Precision Argon ion mill system

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The requested precision Argon ion mill is an excellent specimen preparation system for creating the high-quality thin specimens needed for advanced transmission electron microscopy (TEM) imaging and analysis. It will be used for both, post-FIB (focused ion beam) processing of TEM lamella as well as the enhancement of conventionally prepared specimens. Amorphous surface layers, formed during the FIB process, will be significantly reduced by using the Ar ion mill. This leads to a substantial improvement of the image quality in analytical TEM performed in the research group of the applicant as well as a service for other research groups, institutes, faculties and collaborations.Furthermore, the precision Argon ion mill is a key tool, in particular for the nanoscale luminescence investigations of our group: Low-temperature nano-cathodoluminescence spectroscopy performed in our sophisticated STEM (STEM-CL) is a unique measurement technique: realizing a direct correlation of the semiconductor real structure and the electronic and optical properties with an ultimate spatial resolution of 1.8 nm. Our STEM-CL system is an essential part of our research projects.We are currently integrating a He-temperature CL system in our FIB for a precise targeting preparation of selected sample areas-of-interest, which are still luminescent after FIB preparation. However, the beam damage by Ga ions and formation of thin amorphous surface layers induced by the FIB process negatively affect the quantum efficiency of the emitted photons and spatial resolution in STEM-CL experiments. Near-surface point defects generated by Ga bombardment lead to nonradiative recombination of excess carriers.Based on several years of experience in the research group of the applicant, a unique preparation technique for STEM-CL specimens has been developed. The FIB-related surface damage can be reduced by subsequent gentle milling of the damaged layers using low energy Ar ion etching. For the final preparation of TEM lamella of highest optical quality (i.e. highest possible CL efficiency) after FIB processing, a precision Argon ion milling is therefore absolutely essential.The final thinning of the lamella is used to reduce amorphous surface layers and improve the sample surfaces directly after FIB processing. A focused Ar beam precisely etches a specifically selected area of few micrometer in spot or scanning mode. For direct imaging, secondary electron detectors are used to observe the position of the ion beam and directly control the etching process. Thus, TEM specimens of targeted thickness, shape and free of amorphous surface layers can be produced. Such lamellas are an elementary requirement for TEM analysis in order to avoid misinterpretations or even artifacts in the prepared material.The precision Argon ion mill enables gentle final preparation of TEM specimens of the highest quality and thus represents an essential extension of existing preparation methods.