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A topological insulator (TI) is an exotic material that has a bulk insulating gap and metallic surface states with unique spin-momentum locking characteristics. Despite its various important applications, large scale integration of TI into MOSFET technologies and its coherent transport study are still rarely explored. Here, we report the growth of high quality Bi2Se3 thin film on amorphous SiO2/Si substrate using MBE. By controlling the thickness of the film at ~7 nm and capping the as grown film in situ with a 2 nm-thick Se layer, largest electrostatic field effect is obtained and the resistance is changed by almost 300%. More importantly, pronounced gate-tunable weak antilocalization (WAL) is observed, which refers to modulation of α from ~-0.55 to ~-0.2 by applying a back gate voltage. The analysis herein suggests that the significant gate-tunable WAL is attributable to the transition from weak disorder into intermediate disorder regime when the Fermi level is shifted downward by increasing the negative back gate voltage. Our findings may pave the ways towards the development of TI-based MOSFET and are promising for the applications of electricfield controlled spintronic and magnetic device. [ABSTRACT FROM AUTHOR]

The structural evolution during deformation is investigated in a work hardenable ductile TiCu-based bulk metallic glass by high-resolution electron microscopies. Two categories of crystalline morphologies, the scattered nanocrystallites and the nanocrystalline bands, are observed during the deformation. The nanocrystallization induced by deformation has implications for interpreting the unusual mechanical behavior of the glass. [ABSTRACT FROM AUTHOR]

By introducing the AlInGaN/AlGaN quaternary system as an active region, we fabricated an UV light-emitting diode (LED) with an emission wavelength of 348 nm. The optical power is 1 mW at an injection current of 50 mA under a bare-chip geometry, which is the highest report among UV-LEDs with an emission wavelength of around 350 nm grown on sapphire substrate. It means that the optical power of such LEDs is high enough to be used in practical application. In contrast to it, a similar UV-LED based on GaN/AlGaN system as an active region has been also grown, whose optical power is less than that of the AlInGaN/AlGaN-based UV-LED by one order of magnitude. The temperature-dependent photoluminescence study indicates that there exists a strong exciton-localization effect in the AlInGaN/AlGaN material system, while there is no distinguished exciton-localization effect in the GaN/AlGaN material system. Therefore, the high performance of the AlInGaN/AlGaN-based UV-LED can be attributed to the enhanced exciton-localization effect. [ABSTRACT FROM AUTHOR]

The authors report the observations of periodic morphology evolution on fracture surface of a brittle metallic glassy ribbon, suggesting a wavy local stress intensity factor along the crack propagation. The authors find that the formation of nanoscale damage cavity structure is a common characteristic morphology on the fracture surfaces. On the surface of the hackle zone, these cavities assemble and generate the nanoscale swirling periodic corrugations. The elastic waves interfering with the plastic process zone on the crack front is proposed to explain such dynamic crack instability. The authors’ observations support the notion of an impinging effect of elastic waves on propagating crack front. [ABSTRACT FROM AUTHOR]

Searching strain sensitive materials for electronic skin is of crucial significance because of the restrictions of current materials such as poor electrical conductivity, large energy consumption, complex manufacturing process, and high cost. Here, we report a flexible strain sensor based on the Zr55Cu30Ni5Al10 metallic glass thin film which we name metallic glass skin. The metallic glass skin, synthesized by ion beam deposition, exhibits piezoresistance effects with a gauge factor of around 2.86, a large detectable strain range (~1% or 180° bending angle), and good conductivity. Compared to other e-skin materials, the temperature coefficient of resistance of the metallic glass skin is extremely low (9.04 x 10-6K-1), which is essential for the reduction in thermal drift. In addition, the metallic glass skin exhibits distinct antibacterial behavior desired for medical applications, also excellent reproducibility and repeatability (over 1000 times), nearly perfect linearity, low manufacturing cost, and negligible energy consumption, all of which are required for electronic skin for practical applications. [ABSTRACT FROM AUTHOR]

Perpendicular magnetic tunnel junctions with GdOX tunneling barriers have shown a unique voltage controllable interlayer magnetic coupling effect. Here, we investigate the quality of the GdOX barrier and the coupling mechanism in these junctions by examining the temperature dependence of the tunneling magnetoresistance and the interlayer coupling from room temperature down to 11 K. The barrier is shown to be of good quality with the spin independent conductance only contributing a small portion, 14%, to the total room temperature conductance, similar to AlOX and MgO barriers. The interlayer coupling, however, shows an anomalously strong temperature dependence including sign changes below 80 K. This non-trivial temperature dependence is not described by previous models of interlayer coupling and may be due to the large induced magnetic moment of the Gd ions in the barrier. [ABSTRACT FROM AUTHOR]

Strain-induced graphene phonon softening and phonon band splitting are indeed fascinating, which were attributed to the phonon double resonant scattering without intrinsic involvement of C-C bond relaxation. Here, we show that the lengthening and weakening of the C-C bond softens the phonon and that the mismatching between the uniaxial strain and the C3v bond geometry splits the band. In addition to the force constant of 11.8 N/m for a C-C bond in graphene, consistency between theory and measurements derives that if the strain is along a bond, maximal band splitting happens; if the strain is perpendicular, no band splitting occurs. [ABSTRACT FROM AUTHOR]

The effect of structural relaxation on shear transformation zones (STZs) in a Zr70Ni16Cu6Al8 glassy alloy is evaluated. Upon annealing, the measured STZ size dramatically decreases with moderate augment of mass density caused by the increase of icosahedra short-range orders. The greater atomic packing density gives rise to involvement of lesser atoms in the formation of STZs and thereby degradation of ductility. This study demonstrates that STZ volume is a key parameter reflecting the intrinsic relationship between atomic structure and mechanical properties of metallic glasses. [ABSTRACT FROM AUTHOR]

Single-phase samples of Bi(Fe1-xCrx)O3 with x=0, 0.1, and 0.2 were synthesized by a combustion method. X-ray diffraction reveals that the lattice parameters of Bi(Fe1-xCrx)O3 perovskites decrease linearly with the Cr content, indicating that Cr ions substitute for Fe ions to form a solid solution. X-ray photoelectron spectroscopy investigation shows that Cr ions have the Cr3+ valence state in Bi(Fe1-xCrx)O3. The frequency dependence of dielectric constants was investigated at room temperature. Magnetic measurements show hysteresis loops at both 5 and 300 K and the substitution of Cr for Fe enhances the magnetization. [ABSTRACT FROM AUTHOR]

Homogeneous MnxGe1-x ferromagnetic semiconductor films with high Mn concentration were prepared, contrasting with dilute inhomogeneous MnxGe1-x magnetic semiconductors. The saturation magnetization of Mn0.57Ge0.43 films is high, up to 327 emu/cm3 (1.04μB/Mn) at 5 K, and the Curie temperature is about 213 K. The Mn0.57Ge0.43 films show semiconducting resistance, but the magnetoresistance is negligibly small. The anomalous Hall effect was observed below the Curie temperature, which is consistent with the magnetic measurements. The global ferromagnetism was discussed based on s,p-d exchange coupling between the weakly localized s,p hole carriers and the strongly localized d electrons of the Mn atoms. [ABSTRACT FROM AUTHOR]

The reliability of electroluminescence from metal-oxide-silicon (MOS) tunneling diodes was improved by the incorporation of deuterium. The deuterium was incorporated by the deuterium prebake and the postoxide deuterium annealing. At constant current stress of 100 mA, a deuterium-treated n-channel MOS tunneling light-emitting diode shows that the integrated light emission intensity increases slightly about 6% after 10 000 s operation, while the hydrogen-treated device shows a 30% decrease of the integrated light emission intensity. The hydrogen release by the electrons tunneling from the gate electrode to Si and the formation of interface defects are responsible for the degradation of light output in the hydrogen-treated samples. An annealing model is also given to explain the slight increase of light output in the deuterium-treated samples. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Tl-Ba-Ca-Cu-O superconducting thin films with zero-resistance temperatures up to 115 K have been prepared using a Tl2 O3 vapor process on Ba-Ca-Cu-O precursor thin films. The Ba-Ca-Cu-O thin films were made by laser deposition on Y-stabilized ZrO2 substrates. This technique minimizes problems caused by the toxicity of Tl2 O3, and its subsequent decomposition to the volatile and toxic Tl2 O upon heating. Therefore, it may have practical application in the fabrication of high Tc Tl-Ba-Ca-Cu-O superconducting thin-film devices. [ABSTRACT FROM AUTHOR]