Abstract
The precise positioning of dopant atoms within bulk crystal lattices could enable novel applications in areas including solid-state sensing and quantum computation. Established scanning probe techniques are capable tools for the manipulation of surface atoms, but at a disadvantage due to their need to bring a physical tip into contact with the sample. This has prompted interest in electron-beam techniques, followed by the first proof-of-principle experiment of bismuth dopant manipulation in crystalline silicon. Here, we use first-principles modeling to discover a novel indirect exchange mechanism that allows electron impacts to non-destructively move dopants with atomic precision within the silicon lattice. However, this mechanism only works for the two heaviest group V donors with split-vacancy configurations, Bi and Sb. We verify our model by directly imaging these configurations for Bi and by demonstrating that the promising nuclear spin qubit Sb can be manipulated using a focused electron beam.
Highlights
Quantum information processing has surged in recent decades from a speculative idea[1] into a technological race for quantum supremacy.[2]
A degree of deterministic placement control has been enabled by scanning tunneling microscopy-based hydrogen depassivation lithography of Si surfaces,[10] followed by molecular beam epitaxy growth to complete the crystal over a chemically introduced donor.[11]
To uncover the mechanism of directed dopant movement in silicon, we performed density functional theory molecular dynamics (DFT/MD) simulations to model the effect of momentum-conserving elastic electron scattering on the lattice atoms
Summary
Quantum information processing has surged in recent decades from a speculative idea[1] into a technological race for quantum supremacy.[2]. Phosphorus (31P) as a dopant has attracted the greatest interest due to its long nuclear spin coherence lifetime, enabling it to function as a quantum memory.[8] Typically, traditional non-deterministic ion implantation and post-hoc lithography have been used for fabricating devices.[9] A degree of deterministic placement control has been enabled by scanning tunneling microscopy-based hydrogen depassivation lithography of Si surfaces,[10] followed by molecular beam epitaxy growth to complete the crystal over a chemically introduced donor.[11] the spin dephasing time for the hyperfine-coupled electron on P sites is rather short,[12] hindering its electric-field control. Antimony (Sb) has been suggested as a promising alternative, with 2 orders of magnitude, higher dephasing time, and robust electrical control via its nuclear quadrupole moment.[13]
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