Abstract:We review a wet chemical process to prepare the high quality hydrogen-terminated Si( 111)-(1×1) surface and show that the two key issues for the high reproducibility are the etching time and the oxygen in the etching solution. We add ammonium sulfite to remove the oxygen according to the previous report [Appl. Surf. Sci. 130, 146 (1998)]. To elucidate the optimal etching time, the vibrational properties and the surface morphology are investigated by high-resolution electron-energy-loss spectroscopy (HREELS), … Show more
“…Vicinal surfaces of Si(111) wafers were tilted toward the [112̄] direction (the step direction [11̄0]), and Si(111) wafers used in our experiments have average interstep distances of 350, 100, 10, and 4.5 nm (off-cut angle 0.05°, 0.5°, 1.8°, 4.0°, respectively) (Figure ). The H−Si(111) substrates were prepared according to the recipe reported by Suto et al , After the removal of organic contaminations by ultrasonic cleaning with solfine and acetone, substrates were oxidized in a solution of H 2 SO 4 /H 2 O 2 = 3:1 for 2−10 min and etched with NH 4 F for 5−21 min. 1 A schematic illustration of an off-cut H−Si(111) surface and incident directions of a Pn molecular beam (arrows a and b).…”
We investigate thin film crystals of an organic semiconductor, pentacene (Pn), grown on hydrogen-terminated Si(111) (H−Si(111)) surfaces with various interstep distances to elucidate the effects of vicinal steps of H−Si(111) on the growth of
the Pn layers. By observing the morphology of the thin films with atomic force microscopy, we conclude that the vicinal steps
induce significant anisotropy in the growth of the first layers of Pn: dendritic branches evolve in a lower-terrace side (the Si[112̄]
direction), but a compact shape appears in an upper-terrace side (the Si[1̄1̄2] direction), although the first layers grow in an isotropic
shape on a flat H−Si(111) surface. Furthermore, the growth of the first layers is much faster in the lower-terrace-side direction than
in the upper-terrace-side direction. The anisotropy of the growth increases with decreasing interstep distances of H−Si(111), in
particular ≤10 nm. Since such anisotropic growth was observed in a similar way irrespective of the directions of an incident Pn
molecular beam, we conclude that the cause of the anisotropic growth is not the anisotropy of the surface diffusion and admolecule
distribution of Pn molecules. Under the substrate temperature of 30−90 °C, the degree of the anisotropy remained constant within
experimental error.
“…Vicinal surfaces of Si(111) wafers were tilted toward the [112̄] direction (the step direction [11̄0]), and Si(111) wafers used in our experiments have average interstep distances of 350, 100, 10, and 4.5 nm (off-cut angle 0.05°, 0.5°, 1.8°, 4.0°, respectively) (Figure ). The H−Si(111) substrates were prepared according to the recipe reported by Suto et al , After the removal of organic contaminations by ultrasonic cleaning with solfine and acetone, substrates were oxidized in a solution of H 2 SO 4 /H 2 O 2 = 3:1 for 2−10 min and etched with NH 4 F for 5−21 min. 1 A schematic illustration of an off-cut H−Si(111) surface and incident directions of a Pn molecular beam (arrows a and b).…”
We investigate thin film crystals of an organic semiconductor, pentacene (Pn), grown on hydrogen-terminated Si(111) (H−Si(111)) surfaces with various interstep distances to elucidate the effects of vicinal steps of H−Si(111) on the growth of
the Pn layers. By observing the morphology of the thin films with atomic force microscopy, we conclude that the vicinal steps
induce significant anisotropy in the growth of the first layers of Pn: dendritic branches evolve in a lower-terrace side (the Si[112̄]
direction), but a compact shape appears in an upper-terrace side (the Si[1̄1̄2] direction), although the first layers grow in an isotropic
shape on a flat H−Si(111) surface. Furthermore, the growth of the first layers is much faster in the lower-terrace-side direction than
in the upper-terrace-side direction. The anisotropy of the growth increases with decreasing interstep distances of H−Si(111), in
particular ≤10 nm. Since such anisotropic growth was observed in a similar way irrespective of the directions of an incident Pn
molecular beam, we conclude that the cause of the anisotropic growth is not the anisotropy of the surface diffusion and admolecule
distribution of Pn molecules. Under the substrate temperature of 30−90 °C, the degree of the anisotropy remained constant within
experimental error.
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