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Atomic-Scale Patterning of Arsenic in Silicon by Scanning Tunneling Microscopy
journal contribution
posted on 2020-03-12, 20:04 authored by Taylor J. Z. Stock, Oliver Warschkow, Procopios C. Constantinou, Juerong Li, Sarah Fearn, Eleanor Crane, Emily V. S. Hofmann, Alexander Kölker, David R. McKenzie, Steven R. Schofield, Neil J. CursonOver
the past two decades, prototype devices for future classical
and quantum computing technologies have been fabricated by using scanning
tunneling microscopy and hydrogen resist lithography to position phosphorus
atoms in silicon with atomic-scale precision. Despite these successes,
phosphine remains the only donor precursor molecule to have been demonstrated
as compatible with the hydrogen resist lithography technique. The
potential benefits of atomic-scale placement of alternative dopant
species have, until now, remained unexplored. In this work, we demonstrate
the successful fabrication of atomic-scale structures of arsenic-in-silicon.
Using a scanning tunneling microscope tip, we pattern a monolayer
hydrogen mask to selectively place arsenic atoms on the Si(001) surface
using arsine as the precursor molecule. We fully elucidate the surface
chemistry and reaction pathways of arsine on Si(001), revealing significant
differences to phosphine. We explain how these differences result
in enhanced surface immobilization and in-plane confinement of arsenic
compared to phosphorus, and a dose-rate independent arsenic saturation
density of 0.24 ± 0.04 monolayers. We demonstrate the successful
encapsulation of arsenic delta-layers using silicon molecular beam
epitaxy, and find electrical characteristics that are competitive
with equivalent structures fabricated with phosphorus. Arsenic delta-layers
are also found to offer confinement as good as similarly prepared
phosphorus layers, while still retaining >80% carrier activation
and
sheet resistances of <2 kΩ/square. These excellent characteristics
of arsenic represent opportunities to enhance existing capabilities
of atomic-scale fabrication of dopant structures in silicon, and may
be important for three-dimensional devices, where vertical control
of the position of device components is critical.
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equivalent structuresin-plane confinementsheet resistancesAtomic-Scale Patterningalternative dopant speciesmonolayer hydrogen maskphosphinesurface chemistrydifferences resultarsenic delta-layerslithography techniqueoffer confinementprototype devicesplace arsenic atomsatomic-scale fabricationreaction pathwaysscanning tunneling microscopysiliconScanning Tunneling Microscopyprecursor moleculedopant structuresdevice componentsatomic-scale placementdonor precursor moleculeatomic-scale structuressurface immobilizationbeam epitaxyarsineSiatomic-scale precisioncharacteristicphosphorus layersscanning tunneling microscope tipArsenic delta-layersposition phosphorus atomsarsenic saturation density
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