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Prof. Dr. Hans-Christian Hofsäss
II. Physikalisches Institut
Georg-August-Universität Göttingen
Friedrich-Hund-Platz 1
37077 Göttingen
Deutschland

Telephone: +49 551 39 7669
Email: hhofsae [at] uni-goettingen [punkt] de

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Publications
Ionenstrahltreffen 2017
Analytical & Implantation Services
Besichtigung Beschleunigerlabor
Themen Bachelor/Master Arbeiten
Homepage Prof. Hofsäss



Research group of Prof. Hans-Christian Hofsäss


Research topics

This is a brief overview of some of the currently running research projects of the ion beam and nuclear solid state physics group. For more information on or a bachelor/master theses within these projects please contact us.


Supported by: DFG, BMBF University of Göttingen

Ultra-low energy ion implantation of 2D materials
Contact: Hans Hofsäss

Fluence dependent proton beam writing of 3D microstructures

Creating 3D structures for MEMS applications in p-GaAs has been recently demonstrated by our group for the first time using fluence dependent proton beam writing. Currently we are modelling the etching behavior of such proton irradiated substrated with FEM methods, using the FEM package DUNE. Application of such MEMS structures are high frequency SAW and BAW filters, energy harvesters and others.

Recent publications:

Martina Schulte-Borchers, Ulrich Vetter, Tristan Koppe, Hans Hofsäss, J. Micromech. Microeng 22 (2012) 025011

Contact: Alrik Stegmaier, Clemens Beckmann, Hans Hofsäss


PIXE elemental analysis with external proton beam

Contact: Hans Hofsäss


RBS Rutherford backscattering elemental analysis


  • conventional RBS with 900 keV He2+

  • High resolution RBS with 450 keV He+ and 1-2 nm depth resolution




External proton beam Rutherford backscattering elemental analysis

contact:Masahiro Saito, Kim Holm, Hans Hofsäss



Ion-induced self-organized surface pattern formation

Surfactant sputtering

Recent publications:

H. Hofsäss and K. Zhang, Nucl. Instr. Meth. . B267 (2009) 2731
H. Hofsäss and K. Zhang, Applied Physics A: materials Science and Processing, 92 (2008) 517

Contact: Omar bobes Hans Hofsäss


All-digital PAC spectrometry - Digipac

You think that processing photomultiplier signals is old hat? Far form it! Our high-speed gamma-gamma angular correlation spectrometer features unprecedented data rates at high speed and excellent time resolution, which is also of potential interest to LIDAR, RADAR and other applications. Ever wanted to know how to develop multithreaded applications for digital signal processing on high-end computers and what really makes up a detector?s signal? Here you go.

Recent publications:

M.Nagl et al. Rev. Sci. Instruments 81 (2010) 0735801


Contact: Matthias Nagl, Hans Hofsäss



Swift heavy Ion tracks in materials

The impact of single ions of high energy (1 GeV) on targets shows potential for field emitting and many other nanoscale devices based on induced ion tracks. So far only ta-C (tetrahedral amorphous carbon) shows conducting nano tracks at room temperature. Join us and accept the challenge of searching for new potential materials and applications of ion tracks such as single ion track lithography.

Contact: Hans Hofsäss

Recent publications:


MASS diodes (Metal / Amorphous Semiconductor / Semiconductor diodes)


MASS Diodes are a new class of diodes recently invented by our group and currently investigated in detail (I-V- and C-V-characterization, FIB preparation and TEM-measurements). This type of diode, which is grown by means of mass selected ion beam deposition, features a strong rectifying behavior with high breakdown-voltages. In addition, these diodes show several unique features which makes them interesting as photodiodes/-resistors.

Recent publications:

M. Brötzmann et al.,. Appl. Phys. 106 (2009) 063704
M. Brötzmann et al., Phys. Stat. Sol. C 7, 2 (2010) 256-259


Contact: Hans Hofsäss

Wide band gap semiconductors: optical and acoustic properties

Wide band gap semiconductors are used for blue and UV light emitting devices, but also bear potential for high power, fast electronic devices frequently employed in space and military applications. Our group is involved in research of wide band gap semiconductors for more than a decade with our current focus on the optical and acoustic properties of AlN as well as BN. The picture shows a HF setup for SAW and BAW studies of AlN devices made in our lab. The behavior is modeled with large scale FEM simulations.

Recent publications:

U.Vetter et al.,Diamond and Related Materials 20 (2011) 782


Contact: Hans Hofsäss


Rare earth based light emitters and naophosphors


Lanthanides, often denoted as rare earths, are used in solid state lasers and various light emitting devices since the 1960?s, mostly in the trivalent state Re3+. With its sharp luminescent intra-4f electron transitions they are probes of the local crystal field around the ions on their own. Our group has a capacious knowledge of the optical properties of rare earth doped systems, currently focussing on rare earth doped aluminum nitride and boron nitride in an international collaboration with American and Japanese scientists.

J.B. Gruber, U. Vetter, T. Taniguchi, G.W. Burdick, H. Hofsäss, S. Chandra, D.K. Sardar, J. Appl. Phys. 110 (2011) 023104


Contact: Hans Hofsäss


MAX phases


Years ago a new class of materials emerged that are nowadays called MAX phases - nanolaminated layered ternary carbides and nitrides with an unusual set of properties of both metals and high-performance ceramics. We are having a closer look at the microscopic properties of these fascinating materials under temperature and pressure variation with the use of radioactive probe nuclei.

Recent publications:

D. Jürgens and M. Uhrmacher, Hyperfine Int. 178 (2007) 23
D. Jürgens, M. Uhrmacher, H. Hofsäss: Nucl. Instr. Meth. 268 B (2010) 2185


Contact: Hans Hofsäss