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Indistinguishable single-photon sources at telecom wavelengths are the key photonic qubits for transmitting quantum information over long distances in standard optical fibers with minimal transmission losses and high fidelity. This enables secure quantum communication over the quantum internet and, in turn, a modular approach to quantum computing. The monolithic integration of single-photon sources with reconfigurable photonic elements and single-photon detectors in a silicon chip is a key enabling step toward demonstrating scalable quantum hardware such as quantum photonic integrated circuits (QPICs). Nowadays, nearly all the necessary components for QPICs are available such as superconducting single-photon detectors, low-loss photonic waveguides, delay lines, modulators, phase shifters, and low-latency electronics. Yet, the practical implementation of scalable quantum hardware has been largely hampered by the lack of on-chip single-photon emitters in silicon that can be created at desired locations on the nanoscale. Here, we demonstrate two complementary wafer-level protocols for the creation of single telecom-wavelength color centers in silicon with a probability exceeding 50%. Both approaches are fully compatible with current silicon technology and enable the scalability of millions of single telecom quantum emitters that are created at desired nanoscale positions on a silicon chip. These results unlock a clear pathway for industrial-scale QPICs.

Raw data for the publication: "Epitaxial lateral overgrowth of tin spheres driven and directly observed by helium ion microscopy". It contains helium ion microscopy, transmission electron microscopy, scanning electron microscopy as well as gallium focused ion microscopy images and XPS data. It shows how the irradiation of tin spheres with keV He ions causes epitaxial lateral overgrowth.

Most approaches to implant single or few ions for quantum applications require the use of focused ion beams (FIB). In addition to the detection of ion implantation and laterally precise placement, the first consideration should also be the species as well as the emittance of the ion beam itself. While elements that are gaseous at room temperature can mainly provided by Gas Field Ion Sources or Plasma Ion Sources, most of the metals and semimetals afford the utilization of Liquid Metal Ion Sources (LMIS). Gallium has established in industry and science as easiest and most stable type of LMIS. For quantum applications other ion species like Li, B, C, N, Al, Si, P, Sb, Bi or the rare earth elements became from higher interest [1-6]. We give an overview about published metal alloys for FIBs and give an insight into the development and production of new sources. Finally, we give an outlook on current and future applications and activities. [1] L. Bischoff, et al., Micro Eng. 13, 367 (1991), 10.1016/0167-9317(91)90113-R [2] P. Mazarov, et al., JVST B 27, L47-L49 (2009), 10.1116/1.3253471 [3] L. Bischoff, et al., Appl. Phys. Rev. 3, 021101 (2016), 10.1063/1.4947095 [4] W. Pilz, et al., JVST B 37, 021802 (2019), 10.1116/1.5086271 [5] L. Bischoff, et al., JVST B 38, 042801 (2020), 10.1116/6.0000073 [6] N. Klingner, et al., BJNANO 11, 1742 (2020), 10.3762/bjnano.11.156

We have successfully employed high-brightness liquid metal ion sources (LMIS) for the investigation of the interaction of metal and metalloid ions with strong field laser beams. The gold and silicon ions, generated in the LMIS by electrostatic field ionization, can be further ionized up to Au11+ and Si4+ with Thales laser (1 kHz) at intensities of up to 4e16 W/cm2. Furthermore, we employed the fiber laser with 100 kHz to manipulate the recoil momenta with subcycle resolution.

Broad ion beams have shown their wide applications for materials modification. Focused ion beams can be used in a similar way while simultaneously providing process monitoring. Here, we demonstrate this on a new kind of ion-induced structural evolution. Sub-micrometer Sn spheres were irradiated in a helium ion microscope with a sub-nm beam of 30 keV He ions. Above a fluence of ~10^17/cm², Sn extrusions appeared on the surface of the spheres, which were imaged using the secondary electron signal. Initially, small, pyramid-like faceted extrusions form at the equator of the spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered by the extrusions. A model was developed that assumes that each He ion generate ~70 Frenkel pairs. The implanted helium atoms, interstitials, and vacancies will be confined by the oxide skin of the spheres. Some He atoms will occupy vacancies, which partially prevent their recombination with interstitials. Furthermore, the ion irradiation leads to erosion and opening of the SnO skin. The interstitials can now escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the exterior. Transmission electron microscopy, Auger electron spectroscopy as well as TRI3DYN [1] and 3D kinetic lattice Monte Carlo [2] simulations support these findings. In addition, we provide a perspective on focused ion beams from our in-house development and production of liquid metal alloy ion sources, which can be used for applications from self-organized patterning, over altering magnetic or electrical properties, to quantum photonics and computation [3]. [1] Möller, Nucl. Instr. Meth. B 322 (2014) 23 [2] Strobel et al., Phys. Rev. B 64 (2001) 245422 [3] www.hzdr.de/fib

We present results for direct maskless magnetic patterning of ferromagnetic nanostructures using a special liquid metal alloy ion source for focused ion beam (FIB) systems. We used a Co36Nd64 alloy as the FIB source [1]. A Wien mass filter allows for quick switching between the ion species in the alloy without changing the FIB source. A 5000×1000×50 nm3 permalloy strip served as the sample. Using the FIB we implanted a 300-nm-wide track with Co ions (see Fig.1). We observed the Co-induced changes by measuring the sample with microresonator ferromagnetic resonance before and after the implantation. Structures as small as 30 nm can be implanted up to a concentration of 10 % near the surface. Such lateral resolution is hard to reach for other lithographic methods. This allows for easy magnetic modification of edge-localized spin waves. In another set of samples, we implanted Dy ions to locally increase the damping in a stripe pattern of ~120-nm-wide strips with 400 nm periodicity on a total area of 1×1 mm². Thus, the Gilbert damping parameter can be easily increased by one order of magnitude with a lateral resolution of about 100 nm. In contrast to electron beam lithography in combination with broad-beam ion implantation, the maskless FIB process does not require the cumbersome and difficult removal of the ion-hardened resist if optical measurements like BLS or TR-MOKE are needed.

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. Therefore, we have extended the FIB technology towards the stable delivery of multiple ion species by liquid metal alloy ion sources (LMAIS) [2]. These LMAIS provides single and multiple charged ion species of different masses. As an example we introduce the GaBiLi LMAIS [3]. Such “universal” source enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from the same ion source. Light ions are of increasing interest due to the available high resolution in the nanometer range and their special chemical and physical behavior in the substrate. We compare helium and neon ion beams from a helium ion microscope with beams such as lithium, boron, and silicon, obtained from a mass-separated FIB using a LMAIS with respect to the imaging and milling resolution, as well as the current stability [4]. The bombardment of solids by poly-atomic (cluster) ions leads to nonlinear collision cascades in near-surface regions. In comparison with linear cascades by monoatomic ions, much higher energy deposition occurs up to local surface melting [5]. Here, we also report the study on the sputter yield of Si under the bombardment by atomic Bi+ and cluster Bin+ (n = 2-4) ions with the same specific energy related to one incidence single atom [6]. [1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63 (2020) 1219. [2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101. [3] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37(2), Mar/Apr (2019) 021802. [4] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, L. Bischoff, Imaging and Milling Resolution of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs, Beilstein J. Nanotechnol. 11 (2020) 1742. [5] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko, and W. Pilz, Self-organization of Ge nanopattern under erosion with heavy Bi monomer and cluster ions, Nucl. Instr. Meth. B 272 (2012) 198. [6] A. Tolstogouzov, P. Mazarov, A. Ieshkin, S.Belykh, N. Korobeishchikov, V. Pelenovich, D.J. Fu, Sputtering of silicon by atomic and cluster bismuth ions: An influence of projectile nuclearity and specific kinetic energy on the sputter yield, Vacuum 188 (2021) 110188.

Extreme states of matter exist throughout the universe e.g. inside planetary cores, stars or astrophysical jets. Such conditions can be generated in the laboratory in the interaction of powerful lasers with solids. Yet, the measurement of the subsequent plasma dynamics with regard to density, temperature and ionization is a major experimental challenge. However, ultra-short X-ray pulses provided by X-ray free electron lasers (XFELs) allow for dedicated studies, which are highly relevant to study laboratory astrophysics, laser-fusion research or laser-plasma-based particle acceleration. Here, we report on experiments that employ a novel ultrafast method, which allows to simultaneously access temperature, ionization state and nanometer scale expansion dynamics in high-intensity laser-driven solid-density plasmas with a single X-ray detector. Using this method, we gain access to the expansion dynamics of a buried layer in compound samples, and we measure opacity changes arising from bound-bound resonance transitions in highly ionized copper. The presence of highly ionized copper leads to a temperature estimate of at least 2 million Kelvin already after the first 100 femtoseconds following the high-intensity laser irradiation. More specifically, we make use of asymmetries in small-angle X-ray scattering (SAXS) patterns, which arise from different spatial distributions of absorption and scattering cross sections in nanostructured grating samples when we tune an XFEL to atomic resonant energies of copper. Thereby, changes in asymmetry can be connected with the evolution of the plasma expansion and ionization dynamics. The potential of XFEL-based resonant SAXS to obtain three-dimensional ultrafast, nanoscopic information on density and opacity may offer a unique path for the characterization of dynamic processes in High Energy Density plasmas.

Ion-irradiation and the induced nanostructuring was found, over the last century, to be a very powerful technique for surface modifications on a vast amount of different materials. Especially the formation of nanostructures by strong electronic excitation mediated by slow highly charged ions and swift heavy ions received lots of interest in recent years. The ionic crystal CaF2 was a model system for the underlying processes. In our investigations we reveal the formation of nano-hillocks by slow individual Au-cluster-irradiation on CaF2(111) surface that were found to be very similar to nano-hillocks in former studies with highly charged ions. We show that the high energy density directly transferred to the atomic lattice of the target leads to the same hillock-like structures as in case of indirect energy transfer for slow highly charged ions.

Gold and silicon ions emitted from high brightness liquid metal ion sources (LMIS) are used as ionic targets for strong field laser interaction with femtosecond laser beams. Field ionization processes in the field emission source at electrostatic fields of some 10 V/nm allow the generation of various metallic and metalloid ion beams with charge states such as Au2+ and Si2+. Studying the ionization in strong femtosecond laser fields with intensities of up to 1016 W/cm2, we observed for these elements charge states of up to Au11+ and Si4+.

Focused Ion Beam (FIB) processing is established as a well-suited and promising technique in R&D in nearly all fields of nanotechnology for patterning and prototyping on the μm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent an alternative to expand the FIB application fields beside all other source concepts [1]. Due to the interest on light elements, especially boron, various alloys were investigated and characterized. In this contribution we will describe Co31Nd64B5 as the most promising alloy in more detail. The mass spectrum of such a source was obtained in a VELION FIB-SEM system (Raith GmbH) [2]. The source operation life time was longer than 600 μAh and a first imaging characterization showed a lateral resolution of (30 ± 5) nm so far. This LMAIS is suited for several mass-filtered FIB applications like implantation, high rate sputtering, surface patterning or ion lithography [3]. The switching between the certain ion species. B – very light, suitable for ion lithography or writing p-type doping. Co – medium mass for applications in the field of nano-magnetics or CoSi2 for ion beam synthesis of conductive nano-structures on Si. Finally Nd as double charged heavy ion for ion sputtering. The change between ion species can be done in seconds and leads to remarkable expansion of the application spectrum of FIB technology. [1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources - An Alternative for Focused Ion Beam Technology; Appl. Phys. Rev. 3 (2016) 021101. [2] L. Bischoff, N. Klingner, P. Mazarov, W. Pilz, and F. Meyer, Boron Liquid Metal Alloy Ion Sources for special FIB applications, JVST B 38 (2020) 042801. [3] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of Technologies for Nano Device Prototyping with a Special Focus on Ion Beams – A Review, Appl. Phys. Rev. 4 (2017), 011302.

Light ions are of increasing interest by application of focused ion beam (FIB) techniques due to the available high beam resolution in the nanometer range and their special chemical and physical behavior in the substrate [1, 2]. We compare helium and neon ion beams from a helium ion microscope with ion beams such as lithium, 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 [3]. While He+ offers, experimentally and in simulations, the smallest minimum trench width, light ion species such as Li+ from a LMAIS [4] 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 and time for milling. References [1] L. Bischoff et al., Appl. Phys. Rev. 3 021101 (2016). [2] P. Mazarov et al., Phys. Usp. 63 1219–1255 (2020). [3] N. Klingner et al., Beilstein J. Nanotechnol. 11 1742–1749 (2020). [4] W. Pilz et al., JVSTB 37 021802 (2019).

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. In addition, nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution and stability [2]. Therefore, we have extended the technology towards a stable supply of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [3]. This LMAIS provides single and multiple charged ion species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are thus made available in the FIB technology because of continuous research in this area [4]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution, the operation principle, first results and prospective domains for modern FIB applications will be presented. As examples, we will introduce the AuGeSi and GaBiLi LMAIS [5, 6]. Both sources provide light and heavy ions available from a single source to tailor chemical and physical properties of resulting nanostructures. GaBiLi enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source. [1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63, 1219 (2020). [2] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017). [3] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3, 021101 (2016). [4] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018). [5] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019). [6] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, and L. Bischoff, Imaging and milling resolution of light ion beams from helium ion microscopy and FIBs driven by liquid metal alloy ion sources, Beilstein J. Nanotechnol. 11, 1742 (2020).

In this work, we have generated ion beam targets of metal and metalloid ions using a high-brightness liquid metal ion source (LMIS) originally applied in focused ion beam systems. Using an eutectic Au-Si alloy as a low melting point source feed material, ions of different ion species were detected: Si^{2+}, Si^+, Au^{2+}, Au^+, Au^{2+}, Au^{3+} and Au^{32+}. The source current between emitter needle and extractor electrode is in the range of 10 - 60 μA and can be adjusted up to about 150 μA. The ion source is characterized by high ion current stability and a suitable emission lifetime of several days, which is limited by the amount of material and can be further increased. To study the strong-field laser ionization, we used a E x B filter and selected Si^{2+} and Au+ ions as ionic targets, because of their high beam intensity. We investigated ultrafast laser-induced ionization, which leads to higher charge states after multiple ionization of both ion species. Laser intensities of up to 10^{16} W/cm^2 allow observation of up to 10-fold ionization of Au^+ ions and 3-fold ionization of Si^{2+} ions. The aim of further work is to extend the available ion beam targets to other elements of the periodic table to study ultrafast laser-induced fragmentation and ionization dynamics of atoms and molecules in strong laser fields. Another goal is the further increase of the density of ion laser targets for more reliable statistics and shorter measurement times. Further steps are technical improvements of ion source and ion optics as well as the investigation of heavy metal dimers such as Au^{2+}.

Au and Si ions from high brightness liquid metal ion sources (LMIS) are used as ionic targets for strong-field laser interaction with femtosecond laser beam. Field ionization processes in the field emission source at electrostatic fields of some 10 V/nm allow the generation of various metallic and metalloid ion beams with charge states such as Au^{2+} and Si^{2+}. Studying the ionization in strong femtosecond laser fields with intensities of up to 1E16 W/cm^2, we observed for these elements charge states up to Au^{11+} and Si^{4+}.

Resonant Small-angle x-ray scattering raw data obtained in measurements at MEC at LCLS and evalutation of the asymmetry in the scattering patterns. The data set is structured in case 1/Si-Cu-compound targets and case 2/Cu-only-targets as presented in the publication for on- and off-resonant XFEL probe energies.

Spatially resolved tunable diode-laser absorption measurements of the absolute densities of He-I (23S1) metastables in a micro atmospheric pressure plasma jet operated in He/N2 and driven by 'peaks'- and 'valleys'-type tailored voltage waveforms are presented. The measurements are performed at different nitrogen admixture concentrations and peak-to-peak voltages with waveforms that consist of up to four consecutive harmonics of the fundamental frequency of 13.56 MHz. Comparisons of the measured metastable densities with those obtained from particle-in-cell/Monte Carlo collision simulations show a good quantitative agreement. The density of helium metastables is found to be significantly enhanced by increasing the number of consecutive driving harmonics. Their generation can be further optimized by tuning the peak-to-peak voltage amplitude and the concentration of the reactive gas admixture. These findings are understood based on detailed fundamental insights into the spatio-temporal electron dynamics gained from the simulations, which show that voltage waveform tailoring allows to control the electron energy distribution function to optimize the metastable generation. A high degree of correlation between the metastable creation rate and the electron impact excitation rate from the helium ground state into the He-I ((3s)3S1) level is observed for some conditions which may facilitate an estimation of the metastable densities based on phase resolved optical emission spectroscopy measurements of the 706.5 nm He-I line originating from the above level and metastable density values at proper reference conditions.

The application of Focused Ion Beams (FIB) has become a well-established and promising technique for patterning and prototyping on the nm-scale in research and development. 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 nm range and their special chemical and physical behavior in the substrate. In this work helium and neon ion beams from a Helium Ion Microscope (HIM) are compared with ion beams like beryllium, lithium, boron, carbon and silicon obtained from a mass separated FIB using Liquid Metal Alloy Ion Sources (LMAIS) with respect to their imaging and milling resolution.

Si nanopillars for the fabrication of vertical nanowire gate-all-around Single Electron Transistors [1], have been irradiated with Si++, Pb+, Pb++, Au +, Au++, Au2 +, and Au3 + ions accelerated by 30 kV. A FIB of mass separated ions, extracted from a Liquid Metal Alloy Ion Source [2], has been scanned over regular arrays of Si nanopillars of different diameters and pillar distances. The irradiations have been performed at RT and 400∘C. Different morphological changes of the pillars like thinning, height reduction, tilting etc. have been observed which can be attributed to ion erosion (sputtering), impact-induced viscous flow or even transient nanosecond-scale melting [3]. The pillars were imaged by AFM, SEM, TEM and HIM. 3D Monte Carlo simulations [4] of ion and recoil trajectories based on the Binary Collision Approximation and Molecular Dynamics calculations have been carried out in order to discriminate the dominating processes. [1] EU project Ions4SET, Horizon 2020 grant No. 688072 [2] L.Bischoff, et al., Appl. Phys. Rev. 3 (2016) 021101 [3] C. Anders, K.-H. Heinig, H. Urbassek, Phys. Rev. B87 (2013) 245434 [4] W. Möller,NIM B322 (2014) 23

Atmospheric pressure capacitively coupled radio frequency discharges operated in He/N2 mixtures and driven by tailored voltage waveforms are investigated experimentally using a COST microplasma reference jet and by means of kinetic simulations as a function of the reactive gas admixture and the number of consecutive harmonics used to drive the plasma. Pulse-type 'peaks'-waveforms, that consist of up to four consecutive harmonics of the fundamental frequency (f = 13.56 MHz), are used at a fixed peak-to-peak voltage of 400 V. Based on an excellent agreement between experimental and simulation results with respect to the DC self-bias and the spatio-temporal electron impact excitation dynamics, we demonstrate that Voltage Waveform Tailoring allows for the control of the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and, thus, the generation of atomic nitrogen as well as helium metastables, which are highly relevant for a variety of technological and biomedical applications. By tuning the number of driving frequencies and the reactive gas admixture, the generation of these important species can be optimised. The behaviour of the DC self-bias, which is different compared to that in low pressure capacitive radio frequency plasmas, is understood based on an analytical model.

Nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution, stability and the support of new processing techniques. Additionally, the type of ion defines the nature of the interaction mechanism with the sample and thus has significant consequences on the resulting nanostructures [1]. Therefore, we have extended the technology towards the stable delivery of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [2]. This LMAIS provides single and multiple charged mon- as well as polyatomic ion species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are thus made available in the FIB technology as a result of continuous research in this area [3]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution, the operation principle, the preparation and testing process as well as prospective domains for modern FIB applications will be presented. As an example we will introduce the GaBiLi LMAIS. It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the AuSiGe-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source. [1] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017). [2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101. [3] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36 (2018). [4] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37(2), Mar/Apr (2019).

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 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.

Focused Ion Beams (FIB) gain an increasing interest in the field of nanotechnology particular for prototyping of microelectronic devices, patterning of 2D materials, high resolution imaging or high resolution ion lithography1. Concerning ion beam resolution and minimization of unwanted damage, light ions like He or Li are preferred candidates. Liquid metal alloy ion sources (LMAIS) with a life time of more than 1000 µAh on the basis of Ga35Bi60Li5 and Sn95Li5 alloys were developed, characterized and finally applied in a commercial mass-separated VELION FIB-SEM system (Raith GmbH). The resolution for imaging and also for the formation of nanostructures using a thin gold film was determined. In the case of Li ions from the mass separated FIB a lateral resolution of 5.6 nm could be obtained in first experiments2 and the sputter yield was determined to 0.4 for 35 keV Li ions on Au. For reference, the helium ion microscope (HIM) has a lateral resolution of about 0.5 nm and 1.8 nm, for He and Ne respectively, He has a sputter yield of 0.13. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the SnLi-FIB could therefore be considered alternatives to the HIM with the benefit of providing additional ion species in a mass separated FIB without changing the ion source. 1 L. Bischoff et al. Appl. Phys. Rev. 3, 021 101 (2016). 2 W. Pilz et al. J. Vac. Sci. Technol. B A-18-399 (submitted, 2018). 3 G. Hlawacek et al. J. Vac. Sci. Technol. B 32, 020 801 (2014).

Soft robots have been designed and developed to fulfil the demands of better deformability and adaptability to changing environment [1-2]. These soft robots could be made of various stimuli responsive materials that can be actuated by magnetic field [3], light [4], temperature [5], electric fields [6], chemicals [7], pressure [8], etc. In contrast to other actuation mechanisms, magnetic fields are appealing for numerous application scenarios (e.g. environmental, biological, medical), where the benefits stem from their long-range penetration, easy accessibility, and controllability [2]. Very recently, there are already impressive demonstrations of magnetically triggered millimetre- and centimetre- scaled soft robots performing multimodal locomotion [9] and complex 3D actuations [10]. However, their thick and bulky bodies [9-10] challenge themselves to reveal better performances for specific implantations which require more, for instance, high actuation speed, and reversible large-scale actuation amplitude by a rather low magnetic field. Here, we present an ultrathin (7-100 μm) and lightweight (1.2-2.4 g/cm3) soft robot that can be actuated in a tiny magnetic field of 0.2 mT reaching full actuation amplitude with a reaction time of 10 ms only. By programming the foils into different geometries, these soft robots are readily used for multifunctional nature-mimicking motion with a magnetic coil or a permanent magnet, such as a quick fly gripping and releasing, complex fast human cross-clapping mimicking, etc. [1] D. Rus et al., Nature 521, 467 (2015) [2] L. Hines et al., Adv. Mater. 29, 13 (2017) [3] J. Y. Kim et al., Nature materials 10, 747 (2011) [4] J. Deng et al., J. Am. Chem. Soc. 138, 225 (2016) [5] Y. S. Kim et al., Nature Materials 14, 1002 (2015) [6] T. Mirfakhrai et al., Materials Today, 10, 30 (2007) [7] Q. Zhao et al., Nature communications 5 (2014) [8] SA. Morin et al., Science, 337, 828 (2012) [9] W. Hu et al., Nature, 554, 81(2018) [10] Kim. Y, et al., Nature, 558, 274 (2018)

Focused Ion Beam (FIB) processing has been developed into a well-established and still promising technique for direct patterning and proto-typing on the nm scale. Exploring the Liquid Metal Alloy Ion Sources (LMAIS) potential represents a promising alternative to expand the global FIB application fields. Especially, Ion Beam Lithography (IBL) as direct, resistless and three-dimensional patterning enables a simultaneous in-situ process control by cross-sectioning and inspection. Thanks to this, nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources to an alternative technology feasible for nano-patterning challenges, e.g. to tune electrical, optical, magnetic or mechanical properties. In this contribution the operation principle, the preparation and testing process as well as prospective domains for modern FIB applications will be presented. As an example we will introduce a Ga35Bi60Li5 LMAIS in detail. It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Appl. Phys. Rev. 3, 021101 (2016).

Focused Ion Beam (FIB) processing has been developed into a well-established and still promising technique in nearly all fields of nano-technology in particular for direct patterning and proto-typing on the µm scale and well below. Beside new ion source developments based on gas field emission (GFIS), on ionic liquids (ILIS), on magneto-optical traps (MOTIS) or on ICP or ECR sources for Xe-FIB as well as the nearly exclusively used gallium Liquid Metal Ion Sources (LMIS), the replacement of Ga by alloys therein with an adapted FIB optics design can open bright field of new employments. Local ion implantation, ion beam mixing, ion beam synthesis or Focused Ion Beam Lithography (IBL) in the µm- or nm range can benefit from ion species purposely selected in parallel to gallium or noble gases. Therefore, exploring the Liquid Metal Alloy Ion Sources (LMAIS) potential represent a promising alternative to expand the global FIB application fields. Especially, IBL as direct, resistless and three-dimensional patterning enables a simultaneous in-situ process control by cross-sectioning and inspection. Thanks to this nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources as an alternative technology feasible for nano patterning challenges e.g. to tune electrical, optical, magnetic or mechanic properties. In this contribution the operation principle, the preparation and testing technology as well as prospective domains for modern FIB applications will be presented. As an example we will introduce a Ga35Bi60Li5 LMAIS in detail. It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Appl. Phys. Rev. 3, 021101 (2016).

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

The transistor pathway predicts an evolution from lateral MOSFETs via FinFETs to vertical nanowire gate-all-around FETs (vNW GAA-FET). Aiming at low-power electronics we replace the channel of the vNW GAA-FET by a SiO2 layer with an embedded Si Quantum Dot (QD), thus manufacturing a Single Electron Transistor (SET). To achieve room temperature (RT) operation of the vNW GAA-SET, Si QDs of ~3 nm diameter and tunneling distances of < 1 nm have to be manufactured. This is far beyond the present possibilities of lithography. The challenge of such tiny structures has been solved in the framework of our European project IONS4SET [1] by means of a controlled self-organization and self-alignment process. Nanopillars with diameters down to ~20nm have been fabricated from Si/SiO2/Si layer stacks by Electron Beam Lithography and Reactive Ion Etching (RIE), a further diameter reduction to ~10nm has been achieved by sacrificial plasma oxidation. Before RIE the SiO2 layer is transferred to SiOx by Si+ ion beam mixing, which allows a controlled self-organization of a Si QD during thermally activated phase separation using RTA. During phase separation the Si QD becomes also self-aligned with respect of the upper and lower Si, thus forming the tunnel distances of ~1nm. [1] This work has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 688072 (www.ions4set.eu).