4,218 publications from this institution
Piezoelectric semiconductor materials, such as wurtzite ZnO, GaN, InN, and CdS, have drawn intensive research interests for fabricating functional electronics. Under an externally applied mechanical strain, piezoelectric charges (piezocharges) are created at a metal-semiconductor interface or a pn junction, which are likely to tune the local Schottky contact or charge-depletion zone and can be used as a new means for "gating" carrier transport. Piezotronics is a new emerging field using piezoelectric semiconductor[1]. Piezotronic effect has been studied and utilized for two-terminal strain gated transistors [2], logic devices and memory units [3], enhancing solar cell and LED efficiency [4], and enhanced sensing [5]. Recently, piezotronic array and chip devices have been developed as flexible human-machine interfacing [6] and photonic-strain mapping [7], setting a milestone from fabricating single devices to an array of devices and even to an integrated system [8].
Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.
Understanding the spin relaxation in superconducting quantum circuit and solid-state spin hybrid systems is of great importance especially for quantum storage purposes. We have studied the longitudinal relaxation for electron spins of substitutional nitrogen (P1) centers in a hybrid quantum device containing a diamond and a superconducting coplanar waveguide resonator. From a series of pump-probe experiments we conclude that the dominated spin relaxation mechanism is a cross-relaxation process induced by a four-spin interaction (four-spin cross relaxation) among different hyperfine split spin transitions. Some features of the four-spin process are discussed based on a set of rate equations. This work provides interesting perspectives in understanding the coherence properties of the hyperfine split spin ensembles in a hybrid quantum system.
We demonstrate a generic approach for the synthesis of single-crystal complex oxide nanostructures of various structure types, such as perovskites, spinels, monoclinic, corundum, CaF2 structured, tetragonal, and even metal hydroxides. The method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide eutectic at ∼200 °C and normal atmosphere without using an organic dispersant or capping agent. The synthesis technique is cost-effective, one-step, easy to control, and is performed at low temperature and normal atomospheric pressure. The technique can be expanded to many material systems, and it provides a general, simple, convenient, and innovative strategy for the synthesis of nanostructures of complex oxides with important scientific and technological applications in ferroelectricity, ferromagnetism, colossal magnetoresistance, fuel cell, optics, and more.
Abstract Sensor networks are a key technological and economic driver for global industries in the near future, with applications in health care, environmental monitoring, infrastructure monitoring, national security, and more. Developing technologies for self‐powered nanosensors is vitally important. This paper gives a brief summary about recent progress in the area, describing nanogenerators that are capable of providing sustainable self‐sufficient micro/nanopower sources for future sensor networks.
The influence of sodium and phosphorus on the oxidation state of vanadium and molybdenum species and on the redox process of a V-Mo-O catalyst was studied by X-ray photoelectron spectroscopy and thermal gravimetric analysis. Why the sodium doping increased activity and the phosphorus doping improved selectivity in the V-Mo-O catalyst is explained. The sodium ions in the V-Mo-O catalyst seem to decrease the dissociation energy of adsorbed oxygen molecules and therefore make it favorable to the reoxidation of reduced molybdenum and vanadium species; the sodium ions in the V-Mo-O catalyst also weaken the M=O bonds, and therefore promote the vanadium species to be reduced. In other words, the sodium doping promotes the redox process of the V-Mo-O catalyst. The phosphorus ions in the V-Mo-O catalyst tend to keep the reduced vanadium species in a V4+ state and prevent the vanadium species from being significantly reduced, which may be an important reason for improving the selectivity of the V-Mo-O catalyst. In addition, both the sodium and the phosphorus doping in the V-Mo-O catalyst seem to be also helpful in diffusing lattice oxygen.
