Da Peng Yu

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Large heat currents are obtained in Co/Cu/Co spin valves positioned at the middle of Cu nanowires. The second harmonic voltage response to an applied current is used to investigate the effect of the heat current on the switching of the spin valves. Both the switching field and the magnitude of the voltage response are found to be dependent on the heat(More)
Si nanowires ~NWs! were doped with large amounts of Li ions by an electrochemical insertion method at room temperature. Si NWs with different doping levels were obtained by controlling the discharging/charging of Li/Si NWs cell. The microstructures of Si NWs with different doses of Li ions were investigated by high-resolution electron microscopy. The(More)
* This work is supported by DOE SBIR No. DE-FG03-96ER82213. Abstract We consider novel designs that provide field flatness of fundamental mode in transverse dimensions of planar rf structures. These designs include waveguides with slotted irises and/or dielectric loaded side openings. The specially modified, advanced planar structures can be produced with(More)
We present here a design of a 15.6-GHz ceramic power extractor. Design features include an upstream parasitic mode damper with additional tapering, and a single-port coupler considered in two variants. Performance analysis includes coupler tolerances and overvoltage, dipole mode wake and BBU, as well as wakefield losses induced in the damper, tapers, and(More)
We report on the thermal conductivity measurement of Ge quantum dot superlattices. The samples used were grown using molecular beam epitaxy. The typical dot sizes were determined by transmission electron microscopy measurements to be 75 nm in base and 7 nm in height. A differential 3o method was employed to characterize the thermal conductivity of the(More)
* This work is supported by DOE SBIR No. DE-FG03-96ER82156. Abstract Performance of a single-section, S-band, Plane-WaveTransformer (PWT) photoelectron linac is characterized by a high (multi-ampere) average current required for advanced applications such as Compton x-ray sources and linear collider. Single bunch dynamics and multi-bunch beam loading(More)
Large-area ZnO nanorod arrays have been synthesized successfully on a stainless steel grid at a mild growth temperature of around 400 degrees C. The as-grown ZnO nanorods have uniform diameters of about 30-50 nm with approximately 5 nm tips. Patterned growth can be realized by engineering the shape of the grid in the growth. Photoluminescence demonstrates a(More)
In a comment on our recent letter, Yu first pointed out that there was strong alloying between the Ge dots and Si barrier layers because of the appearance of Si–Ge modes as also observed in SiGe alloys. It is correct that the Ge dot samples reported in our letter have some degrees of alloying due to interdiffusion. This was due to the fact that the samples(More)
High gradient pre-acceleration of photoelectron in a pulsed high voltage, dc gap and its subsequent injection into an rf gun is a promising method to improve electron beam emittance in rf accelerators. Simulation work has been performed in order to improve beam properties by optimizing the geometric shapes of a cylindrically symmetric dc/rf gun. Variations(More)
Continuous process-level and system-level innovation has driven Moore's Law scaling for the last fifty years, and will continue to do so in the next decades. In the last two decades, there has been an acceleration of new materials and devices into semiconductor manufacturing, such as low-k, strained Si, high-k, and FinFET, in order to continue process and(More)