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- Jemander, S.T., et al.
(författare)
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STM study of the C-induced Si(100)-c(4×4) reconstruction
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Sociaty. - 1098-0121 .- 1550-235X. ; 65:11, s. 115321-
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Tidskriftsartikel (refereegranskat)abstract
- We report a direct and reliable way to produce the Si(100)-c(4×4) reconstruction by submonolayer deposition from a SiC source and subsequent annealing. Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM) investigations reveal that a C amount equivalent to 0.07 monolayers (ML’s) is sufficient to obtain full coverage of the c(4×4) reconstruction. A deposition of 0.035 ML’s C produces a c(4×4) coverage of only 19%, indicating that C is not only present in the c(4×4) areas, but also in the 2×1 areas. There is not enough C to make it a regular part of the c(4×4) reconstruction and we therefore conclude that the c(4×4) reconstruction is strain induced. We find that a combination of the mixed ad-dimer and buckled ad-dimer models explains all main features observed in the STM images. Images of freshly prepared c(4×4) surfaces exhibit a decoration of approximately 50% of the unit cells, which is attributed to perpendicular ad-dimers. Long exposures (>20 h) to the UHV background gas quench these features and the c(4×4) reconstruction appears as if more homogeneous.
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- Larsson, Mats, 1976-, et al.
(författare)
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Luminescence study of Si/Ge quantum dots
- 2003
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 16:3-4, s. 476-480
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Tidskriftsartikel (refereegranskat)abstract
- We present a photoluminescence (PL) study of Ge quantum dots embedded in Si. Two different types of recombination processes related to the Ge quantum dots are observed in temperature-dependent PL measurements. The Ge dot-related luminescence peak near 0.80 eV is ascribed to the spatially indirect recombination in the type-II band lineup, while a high-energy peak near 0.85 eV has its origin in the spatially direct recombination. A transition from the spatially indirect to the spatially direct recombination is observed as the temperature is increased. The PL dependence of the excitation power shows an upshift of the Ge quantum dot emission energy with increasing excitation power density. The blueshift is ascribed to band bending at the type-II Si/Ge interface at high carrier densities. Comparison is made with results derived from measurements on uncapped samples. For these uncapped samples, no energy shifts due to excitation power or temperatures are observed in contrast to the capped samples.
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- Larsson, Mats, 1976-, et al.
(författare)
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Photoluminescence study of Si/Ge quantum dots
- 2003
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 532-535, s. 832-836
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Tidskriftsartikel (refereegranskat)abstract
- Ge quantum dots embedded in Si are studied by means of photoluminescence (PL). The temperature dependent PL measurements show two different types of recombination processes related to the quantum dots. We ascribe a peak near 0.80 eV to the spatially indirect recombination in the type-II band lineup where the electron is located in the surrounding Si close to the interface and the hole in the Ge dot. Furthermore, a peak near 0.85 eV is attributed to the spatially direct recombination. We observe a transition from the spatially indirect to the spatially direct recombination as the temperature is increased. The measurements also show an up-shift of the Ge quantum dot emission energy with increasing excitation power density. The blueshift is primarily ascribed to an enhanced confinement of the electron associated with the increased band bending at the type-II Si/Ge interface at high carrier densities. Comparison is made with results, derived from measurements on uncapped samples. For these uncapped samples, no energy shifts due to excitation power or temperatures are observed in contrast to the capped samples. ⌐ 2003 Elsevier Science B.V. All rights reserved.
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- Robbie, K., et al.
(författare)
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Formation of Ni-graphite intercalation compounds on SiC
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 64, s. 155401-15540111
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Tidskriftsartikel (refereegranskat)
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