| 1. |
- Wu, Y.-H., et al.
(författare)
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Surface diffusion limited nucleation of Ge dots on the Si(001) surface
- 2002
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Konferensbidrag (refereegranskat)abstract
- The formation of Ge islands during MBE growth is a spontaneous process and these islands, i.e. dots, are usually randomly arranged. In order to implement these nanoscaled islands into device applications, ordering of epitaxial dots is a crucial step. We report a study on the MBE growth of Ge islands on Si(001) substrates, containing <110>-oriented square and long stripe type patterns defined by anisotropic wet etching of Si, in order to provide more understanding of how surface diffusion of Ge atoms would influence the formation of Ge islands on various types of surfaces. It has been found that there were preferential nucleation sites for Ge islands along the bottom edges of the Si ridges. The Ge islands at the edge positions were larger than those formed on the free surface and they could be regularly spaced. Due to the consumption of Ge at the bottom edges of ridge patterns, the density of Ge dots on the free surface varied between ˜ 3 × 108 and ˜ 1 × 109 cm-2 when changing the spatial separation between two adjacent Si ridges (2-100 µm). A Ge mean diffusion length of ˜ 7.5 µm has been determined for Ge growth at 700 °C. © 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Analysis of band anticrossing in GaNxP1-x alloys
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70, s. 085209-
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-dependent absorption, photoluminescence excitation, and spectroscopic ellipsometry measurements are employed to accurately determine compositional and temperature dependences of the conduction band (CB) states in GaNP alloys. The CB edge and the higher lying Γc CB minimum (CBM) are shown to exhibit an apparently anticrossing behavior, i.e., the N-induced redshift of the bandgap energy is accompanied by a matching blueshift of the Γc CBM. The obtained data can be phenomenologically described by the band anticrossing model. By considering strong temperature dependence of the energy of the interacting N level, which has largely been overlooked in earlier studies of GaNP, the interacting N level can be attributed to the isolated substitutional NP and the coupling parameter is accurately determined.
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| 3. |
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| 4. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys : a proof for a general property of dilute nitrides
- 2004
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 70:24, s. 245215-245219
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Tidskriftsartikel (refereegranskat)abstract
- Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.
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| 5. |
- Lai, Xin-He, et al.
(författare)
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Francisella strains express hemolysins of distinct characteristics
- 2003
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Ingår i: FEMS Microbiology Letters. - : Elsevier. - 0378-1097 .- 1574-6968. ; 224:1, s. 91-95
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Tidskriftsartikel (refereegranskat)abstract
- Historically, Francisella strains have been described as nonhemolytic. In this study, we show by use of solid and liquid hemolysis assays that some Francisella strains have hemolytic properties. The Francisella novicida type strain U112 is hemolytic to horse erythrocytes and Francisella philomiragia type strain FSC144 is hemolytic towards both human and horse erythrocytes. The F. novicida strain U112 released a protein (novilysin A) into the culture supernatant which cross-reacted with antiserum against Escherichia coli HlyA whereas there was no similar protein detectable with this cross-reactive property from the supernatant of the F. philomiragia strain.
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| 6. |
- Thinh, N. Q., et al.
(författare)
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Formation of Ga interstitials in (Al,In)yGa1-yNxP1-x alloys and their role in carrier recombination
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85, s. 2827-
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Tidskriftsartikel (refereegranskat)abstract
- Formation of complex defects involving a Ga interstitial (Gai) in (Al,In)yGa1-yNxP1-x alloys and their effects on optical quality are studied by photoluminescence (PL) and optically detected magnetic resonance spectroscopies. Introduction of these defects is shown to be largely promoted by incorporation of N. In quaternary alloys, concentrations of the defects are found to critically depend on the group III atoms that replace Ga, i.e., it is largely enhanced by the presence of Al in alloys, but is only marginally affected by In incorporation. The effect is attributed to differences in surface adatom mobilities of the group III atoms involved and their bonding strength with N. The revealed Gai complexes are shown to act as efficient nonradiative recombination centers degrading the PL efficiency. The defects exhibit high thermal stability and can only be partially removed by postgrowth rapid thermal annealing.
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