lateral dimensions similar or smaller than their length, a careful analysis of the displacement current reveals that a time shorter than the transit time controls their high-frequency performance.
Dexterous manipulation of microparticles using Bessel-function acoustic pressure fields
Charles R. P. Courtney, Bruce W. Drinkwater, Christine E. M. Demore, Sandy Cochran, Alon Grinenko, and Paul D. Wilcox
The authors show that Bessel-function acoustic pressure fields can be used to trap and controllably position microparticles. A circular, 16-element ultrasound array generates and manipulates an acoustic field within a chamber, trapping microparticles and agglomerates.
Tuning magnetic anisotropy in (001) oriented L10 (Fe1−xCux)55Pt45 films
Dustin A. Gilbert, Liang-Wei Wang, Timothy J. Klemmer, Jan-Ulrich Thiele, Chih-Huang Lai, and Kai Liu
The authors have achieved (001) oriented L10 (Fe1−xCux)55Pt45 thin films, with magnetic anisotropy up to 3.6 × 107 erg/cm3, using atomic-scale multilayer sputtering and post annealing at 400 °C for 10 s. By fixing the Pt concentration, structure and magnetic properties are systematically tuned by the Cu addition.
Band alignment in SnS thin-film solar cells: Possible origin of the low conversion efficiency
Lee A. Burton and Aron Walsh
Tin sulfide is an attractive absorber material for low-cost thin-film solar cells. Despite the ideal physical properties of bulk SnS, the photovoltaic conversion efficiencies achieved in devices to date have been no greater than 2%.
Planar junctionless transistor with non-uniform channel doping
Partha Mondal, Bahniman Ghosh, and Punyasloka Bal
The authors propose a planar junctionless transistor (JLT) in silicon-on-insulator (SOI) with non-uniform channel doping in vertical direction to improve the ON to OFF drain current ratio. In single gate JLT in SOI, a thin device layer is depleted in the off-state from the top of the layer and the leakage current flows through bottom of the device layer, and the leakage current depends on the device layer thickness.
Study of gate oxide traps in HfO2/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors by use of ac transconductance method
X. Sun, O. I. Saadat, K. S. Chang-Liao, T. Palacios, S. Cui, and T. P. Ma
The authors introduce an ac-transconductance method to profile the gate oxide traps in a HfO2 gated AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors (MOS-HEMTs) that can exchange carriers with metal gates, which in turn causes changes in analog and pulsed channel currents. The method extracts energy and spacial distributions of the oxide and interface traps under the gate from the frequency dependence of ac transconductance.
Effect of the magnetic order on the room-temperature band-gap of Mn-doped ZnO thin films
X. L. Wang, C. Y. Luan, Q. Shao, A. Pruna, C. W. Leung, R. Lortz, J. A. Zapien, and A. Ruotolo
Exchange interaction between localized magnetic moments mediated by free charge carriers is responsible for a non-monotonic dependence of the low-temperature energy band-gap in dilute magnetic semiconductors. The authors found that in weakly doped Mn-ZnO films, increasing the exchange interaction by increasing the concentration of free charge carriers results in a red-shift of the near-band-edge emission peak at room temperature.
Electric-field control of the magnetic anisotropy in an ultrathin (Ga,Mn)As/(Ga,Mn)(As,P) bilayer
T. Niazi, M. Cormier, D. Lucot, L. Largeau, V. Jeudy, J. Cibert, and A. Lemaître
The authors report on the electric control of the magnetic anisotropy in an ultrathin ferromagnetic (Ga,Mn)As/(Ga,Mn)(As,P) bilayer with competing in-plane and out-of-plane anisotropies. The carrier distribution and therefore the strength of the effective anisotropy are controlled by the gate voltage of a field effect device.