Abstract: Using a tight-binding atomistic simulation, we simulate the recent atomic-force microscopy experiments probing the slipperiness of graphene flakes made slide against a graphite surface. Compared to previous theoretical models, where the flake was assumed to be geometrically perfect and rigid, while the substrate is represented by a static periodic potential, our fully-atomistic model includes quantum mechanics with the chemistry of bond breaking and bond formation, and the flexibility of the flake. These realistic features, include in particular the crucial role of the flake rotation in determining the static friction, in qualitative agreement with experimental observations.
Abstract: By combining continuum elasticity theory and tight-binding atomistic simulations, we work out the constitutive nonlinear stress-strain relation for graphene stretching elasticity and we calculate all the corresponding nonlinear elastic moduli. Present results represent a robust picture on elastic behavior and provide the proper interpretation of recent experiments. In particular, we discuss the physical meaning of the effective nonlinear elastic modulus there introduced and we predict its value in good agreement with available data. Finally, a hyperelastic softening behavior is observed and discussed, so determining the failure properties of graphene.
Abstract: The scaling down of Flash memories can be pursued using theconventional stacked gate architecture only with major changesof the active dielectrics, mainly the inter-poly dielectric(IPD).The required 4-6 nm EOT thickness for the IPD cannot beachieved by the conventional ONO (Oxide-Nitride-Oxide)technology which starts failing in the 10-12 nm range in termsof charge retention properties. Therefore high-k materials arecurrently investigated for IPD formation in future Flashmemories. It is worth noticing that the requirements for IPD arevery different from those of the gate dielectrics used inlogics. Alumina and alumina based materials (like hafniumaluminates) are among the possible candidates. Promising andtunable electrical and structural properties are achieved forthese materials by varying the high-k stack chemicalcompositions and post- deposition thermal treatments. Differentmaterial combinations have been selected as potential solutionsfor the replacement of the conventional ONO(Oxide-Nitride-Oxide) stack.
