The isolation of qubits from noise sources, such as surrounding nuclear spins and spin-electric susceptibility , has enabled extensions of quantum coherence times in recent pivotal advances towards the concrete implementation of spin-based quantum computation. In fact, the possibility of achieving enhanced quantum coherence has been substantially doubted for nanostructures due to the characteristic high degree of background charge fluctuations . Still, a sizeable spin-electric coupling will be needed in realistic multiple-qubit systems to address single-spin and spin-spin manipulations . Here, we realize a single-electron spin qubit with an isotopically enriched phase coherence time (20 μs) and fast electrical control speed (up to 30 MHz) mediated by extrinsic spin-electric coupling. Using rapid spin rotations, we reveal that the free-evolution dephasing is caused by charge noise-rather than conventional magnetic noise-as highlighted by a 1/f spectrum extended over seven decades of frequency. The qubit exhibits superior performance with single-qubit gate fidelities exceeding 99.9% on average, offering a promising route to large-scale spin-qubit systems with fault-tolerant controllability.

Pronounced Purcell enhancement of spontaneous emission in CdTe/ZnTe quantum dots embedded in micropillar cavities Appl. Phys. Lett. 101, 132105 (2012) Effects of Co content on the structural, luminescence, and ferromagnetic properties of Zn1−xCoxSy films J. Appl. Phys. 112, 063712 (2012) Mechanisms of infrared photoluminescence in HgTe/HgCdTe superlattice J. Appl. Phys. 112, 063512 (2012) Leaky mode analysis of luminescent thin films: The case of ZnO on sapphire J. Appl. Phys. 112, 063112 (2012) Observation of In-related collective spontaneous emission (superfluorescence) in Cd0.8Zn0.

Impact of atomic layer deposition temperature on HfO2/InGaAs metal-oxide-semiconductor interface properties J. Appl. Phys. 112, 084103 (2012) Method for investigating threshold field of charge injection at electrode/dielectric interfaces by space charge observation Appl. Phys. Lett. 101, 172902 (2012) An accurate characterization of interface-state by deep-level transient spectroscopy for Ge metal-insulatorsemiconductor capacitors with SiO2/GeO2 bilayer passivation J. Appl. Phys. 112, 083707 (2012) Electron transport properties of carbon nanotube-graphene contacts Appl. Phys. Lett. 101, 153501 (2012) Response to "Comment on 'Broadening of metal-oxide-semiconductor admittance characteristics: Measurement, sources, and its effects on interface state density analyses'" [J. Appl. Phys. 112, 076101 (2012) (111)-oriented Ge thin films on insulators are essential for advanced electronics and photovoltaic applications. We investigate Al-induced crystallization of amorphous-Ge films (50-nm thickness) on insulators focusing on the annealing temperature and the diffusion controlling process between Ge and Al. The (111)-orientation fraction of the grown Ge layer reaches as high as 99% by combining the low-temperature annealing (325 C) and the native-oxidized Al (AlO x ) diffusioncontrol layer. Moreover, the transmission electron microscopy reveals the absence of defects on the Ge surface. This (111)-oriented Ge on insulators promises to be the high-quality epitaxial template for various functional materials to achieve next-generation devices. V C 2012 American Institute of Physics. [http://dx

a b s t r a c t a-Axis-oriented undoped n-BaSi 2 epitaxial films were grown on Si(111) substrates by molecular beam epitaxy, and the crystalline quality and grain boundaries were investigated by means of reflection highenergy electron diffraction, X-ray diffraction, and transmission electron microscopy (TEM). The grain size of the BaSi 2 films was estimated to be approximately 0.1-0.3 mm, and straight grain boundaries (GBs) were observed in the plan-view TEM images. Dark-field TEM images under a two-beam diffraction condition showed that these GBs consist mostly of BaSi 2 {011} planes. The diffusion length of minority carriers in nBaSi 2 was found to be approximately 10 mm by an electron-beam-induced current technique.

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We present a photoluminescence (PL) study on the growth mode changeover during growth of Ge on Si(100) substrates. Intense PL signals originating from both the flat Ge layer and the three-dimensional (3D) Ge islands are observed from Si/Ge/Si quantum wells with various Ge coverage. The onset of the 3D island formation is determined to be 3.7 monolayers (ML). It is also found that the 3D islands grow with only 3.0 ML of the flat Ge layer retained. This implies that only the 3.0 ML Ge is thermodynamically stable on Si(100) and hence corresponds to the ‘‘equilibrium’’ critical thickness.

ZnO tubes were epitaxially grown on sapphire (0001) substrates by metalorganic chemical vapor deposition. The tubes grew along the substrate normal and were characterized by hexagon-shaped cross sections. All of the tubes possessed the same epitaxial relationships with respect to the substrate. Both reactor pressure and growth temperature were found to play an important role in the formation of ZnO tubes. Spiral column growth mode was found to be responsible for the formation of ZnO tubes.

Semiconducting barium disilicide (BaSi2), which is composed of earth-abundant elements, has attractive features for thin-film solar cell applications; both a large absorption coefficient comparable to copper indium gallium diselenide and a minority-carrier diffusion length much larger than the grain size of BaSi2 can be used to improve solar cells properties. In this review article, we explore the potential of semiconducting BaSi2 films for thin-film solar cell applications. We start by describing its crystal and energy band structure, followed by discussing thin-film growth techniques and the optical and electrical properties of BaSi2 films. We used a first-principle calculation based on density-functional theory to calculate the position of the Fermi level to predict the carrier type of impurity-doped BaSi2 films using either a Group 13 or 15 element, and compare the calculated results with the experimental ones. Special attention was paid to the minority-carrier properties, such as minority-carrier lifetime, minority-carrier diffusion length, and surface passivation. The potential variations across the grain boundaries measured by Kelvin-probe force microscopy allowed us to detect a larger minority-carrier diffusion length in BaSi2 on Si(111) compared with in BaSi2 on Si(001). Finally, we demonstrate the operation of p-BaSi2/n-Si heterojunction solar cells and discuss prospects for future development.