Al-alkyls as acceptor dopant precursors for atomic-scale devices.

Atomically precise ultradoping of silicon is possible with atomic resists, area-selective surface chemistry, and a limited set of hydride and halide precursor molecules, in a process known as atomic precision advanced manufacturing (APAM). It is desirable to expand this set of precursors to include dopants with organic functional groups and here we consider aluminium alkyls, to expand the applicability of APAM. We explore the impurity content and selectivity that results from using trimethyl aluminium and triethyl aluminium precursors on Si(001) to ultradope with aluminium through a hydrogen mask. Comparison of the methylated and ethylated precursors helps us understand the impact of hydrocarbon ligand selection on incorporation surface chemistry. Combining scanning tunneling microscopy and density functional theory calculations, we assess the limitations of both classes of precursor and extract general principles relevant to each.

Field-directed sputter sharpening for tailored probe materials and atomic-scale lithography.

Fabrication of ultrasharp probes is of interest for many applications, including scanning probe microscopy and electron-stimulated patterning of surfaces. These techniques require reproducible ultrasharp metallic tips, yet the efficient and reproducible fabrication of these consumable items has remained an elusive goal. Here we describe a novel biased-probe field-directed sputter sharpening technique applicable to conductive materials, which produces nanometer and sub-nanometer sharp W, Pt-Ir and W-HfB(2) tips able to perform atomic-scale lithography on Si. Compared with traditional probes fabricated by etching or conventional sputter erosion, field-directed sputter sharpened probes have smaller radii and produce lithographic patterns 18-26% sharper with atomic-scale lithographic fidelity.

Patterning of sub-1 nm dangling-bond lines with atomic precision alignment on H:Si(100) surface at room temperature.

We have patterned sub-1 nm dangling-bond (DB) lines on a H-terminated Si(100)-2 × 1 surface aligned with atomic precision at room temperature using a scanning tunneling microscope (STM) to controllably desorb hydrogen atoms from a H:Si(100) surface. In order to achieve continuous and aligned DB lines, we have performed a detailed investigation of the effects of patterning parameters such as the writing voltage, writing current and electron dosage, as well as STM tip apex geometry on the fabrication and alignment of Si DB lines. We show that there exists an optimum set of patterning parameters which enables us to obtain near-perfect Si DB lines and align them with near atomic precision in a highly controllable manner. In addition, our results indicate that the pattern quality is weakly dependent on the STM tip apex quality when the patterning parameters are within the optimum parameter space.