V. Brien

Transversal growth microstructures of quasicrystalline Ti–Zr–Ni films

Abstract Pulsed laser deposition from a Nd:YAG laser was employed in the production of hundreds of nanometer thick quasicrystalline Ti–Zr–Ni films on glass substrate. The influence of deposition temperature Ts on the structure, morphology and microstructure of the films across their thickness was investigated. The morphology and microstructure features were evaluated by X-ray diffraction and transmission electron microscopy techniques. The low deposition temperatures were found to produce films with nanometer sized grains embedded in an amorphous matrix. The grains exhibit quasicrystalline order. The higher deposition temperatures lead to films whose structure is not uniform all along the growth direction. The layer in contact with the substrate is a very thin amorphous layer. The main part of the film consists of crystallized columns. The columns have grown from a nanocrystallized layer where the size of crystallites increases with increasing thickness.

Optical reflectivity as a simple diagnostic method for testing structural quality of icosahedral quasicrystals

The optical reflectivity of Al-based and Ti-based quasicrystalline and approximant samples were investigated versus the quality of their structural morphology using optical reflectometry, x-ray diffraction, and transmission electron microscopy. The different structural morphologies were obtained using three different preparation processes: sintering, pulsed laser deposition, and reactive cathodic magnetron sputtering. The work demonstrates that the canonical behavior of icosahedral state in specular reflectivity is extremely sensitive to different and very fine aspects of the microstructure: sizes of grains smaller than 50nm, slight local diffuse disorder, and shifts away from the icosahedral crystallographic structure (approximants). The work explains why the optical properties of the same kind of quasicrystals found in literature sometimes reveal a different behavior from one author to another. The study then confirms the work of some authors and definitely shows that the canonical behavior of icosahedr...

Influence of substrate temperature on the achievement of Ti-Ni-Zr quasi-crystalline films grown by pulsed laser deposition

Pulsed laser deposition has been used to prepare films in the Ti- Ni-Zr system. Morphology and structure of the obtained films have been studied as a function of substrate temperature being in the range 25 - 350 degree(s)C. Morphological and structural modifications have been followed by grazing incidence and (theta) -2(theta) X-ray diffraction, transmission, electron diffraction and imaging. Chemical composition has been analysed by electron probe micro- analysis. The in-depth variation of composition has been studied by secondary neutral mass spectroscopy. This study leads to the determination of the best growth temperature giving rise to the known quasicrystalline phase recently discovered in the Ti-Ni-Zr ternary system.