Papers by Keyword: Quantum Wire

Abstract: Abstract:Electron mobility limited by surface roughness scattering in free-standing GaAs thin ribbon with an internal parabolic quantum well caused by surface state is investigated in detail. Based on analyzing the parabolic quantum well including the energy subband level, wave function and the confined potential profile in the thin ribbon by solving Schrödinger and Poisson equations self-consistently, the electron mobility could be investigated. Conclusion indicates that remote surface roughness (RSR) of the thin ribbon will change the two dimensional electron gas (2DEG) mobility through the medium of barrier height fluctuation of the parabolic well in atomic scale. Calculation results reveal that the 2DEG mobility decreases with increasing roughness amplitude, which is characterized in terms of the surface roughness height and the roughness lateral size.

Abstract: Using Transfer Matrix Method (TMM) the Eigen energy of the GaN/AlGaN quantum wire has been evaluated. Peak density results show the confinement and tunneling of electron distribution in quantum wire due to band offset of GaN (wire region) and AlGaN (barrier region). The impact of this band offset results in variation in Eigen energy and is significant in Tunneling phenomenon study to realize the transmission coefficient across the cross-section. Our analysis reveals that for wider wires transmission coefficient reaches to its peak for lower Eigen energy values. Likewise, increase in aluminum mole fraction in AlGaN decreases tunneling effect.

Abstract: In the framework of effective mass approximation, the LandauPekar variational procedure is adopted to study the ground-state binding energy of a hydrogenic impurity in a semiconductor nanowire with finite confining potential subjected to both external fields (electric and magnetic) and electronpolar optical phonon interaction taking into account the phonon confinement effect. The results for the binding energy as well as polaronic correction are obtained as a function of the wire radius, impurity position and applied fields. Calculated results reveal that the values of the polaronic shifts of impurity binding energy can be quite different for cases with finite and infinite confining potentials.

Abstract: Stable iron quantum wire with atomic-scale was successfully fabricated and electrically characterized with an electrochemical method in solution by a home-made electrochemically controlled system. By careful controlling the etching/deposition process, stepwise conductance behavior could be clearly observed. The I-V curve of the formed iron quantum wire showed the ohmic behavior with low bias voltage. The work is of great significance for molecular electronics, interface electrochemistry and sensing.

Abstract: We have fabricated site-controlled InAs quantum wires (QWRs) on the cleaved surface (110) of AlGaAs/GaAs superlattices (SLs) structures by using Ga-assisted deoxidation method. In the surface of SLs regions, InAs QWRs were nucleated on GaAs in stead of AlGaAs. In the (110) surface without superlattices(SLs) structures, QDs with a large size were obtained, which is considered hard to realize. To understand the different InAs growth phenomena in the regions with and without superlattices structures, we suggest that indium adatoms have an apparent trend to migrate to the SLs area.

Abstract: Nano-scale spatial wavelength engineering of quantum nanostructures using nitrogen ion-implantation induced intermixing has been developed for tuning the bandgap of quantum-well, quantum-dash-in-well, and quantum-dot nanostructures. High performance bandgap-tuned quantum-well and quantum-dash lasers fabricated using this technique has been demonstrated.

Abstract: The different aspects of molecular beam epitaxy (MBE) for producing two-dimensional (Quantum well), one-dimensional (Quantum wire and rod), and zero-dimensional (Quantum dot) structures based on SiC for functional applications are discussed. Development and implementation of a suitable MBE growth procedure for fabrication of heteropolytypic layer sequences are demonstrated in context with thermodynamic considerations. Furthermore, the growth of onedimensional structures based on cubic wires and nanorod arrays, also grown on Si(111), is shown. Moreover, the perspectives of quantum dot structures and a novel way to form 3C-SiC-dot structures within α-SiC has been discussed.

Abstract: Well-ordered self-assembled SrTiO3 thin film, as a template for complex oxide quantum wires, was fabricated on LaAlO3 (100) single crystal substrates with laser molecular beam epitaxy. The self-assembled growth was in-situ monitored by reflective high energy electron diffraction. The morphology evolutions of the films as a function of thickness were studied by ex-situ atomic force microscopy. As the thickness of the films increased from 3.875nm to 46.5nm gradually, the compressive stress-induced SrTiO3 films exhibited a periodic well-ordered ripple structure, which formed a unique nanoassembled template for the fabrication of quantum wires. Small angle X-ray scattering technique was employed to investigate the structure. Symmetric satellite peaks were discovered, indicating the well-ordered superstructure. In contrast, the similar superstructure was not observed during the growth of the tensile stress-induced LaAlO3 films on SrTiO3 substrates. The Compressive stress was considered as the main reason of the self-assembled growth, and systematical elucidation about strain mechanism was discussed. These results might provide an efficient method for the controllable formation of well-aligned template of quantum wire for complex oxide with desirable structure via proper modulation of strains.

Abstract: The effect of a longitudinal magnetic field and the dielectric constants mismatch of a size- quantized wire and surrounding medium on the impurity scattering of charge carriers is considered. The expressions for the momentum relaxation rate are carried out for scattering on charged Coulomb centers located on the wire axis. The dependences of the momentum relaxation rate on the magnetic field induction, dielectric inhomogeneity parameter, and also on the wire radius are obtained.