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Tunneling probe-based identification of the sp${}^3$ dangling bond on the H-C(100):$2\times1$ surface

Lachlan Oberg, Yi-Ying Sung, Cedric Weber, Marcus W. Doherty, Christopher I. Pakes

TL;DR

This work tackles the challenge of identifying sp$^3$ dangling bonds on the H-terminated diamond surface, a defect that affects diamond-based quantum technologies. It presents a framework that merges STS experiments with density functional theory and electrostatic modeling to interpret defect-related spectra under band bending on the H--C(100):$2\times1$ surface. Two key STS features are assigned to the sp$^3$ dangling bond: a mid-gap unoccupied state at $+$3.0 eV and an occupied state near the VBM at $-1.9$ V, with the energies modulated by Stark shifts and surface fields. The approach enables extraction of the acceptor concentration $N_A$ and the tip-sample distance $t_H$ from STS data, providing a robust identification method that supports scalable, lithography-driven fabrication of diamond quantum devices.

Abstract

The sp${}^3$ dangling bond on the diamond surface plays a critical role in the performance and fabrication of diamond quantum technologies. For the former, the magnetic and electric properties of this defect can impede the performance of quantum sensors and computers. For the latter, the chemical properties of the dangling bond are integral to proposed methods for bottom-up fabrication of scalable diamond quantum devices. In pursuit of high performance and scalable diamond quantum technology, tunneling probe-based techniques offers the ability to create and modify the sp${}^3$ dangling bond with atomic-scale precision. However, these capabilities cannot be realised either deterministically or at scale without a means for identifying the sp${}^3$ dangling bond amidst the myriad of other defects on the diamond surface. Consequently, in this work we provide a comprehensive experimental and theoretical framework for STS-based characterisation of the sp${}^3$ defect on the H-terminated (100) diamond surface. This capability provides the foundation for future tunneling probe studies in the modification of dangling bonds.

Tunneling probe-based identification of the sp${}^3$ dangling bond on the H-C(100):$2\times1$ surface

TL;DR

This work tackles the challenge of identifying sp dangling bonds on the H-terminated diamond surface, a defect that affects diamond-based quantum technologies. It presents a framework that merges STS experiments with density functional theory and electrostatic modeling to interpret defect-related spectra under band bending on the H--C(100): surface. Two key STS features are assigned to the sp dangling bond: a mid-gap unoccupied state at 3.0 eV and an occupied state near the VBM at V, with the energies modulated by Stark shifts and surface fields. The approach enables extraction of the acceptor concentration and the tip-sample distance from STS data, providing a robust identification method that supports scalable, lithography-driven fabrication of diamond quantum devices.

Abstract

The sp dangling bond on the diamond surface plays a critical role in the performance and fabrication of diamond quantum technologies. For the former, the magnetic and electric properties of this defect can impede the performance of quantum sensors and computers. For the latter, the chemical properties of the dangling bond are integral to proposed methods for bottom-up fabrication of scalable diamond quantum devices. In pursuit of high performance and scalable diamond quantum technology, tunneling probe-based techniques offers the ability to create and modify the sp dangling bond with atomic-scale precision. However, these capabilities cannot be realised either deterministically or at scale without a means for identifying the sp dangling bond amidst the myriad of other defects on the diamond surface. Consequently, in this work we provide a comprehensive experimental and theoretical framework for STS-based characterisation of the sp defect on the H-terminated (100) diamond surface. This capability provides the foundation for future tunneling probe studies in the modification of dangling bonds.
Paper Structure (12 sections, 2 equations, 7 figures)

This paper contains 12 sections, 2 equations, 7 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Experimental
  4. Density functional theory
  5. Electrostatic modeling
  6. Results
  7. Experimental STS
  8. Electronic band structure
  9. Band bending
  10. Discussion
  11. Conclusion
  12. Built-in voltage determination

Figures (7)

  • Figure 1: Atomic structure of the sp${}^3$ dangling bond on the H--C(100):$2\times1$ surface. Hydrogen ions are white and carbon atoms are grey. A single hydrogen ion has been removed from the dimerised surface, exposing a bare surface carbon with an sp${}^3$ dangling bond. This dangling bond produces localised states within the diamond band gap which can be visualised using STM. Depicted in purple is the charge density corresponding to an unoccupied mid-gap state.
  • Figure 2: Experimental spectra of the (100) diamond surface.
  • Figure 3: One-electron energies for the occupied and unoccupied orbitals corresponding to the sp${}^3$ dangling bond on the H--C(100):$2\times1$ surface.
  • Figure 4: The voltage drop and electric field as a function of applied bias. Due to screening effects produced by holes and ionised acceptors, the tip Fermi level does translate commensurately with the applied bias relative to the band structure of the sample surface.
  • Figure 5: Theoretical peak position for each of the four electronic states in the tunneling spectrum.
  • ...and 2 more figures