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Articles 1 - 8 of 8
Full-Text Articles in Physics
Interfacial Coherency And Ferroelectricity Of Batio3/Srtio3 Superlattice Films, Y. L. Li, S. Y. Hu, Dmitri Tenne, A. Soukiassian, D. G. Schlom, X. X. Xi, K. J. Choi
Interfacial Coherency And Ferroelectricity Of Batio3/Srtio3 Superlattice Films, Y. L. Li, S. Y. Hu, Dmitri Tenne, A. Soukiassian, D. G. Schlom, X. X. Xi, K. J. Choi
Physics Faculty Publications and Presentations
We studied the phase transitions, domain morphologies, and polarizations in BaTiO3/SrTiO3 superlattices grown on SrTiO3 substrates. Using the phase field approach, we discovered the remarkable influence of film/substrate interfacial coherency on the ferroelectricity of the SrTiO3 layers within a superlattice: it is an orthorhombic ferroelectric for an incoherent interface while it exhibits only induced polarization by the adjacent BaTiO3 layers for a coherent interface. We presented the domain morphologies within individual BaTiO3 and SrTiO3 layers which have different ferroelectric symmetries. The results are compared to ultraviolet Raman spectroscopy and variable temperature x-ray …
Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes
Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes
Paul J. Simmonds
Two-dimensional electron gases (2DEGs) were formed in undoped In0.75Al0.25As / In0.75Ga0.25As / In0.75Al0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm2/V s and n = 1.36 × 1011 cm−2 at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a significantly thinner InAlAs …
Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields
Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields
Paul J. Simmonds
Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In0.53Ga0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10-6 ns-1. This corresponds to an internal efficiency of 6.3%.
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Paul J. Simmonds
The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In0.53Ga0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10−6 ns−1 for 1310 nm photons.
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Paul J. Simmonds
The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In0.524Al0.476As. InAs QDs both buried in, and on top of, In0.524Al0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of almost 700 nm. Increasing growth …
The Challenge Of Understanding Radical Constructivism, Dewey I. Dykstra
The Challenge Of Understanding Radical Constructivism, Dewey I. Dykstra
Physics Faculty Publications and Presentations
Purpose: This contribution to the Festschrift honoring Ernst von Glasersfeld gives some insight into the perpetual problem of understanding radical constructivism (RC). Parallels with the Middle Way school of Buddhism appear to shed light on this challenge. Conclusions: The hegemony realism has over the thinking of even the most highly educated in our civilization plays a major role in their failure to understand RC. Those still subject to realism in their thinking interpret statements by those in RC in ways incompatible with RC. Until realists disequilibrate over mismatches between realist expectations and experiences, no alternative way of thinking is accessible …
“Once More Into The Breech…”, Dewey I. Dykstra
“Once More Into The Breech…”, Dewey I. Dykstra
Physics Faculty Publications and Presentations
No abstract provided.
Raman Study Of Oxygen Reduced And Re-Oxidized Strontium Titanate, Dmitri Tenne, I. E. Gonenli, A. Soukiassian, D. G. Schlom, S. M. Nakhmanson, K. M. Rabe, X. X. Xi
Raman Study Of Oxygen Reduced And Re-Oxidized Strontium Titanate, Dmitri Tenne, I. E. Gonenli, A. Soukiassian, D. G. Schlom, S. M. Nakhmanson, K. M. Rabe, X. X. Xi
Physics Faculty Publications and Presentations
We report Raman study of oxygen-reduced single crystal strontium titanate. Oxygen reduction leads to the appearance of the forbidden first order Raman peaks, as well as new spectral features attributed to the local vibrational modes associated with oxygen vacancies. This assignment is supported by ab initio calculations of phonon modes in SrTiO3 with introduced oxygen vacancies. Raman studies of re-oxidized samples show the same spectra as the initial single crystals. Comparison of Raman spectra of SrTiO3 thin films and reduced SrTiO3 single crystals demonstrates the importance of other factors such as polar grain boundaries in the lattice …