| 1. |
- Marinova, Maya, et al.
(författare)
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Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator
- 2015
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 15:4, s. 2533-2541
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Tidskriftsartikel (refereegranskat)abstract
- The electric field control of functional properties is a crucial goal in oxide-based electronics. Nonvolatile switching between different resistivity or magnetic states in an oxide channel can be achieved through charge accumulation or depletion from an adjacent ferroelectric. However, the way in which charge distributes near the interface between the ferroelectric and the oxide remains poorly known, which limits our understanding of such switching effects. Here, we use a first-of-a-kind combination of scanning transmission electron microscopy with electron energy loss spectroscopy, near-total-reflection hard X-ray photoemission spectroscopy, and ab initio theory to address this issue. We achieve a direct, quantitative, atomic-scale characterization of the polarization-induced charge density changes at the interface between the ferroelectric BiFeO3 and the doped Mott insulator Ca1-xCexMnO3, thus providing insight on how interface-engineering can enhance these switching effects.
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| 2. |
- Marinova, Maya, et al.
(författare)
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Influence of Post-Growth Annealing on the Defects Nature and Distribution in VLS Grown (111) 3C-SiC Layers
- 2011
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Ingår i: Silicon Carbide and Related Materials 2010. ; , s. 241-244
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Konferensbidrag (refereegranskat)abstract
- The current communication focuses on the influence of a post-growth annealing on the evolution of defects inside (111) 3C-SiC layers grown by the Vapour Liquid Solid (VLS) mechanism in SiGe melts on Si-face on- and off axis 6H-SiC substrates. The layers are studied by Transmission Electron Microscopy (TEM) and Low Temperature Photoluminescence (LTPL). It was found that the growth on off-axis substrates results in a 3C-SiC layer containing mainly stacking faults (SFs) and microtwins (MT). The density of MT lamellae and SFs reduces in the layers grown on the on-axis substrate compared to off-axis substrate. In the layers grown on off-axis substrates the annealing strongly reduces the density of SFs inclined to the 3C/6H-SiC interface. Additionally, 3C to 6H polytypic transformation appears only at the interface, most probably starting from substrate step edges. This was only seen on off-axis seed since the step edges are more.
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| 3. |
- Marinova, Maya, et al.
(författare)
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Structural and Optical Investigation of VLS Grown (111) 3C-SiC Layers on 6H-SiC Substrates in Sn-Based Melts
- 2011
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Ingår i: Silicon Carbide and Related Materials 2010. ; , s. 165-168
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Konferensbidrag (refereegranskat)abstract
- The current communication focuses on the investigation of 3C-SiC layers grown by the Vapour-Liquid-Solid mechanism on on-axis Si-face 6H-SiC substrates in SiSn melts with different compositions and at different growth temperatures. The layers are studied by Transmission Electron Microscopy and Low Temperature Photoluminescence. It was found that for melts with Sn concentration higher than 60 at% large Sn-related precipitates are formed. The depth distribution of the Sn precipitates strongly depends not only on the melt composition but also on the growth temperature. Their formation strongly influences the stacking fault density and the dopant incorporation in the layers. Lower Sn concentrations combined with higher growth temperatures should result in 3C-SiC layer with enhanced structural quality.
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| 4. |
- Robert, Teddy, et al.
(författare)
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Effect of Inter-Well Coupling between 3C and 6H in-Grown Stacking Faults in 4H-SiC Epitaxial Layers
- 2011
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Ingår i: <em>Materials Science Forum Vols. 679-680 (2011) pp 314-317</em>. - : Trans Tech Publications Inc.. ; , s. 314-317
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Konferensbidrag (refereegranskat)abstract
- Both 3C and 6H stacking faults have been observed in a low doped 4H-SiC epitaxial layer grown in a hot-wall CVD reactor on a heavily doped (off-axis) 4H-SiC substrate. They appear differently on the different parts of sample, with energetic dispersion ranging from 3.01 eV to 2.52 eV. Since they behave as natural type-II quantum wells in the 4H-SiC matrix, the thickness dependence of the excitonic recombination is investigated using the standard effective mass approximation. The results are discussed in terms of built-in electric field and inter-well coupling effects.
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| 5. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Nucleation Control of Cubic Silicon Carbide on 6H- Substrates
- 2012
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 12:1, s. 197-204
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Tidskriftsartikel (refereegranskat)abstract
- The nucleation of cubic (3C) SiC on on-axis 6H-SiC was investigated in the temperature range 1500–1775 °C by the technique of sublimation epitaxy. We have studied two different cases: (i) the initial homoepitaxial growth of 6H-SiC followed by nucleation of 3C-SiC and (ii) nucleation of homoepitaxial 6H-SiC islands. The supersaturation in the growth cell was calculated using the modeled source to substrate temperature difference. We show that, at low temperature and supersaturation, growth of 6H-SiC commences in spiral growth mode, which prepares the surface for 3C-SiC nucleation. Provided the supersaturation is high enough, the 3C-SiC nucleates as two-dimensional islands on terraces of the homoepitaxial 6H-SiC. Detailed structural study indicates that the 3C-SiC began to grow on defect free surfaces. From the experimental and modeling results, we show that the growth parameter window for 3C-SiC is rather narrow. Deviation from it can result in 6H-SiC growth in spiral or 2D-nucleation mode, which suggests the importance of knowledge of supersaturation.
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