g-Factor Tuning and Manipulation of Spins by an Electric Current
Zbyslaw Wilamowski, Hans Malissa, Friedrich Schaffler, and Wolfgang Jantsch
We investigate the Zeeman splitting of the two-dimensional electron gas in an asymmetric silicon quantum well, performing electron-spin-resonance (ESR) experiments. Applying a small dc current we observe a shift in the resonance field due to the additional current-induced Bychkov-Rashba type of spin ... [Phys. Rev. Lett. 98, 187203 (2007)] published Thu May 3, 2007.
Effect of arsenic species on the formation of (Ga)InAs nanostructures after partial capping and regrowth
S. Suraprapapich, S. Panyakeow, and C. W. Tu
Surface morphologies of self-assembled (Ga)InAs nanostructures grown by partial-capping-and-regrowth technique using gas-source molecular beam epitaxy (GSMBE) and solid-source molecular beam epitaxy (SSMBE) are compared. With SSMBE under an As[sub 4] ambient, as-grown quantum dots (QDs) change to a ... [Appl. Phys. Lett. 90, 183112 (2007)] published Wed May 2, 2007.
Surface heterostructure nanomechanical actuators with atomic resolution
Jan D. Makowski and Joseph J. Talghader
A continuously tunable vertical actuator with subnanometer resolution is presented. It consists of a heterostructure cantilever which has collapsed over a 125 nm thick nanogap. Its operating principle relies on the temperature dependence of the adhesion energy between two InGaAs surface quantum wel ... [Appl. Phys. Lett. 90, 183111 (2007)] published Wed May 2, 2007.
Photonic crystal effect on light emission from InGaN/GaN multi-quantum-well structures
Keunjoo Kim, Jaeho Choi, Sang Cheol Jeon, Jin Soo Kim, and Hee Mok Lee
Triangular hole arrays with nanoscaled lattice constants of 230 and 460 nm were fabricated on a p-type GaN epitaxial layer grown on an InGaN/GaN multi-quantum-well light emitting diode structure by metal-organic chemical vapor deposition. The hole geometries of dry-etched thin slabs for triangular ... [Appl. Phys. Lett. 90, 181115 (2007)] published Wed May 2, 2007.
Anisotropy and order of epitaxial self-assembled quantum dots
Lawrence H. Friedman
Epitaxial self-assembled quantum dots (SAQDs) represent an important step in the advancement of semiconductor fabrication at the nanoscale that will allow breakthroughs in electronics and optoelectronics. In these applications, order is a key factor. Here, the role of crystal anisotropy in promoting ... [Phys. Rev. B 75, 193302 (2007)] published Wed May 2, 2007.
In-plane self-arrangement of high-density InAs quantum dots on GaAsSb/GaAs(001) by molecular beam epitaxy
Toru Kanto and Koichi Yamaguchi
InAs quantum dots (QDs) were grown on GaAsSb/GaAs(001) buffer layers by molecular beam epitaxy using a Stranski-Krastanov mode. A high QD density of about 1 x 10[sup 11] cm[sup 2] was obtained for an Sb flux ratio of more than 0.14. In the case of high-density QD growth on the GaAsSb layers, many na ... [J. Appl. Phys. 101, 094901 (2007)] published Wed May 2, 2007.
Correlation-Induced Resonances and Population Switching in a Quantum-Dot Coulomb Valley
Hyun-Woo Lee and Sejoong Kim
Strong correlation effects on electron transport through a spinless quantum dot are considered. When two single-particle levels in the quantum dot are degenerate, a conserved pseudospin degree of freedom appears for generic tunneling matrix elements between the quantum dot and leads. Local fluctuati ... [Phys. Rev. Lett. 98, 186805 (2007)] published Wed May 2, 2007.
Room-Temperature Electron Spin Dynamics in Free-Standing ZnO Quantum Dots
William K. Liu, Kelly M. Whitaker, Alyssa L. Smith, Kevin R. Kittilstved, Bruce H. Robinson et al.
Conduction band electrons in colloidal ZnO quantum dots have been prepared photochemically and examined by electron paramagnetic resonance spectroscopy. Nanocrystals of 4.6 nm diameter containing single S-shell conduction band electrons have g[sup *]=1.962 and a room-temperature ensemble spin-dephas ... [Phys. Rev. Lett. 98, 186804 (2007)] published Wed May 2, 2007.
Dimensional transition of Cd[sub x]Zn[sub 1 - x]Te nanostructures grown on ZnTe layers
H. S. Lee, H. L. Park, and T. W. Kim
The atomic force microscopy images showed that the dimensional structural transformation from Cd[sub x]Zn[sub 1x]Te quantum dots (QDs) with Cd mole fractions of 0.5 and 0.6 to Cd[sub x]Zn[sub 1x]Te quantum wires occurred at a Cd mole fraction of 0.8. Photoluminescence spectra showed that the exciton ... [Appl. Phys. Lett. 90, 181909 (2007)] published Tue May 1, 2007.
Photon number resolving detector based on a quantum dot field effect transistor
B. E. Kardynal, S. S. Hees, A. J. Shields, C. Nicoll, I. Farrer et al.
The authors show that the change in current flowing through the channel of a quantum dot field effect transistor is proportional to the number (N) of photons absorbed from an incident pulse. Distinct features due to photon number state up to N=3 are resolved. With improvement of external quantum eff ... [Appl. Phys. Lett. 90, 181114 (2007)] published Tue May 1, 2007.
Mesoscopic to Universal Crossover of the Transmission Phase of Multilevel Quantum Dots
C. Karrasch, T. Hecht, A. Weichselbaum, Y. Oreg, J. von Delft et al.
Transmission phase alpha measurements of many-electron quantum dots (small mean level spacing delta) revealed universal phase lapses by pi between consecutive resonances. In contrast, for dots with only a few electrons (large delta), the appearance or not of a phase lapse depends on the dot paramete ... [Phys. Rev. Lett. 98, 186802 (2007)] published Tue May 1, 2007.
Fock-Darwin States of Dirac Electrons in Graphene-Based Artificial Atoms
Hong-Yi Chen, Vadim Apalkov, and Tapash Chakraborty
We investigate the Fock-Darwin states of the massless chiral fermions confined in a graphitic parabolic quantum dot. In light of Klein tunneling, we analyze the condition for confinement of the Dirac fermions in a cylindrically symmetric potential. New features of the energy levels of the Dirac elec ... [Phys. Rev. Lett. 98, 186803 (2007)] published Tue May 1, 2007.
Quantum inductance and negative electrochemical capacitance at finite frequency in a two-plate quantum capacitor
Jian Wang, Baigeng Wang, and Hong Guo
We report on theoretical investigations of frequency-dependent quantum capacitance. It is found that at finite frequency, a quantum capacitor can be characterized by a classical RLC circuit with three parameters: a static electrochemical capacitance, a charge relaxation resistance, and a quantum ind ... [Phys. Rev. B 75, 155336 (2007)] published Mon Apr 30, 2007.
Magnetization switching in alternating width nanowire arrays
S. Goolaup, A. O. Adeyeye, N. Singh, and G. Gubbiotti
A systematic investigation of the magnetization reversal mechanism in arrays of Ni[sub 80]Fe[sub 20] nanowires with alternating width is presented. The structures were fabricated using deep ultraviolet lithography followed by lift-off technique at 248 nm exposure wavelength. We have mapped the magn ... [Phys. Rev. B 75, 144430 (2007)] published Mon Apr 30, 2007.
Size-dependent radiative lifetime in vertically stacked (In,Ga)As quantum dot structures
Y. C. Zhang, A. Pancholi, and V. G. Stoleru
The radiative lifetime dependence on the dot size in multilayer (In,Ga)As quantum dot structures with different thickness GaAs barriers was studied via photoluminescence. In the structure with thick barriers and isolated dots, the radiative lifetime increased monotonically with the dot size, which w ... [Appl. Phys. Lett. 90, 183104 (2007)] published Mon Apr 30, 2007.
Controlled InAs quantum dot nucleation on faceted nanopatterned pyramids
P. S. Wong, G. Balakrishnan, N. Nuntawong, J. Tatebayashi, and D. L. Huffaker
The selective quantum dot (QD) nucleation on nanofaceted GaAs pyramidal facets is explored. The GaAs pyramids, formed on a SiO[sub 2] masked (001) GaAs substrate, are characterized by well-defined equilibrium crystal shapes (ECSs) defined by three crystal plane families including {11n}, {10n}, and ( ... [Appl. Phys. Lett. 90, 183103 (2007)] published Mon Apr 30, 2007.
Sn quantum dots embedded in SiO[sub 2] formed by low energy ion implantation
J. P. Zhao, Y. Meng, D. X. Huang, W. K. Chu, and J. W. Rabalais
Extremely small Sn nanodots embedded in the subsurface of SiO[sub 2], i.e., SnSiO[sub 2] quantum dot composites, have been formed by ion implantation of the [sup 120]Sn[sup +] isotope into (0001) Z-cut quartz at a low kinetic energy of 9 keV at room temperature. Transmission electron microscopy ima ... [J. Vac. Sci. Technol. B 25, 796 (2007)] published Mon Apr 30, 2007.
Excited states of Na nanoislands on the Cu(111) surface
T. Hakala, M. J. Puska, A. G. Borisov, V. M. Silkin, N. Zabala et al.
Electronic states of one monolayer high Na nanoislands on the Cu(111) surface are studied as a function of the nanoisland size. Properties of nanoislands such as one-electron states, the electron density, and the associated potential are obtained self-consistently within the density-functional forma ... [Phys. Rev. B 75, 165419 (2007)] published Fri Apr 27, 2007.
Excited excitonic states observed in semiconductor quantum dots using polarization resolved optical spectroscopy
V. Troncale, K. F. Karlsson, D. Y. Oberli, M. Byszewski, A. Malko et al.
We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in the less conventional cleaved-edge geometry, ... [J. Appl. Phys. 101, 081703 (2007)] published Fri Apr 27, 2007.
Atomic scale study of the impact of the strain and composition of the capping layer on the formation of InAs quantum dots
J. M. Ulloa, C. Celebi, P. M. Koenraad, A. Simon, E. Gapihan et al.
The impact of the capping material on the structural properties of self-assembled InAs quantum dots (QDs) was studied at the atomic scale by cross-sectional scanning tunneling microscopy. Capping with lattice matched layers and with strained layers was analyzed. When the different capping materials ... [J. Appl. Phys. 101, 081707 (2007)] published Fri Apr 27, 2007.
Quantum dots with coherent interfaces between rocksalt-PbTe and zincblende-CdTe
W. Heiss, H. Groiss, E. Kaufmann, G. Hesser, M. Boberl et al.
The formation of PbTe quantum dots (QDs) in a crystalline CdTe host matrix is demonstrated by the annealing of a coherent, heteroepitaxial PbTe layer clad between CdTe layers. The resulting QDs have a centrosymmetric shape and they exhibit intense room-temperature mid-infrared photoluminescence due ... [J. Appl. Phys. 101, 081723 (2007)] published Fri Apr 27, 2007.
Optically manipulating spins in semiconductor quantum dots
Wang Yao, Ren-Bao Liu, and L. J. Sham
Physics considered here is the active control of a quantum system and of its decoherence by its environment. The relevance is in the quantum nature of nanoscience and how coherent optics in semiconductor quantum dots can contribute to quantum control. This article reviews: (1) The more recent theory ... [J. Appl. Phys. 101, 081721 (2007)] published Fri Apr 27, 2007.
Correlated and entangled pairs of single photons from semiconductor quantum dots
N. Akopian, N. H. Lindner, E. Poem, Y. Berlatzky, J. Avron et al.
Entangled photon pairs are emitted from a biexciton decay cascade of single quantum dots when spectral filtering is applied. We show this by experimentally measuring the density matrix of the polarization state of the photon pair emitted from a continuously pumped quantum dot. The matrix clearly sat ... [J. Appl. Phys. 101, 081712 (2007)] published Fri Apr 27, 2007.
Imaging correlated wave functions of few-electron quantum dots: Theory and scanning tunneling spectroscopy experiments
Massimo Rontani, Elisa Molinari, Giuseppe Maruccio, Martin Janson, Andreas Schramm et al.
We show both theoretically and experimentally that scanning tunneling spectroscopy (STS) images of semiconductor quantum dots may display clear signatures of electron-electron correlation. We apply many-body tunneling theory to a realistic model, which fully takes into account correlation effects an ... [J. Appl. Phys. 101, 081714 (2007)] published Fri Apr 27, 2007.
Entangled photons from the biexciton cascade of quantum dots
R. J. Young, R. M. Stevenson, A. J. Shields, P. Atkinson, K. Cooper et al.
Single InAs quantum dots embedded in a planar cavity, formed by mismatched sets of GaAs/AlAs distributed Bragg reflectors, can be a useful source of triggered polarization-entangled photon pairs. We demonstrate this with a fidelity exceeding 70% for the expected entangled state. Quantum dot based de ... [J. Appl. Phys. 101, 081711 (2007)] published Fri Apr 27, 2007.
Is inelastic cotunneling phase coherent?
M. Sigrist, T. Ihn, K. Ensslin, M. Reinwald, and W. Wegscheider
For low biases the linear conductance of quantum dots is based on elastic transport processes. At finite bias in the Coulomb blockade regime, inelastic cotunneling sets in once the applied bias exceeds the energy between ground and excited state in the dot. Here we report on transport experiments th ... [J. Appl. Phys. 101, 081701 (2007)] published Fri Apr 27, 2007.
Detection of single electron spin resonance in a double quantum dot
F. H. L. Koppens, C. Buizert, I. T. Vink, K. C. Nowack, T. Meunier et al.
Spin-dependent transport measurements through a double quantum dot are a valuable tool for detecting both the coherent evolution of the spin state of a single electron, as well as the hybridization of two-electron spin states. In this article, we discuss a model that describes the transport cycle in ... [J. Appl. Phys. 101, 081706 (2007)] published Fri Apr 27, 2007.
Spin properties of charged Mn-doped quantum dot
L. Besombes, Y. Leger, L. Maingault, and H. Mariette
The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier are analyzed. The emission of the neutral, negatively and positively charged excitons coupled with a single magnetic atom (Mn) are observed in the same individual quantum dot. The spectrum ... [J. Appl. Phys. 101, 081713 (2007)] published Fri Apr 27, 2007.
Spin-glass shell and magnetotransport properties of a La[sub 0.67]Ca[sub 0.33]MnO[sub 3] nanoring network
M. H. Zhu, Y. G. Zhao, W. Cai, X. S. Wu, S. N. Gao et al.
The magnetotransport and magnetic property of the La[sub 0.67]Ca[sub 0.33]MnO[sub 3] (LCMO) nanoring network (NRN) have been investigated. This NRN-LCMO shows a giant magnetoconductance at low temperatures with strong memory effect of magnetic field. Its high field magnetoconductance shows linear fi ... [Phys. Rev. B 75, 134424 (2007)] published Fri Apr 27, 2007.
Formation and morphology of InGaN nanoislands on GaN(0001)
S. Gangopadhyay, Th. Schmidt, S. Einfeldt, T. Yamaguchi, D. Hommel et al.
The morphology and density of InGaN nanoislands can be controlled by the choice of proper growth conditions for metal organic vapor phase epitaxy. Scanning tunneling microscopy has been used to investigate the dependence of InGaN island morphology on the growth parameters. A heterogeneous nucleation ... [J. Vac. Sci. Technol. B 25, 791 (2007)] published Fri Apr 27, 2007.
Breaking the Phonon Bottleneck for Holes in Semiconductor Quantum Dots
Ryan R. Cooney, Samuel L. Sewall, Kevin E. H. Anderson, Eva A. Dias, and Patanjali Kambhampati
Size dependent hole dynamics are measured in colloidal CdSe quantum dots for a specific state-to-state excitonic transition. These experiments show that the hole energy loss rate increases for smaller quantum dots, contradicting known relaxation mechanisms for holes. These experiments reveal a new m ... [Phys. Rev. Lett. 98, 177403 (2007)] published Fri Apr 27, 2007.
Electrons in Nano Height Cylinders
Vjekoslav Sajfert, Jovan Šetrajčić, and Stevo Jaćimovski
Electrons in cylindrical quantum dots are analysed in this paper. Crucial moment of analyses is the proposed method of calculation of Green's functions in the structures with the broken symmetry. Analyzing this new method it was shown that physical characteristics of quantum dots depend on configura ... [AIP Conf. Proc. 899, 645 (2007)] published Fri Apr 27, 2007.
Time- and locally resolved photoluminescence of semipolar GaInN/GaN facet light emitting diodes
Thomas Wunderer, Peter Bruckner, Joachim Hertkorn, Ferdinand Scholz, Gareth J. Beirne et al.
The authors investigate the carrier lifetime and photoluminescence (PL) intensity of a semipolar GaInN/GaN sample which was realized by growing five GaInN/GaN quantum wells on the {1[overline 1]01} side facets of selectively grown n-GaN stripes that have a triangular shape running along the <11[over ... [Appl. Phys. Lett. 90, 171123 (2007)] published Fri Apr 27, 2007.
Quantum measurement characteristics of a double-dot single electron transistor
HuJun Jiao, Xin-Qi Li, and JunYan Luo
Owing to a few unique advantages, the double-dot single electron transistor has been proposed as an alternative detector for charge states. In this work, we present a further study for its signal-to-noise property, based on a full analysis of the setup configuration symmetry. It is found that the ef ... [Phys. Rev. B 75, 155333 (2007)] published Thu Apr 26, 2007.
Extracting the ground-state spin of a quantum dot from the conductance peaks in a parallel magnetic field at a finite temperature
Daniel Huertas-Hernando and Y. Alhassid
We derive a closed expression for the finite-temperature conductance of a Coulomb-blockade quantum dot in the presence of an exchange interaction and a parallel magnetic field. Parallel-field dependence of Coulomb-blockade peak position has been used to determine experimentally the ground-state spin ... [Phys. Rev. B 75, 153312 (2007)] published Thu Apr 26, 2007.
Surface anisotropy and magnetic freezing of MnO nanoparticles
M. A. Morales, R. Skomski, S. Fritz, G. Shelburne, J. E. Shield et al.
Nanoparticles of bulk antiferromagnets often exhibit ferromagnetic behavior due to uncompensated surface spins. The peak temperature in the zero-field-cooled magnetization of MnOin contrast to other antiferromagnetic nanoparticleshas anomalous behavior, shifting to higher temperatures with decreasin ... [Phys. Rev. B 75, 134423 (2007)] published Thu Apr 26, 2007.
Tensile-strained GaAsN quantum dots on InP
P. Pohjola, T. Hakkarainen, H. Koskenvaara, M. Sopanen, H. Lipsanen et al.
Self-assembled quantum dots are typically fabricated from compressive-strained material systems, e.g., InAs on GaAs. In this letter, self-assembled quantum dots from tensile-strained GaAsN on InP are demonstrated. GaAsN on InP has type-I band alignment. Stranski-Krastanov growth mode is not observed ... [Appl. Phys. Lett. 90, 172110 (2007)] published Thu Apr 26, 2007.
Detection of charge states in nanowire quantum dots using a quantum point contact
D. Wallin, A. Fuhrer, L. E. Froberg, L. Samuelson, H. Q. Xu et al.
The authors demonstrate operation of a charge readout scheme for quantum dots in a semiconductor nanowire using a quantum point contact defined in a GaAs/AlGaAs two-dimensional electron gas beneath the nanowire. The quantum dots were fabricated by epitaxial growth of InP barriers along a n-type InAs ... [Appl. Phys. Lett. 90, 172112 (2007)] published Thu Apr 26, 2007.
Quantum dot structures grown on Al containing quaternary material for infrared photodetection beyond 10 mu m
P. L. Souza, A. J. Lopes, T. Gebhard, K. Unterrainer, M. P. Pires et al.
Different InAs quantum dot structures grown on InGaAlAs lattice matched to InP were investigated for quantum dot infrared photodetectors. Extremely narrow photocurrent peaks were observed, demonstrating great potential for fine wavelength selection. Structures which can detect radiation beyond 10 [ ... [Appl. Phys. Lett. 90, 173510 (2007)] published Thu Apr 26, 2007.