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Quantum engineering at the silicon surface using dangling bonds.

Schofield SR, Studer P, Hirjibehedin CF, Curson NJ, Aeppli G, Bowler DR - Nat Commun (2013)

Bottom Line: Here we use a scanning tunnelling microscope to fabricate interacting chains of dangling bond defects on the hydrogen-passivated silicon (001) surface.We image both the ground-state and the excited-state probability distributions of the resulting artificial molecular orbitals, using the scanning tunnelling microscope tip bias and tip-sample separation as gates to control which states contribute to the image.Our results demonstrate that atomically precise quantum states can be fabricated on silicon, and suggest a general model of quantum-state fabrication using other chemically passivated semiconductor surfaces where single-atom depassivation can be achieved using scanning tunnelling microscopy.

View Article: PubMed Central - PubMed

Affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK. s.schofield@ucl.ac.uk

ABSTRACT
Individual atoms and ions are now routinely manipulated using scanning tunnelling microscopes or electromagnetic traps for the creation and control of artificial quantum states. For applications such as quantum information processing, the ability to introduce multiple atomic-scale defects deterministically in a semiconductor is highly desirable. Here we use a scanning tunnelling microscope to fabricate interacting chains of dangling bond defects on the hydrogen-passivated silicon (001) surface. We image both the ground-state and the excited-state probability distributions of the resulting artificial molecular orbitals, using the scanning tunnelling microscope tip bias and tip-sample separation as gates to control which states contribute to the image. Our results demonstrate that atomically precise quantum states can be fabricated on silicon, and suggest a general model of quantum-state fabrication using other chemically passivated semiconductor surfaces where single-atom depassivation can be achieved using scanning tunnelling microscopy.

No MeSH data available.


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An isolated DB on an n-type Si(001):H surface.(a,b) Filled- and empty-state STM images (±1.7 V; 25 pA; 16 × 14 nm2) of a single DB taken at 77 K, with corresponding line profiles shown in c and d. Length measurements have associated uncertainties of ±0.05 nm. The screening length of 2.1 nm calculated from the filled-state image is in agreement with a Thomas–Fermi estimate16. The empty-state image exhibits a ~12 nm diameter enhancement disc due to ionization of the DB and a ~5-nm depression due to non-equilibrium charging of the DB. These features exhibit the expected dependence on the applied bias (see Supplementary Note S1 and Supplementary Fig. S1).
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f1: An isolated DB on an n-type Si(001):H surface.(a,b) Filled- and empty-state STM images (±1.7 V; 25 pA; 16 × 14 nm2) of a single DB taken at 77 K, with corresponding line profiles shown in c and d. Length measurements have associated uncertainties of ±0.05 nm. The screening length of 2.1 nm calculated from the filled-state image is in agreement with a Thomas–Fermi estimate16. The empty-state image exhibits a ~12 nm diameter enhancement disc due to ionization of the DB and a ~5-nm depression due to non-equilibrium charging of the DB. These features exhibit the expected dependence on the applied bias (see Supplementary Note S1 and Supplementary Fig. S1).

Mentions: DBs at the surface of Si are particularly interesting because in contrast to most other defects they can be introduced deterministically via STM writing at the atomic scale. This enables the creation of systems of DBs, and we show here that closely spaced DBs can interact to form artificial ‘molecules’ and one- and two-dimensional ‘solids’. The procedure is simple and reproducible: start with a clean Si(001) surface, passivate it with atomic hydrogen, image the surface at low voltage and then desorb selected H atoms using ramps to elevated voltages. Figure 1a shows STM topographs of a single DB ‘atom’ measured with negative and positive sample bias, respectively. Figure 1c shows height profiles across these images. What is immediately apparent is the large extent of the disturbance produced by what one might have thought to be, and what is usually considered as a highly localized object, as well as the qualitatively different appearance for negative and positive voltages. The long-range effects are the result of charge localization at the DB site, which has a strong impact on the images, as the resulting screened Coulomb potentials make the effective bias voltages position dependent.


Quantum engineering at the silicon surface using dangling bonds.

Schofield SR, Studer P, Hirjibehedin CF, Curson NJ, Aeppli G, Bowler DR - Nat Commun (2013)

An isolated DB on an n-type Si(001):H surface.(a,b) Filled- and empty-state STM images (±1.7 V; 25 pA; 16 × 14 nm2) of a single DB taken at 77 K, with corresponding line profiles shown in c and d. Length measurements have associated uncertainties of ±0.05 nm. The screening length of 2.1 nm calculated from the filled-state image is in agreement with a Thomas–Fermi estimate16. The empty-state image exhibits a ~12 nm diameter enhancement disc due to ionization of the DB and a ~5-nm depression due to non-equilibrium charging of the DB. These features exhibit the expected dependence on the applied bias (see Supplementary Note S1 and Supplementary Fig. S1).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644071&req=5

f1: An isolated DB on an n-type Si(001):H surface.(a,b) Filled- and empty-state STM images (±1.7 V; 25 pA; 16 × 14 nm2) of a single DB taken at 77 K, with corresponding line profiles shown in c and d. Length measurements have associated uncertainties of ±0.05 nm. The screening length of 2.1 nm calculated from the filled-state image is in agreement with a Thomas–Fermi estimate16. The empty-state image exhibits a ~12 nm diameter enhancement disc due to ionization of the DB and a ~5-nm depression due to non-equilibrium charging of the DB. These features exhibit the expected dependence on the applied bias (see Supplementary Note S1 and Supplementary Fig. S1).
Mentions: DBs at the surface of Si are particularly interesting because in contrast to most other defects they can be introduced deterministically via STM writing at the atomic scale. This enables the creation of systems of DBs, and we show here that closely spaced DBs can interact to form artificial ‘molecules’ and one- and two-dimensional ‘solids’. The procedure is simple and reproducible: start with a clean Si(001) surface, passivate it with atomic hydrogen, image the surface at low voltage and then desorb selected H atoms using ramps to elevated voltages. Figure 1a shows STM topographs of a single DB ‘atom’ measured with negative and positive sample bias, respectively. Figure 1c shows height profiles across these images. What is immediately apparent is the large extent of the disturbance produced by what one might have thought to be, and what is usually considered as a highly localized object, as well as the qualitatively different appearance for negative and positive voltages. The long-range effects are the result of charge localization at the DB site, which has a strong impact on the images, as the resulting screened Coulomb potentials make the effective bias voltages position dependent.

Bottom Line: Here we use a scanning tunnelling microscope to fabricate interacting chains of dangling bond defects on the hydrogen-passivated silicon (001) surface.We image both the ground-state and the excited-state probability distributions of the resulting artificial molecular orbitals, using the scanning tunnelling microscope tip bias and tip-sample separation as gates to control which states contribute to the image.Our results demonstrate that atomically precise quantum states can be fabricated on silicon, and suggest a general model of quantum-state fabrication using other chemically passivated semiconductor surfaces where single-atom depassivation can be achieved using scanning tunnelling microscopy.

View Article: PubMed Central - PubMed

Affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK. s.schofield@ucl.ac.uk

ABSTRACT
Individual atoms and ions are now routinely manipulated using scanning tunnelling microscopes or electromagnetic traps for the creation and control of artificial quantum states. For applications such as quantum information processing, the ability to introduce multiple atomic-scale defects deterministically in a semiconductor is highly desirable. Here we use a scanning tunnelling microscope to fabricate interacting chains of dangling bond defects on the hydrogen-passivated silicon (001) surface. We image both the ground-state and the excited-state probability distributions of the resulting artificial molecular orbitals, using the scanning tunnelling microscope tip bias and tip-sample separation as gates to control which states contribute to the image. Our results demonstrate that atomically precise quantum states can be fabricated on silicon, and suggest a general model of quantum-state fabrication using other chemically passivated semiconductor surfaces where single-atom depassivation can be achieved using scanning tunnelling microscopy.

No MeSH data available.


Related in: MedlinePlus