Interaction ofH2withSi(001)−(2×1): Solution of the Ba

Abstract

The sticking probability of H2 on Si(001) is immeasurably small at room temperature, indicating the presence of a large energy barrier to adsorption. Surprisingly, the final state energy distributions of H2 molecules desorbing from Si(001) show no signs of having traversed such a barrier, in apparent contradiction with microscopic reversibility. Here we report experimental and theoretical evidence resolving this long-standing puzzle. Adsorption and desorption proceeding along two distinct, microscopically reversible pathways can explain all observations.

A tool for the spectroscopic investigation of hydrogen–silicon interaction

“…The multiple assignments originate from the patchwise heterogeneity of the inner surface, while the unassigned signals could be related to both the intermediate species which can be involved in adsorption, [1,2] and to the very unusual surfaces at the NC walls (namely the (5 1 1) in addition to the more frequent (3 1 1)), whose IR responses have not been studied yet. A refinement of the spectral analysis showed in Refs [3,9] suggests that the frequency ν as of the monohydride dimer (mode D) falls at 2086.5 cm −1 .…”

“…[1] Adsorption kinetics are thus expected to go to completion after exposures of 10 5 -10 11 L, while in UHV equipment the experiments cannot exceed 10 4 L. The observation that nanocavities (NCs) in silicon offer a very clean environment where H 2 can be injected at high pressure by simple immersion in HF solution, [3] thus preserving the cleanliness of the surface, is expected to be able to change this state of affairs.…”

“…Adsorption and desorption of H 2 on or from the silicon surface play a special role not only from the fundamental but also from the technological point of view; [1] however, in spite of the numerous studies, their very mechanisms are still objects of hot debate. [2] The limiting factors are the need to work in ultra-high vacuum (UHV) conditions to allow the Si surface to be clean and well-ordered, and the tiny sticking coefficient of the reaction (reported to range from 10 −11 at room temperature (RT) to 10 −5 at 500…”

Anatomy of a Spin: The Information-Theoretic Structure of Classical Spin Systems

“…Simple Ising models have been broadly adapted to understand simple collective phenomena in fields ranging from surface physics [35,36] and biophysics [37,38] to economics [39]. The Ising model on a one-dimensional lattice (L = Z) can be fully analyzed in closed form.…”

Quantum Monte Carlo Calculations ofH2Dissociation on Si(001)

“…Microscopically, these observations were originally interpreted in terms of an intra-dimer mechanism, where the hydrogen molecule interacts with one single dimer of the Si(001) surface [3]. However, very recent experiments have pointed to additional mechanisms involving not just a single dimer but nearby dimers [4,5]. The existence of highly reactive pathways was first demonstrated on steps [6] or H-precovered surfaces [7], and evidence that H 2 reacts with two adjacent dimers has also now been given for the clean surface [8].…”