Large Equipments

Main components:

• Fieldemission scanning electron microscope Quattro S manufactured by FEI
• Cathodoluminescence system SPARC manufactured by Delmic
• Streak camera StreakScope S-20 manufactured by Hamamatsu

With the new cathodoluminescence measurement system, nanostructures can be investigated with high spatial resolution (Δx<50 nm), and time resolution (Δt<100 ps). Cathodoluminescence is based on the generation of electron-hole-pairs and their radiative recombination as a result of excitation with an electron beam. Time-resolution on a sub-nanosecond time scale is achieved by use of a pulsed electron beam. The recombination kinetics of the electron-hole-pails generates photons, which can be analyzed with the detector of the steak camera. From the emission spectra, e.g. information about the material composition, the electric structure and defects can be determined.

The measurement system consists of a scanning electron microscope Quattro S (FEI). A Schottky field emission cathode is used to generate the electron beam, whereby a spatial resolution of less the 50 nm is achieved. By deflecting the electron beam, electron pulses as short as 100 ps can be generated. Future research projects will reduce the time resolution to less than 10 ps.

The emitted light is detected by the SPARC-System (Delmic). Pan- and monochromatic spectra can be detected in a wavelength range from 200 nm (middle UV range) to 1000 nm (infrared range).

Time-resolved signals are detected using the streak camera StreakScope S-20 of Hamamatsu. Incident photons hit a photocathode and generate electrons. These are deflected by a time-dependent electric field before they hit a detector.

The measuring system is equipped with a cryostat to reduce the temperature of the sample down to 4 K.

Contact Person:
Jörgen Jungclaus, M.Sc.
joergen.jungclaus(at)tu-braunschweig.de

Phone: +49 (0) 531 391-65443 (Office)

Phone: +49 (0) 531 391-65345 (Lab)

Mit harten und weichen Projektilen
Interview mit einem Großgerät: Das XPS

Plasma-profiling Time-of-Flight Mass Spectrometer (PP-TOFMS) from Horiba

The device is a universal depth profiling tool that enables precise Time-of-Flight mass spectrometry (TOF MS) measurements of thin film structures with high throughput. This includes the precise determination of the composition of materials with a high depth resolution in the nm range. The depth profiling is achieved by forming a crater by plasma etching on the surface of the sample and then etching it vertically layer by layer and analyzing the formed ions by TOF MS. The required high sputtering rate is realized by the high ion density of the glow discharge plasma. The device ensures TOF mass spectrometry measurements on inorganic materials. Application examples include the analysis of dopants in semiconductors (incorporation behavior of dopants, diffusion), the detection and identification of surface contaminants. The device has a high level of availability as it is one of the key facilities at the new LENA research center, which will be used in parallel by several groups in physics, electrical engineering and chemistry.

Worldwide up to now only two more similar setups are installed.
https://arxiv.org/abs/1909.12779

Contact:
Apl. Prof. Dr. A. Bakin
Institut für Halbleitertechnik
Technische Universität Braunschweig 
+49 (0)531/ 391-3779 (Office)

+49 (0)531/ 391-65341 (PPTOF-Lab)

A.Bakin(at)tu-braunschweig.de

The high resolution, double aberration corrected transmission electron microscope (JEOL Neoarm 200F) allows imaging nanostructures and thin films with atomic resolution. This system offers both the conventional transmission electron microscopy mode with parallel beam illumination (TEM) as well as scanning with a converged electron beam (STEM). Spherical aberration correctors as well as correctors for astigmatism up to 6^th order for both TEM and STEM mode are built in. The specified spatial resolution is below80 pm. A cold FEG is used as electron source. The TEM samples can for example be prepared using our FIB to cut out lamellas from bulk samples. The double aberration corrected TEM is equipped with a number of different detector which allows for a manifold of investigation. These include bright field, annular bright field, and segmented high angle annular dark field detectors, as well as a backscattered electron detector. Besides spatial imaging and local diffraction, we can study the energy loss of the transmitted electrons (EELS) with an energy resolution below 0.3 eV. In addition, x-rays emitted due to excitations of atomic shell transitions by the transmitting electrons can be detected with spectral resolution (EDX) within a solid angle of 0.8 sr. This gives us the possibilities to study excitations or chemical composition of the investigated systems. Both EELS as well as EDX are possible in STEM mode which allows spatial mapping.

How Long is a Picometer? – The View of a Single Atom

Contact

Institut für Angewandte Physik

Dr. Markus Etzkorn
mail: m.etzkorn(at)tu-bs.de
phone: +49 531 391 65386

Dr. Andreas Hangleiter
Email: a.hangleiter(at)tu-bs.de
Tel: +49 531 391 8501

https://www.tu-braunschweig.de/mib/lena/quanomet/elektronenmikroskopie-np4

The MPMS-3 from Quantum Design is a SQUID-based magnetometer, which allows the highly sensitive measurement of the magnetic moment of solid and liquid samples in the temperature range from 1.8 K to 400 K in magnetic fields up to 7 T. The instrument is equipped with a closed-cycle cryostat and allows measurement in dc extraction as well as in vibrating sample mode (VSM). The latter allows measurements of magnetic moments < 10^-11 Am² in magnetic fields 250 mT. Complete hysteresis loops can be recorded in less than 1 h, depending on the magnitude of the magnetic moment. The MPMS-3 is additionally equipped with the AC option, which allows measurements of the complex magnetic susceptibility in the frequency range 0.1 Hz – 1 kHz at AC field amplitudes up to 1 mT.

The system allows the characterization of diluted samples of magnetic nanoparticles (both as suspensions, i.e. in the liquid state, as well as in the freeze-dried state) and of various thin-film samples with layer thicknesses down to 1 nm at a layer area of 5x5 mm² and a magnetization of µ₀M = 500 mT. The measuring system allows the investigation of samples with smallest magnetic moments as well as materials with large volumes and very large magnetic moments. For measurements of very small magnetic moments, the MPMS-3 is to be extended in perspective with the option of carrying out measurements in very small background fields.

Of Magnetic Moments and Iron Oxide
Short portrait of Tamara Kahmann from the NanoMet Research Training Group

Contact:
apl. Prof. Dr. Frank Ludwig
f.ludwig(at)tu-braunschweig.de
+49 (0) 531 391-3863/-65413/-65425

The inverse STED microscope from Abberior Instruments can be used for recording supperresolved fluorescence images with a resolution of 30 nm or better (depending on the sample).

The STED-wavelength is 775 nm (high-power-laser with > 2700 mW @ 40 MHz), excitation wavelengths are 561 nm and 640 nm. Suitable fluoresencce dyes include Atto647N, Abberior Star RED, Abberior STAR580 (for 2color imaging) as well as the fluorescent protein mCherry. Alternatively, protein labels like SNAP- and Halo-Tags can be used for live-cell-imaging.

The microscope includes a 2-channel detector unit, a FLIM-unit, a spectral detection module as well as different approaches for reducing phototoxicity and -bleaching (RESCue, DyMN und MINFIELD).

Estimated installation:
August 2018 in LENA

Contact:
Dr. Birka Lalkens, BRICS, Rebenring 56; b.lalkens@tu-bs.de

This measurement setup for time-resolved femtosecond optical spectroscopy makes temperature- and power-dependent measurements of optical properties and charge carrier dynamics in nanostructures on different timescales (fs-ms) with high spatial resolution possible.

For the excitation a femtosecond Ti:sapphire laser system with nonlinear converters for wavelengths between 200nm and 2.5µm is used. The photoluminescence detection is realized by a streak camera with preceding spectrometer. This system covers the spectral range between 200 and 900nm with a temporal resolution of up to 1ps. The samples are mounted in a continuous flow helium cryostat and can be measured in reflection, transmission or confocal geometry at temperatures between 3.5K and 500K. Furthermore, an optical delay line for pump-probe experiments is available.

Contact:
Philipp Henning, M.Sc.
E-Mail: p.henning(at)tu-braunschweig.de
Tel.: +49 (0) 531 391-8502

The THz microscope uses a superconducting sensor, the so-called Josephson cantilever, to measure high-frequency radiation up to the terahertz range. The sensor can be moved very precisely in three dimensions by a high-resolution positioning system to also measure spatial radiation distributions. Active high-frequency circuits, such as radar chips or fast computer chips, can be investigated, as well as passive circuits that can be operated up to 40 GHz using a high-frequency generator or up to 7.5 THz using a far-infrared laser system.

The sensor is cooled to about 20 K by a pulse tube cryocooler. A second pulse tube cryocooler can be used to cool samples under investigation to temperatures as low as 4 K. The measuring chamber consists of a 55 x 50 x 50 cm³ shielded vacuum chamber. In addition to many electrical feedthroughs, the far-infrared laser can be quasi-optically coupled into the measuring chamber via another vacuum chamber containing optical setups. The entire setup is located on an actively damped optical table. The extensive measurement electronics in combination with the custom developed software allows many different measurement scenarios, often in cooperation with other groups. We welcome inquiries with ideas for joint measurements.

Magazine articles

• Superconducting Sensors for the Fastest Computer Chips in the World
• From Zero to Terahertz in Three Years | A short portrait of Marco Tollkühn from the NanoMet Research Training Group

Contact person

Dr. Benedikt Hampel
b.hampel(at)tu-braunschweig.de
+49 (0) 531 391 - 3855 / - 65414

In the setup presented, a Bruker Dimension Icon Atomic Force Microscope and a Renishaw inVia confocal Raman Microscope are coupled together by a flexible arm.

This setup enables correlative microscopic measurements. For example, the topography and chemical composition of a sample can be determined in spatial resolution simultaneously.

The Atomic Force Microscope has an interface for the user to upgrade a 3D functionality, which also allows topographic measurements of the side profiles of three-dimensional structures to be recorded in a traceable manner^1,2. The setup is currently taking place in strong collaboration with the PTB.

[1] G. Dai et al., Measurements of CD and sidewall profile of EUV photomask structures using CD-AFM and tilting-AFM, 2014 Meas.Sci.Technol. 25 044002, DOI: 10.1088/0957-0233/25/4/044002
[2] G. Dai et al., New developments at Physikalisch Technische Bundesanstalt in three- dimensional atomic force microscopy with tapping and torsion atomic force microscopy mode and vector approach probing strategy, 2012 Journal of Micro/ Nanolithography, MEMS, and MOEMS. DOI:10.1117/1.JMM.11.1.011004
 

Contact:
Alina Syring
phone: +49 531 391 65444
a.syring@tu-braunschweig.de

The Crossbeam Focused Ion Beam (FIB) allows to create nanostructures by Ga-ion etching. The process can be controlled by a separate electron microscope (SEM). This allows a very versatile use. This system is in particular optimized to cut out TEM lamellas in essentially arbitrary geometry and transfer them to a sample holder for TEM measurements. The Ion beam energies can be varied from 500 eV-30 keV with a high energy resolution provided by a flight energy corrector. The spatial resolution is 4 nm at 30 kV (2,5 nm using selective edge mode) and 500 nm at 500 eV. The system also has a number of characterization possibility using the electron beam. The electrons are emitted from a Schottky Field effect cathode and the electron beam energies can be varied from 20 eV – 30 keV. Secondary Ion and electron detectors allow the use as Scanning Electron/Ion Microscope. In addition, the Scanning electron beam can be used in transmission in a STEM mode. Bright field dark field and high angle annular dark field detectors are available. The STEM resolution is 0.6nm @2kV and 1 nm @ 500V. The electron beam can also be used for electron beam lithography.

The sample stage allows very flexible operations and has a 150 mm travel in x and y (10 mm in z) and a tilt angle of 70°. An in-situ plasma cleaner is integrated.

Contact

Institut für Angewandte Physik

Dr. Markus Etzkorn
mail: m.etzkorn(at)tu-bs.de
phone: +49 531 391 65386

Dr. Andreas Hangleiter
Email: a.hangleiter(at)tu-bs.de
Tel: +49 531 391 8501

https://www.tu-braunschweig.de/mib/lena/quanomet/elektronenmikroskopie-np4