Xenon gas field ion source from a single-atom tip

Reliable preparation and regeneration of well-defined single-atom tips through laser annealing

Single-atom tips (SATs) have crucial scientific and technological applications, such as in scanning probe microscopy and charged particle beam technology. We reported a reliable method of preparing and regenerating noble metal-covered W(111) SATs through laser annealing at approximately 1000 K under ultrahigh vacuum. The field emission patterns obtained during laser heating revealed the self-assembly process of a pyramidal tip. The SATs can be regenerated through laser annealing tens of times with little change in sharpness, indicating a long lifetime. Various pyramidal SATs can be generated and regenerated using visible-light, near-infrared, mode-locked, and continuous-wave lasers at different polarizations relative to the tip axis. The generation of well-defined pyramidal SATs through laser annealing can facilitate various applications of SATs.

Imaging and milling resolution of light ion beams from helium ion microscopy and FIBs driven by liquid metal alloy ion sources

While the application of focused ion beam (FIB) techniques has become a well-established technique in research and development for patterning and prototyping on the nanometer scale, there is still a large underused potential with respect to the usage of ion species other than gallium. Light ions in the range of m = 1-28 u (hydrogen to silicon) are of increasing interest due to the available high beam resolution in the nanometer range and their special chemical and physical behavior in the substrate. In this work, helium and neon ion beams from a helium ion microscope are compared with ion beams such as lithium, beryllium, boron, and silicon, obtained from a mass-separated FIB using a liquid metal alloy ion source (LMAIS) with respect to the imaging and milling resolution, as well as the current stability. Simulations were carried out to investigate whether the experimentally smallest ion-milled trenches are limited by the size of the collision cascade. While He⁺ offers, experimentally and in simulations, the smallest minimum trench width, light ion species such as Li⁺ or Be⁺ from a LMAIS offer higher milling rates and ion currents while outperforming the milling resolution of Ne⁺ from a gas field ion source. The comparison allows one to select the best possible ion species for the specific demands in terms of resolution, beam current, and volume to be drilled.

Time-of-flight secondary ion mass spectrometry in the helium ion microscope

A helium ion microscope, known for high resolution imaging and modification with helium or neon ions, has been equipped with a time-of-flight spectrometer for compositional analysis. Here we report on its design, implementation and show first results of this powerful add-on. Our design considerations were based on the results of detailed ion collision cascade simulations that focus on the physically achievable resolution for various detection limits. Different secondary ion extraction geometries and spectrometer types are considered and compared with respect to the demands and limitations of the microscope. As a result the development and evaluation of a secondary ion extraction optics and time-of-flight spectrometer that allows the parallel measurement of all secondary ion masses is reported. First experimental results demonstrate an excellent mass resolution as well as high-resolution secondary ion imaging capabilities with sub-8 nm lateral resolution. The combination of high resolution secondary electron images and mass-separated sputtered ion distributions have a high potential to answer open questions in microbiology, cell biology, earth sciences and materials research.