Showing papers on "Quantum dot published in 1989"
TL;DR: In this article, the authors realized arrays of quantum dots on InSb and observed intraband transitions between their discrete (zero-dimensional) electronic states with far-infrared magnetospectroscopy.
Abstract: We have realized arrays of quantum dots on InSb and observe intraband transitions between their discrete (zero-dimensional) electronic states with far-infrared magnetospectroscopy. In our devices, the number of electrons can be adjusted by a gate voltage and less than 5 electrons per dot are detectable.
463 citations
TL;DR: In this article, a photoluminescence study of an (AlGa)As-GaAs quantum-well-wire array directly grown by molecular-beam epitaxy on a tilted substrate is described.
Abstract: A photoluminescence study of an (AlGa)As-GaAs quantum-well-wire array directly grown by molecular-beam epitaxy on a tilted substrate is described. A strong anisotropy was observed in the ratio of the electron-light-hole-exciton peak intensity to the electron-heavy-hole-exciton peak intensity. A theory incorporating the optical selection rule for two-dimensional quantum confinement is found to agree very well with the measured data. These results constitute the first evidence of two-dimensional quantum confinement in artificial wire structures having cross-sectional dimensions in the nanometer range.
282 citations
Book•
01 Jan 1989
TL;DR: In this paper, the most important aspects of the MBE apparatus, the physics and chemistry of the crystallization of various materials and device structures, and the characterization methods that relate the structural parameters of the grown (or growing) film or structure to the technologically relevant procedure are described.
Abstract: This study describes a technique in wide-spread use for the production of high-quality semiconductor devices. It discusses the most important aspects of the MBE apparatus, the physics and chemistry of the crystallization of various materials and device structures, and the characterization methods that relate the structural parameters of the grown (or growing) film or structure to the technologically relevant procedure. In this edition two new fields have been added: crystallization of as-grown low-dimensional heterostructures, mainly quantum wires and quantum dots and in-growth control of the MBE crystallization process of strained-layer structures.
255 citations
TL;DR: The general guiding principles for designing DQW structures with optimum excitonic properties are established, and ZnSe is found to be one of the most promising candidates for the barrier material of the GaAs D QW.
Abstract: Excitonic and nonlinear-optical properties of dielectric quantum-well (DQW) structures are investigated theoretically. A DQW is a quantum well sandwiched by barrier materials with a smaller dielectric constant and a larger band gap than the well material. The fundamental physics determining the excitonic properties in a DQW, i.e., exciton binding energy, exciton oscillator strength, and nonlinear-optical response, are clarified. The most important mechanisms for enhancing the excitonic properties are quantum-confinement effect, mass-confinement effect, and dielectric-confinement effect. Quantum confinement increases the spatial overlap between an electron and a hole as a result of the potential well confinement, and it enhances oscillator strength. Mass confinement is based on the penetration of the carrier wave function into barrier layers with a heavier effective mass than the well layer. It increases the exciton reduced mass and hence the exciton binding energy. Dielectric confinement arises from the reduction of the effective dielectric constant of the whole system due to the penetration of the electric field into the barrier medium having a smaller dielectric constant than the well and enhances the Coulomb interaction between the electron and hole. On the basis of these analyses, the general guiding principles are established for designing DQW structures with optimum excitonic properties. Various practical examples of DQW's are examined with respect to the lattice-constant matching, the difference in the dielectric constant, and the difference in the carrier effective masses. ZnSe is found to be one of the most promising candidates for the barrier material of the GaAs DQW.
224 citations
TL;DR: It is found that the frequency dispersion of the third-order nonlinear susceptibility of the biexciton binding energy and the oscillator strength shows an out-of-phase behavior at the one- and two-photon resonances, which is characteristic of the exciton and bIExciton transitions.
Abstract: Biexciton states in semiconductor quantum dots (spherical microcrystallites) are investigated variationally, and the biexciton binding energy and the oscillator strength are calculated as a function of the quantum-dot radius, the electron-to-hole mass ratio, and the dielectric constant ratio of the semiconductor to the surrounding medium. The most important mechanisms for enhancing the biexciton binding energy and the oscillator strength are clarified. One is the quantum confinement effect, which increases the spatial overlap between carriers, leading to enhanced Coulomb interaction. Another is the dielectric confinement effect due to the dielectric constant discontinuity at the interface between a semiconductor microcrystallite and the surrounding medium. This effect arises from the penetration of electric force lines through the surrounding medium with a relatively small dielectric constant and leads to an enhancement of the Coulomb interaction. It is found that the frequency dispersion of the third-order nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}$ shows an out-of-phase behavior at the one- and two-photon resonances, which is characteristic of the exciton and biexciton transitions. For typical materials which are promising for observation of the biexciton state in microcrystallites, the values of the biexciton binding energy, the third-order nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}$, and the two-photon absorption coefficient ${K}_{2}$ of the biexciton state are predicted theoretically.
208 citations
01 Apr 1989
TL;DR: In this article, the optical nonlinearity of 50-A CdS clusters in Nafion film is determined to be −6.1 × 10−7 cm2 W−1 at 480 nm.
Abstract: CdS and PbS clusters with sizes ranging from a few angstroms to 150 A can be synthesized in polymers. The dependence of the band gap on the cluster size deviates from the prediction of a simple particle-in-a-box model owing to the breakdown of the effective-mass approximation. Instead, the dependence can be described by a simple tight-binding cluster model. The optical nonlinearity, expressed as α2/α0, of 50-A CdS clusters in Nafion film is determined to be −6.1 × 10−7 cm2 W−1 at 480 nm. The nonlinearity originates from the bleaching of the excitonic absorption owing to the presence of trapped carriers on the cluster surfaces. By passivating the CdS surfaces with ammonia, we have shown that the nonlinearity can be controlled by surface chemistry. We have determined that the presence of one trapped electron–hole pair can bleach the excitonic absorption of the whole CdS cluster. This efficient bleaching can be understood by using a model that considers the shifting of the exciton resonance and weakening of its oscillator strength in the presence of a trapped electron or hole. We also discuss two new classes of material: superclusters in zeolites and surface-capped clusters. Both represent our first steps toward the systematic synthesis of clusters of controlled surfaces and sizes.
147 citations
IBM1
TL;DR: The magnetic-field-induced bifurcation of quantum levels into surface states and bulk-like Landau States was observed in this paper, where a single-particle energy spectrum was calculated.
Abstract: We observe the magnetic-field-induced bifurcation of quantum levels into surface states and bulklike Landau States. The disruption of the electric field quantization by a magnetic field is most dramatic for electrons bound in two dimensions perpendicular to the magnetic field. The interplay between competing spatial and magnetic quantization mechanisms results in a pronounced and complex level splitting. The observed splitting of zero-dimensional energy levels depends critically on the size of the quantum dots, and can be explained with a calculated single-particle energy spectrum.
140 citations
TL;DR: In this paper, a femtosecond differential absorption measurements of the quantum-confined transitions in CdSe microcrystallites are reported, which are consistently explained by bleaching of one-pair states and induced absorption caused by photoexcited two electron-hole pair states.
Abstract: Femtosecond differential absorption measurements of the quantum-confined transitions in CdSe microcrystallites are reported. Spectral hole burning is observed, which is accompanied by an induced absorption feature on the high-energy side. The spectral position of the burned hole depends on the excitation wavelength. For excitation on the low-energy side of the lowest quantum-confined transition, a slight shift of the hole towards the line center is observed. The hole width increases with pump intensity and the magnitude of the induced transparency saturates at the highest excitation level. The results are consistently explained by bleaching of one-pair states and induced absorption caused by the photoexcited two electron-hole pair states. It is concluded that the presence of one electron in the excited state prevents further absorption of photons at the pair-transition energy and accounts for the major portion of the bleaching of the transition. >
134 citations
TL;DR: In this paper, a microscopic many-electron description of the third-order susceptibilities γijkl(−ω4; ω1, ω2, and ω3) of conjugated structures is reviewed for one-dimensional chains and extended to two-dimensional cyclic structures.
Abstract: Reduced dimensionality and quantum confinement in conjugated organic and polymer structures enhance the effects of electron correlation on virtual electronic excitation processes and nonlinear-optical responses. A microscopic many-electron description of the third-order susceptibilities γijkl(−ω4; ω1, ω2, ω3) of conjugated structures is reviewed for one-dimensional chains and extended to two-dimensional conjugated cyclic structures. Electron correlation effects in effectively reduced dimensions result in highly correlated π-electron virtual excitations that lead to large, ultrafast nonresonant nonlinear-optical responses. The increase of dimensionality from linear to cyclic chains is found to reduce the nonresonant isotropic third-order susceptibility γg. Resonant experimental studies of saturable absorption and optical bistability in ultrathin films of quasi-two-dimensional naphthalocyanine oligomers are also presented. In the saturable-absorption studies, the resonant nonlinear refractive index n2 was measured to be 1 × 10−4 cm2/kW in the wavelength range of operating laser diodes. Based on this result, electronic absorptive optical bistability is observed on a nanosecond time scale in a nonlinear Fabry–Perot interferometer employing the saturably absorbing naphthalocyanine film as the nonlinear-optical medium.
86 citations
TL;DR: In this article, the luminescence efficiency of reactive ion etched quantum dots, varying in diameter from 200 μm down to 60 nm, was investigated using low-temperature cathodoluminescence spectroscopy.
Abstract: Low‐temperature cathodoluminescence spectroscopy was used to investigate the luminescence efficiency of reactive ion etched quantum dots, varying in diameter from 200 μm down to 60 nm. The luminescence efficiency was found to be degraded both with decreasing nanostructure size and with increasing etch depth. A solution to the standard model for diffusion and recombination was applied to the data to determine the surface recombination velocity S. We found that for dots smaller than the diffusion length, the standard diffusion model becomes insensitive to the value of S and fails to predict that there is a size of dot in which the luminescence is completely extinguished. To understand qualitatively the luminescence degradation in etched nanostructures we describe a damage layer thickness ξ. The value of ξ determines the smallest quantum structure that will still emit light. We show that ξ increases with increasing etch depth and is therefore dependent on etching conditions.
74 citations
TL;DR: In this paper, the authors describe a method of confining carriers by deliberately creating large inhomogeneous strain patterns in a quantum well, which modulates the band gap to provide lateral quantum confinement for excitons.
Abstract: We describe a novel method of confining carriers by deliberately creating large inhomogeneous strain patterns in a quantum well The strain modulates the band gap to provide lateral quantum confinement for excitons Here, we generate strain confinement in an InGaAs quantum well by reactive ion beam assisted etching through an overlying compressed pseudomorphic quaternary layer using etch masks patterned by electron beam lithography Photoluminescence spectra of arrays of wires and dots show red‐shifted band gaps in direct evidence of lateral confinement We compare our results to finite element calculations of the inhomogeneous strain in an InP substrate from a compressed overlayer patterned into rectangular wires
TL;DR: In this paper, high-resolution lattice images obtained with transmission electron microscopy of single quantum wells reveal high quality interfaces for both the normal InGaP/GaAs and the inverted GaAs/InGaP interface.
Abstract: High quality quantum wells of GaAs confined by barriers of InGaP have been grown by gas‐source molecular beam epitaxy. High‐resolution lattice images obtained with transmission electron microscopy of single quantum wells reveal high quality interfaces for both the normal InGaP/GaAs and the inverted GaAs/InGaP interface. Multiple‐line low‐temperature photoluminescence emission is observed for the thinnest GaAs quantum well. The range of well thicknesses examined was 0.6–5.2 nm, with the smallest well producing a quantum confinement energy shift of over 410 meV, corresponding to photoluminescence emission at 640 nm (1.94 eV) from GaAs.
TL;DR: In this article, a number of devices based on wave-function interference effects have been proposed for 1D conducting wires made from two-dimensional electron gases (2DEGs) approaching the same size as the deBroglie wavelength of electrons.
Abstract: Remarkable advances in microfabrication technology have allowed physicists to probe into the size regime where quantum mechanical effects begin to dominate transport. When 1D conducting wires made from two‐dimensional electron gases (2DEGs) approach the same size as the deBroglie wavelength of electrons, electronic transport is determined by transmission through a small number of ‘‘waveguide modes’’ of the 1D channel. Low temperature experiments in this size regime show significant wavefunction interference effects. A number of devices based upon these physical phenomena have been proposed. Quantum localization has also been explored in perpendicular electronic transport through heteroepitaxial structures, the simplest case being one‐dimensional resonant tunneling structures that exhibit strong quantum interference up to room temperature. Three‐terminal devices that directly modulate this interference have been demonstrated. Ultimate scaling limitations of heterojunction tunneling devices will only be con...
TL;DR: The biexciton ``binding energy'' in a microsphere is calculated in the limit of vanishing sphere radius by use of ordinary second-order perturbation theory and is found to be always positive and may exceed one excitonic Rydberg.
Abstract: The biexciton ``binding energy'' in a microsphere is calculated in the limit of vanishing sphere radius by use of ordinary second-order perturbation theory. This ``binding energy'' is found to be always positive and may exceed one excitonic Rydberg, depending on the ratio of the dielectric constants of the semiconductor and the cladding material, as well as on the electron-hole mass ratio.
TL;DR: The average size of the microcrystalline depended on the relative area and location of the CdTe chips on the target, as well as the postannealing time; and that of as-deposited films varied from 22 A to 62 A as mentioned in this paper.
Abstract: Semiconducting CdTe microcrystalline was successfully doped in SiO2 films by the magnetron rf-sputtering technique. The average size of the microcrystalline depended on the relative area and location of the CdTe chips on the target, as well as the postannealing time; and that of as-deposited films varied from 22 A to 62 A. From the optical absorption spectra, the absorption edge of the films clearly exhibited blue shifts compared to the bulk CdTe. Thus the quantum size effect could be found for these films.
TL;DR: In this paper, the results of structural and optical studies of semiconductor microparticle composites consisting of small CdSe crystallites embedded in a silicate glass matrix are reported.
Abstract: We report the results of structural and optical studies of semiconductor microparticle composites consisting of small CdSe crystallites embedded in a silicate glass matrix. Raman scattering and x-ray diffraction studies indicate that the microparticles in the present studies are pure CdSe crystallites with a diameter of 6 nm. We outline the analysis of room-temperature optical absorption and photoluminescence data to deduce the particle-size distribution when the band edge is controlled by quantum confinement.
TL;DR: In this article, the first buried GaAs-GaAlAs quantum dots have been grown by MOCVD for the first time, and free-standing quantum dots were formed in GaAs and GaAlAs single quantum well material by a combination of electron beam lithography and dry etching.
Patent•
26 Dec 1989TL;DR: Improved p-channel FETs and optoelectronic devices made use of reduced hole effective mass achieved with quantum confinement as mentioned in this paper, which can be found in a wide range of devices.
Abstract: Improved p-channel FETs and optoelectronic device make use of reduced hole effective mass achieved with quantum confinement. The devices include multiple one-dimensional p-channel FETs which have electrically induced and controllable one dimensional p-type semiconductor wires; square well two-dimensional p-channel FETs; and laser diodes and light emitting diodes which use one dimensional p-type semiconductor wires.
TL;DR: In this article, the MBE growth of GaAs-AlAs "tilted superlattices" (TSLs) having interface planes tilted with respect to the substrate surface plane is reported.
01 Jan 1989
TL;DR: A review of recent results that highlight applications of the light scattering method in studies of quasi-two-dimensional electron systems can be found in this paper, where the authors have shown that the method can be used to measure the excitations associated with the free electron motion in the plane as well as that of the restricted motion normal to the plane.
Abstract: We have presented a review of recent results that highlight applications of the light scattering method in studies of quasi-two-dimensional electron systems. We have seen that the method can be used to measure the excitations associated with the free electron motion in the plane as well as that of the restricted motion normal to the plane. These features, in conjunction with the very advantageous option to measure spectra of collective and single particle excitations, make light scattering a very versatile spectroscopic tool. With the use of optical multichannel detection, and taking advantage of large resonant enhancements, it is possible to carry out experiments at very low laser power densities. This creates the possibility to study remarkable low temperature many-body phenomena, like the fractional quantization of the Hall effect, that are at the frontier of condensed-matter physics. We expect important applications in the area of time-resolved spectroscopy, where the method could reveal dynamical behavior of hot electrons. There is increasing interest in systems where the electrons have one-dimensional behavior (quantum wires) and also in zero-dimensional systems (quantum dots). We expect that inelastic light scattering, especially with the new techniques of micro-Raman spectroscopy, will play a prominent role in the elucidation of the intriguing properties of these novel semiconductor microstructures.
TL;DR: In this paper, a well-resolved multiple peaks are observed in low-temperature photoluminescence (PL) spectra, instead of an expected single peak.
Abstract: Ultrathin InGaAs/InP single quantum well structures, grown by chloride transport vapor levitation epitaxy, have been investigated by low‐temperature photoluminescence (PL). Well‐resolved multiple peaks are observed in the PL spectra, instead of an expected single peak. We attribute this to monolayer (a0/2=2.93 A) variations in quantum well (QW) thickness. Separate peak positions for QW thicknesses corresponding to 2–6 monolayers have been determined, providing an unambiguous thickness calibration for spectral shifts due to quantum confinement. The PL peak corresponding to two monolayers occurs at 1.314 eV, corresponding to an energy shift of 524 meV. Experimental data agree very well with a simple effective mass theory.
TL;DR: In this paper, the transition from isolated to coupled quantum dots in a lateral surface-superlattice structure in the presence of a perpendicular magnetic field was studied, and the coupling between the dots can be tuned by changing the bias of the grid gate.
Abstract: We have studied the transition from isolated to coupled quantum dots in a lateral surface‐superlattice structure in the presence of a perpendicular magnetic field. The coupling between the dots can be tuned by changing the bias of the grid gate. Our magnetocapacitance measurements reveal three distinct regimes: isolated quantum dots where collective effects are not observed, a tight‐binding regime where the measurement results are sensitive to the rationality of flux quanta per unit cell, and a superlattice regime where commensurability effects between the magnetic orbits and the superlattice periodicity are observed.
TL;DR: In this article, the threshold current and the wavelength of a high power ridge waveguide AlGaAs graded index seperate confinement heterostructure quantum well laser have been studied in strong magnetic fields up to 20 T, to simulate the complete quantum confinement of carriers in a quantum box laser.
Abstract: The threshold current and the wavelength of a high‐power ridge waveguide AlGaAs graded index seperate confinement heterostructure quantum well laser have been studied in strong magnetic fields up to 20 T, to simulate the complete quantum confinement of carriers in a quantum box laser. It will be shown both experimentally and theoretically that the threshold current is increased by the application of a strong magnetic field, while its temperature sensitivity is reduced. It will further be shown that at low temperatures (T 100 K) exciton laser emission is only observed after application of a strong magnetic field, i.e., reduction of the dimensionality.
01 Jan 1989
TL;DR: In this article, the electronic transport through 3-dimensionalally confined semiconductor quantum wells (quantum dots) is investigated and analyzed and the spectra correspond to resonant tunneling from laterally confined emitter contact subbands through the discrete 3-dimensionally confined quantum dot states.
Abstract: The electronic transport through 3-dimensionally confined semiconductor quantum wells (quantum dots) is investigated and analyzed. The spectra corresponds to resonant tunneling from laterally-confined emitter contact subbands through the discrete 3-dimensionally confined quantum dot states. Momentum nonconservation is observed in these structures. Results on coupled quantum dot states (molccules) will be presented.
TL;DR: In this paper, a study of nonradiative surface recombination in etched GaAs quantum well structures was conducted, and the relationship between etching damage and quantum well width was determined by using three samples, each consisting of three quantum wells of 2, 4, and 9 nm thickness.
Abstract: We report a study of nonradiative surface recombination in etched GaAs quantum well structures. Low‐temperature cathodoluminescence was used to measure the relative luminescence efficiencies of etched quantum dots as a function of size, etch depth and etching conditions, and quantum well width. The relationship between etching damage and quantum well width was determined by using three samples, each consisting of three quantum wells of 2, 4, and 9 nm thickness, with the placement of the wells relative to the surface varied systematically. Arrays of quantum dots which ranged in size from 5 μm down to 40 nm were produced by electron beam lithography and reactive ion etching or ion beam assisted etching. The nonradiative surface damage produced by the etching process degrades the luminescence efficiency in quantum dots smaller than 1 μm in diameter. We have determined that etching processes which use argon gas increase the nonradiative surface layer thickness compared to etching processes which use xenon. We...
Book•
01 Jan 1989
TL;DR: In this article, the authors present an overview of the origins of the concept of quantum waveform and its application in the field of nanostructures, as well as a discussion of the application of waveform in quantum computing.
Abstract: Overview and Background: M.A. Reed and W.P. Kirk, Overview and Background. Conceptual Origins of Nanostructures: R. Landauer, Nanostructure Physics: Fashion or Depth? A.J. Leggett, Quantum and Classical Concepts at the One-Electron Level. R.A. Webb, Quantum Interference Effects in Condensed Matter Physics. Lateral Periodicity and Confinement: H.I. Smith, K. Ismail, W. Chu, A. Yen, Y.C. Ku, M.L. Schattenburg, and D.A. Antoniadis, Fabrication of Quantum-Effect Electronic Devices Using X-Ray Nanolithography. J.P. Kotthaus, Transport Properties and Infrared Excitations of Laterally Periodic Nanostructures. S.P Beaumont, Fabrication and Overgrowth of Quantum Wires and Dots for Optoelectronic Applications. M. Watt, H.E.G. Arnot, C.M.S. Torres, and S.P. Beaumont, Surface Phonon Studies of Nanostructures. W. Hansen, T.P. Smith III, J.A. Brum, J.M. Hong, K.Y. Lee, C.M. Knoedler, D.P. Kern, and L.L. Chang, Magnetic Effects in Quantum Dots. J.H. Davies, Analytic Self-Consistent Calculations for Inhomogeneous Two-Dimensional Electron Gases. G. Danan, J.S. Weiner, A. Pinczuk, J. Valladares, L.N. Pfeiffer, and K. West, Optical Investigation of a One-Dimensional Electron Gas. S. Bandyopadhyay, Quantum Phase Coherent Effects in the Photoluminescence Spectra of Disordered Mesoscopic Structures. J.A. Nixon, J.H. Davies, and J.R. Barker, Fluctuations in Sub-Micron Semiconducting Devices Caused by the Random Positions of Dopants. W.B. Kinard, M.H. Weichold, G.F. Spencer, and W.P. Kirk, Laterally Confined Resonant Tunneling Diode with Adjustable Quantum-Dot Cross-Section. G. Neofotistos, K. Diff, and J.D. Gunton, Time-Dependent Modeling of Resonant Tunneling Structures Using the 3-Dimenensional Schrodinger Equation: Investigation of the Intrinsic Time Characteristics of a Zero-Dimensional Semiconductor Nanostructure. S.E. Ulloa, Y.C. Lee, and B.S. Mendoza, Interlevel Plasmons in Quasi-One-Dimensional Structures. Quantum Devices and Transistors: D. van der Marel, Theory of the Quantum Ballistic Transport in Constrictions and Quantum Resonance Devices. F. Sols, M. Macucci, U. Ravaioli, and K. Hess, Criteria for Transister Action Based on Quantum Interference Phenomena. D.C. Miller, R.K. Lake, S. Datta, M.S. Lundstrom, M.R. Melloch, and R. Reifenberger, Modulation of the Conductance of T-Shaped Electron Waveguide Structures with a Remote Gate. T. Hiramoto, T. Odagiri, K. Hirakawa, Y. Iye, and T. Ikoma, Anomalous Drain Conductance in Quasi-One-Dimensional AlGaAs/GaAs Quantum Wire Transistors Fabricated by Focused Ion Beam Implantation. S. Bandyopadhyay, G.H. Bernstein, and W. Porod, Quantum Devices Based on Phase Coherent Lateral Quantum Transport. U.K. Reddy, G.I. Haddad, I. Mehdi, and R.K. Mains, Fabrication and Room Temperature Operation of a Resonant Tunneling Transistor with a Pseudomorphic InGaAs Base. J.M. Ryan, J. Han, A.M. Kriman, D.K. Ferry, and P. Newman, Overshoot Saturation in Ultra-Short Channel FETs due to Minimum Acceleration Lengths. S. Bhobe, W. Porod, S. Bandyopadhyay, and D.J. Kirkner, Tailoring Transport Properties by Wavefunction Engineering in Quantum Wells and Its Device Applications. I. Mehdi and G.I. Haddad, InP Based Resonant Tunneling Diodes for Millimeter-Wave-Power Generation. R. Bertoncini, A.M. Kriman, and D.K. Ferry, Field/Scattering Interaction Quantization in High-Field Quantum Transport. Equilibrium and Nonequilibrium Response in Nanoelectronic Structures: A.F.J. Levi and S. Schmitt-Rink, Nonequilibrium Electron Dynamics in Small Semiconductor Structures. M. Heiblum, Ballistic Transport in the Vertical and Horizontal Domains. W.R. Frensley, Quantum Kinetic Theory of Nanoelectronic Devices. S. Datta and M.J. McLennan, Quantum Transport with Dissipation: Linear and Non-linear Response. J.R. Barker, Theory of Quantum Transport in Lateral Nanostructures. M.L. Leadbeater, E.S. Alves, L. Eaves, M. Henini, O.H. Hughes, F.W. Sheard, and G.A. Toombs, High Magnetic Field Studies of Intrinsic Bistability, Electron Thermalization and Ballistic Effects in Resonant Tunneling Devices. B.Y-K. Hu, J.W. Wilkins, and S.K. Sarker, Quantum Transport Equation Approach to Nonequilibrium Screening. C. Lent, S. Sivaprakasam, and D.J. Kirkner, Calculation of Ballistic Transport in Two-Dimensional Quantum Structures Using the Finite Element Method. K. Diff, G. Neofotistos, H. Guo, and J.D. Gunton, Resonant Tunneling in Double-Barrier Diodes. W.W. Lui and J. Frey, A Simplified Method for Quantum Size Effect Analysis in Sub-Micron Devices Including Fermi-Dirac Statistics. R.L. Kamocsai and W. Porod, A Monte Carlo Study of the Influence of Traps on High Field Electronic Transport in a SiO2. J.A. St*alovneng and E.H. Hauge, Tunneling Times and the B*aduttiker-Landauer Model. R.A. Serota and J. Yu, Variance Fluctuations and Sample Statistics for Fluctuating Variable-Range Hopping Conduction. Quantum Wires and Ballistic Point Contacts: M. B*aduttiker, When is the Hall Resistance Quantized? G. Timp, R. Behringer, S. Sampere, J.E. Cunningham, and R.E. Howard, When Isn't the Conductance of an Electron Waveguide Quantized? H. van Houten and C.W.J. Beenakker, Electron Beams and Waveguide Modes: Aspects of Quantum Ballistic Transport. B.J. van Wees, L.P. Kouwenhoven, E.M.M. Willems, and C.J.P.M. Harmans, Quantum Ballistic Transport in High Magnetic Fields. A.D. Stone, A. Szafer, and H.U. Baranger, New Theoretical Results on Ballistic Quantum Transport: Quenching of the Hall Resistance and Quantized Contact Resistance. Y. Imry, Theoretical Considerations for Some New Effects in Narrow Wires. C.J.B. Ford, The Low-Field Hall Effect in Quasi-Ballistic Wires. A. Sachrajda, D. Landheer, R. Boulet, J. Stalica, and T. Moore, Evidence for an Inhomogeneity Size Effect in Micron Size GaAs/A1GaAs Constrictions. S.D. Berger, H.A. Huggins, A.E. White, K.T. Short, and D. Loretto, A New Technique to Produce Single Crystal Epitaxial Nanostructures. M. Cahay, S. Bandyopadhyay, and H.L. Grubin, Doubled Frequency of the Conductance Minima in Electrostatic Aharonov-Bohm Oscillations in One-Dimensional Rings. A. Pruisken and Z. Wang, Mesoscopic Conductance Fluctuations in Disordered Metals. Related Fabrication and Phenomena: A.N. Broers, Resolution Limits of Electron Beam Lithography and Methods for Avoiding These Limits. A. Scherer, M.L. Roukes, and B.P. Van der Gang, Quantum Device Microfabrication at the Resolution Limit of Ion Beam Processing. E.E. Ehrichs and A.L. de Lozanne, Fabrication of Nanometer Features with a Scanning Tunneling Microscope. A.E. Owen, P.J.S. Ewen, A. Zakery, M.N. Kozicki, and Y. Khawaja, Metal-Chalcogenide Photoresists for High Resolution Lithography and Sub-Micron Structures. D.C. Ralph, K.S. Ralls, and R.A. Buhrman, Defect Motion, Electromigration and Conductance Fluctuations in Metal Nanocontacts. C.R. Martin, M.J. Tierney, I.F. Cheng, L.S. Van Dyke, Z. Cai, J.R. McBride, and C.J. Brumlik, Nano- and Microstructures in Chemistry, Electrochemistry, and Materials Science. C. Van Haesendonck, H. Vloeberghs, Y. Bruynseraede, and R. Jonckheere, Electronic Transport in Mesoscopic AuFe Spin-Glasses. N. Giordano, Nature of the Superconducting Transition in Very Thin Wires. L. Reggiani and V. Kozlov, Population Inversion in Superconducting Quantum Wells Under Ballistic Conditions. A. Badakhshan, C. Durbin, A. Giordana, R. Glosser, S.A. Lambert, and J. Liu, Photoreflectance of Semiconductors Beyond the Band Gap. M. Cahay, M.A. Osman, H.L. Grubin, and M. McLennan, Space-Charge Effects in Compositional and Effective-Mass Superlattices. G.Y. Hu and R.F. O'Connell, 1/f Noise in Two-Dimensional Mesoscopic Systems from a Generalized Quantum Langevin Equation Approach. NPF Symposium Participants. Author Index.
TL;DR: In this paper, the fourterminal magnetoresistance and quantised Hall effect through a quantum point contact were investigated in a two-dimensional electron gas (2DEG) based on an n-type (AlGa)As/GaAs single heterostructure.
Abstract: The four-terminal magnetoresistance and quantised Hall effect through a quantum point contact are investigated in a two-dimensional electron gas (2DEG) based on an n-type (AlGa)As/GaAs single heterostructure. Depending on the choice of current and voltage contacts we measure three different magnetoresistances in a quantising magnetic field. The results agree with a simple model based on conduction via edge states and also with a more conventional analysis based on the properties of a bulk 2DEG.
TL;DR: Application de l'approche de Maxwell-Garnett au calcul de la fonction dielectrique effective d'un milieu composite contenant de tels cristallites de CdS and CdSe en utilisant un modele a deux resonances pour the fonctions dieLECTrique.
Abstract: Application de l'approche de Maxwell-Garnett au calcul de la fonction dielectrique effective d'un milieu composite contenant de tels cristallites. Application aux points quantiques de CdS et CdSe en utilisant un modele a deux resonances pour la fonction dielectrique
TL;DR: In this paper, the optical gap increases with decreasing a-Si:H layer thickness and an increase of the Urbach tail and a decrease of the photoconductivity were also observed with decreasing silicon thickness.
TL;DR: A planar quantum-point-contact device is proposed capable of producing focused electron beams and is able to produce interferences by solving the time-independent and time-dependent Schrodinger equation of the 2D system.
Abstract: A planar quantum-point-contact device is proposed capable of producing focused electron beams. This solid-state device consists of a tunnel barrier attached to a quantum point contact. By solving the time-independent and time-dependent Schrodinger equation of the 2D system, it is shown that the angular spread of the emitted beam can be reduced to less than 10°, is coherent and collimated in energy, and is able to produce interferences. By applying a magnetic field for which electron orbits have a radius of 2 µm, it should then be possible to focus the beam down to 0.15 µm.