The role and effectiveness of chemical pre-functionalization of silicon surfaces (with hydrogen, chlorine, and nitride) to minimize interfacial SiO2 formation during atomic layer deposition growth has been investigated using in situ transmission infrared spectroscopy, ex situ Rutherford backscattering spectroscopy, and ex situ medium energy ion scattering spectroscopy. No measurable SiO2 was formed during growth at low temperatures (∼100 °C) with tetrakis(ethylmethylamino) hafnium and heavy water as precursors on H-, Cl-, and nitride-passivated silicon surfaces. Interfacial SiO2 appeared after postdeposition annealing, at the point when the initially amorphous HfO2 film crystallized, as reflected by the appearance of a monoclinic HfO2 phonon peak at ∼780 cm-1 and by a periodic arrangement of atoms observed in high-resolution transmission electron microscopic images. Electrical characterization of as-deposited HfO2 films showed that, while the interfacial defect density was reasonably low at growth temperatures when interfacial hydrogen was still present (∼100 °C), the leakage current was significantly increased after postdeposition annealing (∼700 °C in nitrogen).

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Both dynamic and static thresholds, as well as the gain in the stretch reflex loop, affect the sensitivity of motoneurons to muscle stretch. How the variation in each parameter will influence the mechanical behavior of patients with spasticity is not well understood because of the difficulty in experimentally isolating individual parameters. A neuromuscular dynamic model, based on the pendulum test of spasticity, has been developed to study the specific contribution of individual parameter abnormalities in stretch reflex loops to the observed mechanical abnormalities. The model contains detailed nonlinear dynamics of muscle force generation and stretch reflexes. A computer simulation of the model indicates that the stretch reflex thresholds and the gain have different influences on the leg swing in the pendulum test of spasticity. Individual changes in the static stretch reflex threshold, in the dynamic threshold, or in the gain can not stimulate the whole spectrum of spasticity severity. When simultaneous changes in all three parameters of the stretch reflex loop occur, a small variation of the gain coupled with changes in both static and dynamic thresholds can produce increasing severity of spasticity as the thresholds further decrease. The model is also successful in simulating the effect of posture changes on spasticity.

Photoelectron spectroscopy (PES), thermal programmed desorption (TPD) studies, and scanning tunneling microscopy (STM) investigated the interaction and chemistry of CH 3 (generated by the thermal cracking of azomethane) on Si/Cu(100). Si was deposited on Cu(100) by the thermal decomposition of SiH 4 at 420 K. STM of adsorbate-free Si/Cu(100) at a less than saturation coverage of Si revealed a surface that contained large domains of a Cu 2 Si structure. These Cu 2 Si domains coexisted with regions that were believed to be lower in fractional Si coverage. TPD results showed that (CH 3 ) 3 SiH desorbed near 200 K from CH 3 /Si/Cu-(100) prepared with a low Si concentration. With increasing Si concentration a (CH 3 ) 3 SiH desorption state appeared near 420 K, in addition to the 200 K state. The two observed TPD states of (CH 3 ) 3 SiH at 200 and 420 K were believed to be due to the thermal reaction of CH 3 with the low Si density and high Si density (i.e., Cu 2 Si) regions, respectively. At a saturation coverage of Si, when the well ordered Cu 2 Si phase covered the surface, only the 420 K peak was present during CH 3 /Si/Cu(100) TPD. Results also suggested that (CH 3 )-Si and possibly some (CH 3 ) 2 Si intermediates predominated on the surface below room temperature, and (CH 3 ) 3 -Si species were formed on the surface only at temperatures between 250 and 390 K. Surface hydrogen needed for the final evolution of (CH 3 ) 3 SiH was generated from methyl groups at temperatures above 390 K on the Si-saturated Cu(100). † Part of the special issue "Gabor Somorjai Festschrift".