Interaction of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> with <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Si</mi><mo>(</mo><mn>001</mn><mo>)</mo><mi>−</mi><mo>(</mo><mn>2</mn><mo>×</mo><mn>1</mn><mo>)</mo></math></span>: Solution of the Barrier Puzzle

Frank M. Zimmermann; X. Pan

doi:10.1103/PhysRevLett.85.618

Interaction of $H_{2}$ with $Si (001) - (2 \times 1)$ : Solution of the Barrier Puzzle

Frank M. Zimmermann and X. Pan

Phys. Rev. Lett. 85, 618 – Published 17 July 2000

Abstract

The sticking probability of $H_{2}$ 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 $H_{2}$ 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.