In most models of vacuum breakdown, there is some initial emission of electrons from the cathodic surface, usually employing some form of Fowler-Nordheim emission. While this may be correct for 'textbook' surfaces, it is generally unreliable for real surfaces and fitted parameters are often used. For example, the beta employed is generally unphysical based on usual definitions (e.g., it incorporates more, but unexplained, physics than just a geometry-based field concentration effect). In this work, we describe experimental efforts to better characterize which surface structure parameters influence the vacuum field emission current.
As a first step to porting scanning tunneling microscopy methods of atomic-precision fabrication to a strained-Si/SiGe platform, we demonstrate post-growth P atomic-layer doping of SiGe heterostructures. To preserve the substrate structure and elastic state, we use a T≤800 ° C process to prepare clean Si0.86Ge0.14 surfaces suitable for atomic-precision fabrication. P-saturated atomic-layer doping is incorporated and capped with epitaxial Si under a thermal budget compatible with atomic-precision fabrication. Hall measurements at T=0.3 K show that the doped heterostructure has R□=570±30Ω, yielding an electron density ne=2.1±0.1×1014cm-2 and mobility μe=52±3cm2V-1s-1, similar to saturated atomic-layer doping in pure Si and Ge. The magnitude of μe and the complete absence of Shubnikov-de Haas oscillations in magnetotransport measurements indicate that electrons are overwhelmingly localized in the donor layer, and not within a nearby buried Si well. This conclusion is supported by self-consistent Schrödinger-Poisson calculations that predict electron occupation primarily in the donor layer.
Under the direction of the James W. Todd, Assistant Manager for Engineering within the National Nuclear Security Administration Sandia Field Office, the team listed above has performed the attached study to evaluate the vibration sensitivity of the Center for Integrated Nanotechnolog ies and propose possible mitigation strategies .