Non‐Local Atomic Manipulation on Semiconductor Surfaces in the STM: The Case of Chlorobenzene on Si(111)‐7×7

Abstract

Control over individual atoms with the scanning tunnelling microscope (STM) holds the tantalising prospect of atomic-scale construction, but is limited by its "one atom at a time" serial nature. "Remote control" through non-local STM manipulation-as we have demonstrated in the case of chlorobenzene on Si(111)-7×7-offers a new avenue for future "bottom-up" nanofabrication, since hundreds of chemical reactions may be carried out in parallel. Thus a good understanding of the non-local manipulation process, as provided by recent experiments, is important. Comparison of scanning tunnelling spectroscopy (STS) measurements of the bare Si(111)-7×7 surface and chemisorbed chlorobenzene molecules with the voltage dependence of the non-local STM-induced desorption of chlorobenzene proves particularly instructive. For example, the chlorobenzene LUMO appears at +0.9 V with respect to the Fermi level, whereas non-local manipulation thresholds are found at +2.1 V and +2.7 V. This difference supports a picture in which the voltage thresholds for non-local electron-induced desorption depend principally on the energies of the electronic states of the surface. Furthermore, the demonstration that the non-local process is largely insensitive to surface steps up to five layers in height suggests that either the electron transport in this process is subsurface in character or surface charge transport is responsible but is in some way unaffected by the steps.

Common source of light emission and nonlocal molecular manipulation on the Si(111)−7 × 7 surface

“…We take τ D =200 fs [36] and so convert the β values of figure 4 to the total probability of manipulation per injected electron N as displayed in figure 5(c). This form of analysis should be identical to the original 'scanning' manipulation work and indeed we find our results here match qualitatively and quantitatively with that earlier work [32,39]. Figure 5(c) shows the voltage dependence of both the probability per electron of molecular displacement and the probability per electron of photon emission.…”

“…The main difference is whereas desorption of toluene is an irreversible process, the manipulated silicon adatoms are meta-stable at room temperature and drop back to their original sites before they can be imaged by an STM. We have also reported that the low lying state at ∼+0.5 V is reduced in intensity but still present at the location of the bonding adatom to a chlorobenzene adsorbate [32]. Toluene and chlorobenzene both bond and are manipulated in near identical fashion on the Si(111)-7×7 surface.…”

“…We have previously reported on nonlocal manipulation of chlorobenzene and toluene from the Si(111) −7×7 surface [21][22][23]32]. See [33] for a general review of nonlocal manipulation.…”

Local resonances in STM manipulation of chlorobenzene on Si(111)-7×7: performance of different cluster models and density functionals

“…Both, STM-induced desorption [22] and dissociation [23] of the carbon-chlorine-bond, have been reported in experiments at room temperature. Desorption can be induced by electrons or holes (positive or negative bias voltage) and was found to be largely non-local [8,24]. We characterised physisorbed and chemisorbed chlorobenzene using a cluster approach and density functional theory (DFT) in Ref.…”

Quantum chemical approach to atomic manipulation of chlorobenzene on the Si(111)- 7×7 surface: Resonance localization, vibrational activation, and surface dynamics

“…Desorption [15] of chlorobenzene from a Si(111)-7x7 surface can be induced in a one-electron (positive surface bias voltage) or a one-hole process (negative bias voltage) and is to a large extent non-local [13,16]. Also dissociation of the carbon-chlorine-bond has been reported either in a two-electron process [17] or a thermally assisted one-electron process [18].…”