Peter W. Voorhees

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Consider faceting of a crystal surface caused by strongly anisotropic surface tension, driven by surface diffusion and accompanied by deposition (etching) due to fluxes normal to the surface. Nonlinear evolution equations describing the faceting of 1+1 and 2+1 crystal surfaces are studied analytically, by means of matched asymptotic expansions for small(More)
Microsystems have become an integral part of our lives and can be found in homeland security, medical science, aerospace applications and beyond. Many critical microsys-tem applications are in harsh environments, in which long-term reliability needs to be guaranteed and repair is not feasible. For example, gyroscope microsystems on satellites need to(More)
Semiconductor nanowires show promise for many device applications, but controlled doping with electronic and magnetic impurities remains an important challenge. Limitations on dopant incorporation have been identified in nanocrystals, raising concerns about the prospects for doping nanostructures. Progress has been hindered by the lack of a method to(More)
Synchrotron X-ray computed tomography (SXCT) is increasingly being used for 3-D imaging of material samples at micron and finer scales. The success of these techniques has increased interest in 4-D reconstruction methods that can image a sample in both space and time. However, the temporal resolution of widely used 4-D reconstruction methods is severely(More)
A method is described for quantitatively analyzing the level of interconnectivity of solid-oxide fuel cell electrode phases. The method was applied to the three-dimensional microstructure of a Ni-Y2O3-stabilized ZrO2 (Ni-YSZ) anode active layer measured by focused ion beam scanning electron microscopy. Each individual contiguous network of Ni, YSZ, and(More)
The processes controlling the morphology of dendrites have been of great interest to a wide range of communities, since they are examples of an out-of-equilibrium pattern forming system, there is a clear connection with battery failure processes, and their morphology sets the properties of many metallic alloys. We determine the three-dimensional morphology(More)
First-principles calculations are used to calculate the strain dependencies of the binding and diffusion-activation energies for Ge adatoms on both Si͑001͒ and Ge͑001͒ surfaces. Our calculations reveal that the binding and activation energies on a strained Ge͑001͒ surface increase and decrease, respectively, by 0.21 and 0.12 eV per percent compressive(More)
We used x-ray nanotomography to characterize the three-dimensional ͑3D͒ morphology and topology of dealloyed nanoporous gold after coarsening. The interface shape distribution obtained from the nanotomography measurement shows that the coarsening does not proceed by bulk diffusion. The surface normal distribution shows that the morphology of the nanoporous(More)
A twin-plane based nanowire growth mechanism is established using Au catalyzed Ge nanowire growth as a model system. Video-rate lattice-resolved environmental transmission electron microscopy shows a convex, V-shaped liquid catalyst-nanowire growth interface for a ⟨112⟩ growth direction that is composed of two Ge {111} planes that meet at a twin boundary.(More)