Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector.

Eduardo Serralta,Serge Duarte Pinto,Michael Mousley,Nico Klingner,Tom Wirtz,Santhana Eswara,Gregor Hlawacek,Olivier De Castro

doi:10.3762/bjnano.11.167

Abstract

A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes, such as bright field and dark field or the direct image of the transmitted signal, can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and temporal resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small-angle and high-angle scattering signals. We also detect channeling-related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single-crystalline silicon by comparing the signal transmitted at different directions for the same data set.

Highlights

The helium ion microscope (HIM) is an instrument that has already proven its value for high-resolution imaging, compositional analysis, nanofabrication, and materials modification [1,2]
We present a new system for comprehensive scanning transmission ion microscopy (STIM) analyses that gives more flexibility to the user than the earlier approaches
Bright-field and dark-field contrast In Figure 2, we show images of a carbon film under lacey carbon using the secondary electrons (SEs) imaging mode (Figure 2a), BF STIM (Figure 2b), and annular dark-field (ADF) STIM (Figure 2c)

Summary

Introduction

The helium ion microscope (HIM) is an instrument that has already proven its value for high-resolution imaging, compositional analysis, nanofabrication, and materials modification [1,2]. Transmission imaging signals depend on the particles that pass through the sample and on how they are scattered. In BF mode, the areas of the sample with little or no scattering appear with high intensity in the image, and regions of the sample that scatter more than the collection angle of the detector will appear with low intensity.

Results

Conclusion