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| 2. |
- Hsu, Chih-Wei, et al.
(författare)
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Controlled Growth of GaN Pyramidal template hosting InGaN Quantum Dots
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The emission properties of InGaN grown on hexagonal GaN pyramids with various pitch distances (PD) are studied. Emissions associated with InGaN quantum wells (QWs) and InGaN quantum dots (QDs) can be identified. The emission energies of InGaN QWs and QDs shift toward opposite directions with increasing PD; red-shift for QWs and blue-shift for QDs. Based on the source supply mechanism in a selective area growth process, the formation of InGaN QDs on GaN pyramids is believed to be a combined effect of Stranski-Krastanow growth mode and spinodal decomposition taking place at the microscopic (0001) surfaces on GaN pyramids.
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| 3. |
- Karlsson, Linda H., et al.
(författare)
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Atomically resolved microscopy of ion implantation induced dislocation loops in 4H-SiC
- 2016
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Ingår i: Materials letters (General ed.). - : Elsevier. - 0167-577X .- 1873-4979. ; 181, s. 325-327
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Tidskriftsartikel (refereegranskat)abstract
- During high temperature electrical activation of ion-implanted dopant species in SiC, extrinsic dislocation loops are formed on the basal planes of the SiC lattice. Investigations have suggested Si-based loops are caused in accordance with the well-known +1 model. Herein we apply aberration corrected STEM to resolve the atomic structure of these loops. It is shown that the dislocation loops formed during annealing of Al-implanted SiC consist of an extra inserted Si-C bilayer of the (0001) polar sense, which upon insertion into the lattice causes a local extrinsic stacking fault. The +1 model thus needs to be expanded for binary systems. (C) 2016 Elsevier B.V. All rights reserved.
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| 4. |
- Khatibi, Ali, et al.
(författare)
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Face-Centered Cubic (Al1-xCrx)2O3
- 2011
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 519:8, s. 2426-2429
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of a face-centered cubic (Al1−xCrx)2O3 solid solution [0.60bxb0.70] in films grownonto Si substrates using reactive radio frequency magnetron sputtering from Al and Cr targets at 400 °C. Theproposed structure is NaCl-like with 33% vacancies on the metal sites. The unit cell parameter is 4.04 Å asdetermined by X-ray diffraction. The films have a b100N preferred crystallographic orientation and exhibithardness values up to 26 GPa and an elastic modulus of 220–235 GPa.
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| 5. |
- Lundskog, Anders, et al.
(författare)
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InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids
- 2012
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Ingår i: Nanotechnology. - : Institute of Physics (IOP). - 0957-4484 .- 1361-6528. ; 23:30, s. 305708-
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Tidskriftsartikel (refereegranskat)abstract
- Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal–organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.
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| 6. |
- Lundskog, Anders, et al.
(författare)
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Unexpected behavior of InGaN quantum dot emission energy located at apices of hexagonal GaN pyramids
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- InGaN quantum dots (QDs) have been grown at the apices of hexagonal GaN pyramids. The pyramids were selectively grown on a (0001) oriented GaN template through circular apertures in a SiN mask positioned in square arrays. The emission of the InGaN QDs was shifted towards higher energies when the center-to-center distance of the pyramids was increased, while the emission from InGaN quantum wells located on the {1101} facets of the pyramids was energetically shifted towards lower energies. No energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.
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| 7. |
- Palisaitis, Justinas, et al.
(författare)
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Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:3, s. 034302-
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Tidskriftsartikel (refereegranskat)abstract
- The early stages of InGaN/GaN quantum wells growth for In reduced conditions have been investigated for varying thickness and composition of the wells. The structures were studied by monochromated STEM–VEELS spectrum imaging at high spatial resolution. It is found that beyond a critical well thickness and composition, quantum dots (>20 nm) are formed inside the well. These are buried by compositionally graded InGaN, which is formed as GaN is grown while residual In is incorporated into the growing structure. It is proposed that these dots may act as carrier localization centers inside the quantum wells.
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| 8. |
- Persson, Per, et al.
(författare)
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Dislocation loop evolution in ion implanted 4H-SiC
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:11, s. 9395-9397
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of dislocation loop in the ion implanted 4H-SiC epilayers was investigated. The formation of dislocation loop after high temperature annealing was studied using transmission electron microscopy (TEM). The variation in the loop area with increase in implanted dose was found to be linear. For both, prolonged annealing and increasing temperature, the amount of interstitials bound to loops remained constant.
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| 9. |
- Persson, Per, et al.
(författare)
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On the nature of ion implantation induced dislocation loops in 4H-silicon carbide
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:5, s. 2501-2505
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Tidskriftsartikel (refereegranskat)abstract
- Transmission electron microscopy was used to investigate B-11, C-12, N-14, Al-27, Si-28, and Ar-37 ion-implanted 4H-SiC epilayers and subsequent defect formation after high temperature annealing. During the annealing process extrinsic dislocation loops of interstitial type are formed on the SiC basal plane with a depth distribution roughly corresponding to the distribution of the implanted ions. The investigation reveals that in samples where the implanted ions are substituting for a position in the silicon sublattice, generating an excess of interstitial silicon, the dislocation loops are more readily formed than in a sample implanted with an ion substituting for carbon.
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| 10. |
- Persson, Per, et al.
(författare)
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Ostwald ripening of interstitial-type dislocation loops in 4H-silicon carbide
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 100:5
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Tidskriftsartikel (refereegranskat)abstract
- The annealing behavior of interstitial-type basal plane dislocation loops in Al ion implanted 4H-SiC is investigated. It is shown that the loops undergo a dynamical ripening process. For annealing below 1700 degrees C the total area of dislocation loops increases, indicating that point defects are still available for accumulation, but for annealing times longer than 100 min at this temperature the value of the total loop area saturates. For longer annealing times, or higher temperatures, the dislocation loops are subjected to a conservative coarsening process, also known as Ostwald ripening. In this process the mean loop radius increases with increasing annealing time and temperature while the number of loops decreases. Meanwhile the summarized area of the loops stays constant. The observed ripening is suggested to occur by a mechanism, which involves coarsening by direct loop coalescence. Through this mechanism, loops on the same basal plane move towards each other until they coalesce into one, but loops on neighboring basal planes can only move until their loop edges meet (in a basal plane projection) where they remain. Climb along the c axis is not favorable as shown by experimental results and is suggested to be caused by the atomic configuration of the loop. Upon continuous annealing, this results in a situation where the loops are confined in clusters.
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