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This work reports the CMOS compatible and monolithic fabrication of a conventional planar field effect transistor (FET) co-integrated with a quantum dot (QD) based single electron transistor (SET). The FET process fabrication is adapted to fulfill the restrictions imposed by the pre-fabricated SET, such as reduced thermal budget, extra protection layers and modified doping in order to obtain low threshold voltage. The resulting FET presents good subthreshold characteristics and the SET preserves its integrity at the end of the fabrication.

The inherent three-dimensional topology of vNWs imposes several constraints to their fabrication and their integration in other circuits. We present here the use of Hydrogen silsesquioxane (HSQ) for the fabrication of single electron transistors (SETs) based on vNWs.

A new caesium sputter negative ion source with planar ionizer for Accelerator Mass Spectrometry (AMS) is being built, regarding quantifying the ratios of long-lived cosmogenic radionuclides in micrometeorites. The focus of the ion source is on an optimal ion-optics design, together with a realization of new concepts for the construction and function of the ionizer, with the possibility of the precise in-situ adjustment of the ion-optical components, and optimization of the caesium ion beam and ion transport. In addition, the source is designed for operation with higher cathode voltage (up to 20 kV), which aims to increase the sputter rate of the sample, and in turn to increase the extracted negative current. Higher ion currents and better ion yields mean shorter measuring times, higher precision due to higher counting statistics and/or higher throughput of samples in an AMS runs. The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR’s Ion Beam Center for its essential contribution to the realization of this project.

Helium Ion Microscopy (HIM) has not been thoroughly exploited for biological studies addressing relevant questions that range from the cellular to the subcellular level. One of the benefits of HIM compared to other high-resolution imaging techniques is definitely the large depth of focus, sub-nm resolution, nm surface sensitivity, and especially that no sample coating is needed that can change the nanostructure morphology on the surface. The prerequisite to getting the most from the technique is thus the appropriate sample preparation. Besides, to get the most from understanding the addressed biological question, a successful correlative microscopy approach is necessary. This is best shown in our recently published study (H Kokot, Advanced Materials, 2020), where we have addressed one of the most critical issues in toxicology, that is the poor understanding of chronic inflammation initiation in lung tissue caused by inhaled nanoparticles, with the correlative microscopy approach using advanced multimodal optical microscopy and HIM. HIM nicely revealed the TiO2 nanotube organization and passivation on the cell surface and confirmed lipid and protein binding to the TiO2 surface (Figure below), identified as well by in silico simulations. In brief, HIM is an extremely powerful technique for the surface, and in the case of porous samples also in-depth morphology characterization on an nm scale. In combination with complementary imaging techniques and proper sample preparation, many relevant biological questions can be addressed and solved. Still, there are many limitations and challenges in cell preparation and imaging using helium ions, such as imaging of internal structures, definitely pursuing discussions and new developments in the future.

Ion beam induced amorphization of semiconductor nanostructures limits the applicability of ion beam processing to semiconductor nanostructures. Here, we present an approach that not only avoids this amorphization but in addition allows to tailor the lateral device dimensions of pillars and fins used in modern GAA and Fin-FET designs. Si nanopillars (diameter: 25–50 nm) have been irradiated by either 50 keV broad beam Si + or 25 keV focused Ne + beam from a helium ion microscope (HIM) at various temperatures using fluences of 2×10 16 cm −2 and higher. While at room temperature strong deformation of the nanopillars has been observed, the pillar shape is preserved above 325 ∘ C. This is attributed to ion beam induced amorphization of Si at low temperatures allowing plastic flow due to the ion hammering effect and surface capillary forces. Plastic deformation is suppressed for irradiation at elevated temperatures. Above 325 ∘ C, as confirmed by diffraction contrast in BF-TEM, the nanopillars remain crystalline, and are continuously thinned radially with increasing fluence down to 10 nm. This is due enhanced forward sputtering through the sidewalls of the pillar, and agrees well with 3D ballistic computer simulations. Supported by the H-2020 under Grant Agreement No. 688072.

The integration of an ion source having very high spatial resolution with a tandem accelerator is a long-standing concept for improving analytical selectivity and sensitivity by orders of magnitude [1]. Translating this design concept into reality has its challenges [e.g. 2,3], meaning this approach has seldom be used in the framework of geochemical research [e.g. 4]. Supporting a strong focus on natural, metallic and mineral resources, the Helmholtz Institute Freiberg for Resource Technology installed a so-called Super-SIMS at the Ion Beam Center at HZDR; this highly novel tool is devoted to the characterization of minerals and ores. The secondary ion beam from a CAMECA IMS 7f-auto is injected into the 6MV Dresden Accelerator Mass Spectrometry [5] facility, which quantitatively eliminates effectively all molecular species from the ion beam. We will present the current status of this initiative and will report on the performance parameters of the Dresden Super-SIMS as well as first results from halogen determinations in sphalerite and galena. Furthermore, we will describe our concepts for the quantification of these data at the ultratrace level. [1] Matteson (2008) Mass Spec Rev 27, 470-484. [2] Ender et al. (1997) NIMB 123 575-578. [3] Fahey et al. (2016) Anal Chem 88, 7145-7153. [4] Sie et al. (2000) NIMB 172, 228-234. [5] Rugel et al. (2016) NIMB 370 94-100.

Ion beam induced collateral damage is becoming an issue in FIB processing, as it limits the application of ion beams for nanostructure fabrication. This is of special importance for the application of focused ion beams for nanostructure fabrication. Here, we present an approach to mitigate the ion beam induced damage inflicted on semi - conductor nanostructures during ion beam irradiation. Nanopillars (with a diameter of 35 nm and a height of 70 nm) have been irradiated with both, a 50 keV Si + broad beam and a 25 keV focused Ne + beam from a helium ion microscope (HIM). Upon irradiation of the nanopillars at room temperature with a medium fluence (2x10 16 ions/cm2), strong plastic deformation has been observed which hinders further device integration. The shape and crystallinity has been studied by HIM and TEM. This differs from predictions made by Monte-Carlo based simulations using the TRI3DYN. However, irradiation at elevated tem- peratures with the same fluence not only preserves the shape of the nanopillars but allows for controlled diameter reduction by as much as 50 % without significant change in pillar height. It is well known that above a critical temperature amorphization of silicon is prevented in- dependent of the applied fluence. At high enough temperatures and for not too high flux this prevents the ion beam hammering and viscous flow of the nanostructures. These two effects are responsible for the shape change observed at low temperature. We find that ir- radiation above 650 K preserves the crystalline nature of the pillars and prevents viscous flow. In addition, a steady thinning process of the nanopillars to a diameter of 10 nm with- out a significant change in height is observed for higher fluencies at elevated temperatures. As the original pillar diameter is smaller than the size of the collision cascade, enhanced forward sputtering through the sidewalls of the pillar is responsible for this pillar-thinning effect. Results for various ion beam energies, fluencies, fluxes and temperatures will be presented and compared to TRI3DYN simulations. Such a reliable and CMOS-compatible process could serve as a potential down scaling technique for large-scale fabrication of nanostructure based electronics and many other FIB based milling applications.

The usage of ion beam irradiation on vertical nanopillar structures is a prerequisite for fabricating a CMOS-compatible, vertical gate-all-around(GAA) SET device. After either 50 keV broad beam Si+ or 25 keV focused Ne+ beam from a helium ion microscope (HIM) irradiation of the nanopillars (with diameter of 35 nm and height of 70 nm) at room temperature with a medium fluence (2e16 ions/cm2), strong plastic deformation has been observed which hinders further device integration. This differs from predictions made by the Monte-Carlo based simulations using the program TRI3DYN. We assume that it is the result from the ion beam induced amorphization of Si accompanied by the ion hammering effect. The amorphous nano-structure behaves viscously and the surface capillary force dictates the final shape. To confirm such a theory, ion irradiation at elevated temperatures (up to 672 K) has been performed and no plastic deformation was observed under these conditions. Bright-field transmission electron microscopy micrographs as well as Electron Beam Diffraction confirmed the crystallinity of the substrate and nanopillars after HT-irradiation. In addition, a steady thinning process of the nanopillars to a diameter of 10 nm has been observed at higher fluencies. As the original pillar diameter is comparable to the size of the collision cascade, instead of direct knock-on sputtering, enhanced forward sputtering through the sidewalls of the pillar is responsible for this effect. The relation between ion beam energy, flux and temperature with the observed thinning of the nanopillars has been studied experimentally and compared to TRI3DYN simulations. Such a reliable and CMOS-compatible process could serve as a potential downscaling technique for large-scale fabrication of nanopillar-based electronics.

Clear understanding of molecular events followed by lung epithelial cells/tissue response to inhaled nanoparticles is still lacking. As these interaction events in lungs eventually lead to diseases and potentially persistent inflammation [1,2], one urgently needs new and relevant investigation methods which could provide new insights into the key mechanisms of interaction. In our latest research we have thus focused on this toxicology problem first by developing an appropriate in vitro lung epithelial model and second by developing and implementing relevant advanced correlative imaging techniques capable of gathering more insight of interaction properties on scales well below optical resolution limit. In order to understand the mechanisms of molecular initiative events we have first performed live cell imaging using STED super-resolution microscopy by which few tens to hundred nm resolution was achieved locally. As the technique is incapable of providing resolution further down to nm and lacks the visualization of non-labeled surrounding structures and morphology, we thus introduced suitable complementary correlative microscopy techniques with high surface contrast, SEM and Helium Ion Microscopy (HIM). Main focus, besides sample and sample holder preparation for these high vacuum techniques, was dedicated to HIM measurements which in general are capable of providing better resolution and sensitivity compared to SEM [3]. From this ongoing study we briefly present the first interesting results of correlative microscopy combining optical, electron and ion based techniques on the epithelial cells exposed to TiO2 nanoparticles from micro to nano scale. References: 1. Li, X., Jin, L. & Kan, H. Air pollution: a global problem needs local fixes. Nature 570, 437–439 (2019). 2. Underwood, E. The polluted brain. Science 355, 342–345 (2017). 3. Hlawacek, G. et Al. Helium Ion Microscopy. J. Vac. Sci. Technol. 32, (2014)

The European H2020 project “ion4SET” is directed to the development of advanced computation and communication devices with significantly lower power consumption. The general objective is to demonstrate the manufacturability of single electron transistors (SETs) using CMOS compatible technology. The basic idea of this SET is a nano-pillar (NP) transistor having a single Si nanodot (ND) in the oxide layer separating source and drain. The ND is formed by ion beam mixing and post annealing from a Si top layer. The ion irradiation under normal incidence is a crucial process for the small nano-pillars which are only 10 to 30 nm in width and about 80 nm in height. In this work the evolution nano-pillars shape is investigated under heavy ion irradiation from a mass separated focused ion beam (FIB) for different ion energies at RT and 400°C target temperature. In particular Si (60 keV), Pb (30 and 60 keV), Au (30 and 60 keV) ions as well as polyatomic projectiles Au2 and Au3 (Uacc = 30 kV) with a fluence of 5 x 1015 cm-2 were applied. Whereas the Si ion irradiation of Si pillars at elevated temperatures only deforms the pillar tip, the heavy ion irradiation leads depending on the fluence up to a total removing of the pillar. The fluence variation was obtained on the slope of the beam profile. The irradiation at RT with Pb ions at 30 keV showed a more pronounced bending of the pillar due to the high energy deposition caused stress and viscous flow than that at 60 keV. The influence of the irradiation is also depending on the thickness and the distance of the pillars in different lithographic prepared fields. For a better comprehension of the irradiation results the experiments were simulated using the TRI3DYN code.

The transistor pathway predicts an evolution from lateral MOSFETs via FinFETs to vertical nanowire gate-all-around FETs (vNW GAA-FET). Our European project IONS4SET [1] goes a step further: Aiming at low-power electronics, the principle of operation of transistors will be changed from field effects to single electron tunneling via a Si quantum dot (QD) in SiO2. Room temperature (RT) operation of Single Electron Transistors (SETs) requires Si QDs of ~3 nm and tunneling distances of < 1 nm. The SiO2 with the embedded Si QD has to be ~ 5nm thick. To fabricate vNW GAA-SETs, Si nanopillars with ~5nm SiO2 have to be fabricated by Electron Beam Lithography and Reactive Ion Etching (RIE). Here we report on a dramatic SiO2 thickness reduction in the Si/SiO2/Si layer stack by RIE of nanopillars. It is strongly pillar diameter dependent: In 100 nm pillars the thickness remains almost unchanged, but for < 20nm it shrinks from 8nm to ~3nm as shown by Energy-Filtered Transmission Electron Beam Microscopy (EFTEM). Modeling, computer simulation and dedicated experiments reveal that it is due to a huge number of electric breakdowns during RIE. A breakdown forms a SiOx filament which emits O in SiO2. Each O atom of the SiO2 becomes many times an O interstitial, which in most cases recombines with an O vacancy. Depending on diameter, some O will emanate from the edge of the SiO2 disk leading to the dramatic oxide thinning. [1] This work has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 688072 (www.ions4set.eu).

Ion beam irradiation of vertical nanopillar structures may be utilized to fabricate a vertical gate-all-around (GAA) single electron transistor (SET) device in a CMOS-compatible way. After irradiation of Si nanopillars (with a diameter of 35 nm and a height of 70 nm) by either 50 keV broad beam Si+ or 25 keV focused Ne+ beam from a helium ion microscope (HIM) at room temperature and a fluence of 2e16 ions/cm2, strong deformation of the nanopillars has been observed which hinders further device integration. This is attributed to ion beam induced amorphization of Si allowing plastic flow due to the ion hammering effect, which, in connection with surface capillary forces, dictates the final shape. However, plastic deformation can be suppressed under irradiation at elevated temperatures (investigated up to 672 K). Then, as confirmed by bright-field transmission electron microscopy, the substrate and the nanopillars remain crystalline and are continuously thinned radially with increasing fluence down to a diameter of 10 nm. This is attributed to enhanced forward sputtering through the sidewalls of the pillar and found in reasonable quantitative agreement with the predictions from 3D ballistic computer simulation using the TRI3DYN program. This work is supported by the European Union’s H-2020 research project ‘IONS4SET’ under Grant Agreement No. 688072.

A single sheet of Si nanoclusters with an average diameter of about 2 nm has been formed in a 30 nm Si / 7 nm SiO2 / Si layer stack by 50 and 60 keV Si+ ion-beam mixing at room temperature and fluences between 8.51015 and 2.61016 ions/cm2, and subsequent thermal annealing at a temperature above 1000°C. Computer modelling of the process is accomplished by TRIDYN dynamic ballistic simulation of ion mixing and subsequent lattice kinetic Monte Carlo simulation of the phase decomposition of sub-stoichiometric silicon oxide into Si nanoclusters in a SiO2 matrix. The simulation algorithms are briefly described with special emphasis on the choice of governing parameters for the present system. In comparison to the experimental results it is concluded that the predicted ion mixing profiles overestimate the interface broadening. This discrepancy is attributed to the neglect of chemical driving forces in connection with thermal-spike induced diffusion, which tends to re-constitute the Si/SiO2 interfaces. With a corresponding correction and a suitable number of Monte Carlo steps, the experimentally obtained areal densities and average diameters of the nanoclusters are successfully reproduced.

Helium Ion Microscopy (HIM) [1, 2] is best known for its high resolution imaging capabilities of both conductive as well as insulating samples. However, since the introduction of Ne as an imaging gas for the gas field ion source (GFIS) an increasing number of nano-fabrication applications are realized. While the use of Neon as an imaging gas results in a somewhat lower lateral resolution (1.8 nm for 25 keV Ne compared to 0.5 nm for 30 keV He) the user usually benefits from the much higher cross section for nuclear stopping. The latter results in a larger number of sputtered atoms and bonds broken directly by small impact parameter collisions. After a brief introduction of the technique I will present results obtained using direct write milling low fluence ion beam irradiation and ion beam based mixing. In all three cases the electronic or magnetic properties of the target material will be altered at the nano-scale in a controlled way to achieve new functionality. The examples comprise ∙ The fabrication of semiconducting graphene nano-ribbons by direct milling [3] ∙ The fabrication of a lateral spin valve structure using low fluence ion irradiation [4] ∙ The formation of individual 3 nm Si clusters for a room temperature single electron transistor [5] For all presented examples the critical length scale of the nanostructure is smaller or in the range of collision cascade. This size regime can not be accessed with traditional broad beam based ion irradiation and holds many promises but also challenges that need to be overcome to enable new device concepts and new functional materials on the nano-scale. This work is supported by the European Union’s H-2020 research project ‘IONS4SET’ under Grant Agreement No. 688072