| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
K9, Defect Structures of B12As2 Single Crystalline Epitaxial Layers on Off-Axis (0001) 4H-SiC Substrates |
| Author(s) |
Yu Zhang, Hui Chen, Michael Dudley, Yi Zhang, James H. Edgar, Yinyan Gong, Silvia Bakalova, Martin Kuball, Lihua Zhang, Dong Su, Yimei Zhu |
| On-Site Speaker (Planned) |
Yu Zhang |
| Abstract Scope |
As a member of icosahedra borides, B<SUB>12</SUB>As<SUB>2</SUB> (abbreviated as IBA) has a wide band gap of 3.2eV, possessing many exceptional properties such as high hardness, high melting point, large Seebeck coefficient at high temperatures and extraordinary resistance against radiation damage via “self-healing” mechanism, which make it promising for the fabrication of high temperature thermoelectronics and high-power beta-voltaic cells. A detailed analysis of the microstructure in IBA single crystalline epitaxial layers grown on (0001) 4H-SiC substrates with 7º offcut toward [1-100] direction and with mixed offcut toward [1-100] and [11-20] directions is presented and compared. Synchrotron white beam x-ray topography (SWBXT) revealed that only one orientation of IBA was present in all the epitaxial layers grown along (111) surface normal, which was also confirmed by cross-sectional high resolution transmission electron microscopy (HRTEM). For IBA epilayers grown on (0001) 4H-SiC substrates with 7º offcut toward [1-100] direction, much higher quality of the films were observed with no intermediate layer between the epilayer and substrate. The slight diregistry between domains which expand and coalesce from nucleation sites can lead to the formation of translational domain boundaries while the in-plane mismatch between substrate and the film (~3.7%) can be accommodated by networks of interfacial dislocations. For IBA epilayers grown on (0001) 4H-SiC substrates with mixed offcut toward [1-100] and [11-20] directions, higher strain level was observed in IBA epilayers with the presence of a disordered transition layer, which is shown to be created by the coalescence of a mosaic of translational variant domains nucleated at the various types of nucleation site available on substrate surface. In this transition layer, competition between the growth of the various domains is mediated in part by the energy of the boundaries created between them as they coalesce. Boundaries between translational variant domains are shown to have unfavorable bonding configurations and hence high energy. These high energy boundaries can be eliminated during mutual overgrowth by the generation of Frank partial dislocations which effectively eliminates the translational variants. The growth mechanism of IBA on off-axis c-plane 4H-SiC are also proposed, which suggests that off-axis c-plane 4H-SiC may be a suitable substrate to grow IBA single crystals. |
| Proceedings Inclusion? |
Undecided |