Probing the Atomic Arrangement of Sub-Surface Dopants in a Silicon Quantum Device Platform

High-density structures of sub-surface phosphorus dopants in silicon continue to garner interest as a silicon-based quantum computer platform, however, a much-needed confirmation of their dopant arrangement has been lacking. In this work, we take advantage of the chemical specificity of X-ray photoelectron diffraction to obtain the precise structural configuration of P dopants in sub-surface Si:P $\delta$-layers. The growth of $\delta$-layer systems with different levels of doping is carefully studied and verified using X-ray photoelectron spectroscopy and low-energy electron diffraction. Subsequent XPD measurements reveal that in all cases, the dopants primarily substitute with Si atoms from the host material. Furthermore, no signs of free carrier-inhibiting P$-$P dimerization can be observed. Our observations not only settle a nearly decade-long debate about the dopant arrangement but also demonstrate that XPD is well suited to study sub-surface dopant structures. This work thus provides valuable input for an updated understanding of the behavior of Si:P $\delta$-layers and the modeling of their derived quantum devices

Disentangling Electron-Boson Interactions on the Surface of a Familiar Ferromagnet

We report energy renormalizations from electron-phonon and electron-magnon interactions in spin minority surface resonances on Ni(111). The different interactions are disentangled and quantified in strength $\lambda$, based on the characteristic shapes of their complex self-energies, and the largely different binding energies at which they occur. The observed electron-magnon interactions reveal a strong dependence on momentum and energy band position in the bulk Brillouin zone. In contrast, electron-phonon interactions from the same bands are observed to be practically momentum- and symmetry-independent. Additionally, a moderately strong ($\lambda>0.5$) electron-phonon interaction is observed from a `buried', near-parabolic spin majority band that does not cross the Fermi level.Comment: QuSpin 202

A Simplified Method for Patterning Graphene on Dielectric Layers

The large-scale formation of patterned, quasi-freestanding graphene structures supported on a dielectric has so far been limited by the need to transfer the graphene onto a suitable substrate and contamination from the associated processing steps. We report μm scale, few-layer graphene structures formed at moderate temperatures (600–700 °C) and supported directly on an interfacial dielectric formed by oxidizing Si layers at the graphene/substrate interface. We show that the thickness of this underlying dielectric support can be tailored further by an additional Si intercalation of the graphene prior to oxidation. This produces quasi-freestanding, patterned graphene on dielectric SiO2 with a tunable thickness on demand, thus facilitating a new pathway to integrated graphene microelectronics

Phonon-Mediated Quasiparticle Lifetime Renormalizations in Few-Layer Hexagonal Boron Nitride

Understanding thecollective behavior of the quasiparticles insolid-state systems underpins the field of nonvolatile electronics,including the opportunity to control many-body effects for well-desiredphysical phenomena and their applications. Hexagonal boron nitride(hBN) is a wide-energy-bandgap semiconductor, showing immense potentialas a platform for low-dimensional device heterostructures. It is aninert dielectric used for gated devices, having a negligible orbitalhybridization when placed in contact with other systems. Despite itsinertness, we discover a large electron mass enhancement in few-layerhBN affecting the lifetime of the & pi;-band states. We show thatthe renormalization is phonon-mediated and consistent with both single-and multiple-phonon scattering events. Our findings thus unveil aso-far unknown many-body state in a wide-bandgap insulator, havingimportant implications for devices using hBN as one of their buildingblocks