Crystalline zinc blende GaAs has been grown on a trigonal c-plane sapphire substrate by molecular beam epitaxy. The initial stage of GaAs thin film growth has been investigated extensively in this paper. When grown on c-plane sapphire, it takes (111) crystal orientation with twinning as a major problem. Direct growth of GaAs on sapphire results in three-dimensional GaAs islands, almost 50% twin volume, and a weak in-plane correlation with the substrate. Introducing a thin AlAs nucleation layer results in complete wetting of the substrate, better in-plane correlation with the substrate, and reduced twinning to 16%. Further, we investigated the effect of growth temperature, pregrowth sapphire substrate surface treatment, and in-situ annealing on the quality of the GaAs epilayer. We have been able to reduce the twin volume below 2% and an X-ray diffraction rocking curve line width to 223 arcsec. A good quality GaAs on sapphire can result in the implementation of microwave photonic functionality on a photonic chip.Découvrez aussi
Physicists at the University of Bath have developed a flexible process allowing the synthesis in a single flow of a wide range of novel nanomaterials with various morphologies, with potential applications in areas including optics and sensors.
The nanomaterials are formed from Tungsten Disulphide – a Transition Metal Dichalcogenide (TMD) – and can be grown on insulating planar substrates without requiring a catalyst. TMDs are layered materials, and in their two-dimensional form can be considered the inorganic analogues of graphene.
Le candidat (H/F) devra disposer d’un doctorat en sciences des matériaux ou équivalent (PhD degree) afin de conduire le projet.
Objectifs : Développer les étapes de synthèse et production des poudres, densification des cibles céramiques, caractérisation des matériaux puis tests et qualification pour une mise en œuvre Industrielle.