Multilayermetal-ceramic films have the potential to serve as strong, tough and environmentally resistant films and coatings for a wide variety of applications.They derive their properties from the multilayer structure (architecture), the microstructure and, hence, mechanical properties of the individual layers and the stress state of the film. However, in order to realize the potential of microlaminates, these features (architecture, microstructure and stress) must be controlled. Ion beam assisted deposition (IBAD) holds the promise to provide this control. In an effort to understand how IBAD can control mechanical properties of films, single trilayer and five-bilayer metal-ceramic, AI-Al,O, films were fabricated on ductile metal substrates using IBAD over a range of thicknesses and normalized energies. Results of bending and tension experiments revealed that the stress state is critical in determining the fracture strain (ductility) of the film. A residual compressive stress is beneficial and can be formed in the oxide phase by bombardment of the film with Ar during deposition.The behavior of film stress correlates well with Ar gas incorporation and the film consists of a high density of small cavities. Gas incorporation into the cavities or the surrounding matrix may be responsible for the observed residual compressive stress. The density of surface cracks at high strains is a function of the film architecture, film strength and the interfacial shear strength. Use of a multilayer structure reduces the crack density over a monolithic oxide film by increasing the strain needed to form through-thickness cracks and by increasing the intrinsic strength of the brittle layers by decreasing their thickness. Ion bombardment of the metal layers resulted in radiation damage and grain size refinement, both of which result in a stronger film and a lower crack density. It was shown that architecture, microstructure and stress are the key ingredients in microlaminate properties and are uniquely controllable by IBAD.
The ability to activate large concentrations of boron at lower temperatures is a persistent contingency in the continual drive for device scaling in Si microelectronics. We report on our experimental observations offering evidence for enhancement of electrical activation of implanted boron dopant in the presence of atomic hydrogen in silicon. This increased electrical activity of boron at lower anneal temperature is attributed to the creation of vacancies in the boron-implanted region, lattice-relaxation caused by the presence of atomic hydrogen, and the effect of atomic hydrogen on boron-interstitial cluster formation.
A computer controlled loading fixture has been designed to allow in situ observation of fracture processes during bending deformation of metal/ceramic microlaminates in an electroscan environmental scanning electron microscope (ESEM). The stage has the capability of accommodating either three- or four-point bending experiments. A unique design feature of the stage is that the specimen surface remains at a fixed distance from the secondary electron detector and, hence, in focus during bending. The sample rests on the fulcrum which remains in a fixed position while the restraints that grip the ends of the sample descend on a ball slide. The system is controlled by a Macintosh IIci computer and National Instruments NB-MIO-16L-9 data acquisition card. National Instruments LabVIEW(R)2 software is used to control the stage displacement and to record the load cell and transducer outputs. The operation of this instrumentation in the ESEM is illustrated by the study of fracture processes in ceramic and ceramic/metal microlaminate films deposited on ductile metallic substrates.
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