Stabilising alloys in non-equilibrium crystal structures by epitaxial growth

[摘要] Thin film and surface science is an active field with important technological applications as illustrated by the transistor and by the recording head. This thesis relates thin film and surface science experiments applied to quasicrystalline materials, ferromagnetic alloys and electron tomography. These systems have strong potentials for technological applications.Epitaxial deposition is a powerful tool to create structures which are non-stable in the bulk state. For a better understanding of the quasicrystals' physical properties, one wants to grow quasicrystalline thin films of reduced chemical complexity. Single elements don't form quasicrystalline thin films beyond a monolayer. This thesis reports the successful growth of binary AlNi quasicrystal thin films in the multilayer regime. This thesis reports also detailed analysis of annealing and phase transition related structures on different surface orientations of d-AlNiCo.The equilibrium structure of MnSb is of the NiAs type but other structures with theoretical 100% polarisation can be stabilised by epitaxy. The surface magnetism of the MnSb thin film with equilibrium bulk structure grown on GaAs(111) has been imaged by spin-polarised low-energy electron microscopy revealing the spin direction mapping of magnetic domains at the surface of MnSb. Atomic resolution is routinely obtained with the current generation of transmission electron microscopes. For three-dimensional atomic resolution, the problem is to obtain suitable samples. In this thesis, we report the development of instruments and a methodology to fabricate atomically flat terraces with nanometre dimension at the tip of etched tungsten wires and the MBE growth of Au clusters on these terraces.

[发布机构] University:University of Birmingham;Department:School of Physics and Astronomy

[关键词] Q Science;QC Physics