Spatially resolved scanning tunneling spectroscopy of single-layer steps on Si(100) surfaces

Wang, Xiqiao; Namboodiri, Pradeep; Li, Kai; Xiao, Deng; Silver, Richard M.

doi:10.1103/physrevb.94.125306

Cited by 8 publications

(5 citation statements)

References 82 publications

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“…The critical dimensions after STM-imaging correction are summarized in Table 2 for all devices in this study (see Methods for details). In addition, our regular use of high-resolution STM imaging over the STMpatterned device region allows us to identify atomic-scale defects in the device region, such as step-edges 18 and buried charge defects 19 , which can potentially affect device performance.…”

Section: Resultsmentioning

confidence: 99%

“…The Si:P SETs are fabricated on a hydrogen-terminated Si(100)2 × 1 substrate (3 10 15 cm À3 boron doped) in an UHV environment with a base pressure below 4 10 À9 Pa (3 10 À11 Torr). Detailed sample preparation, UHV sample cleaning, hydrogen-resist formation, and STM tip fabrication and cleaning procedures have been published elsewhere 11,18,33 . A low 1 × 10 −11 Torr UHV environment and contamination-free hydrogen-terminated Si surfaces and STM tips are critical to achieving highstability imaging and hydrogen-lithography operation.…”

Section: Discussionmentioning

confidence: 99%

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Atomic-scale control of tunneling in donor-based devices

et al. 2020

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Atomically precise donor-based quantum devices are a promising candidate for solid-state quantum computing and analog quantum simulations. However, critical challenges in atomically precise fabrication have meant systematic, atomic scale control of the tunneling rates and tunnel coupling has not been demonstrated. Here using a room temperature grown locking layer and precise control over the entire fabrication process, we reduce unintentional dopant movement while achieving high quality epitaxy in scanning tunnelling microscope (STM)-patterned devices. Using the Si(100)2 × 1 surface reconstruction as an atomically-precise ruler to characterize the tunnel gap in precision-patterned single electron transistors, we demonstrate the exponential scaling of the tunneling resistance on the tunnel gap as it is varied from 7 dimer rows to 16 dimer rows. We demonstrate the capability to reproducibly pattern devices with atomic precision and a donor-based fabrication process where atomic scale changes in the patterned tunnel gap result in the expected changes in the tunneling rates.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Atomic-scale control of tunneling in donor-based devices

et al. 2020

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“…regardless of the higher growth rate. 32 The surface roughness effect from higher locking layer growth rates are not obvious after LL RTA (Figure 3(d)). However, TEM contrast at the LL interface ( Figure 3(c)(d)) remains observable after such a short RTA process.…”

Section: Methodsmentioning

confidence: 96%

“…Detailed preparation procedures have been published elsewhere. 32 Then the surface is dosed (~1.5 Langmuir exposure) with Phosphine (PH3) gas at room temperature to achieve a saturation surface coverage of ~0.37 monolayers of phosphorus species (Figure 1(b)). 22,33 PH3 molecules dissociate into H atoms and PHx (x= 0, 1, 2) groups and terminate the Si dangling bonds on the Si(100) surface.…”

Section: Methodsmentioning

confidence: 99%

Quantifying atom-scale dopant movement and electrical activation in Si:P monolayers

et al. 2018

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Advanced hydrogen lithography techniques and low-temperature epitaxial overgrowth enable the patterning of highly phosphorus-doped silicon (Si:P) monolayers (ML) with atomic precision. This approach to device fabrication has made Si:P monolayer systems a testbed for multiqubit quantum computing architectures and atomically precise 2-D superlattice designs whose behaviors are directly tied to the deterministic placement of single dopants. However, dopant segregation, diffusion, surface roughening, and defect formation during the encapsulation overgrowth introduce large uncertainties to the exact dopant placement and activation ratio. In this study, we develop a unique method by combining dopant segregation/diffusion models with sputter profiling simulation to monitor and control, at the atomic scale, dopant movement using room-temperature grown locking layers (LLs). We explore the impact of LL growth rate, thickness, rapid thermal annealing, surface accumulation, and growth front roughness on dopant confinement, local crystalline quality, and electrical activation within Si:P 2-D systems. We demonstrate that dopant movement can be more efficiently suppressed by increasing the LL growth rate than by increasing the LL thickness. We find that the dopant segregation length can be suppressed below a single Si lattice constant by increasing the LL growth rates at room temperature while maintaining epitaxy. Although dopant diffusivity within the LL is found to remain high (on the order of 10 cm s) even below the hydrogen desorption temperature, we demonstrate that exceptionally sharp dopant confinement with high electrical quality within Si:P monolayers can be achieved by combining a high LL growth rate with low-temperature LL rapid thermal annealing. The method developed in this study provides a key tool for 2-D fabrication techniques that require precise dopant placement to suppress, quantify, and predict a single dopant's movement at the atomic scale.

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“…The 3 × 3 few-dopant quantum dot arrays are fabricated in an ultrahigh vacuum (UHV) environment with a base pressure below Pa ( Torr) using an STM tip to create atomic-scale lithographic patterns of the device by removing individual hydrogen atoms on an hydrogen-terminated, Si(100) 2 × 1 reconstructed surface 44 . Detailed sample preparation, UHV sample cleaning, hydrogen-resist formation, and STM tip fabrication and cleaning procedures have been published elsewhere 47 , 48 . The substrate is then saturation-dosed with PH 3 gas at room temperature, where PH 3 molecules selectively absorb only onto the lithographic regions where chemically reactive Si dangling bonds are exposed.…”

Section: Methodsmentioning

confidence: 99%

Experimental realization of an extended Fermi-Hubbard model using a 2D lattice of dopant-based quantum dots

et al. 2022

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The Hubbard model is an essential tool for understanding many-body physics in condensed matter systems. Artificial lattices of dopants in silicon are a promising method for the analog quantum simulation of extended Fermi-Hubbard Hamiltonians in the strong interaction regime. However, complex atom-based device fabrication requirements have meant emulating a tunable two-dimensional Fermi-Hubbard Hamiltonian in silicon has not been achieved. Here, we fabricate 3 × 3 arrays of single/few-dopant quantum dots with finite disorder and demonstrate tuning of the electron ensemble using gates and probe the many-body states using quantum transport measurements. By controlling the lattice constants, we tune the hopping amplitude and long-range interactions and observe the finite-size analogue of a transition from metallic to Mott insulating behavior. We simulate thermally activated hopping and Hubbard band formation using increased temperatures. As atomically precise fabrication continues to improve, these results enable a new class of engineered artificial lattices to simulate interactive fermionic models.

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Spatially resolved scanning tunneling spectroscopy of single-layer steps on Si(100) surfaces

Cited by 8 publications

References 82 publications

Atomic-scale control of tunneling in donor-based devices

Atomic-scale control of tunneling in donor-based devices

Quantifying atom-scale dopant movement and electrical activation in Si:P monolayers

Experimental realization of an extended Fermi-Hubbard model using a 2D lattice of dopant-based quantum dots

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