Interaction of atomic hydrogen and n-containing aromatic organic molecules with the Si(100) and Ge(100) surfaces

Abstract

$\subsubsection{Absorption of Gas-phase Atomic Hydrogen by Si(100): Effect of Surface Atomic Structures}$ The atomic-scale surface structural evolution of Si(100) exposed to gas-phase thermal hydrogen atoms, H(g), has been investigated by scanning tunneling microscopy (STM) and temperature-programmed desorption (TPD) mass spectrometry. For the substrate temperature (T$_s$) between 420 and 530 K, dihydride species in 3×1:H domains were selectively etched upon extensive exposures to H(g). As a result, etch pits grew laterally along Si surface dimer rows. The presence of these pits correlates with the absorption of H(g) into the bulk of Si(100), confirming our earlier suggestion that atomic-scale surface roughening caused by etching is a prerequisite for H(g) absorption. $\subsubsection{Interaction of Atomic Hydrogen with the Ge(100) surface}$ Adsorption of atomic hydrogens on Ge(100) surface has been investigated in detail using scanning tunneling microscopy (STM) at room temperature. At low coverage, hydrogen atoms singly occupy the dangling bonds of the dimer unit by forming unpaired dangling bonds which are imaged as bright features in STM images. The single H adsorption is found to induce the buckling of the dimer row. At saturation coverage ($Θ_H$ = 1 ML), hydrogen atoms saturate all dangling bonds of the dimers revealing the 2 × 1 monohydride phases. With increasing atomic hydrogen exposure ($Θ_H$ > 1 ML), H breaks the Ge-Ge dimer bond resulting in the formation of the Ge dihydride phases ($GeH_2$) with very local 3 ×1 domains consisting of the alternating monohydride and dihydride units. But, even after extensive exposure of hydrogen, the long range 3×1 or 1×1 phases with the dihydride species are not observed in contrast with the Si(100) case. Instead, incoming hydrogen atoms etch selectively the Ge dihydride species along the dimer rows with retaining the 2×1 monohydride phase. $\subsubsection{Adsorption Structures and Binding Site Conversion of Pyrid...