Organic Bonding to Silicon via a Carbonyl Group:  New Insights from Atomic-Scale Images

Abstract

The ability to covalently attach organic molecules to semiconductor surfaces in a controllable and selective manner is currently receiving much attention due to the potential for creating hybrid silicon-organic molecular-electronic devices. Here we use scanning tunneling microscopy (STM) and density functional theory calculations to study the adsorption of a simple ketone [acetone; (CH(3))(2)CO] to the silicon (001) surface. We show both bias and time-dependent STM images and their agreement with total energy DFT calculations, simulated STM images, and published spectroscopic data. We investigate the stability of the resulting adsorbate structures with respect to temperature and applied STM tip bias and current. We demonstrate the ability to convert from the kinetically favored single-dimer alpha-H cleavage adsorbate structure to thermodynamically favored bridge-bonded adsorbate structures. This can be performed for the entire surface using a thermal anneal or, for individual molecules, using the highly confined electron beam of the STM tip. We propose the use of the carbonyl functional group to tether organic molecules to silicon may lead to increased stability of the adsorbates with respect to current-voltage characterization. This has important implications for the creation of robust single-molecule devices.

Interaction of acetone with the Si(001) surface

“…These transitions have been induced to occur by stimulation via the STM tip, or by increasing the substrate temperature above RT [9]. We also found no evidence for any reversibility of these transitions.…”

“…16. These images were acquired at room temperature (RT), and are analogous to those presented in our earlier paper [9], but provide better definition for the empty-states. Three distinct acetone-derived adsorbate features can be identified in these images.…”

“…Recently we have reported the results of a combined scanning tunneling microscopy (STM) and density functional theory (DFT) study of the interaction of acetone with the Si(0 0 1) surface and identified three distinct adsorbate features in the STM images [8,9]. One of these features was one-dimer wide, while the other two were two-dimers wide.…”

Wet chemical routes to the assembly of organic monolayers on silicon surfaces via the formation of Si–C bonds: surface preparation, passivation and functionalization

“…To introduce a pivotal concept to the discussion of the following paragraphs, where an overview will be given of the available derivatization routes toward functional silicon layers, it should be noted that the silicon hydride phase has indeed a broad reactivity and, beside reactions with unsaturated hydrocarbons and halogens, the immobilization of nitriles, 31 alcohols, 44,81 aldehydes, 168 and ketones 198 have all been documented.…”

Molecules on Si: Electronics with Chemistry

“…[151,152] This is found even at the nanoscopic level. Thus, the conductance of isolated styrene [27] or acetone [182] molecules, adsorbed on Si, is affected strongly by the chemical conditions of neighboring Si atoms, which act as gate for transport across the adsorbed molecules. Meaningful interpretation of transport results in terms of molecular, and not monolayer defect properties, requires a monolayer that is sufficiently ideal so that in the original, reference state, electrical transport is not dominated by defects, analogous to the bulk semiconductor case.…”