Low Dimensional Materials

Our group is developing novel synthesis routes for low dimensional nanostructures & nanomaterials using state of the art deposition techniques and their combinations: atomic layer deposition (ALD), physical vapour deposition (PVD), and local focused electron and ion beam induced chemical vapour deposition (FEBID, FIBID).
Our R&D activities are driven by finding novel nanostructured materials for sustainable energy technology, nanotechnology, and health issues. Special focus is given to the development of:

i) Non-conventional nanodevice prototyping: using and developing our state-of-the art, minimally invasive, maskless, resistless, direct write focused electron/ion beam technique allows us to locally add or remove functional nanomaterial at nanometer scale – to refine, functionalize, or prototype sensors, telecom lasers, or scanning probe tips individually at will in a single-step post-process step.

ii) Functionalization of non-planar substrate architectures: developing ALD for conformal coatings of high-aspect ratio, non-planar substrate architectures, like nanowire or nanotube carpets, perforated membranes, or polystyrene beads.

iii) Development of novel low dimensional nanomaterials: using and developing sequential and co-evaporation concepts for PVD, ALD, and FEB/FIB assisted CVD for thin multilayer films, nano-composites, core-shell structures, and nanowires.

iv) Development of SEM integrated characterization tools: composition, shape, mechanical and electrical properties, gas injection systems.

Minimally invasive nanomaterial synthesis with local focused electron and ion beam induced chemistry

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Minimally invasive FEBIP & FIBIP examples.

Gas assisted Focused Electron/Ion Beam Induced Processing (also known under the acronyms FEBIP and FIBIP) constitutes a non-conventional rapid prototyping platform which allows for synthesis (deposition and etching) of conventional and novel materials for nanodevices. We investigate a) the underlying key physico-chemical processes to gain compositional and shape control over the process, b) the synthesized novel granular and nanocomposite material with respect to electrical, magnetical, mechanical, and op-tical properties using specifically developed SEM-integrated meas-urement setups, c) develop nanodevice prototypes, like magnetic bead sensors, polarization gratings for telecom lasers, and tip en-hanced Raman spectroscopy.

Highlight: I. Utke and A. Goelzhaeuser, Small, Minimally Invasive, Direct: Electrons Induce Local Reactions of Adsorbed Functional Molecules on the Nanoscale, Angew. Chem. Intl. Ed. 49(49) (2010) 9328, DOI: 10.1002/anie.201002677.

Featured: M. Gabureac et al., Granular Co-C nano-Hall sensors by focused-beam-induced deposition, Nanotechnology 21 (11) (2010) 115503, DOI: 10.1088/0957-4484/21/11/115503.

M. Jenke et al., Toward Local Growth of Individual Nanowires on Three-Dimensional Microstructures by Using a Minimally Invasive Catalyst Templating Method, Nanoletters 11(10) (2011) 4213, DOI: 10.1021/nl2021448.

L. Bernau et al. Tunable Nanosynthesis of Composite Materials by Electron-Impact Reaction, Angew. Chem. Intl. Ed. 49 (47) (2010) 8880, DOI: 10.1002/anie.201004220.

Review: I. Utke, P. Hoffmann and J. Melngailis, Gas Assisted fo-cused electron beam and ion beam processing and fabrication, J. Vac. Sci. Technol. B 26 (2008) 1198-1276.

SEM „add on“ Developments

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Scheme of GIS with imping-ing flux simulation

GIS in SEM
Together with Alemnis we develops gas injection systems systems for FEB/FIB induced processing. We also developed a free-ware GIS Simulator program based on the three-dimensional test-particle Monte Carlo method for rarefied gas flow tube which predicts the gas flux Distribution impinging on a substrate when exiting the circular tube. Different tube exit ge-ometries can be chosen: straight, bevelled with FEB/FIB access hole, doubly perforated closed tube, conical tube. The simulations were verified against experimentally measured flux distributions.
Related papers: V. Friedli and I. Utke, Optimized molecule supply from nozzle-based gas injection systems for focused electron- and ion-beam induced deposition and etching: simulation and experiment. J. Phys. D: Appl. Phys. 42 (2009) 125305 (11pp), doi:10.1088/0022-3727/42/12/125305

The latest version of the GIS Simulator program can freely be downloaded from our server. Please consider the use restrictions and report strange behaviour or unexpected results. In this way you can help us to improve the program.
Download the free GIS Simulator software (Windows XP, beta Version 1.5, June 2008, 1.0 MB)

AFM in SEM

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SEM integrated AFM using an A-Probe (Nanosensors™)
A scanning probe and scanning electron hybrid microscope has been developed which transforms the standalone instruments into a univer-sal, versatile nano-analysis and nano-manipulation instrument. Besides AFM topography/roughness measurements on nanostructures, e.g. produced by FIB milling and FIB/FEB induced deposition and etching, additional surface analytical techniques available in SEMs, e.g. energy-dispersive X-ray spectroscopy, allow to characterize the material on the same sample location.

SEM integrated mass sensor

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Mass sensor for in situ pro-cess control
We develop cantilever-based mass and force sensors for use inside a scanning electron microscope. The mass sensor allows quantifying the molecule coverage, the mean residence time of the adsorption - de-sorption equilibrium, the deposit density, and deposition and etch yields. In particular, in situ frequency tracking during deposition and etching with a sensitivity of 1 fg was achieved. This is equivalent to a half sphere of 60 nm radius etched into Si.

Related paper: V. Friedli et al, Mass sensor for in-situ monitoring the focused ion and electron beam induced processes, Appl. Phys. Lett. 90 (2007) 053106.

SEM integrated force sensors

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Nanopillar vibration test

Cantilever based force sensors and vibration setups were developed to measure the deflection and resonant behaviour of FEB/FIB deposited nanowires inside a scanning electron microscope. Image tracking software and finite element analysis are employed to determine Young’s modulus and the density from the SEM observations.

Related book chapter: V.Friedli et al. “AFM Sensors in Scanning Electron and Ion Microscopes: Tools for Nanomechanics, Nano-analytics, and Nanofabrication”, Applied Scanning Probe Methods VIII, Eds. B. Bushan, H. Fuchs, M. Tomitori, Springer 2008, Series: NanoScience and Technology (www.springer.com/978-3-540-74079-7).
V. Friedli, I. Utke, K. Mølhave and J. Michler, Dose and energy de-pendence of mechanical properties of focused electron-beam-induced pillar deposits from Cu(C5HF6O2)2. Nanotechnology 20 (2009) 385304 (11pp), doi:10.1088/0957-4484/20/38/385304

Micro-Plasma assisted charged particle beam sur-face processing

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Microplasma assisted FEBID
Presently, the number of pure materials that can be deposited by electron beam induced deposition is limited. This is due to unselective dissociation of the introduced metal-organic compounds by the focused electron or ion beam impinging with keV energy. Frequently, this results in nanocomposite deposits composed of metal nanocrystals embedded in an amorphous carbonaceous matrix. Plasmas would allow simple direct etching of this carbonaceous matrix. In this project we integrate a SEM compatible microplasma technology which runs together with gas assisted FEB or FIB induced deposition.
Related paper: H. Miyazoe et al, Ultrahigh-frequency microplasma jet as a low-power, high-density, and localized ions/radicals source, J. Vac. Sci. Technol. A 27 (2009) 9.

Equipment/Service

We operate a small grey room facility with electron beam and UV lithography. FIB and FEB are available for prototyping within research projects. Together with Alemnis, an Empa startup, we also offer solutions for gas injection systems which can be retrofitted to existing SEMs or Dual Beam machines. Our SEM add-ons can be operated on your specific samples.

SEM Hitachi S3600N (tungsten electron emitter) with XENOS lithography and ALEMNIS gas injection system and nanomanipulation: Dedicated variable pressure SEM for FEBIP chemistry development and classical e-beam lithography.

FIBSEM, Tescan Vela (W-emitter, Ga-ion source) with lithography and ALEMNIS gas injec-tion, nanmanipulation: for FIBIP, ion milling, FEBIP.

FIBSEM, Tescan Lyra3 (FEG, Ga-ion source) with e-beam/ion lithography and ALEMNIS gas injection system, FIBSIMS.

Residual Gas Analyser: Stanford Research System 300AMU.

RF Plasma Cleaning system, XEI: Evactron 24/25.

More SEM integrated setups: 4-point probing station, compression/indentation setups (10 mN, 1mN), nanomanipulations, nanopositioning systems, superparamagnetic bead detection system, AFM in SEM.

ALD reactor: lab-built reactor allowing for 2-3 inch wafers, 3 gas ports for nanolaminate film deposition, Labview control.

PVD Mantis: 1e-8 mbar, 3 magnetron sputter sources (1 RF), Mini-ebeam evaporator with 4 independent sources.£

In 2008 we organised the 2nd international FEBIP (focused electron beam induced pro-cessing) workshop at Thun with 90 international participants from more than 13 countries all over the world.