About my diploma thesis
The title of it is "Charakterisierung von laseraktiven Chromzentren in Kaliumzinkfluorid"
(Characterisation of laser-active chromium centres in potassium zinc-fluorid). The material
is a made of K, Zn and F which crystalize in Perovskit structure. Chrom substitutes Zink
and can be in two different charge states: 2+ and 3+. The latter one gives rise to a nice
transition which can be used in tunable lasers. The 2+ centre absorbes that radiation, though.
Hence the idea was to investigate the different centres by ODMR.
About my PhD thesis
"Optisch detektierte magnetische Resonanz an intrinsischen Defekten und Akzpetoren in
Zinkoxid und Galliumnitrid".
Zincoxid and Galliumnitrid are two fantastic semiconducters with a wide band gap of
about 3.45 eV. They are interesting for optoelectronical-devices in the blue/UV spectral
range. Both materials turn out to be n-type conductive in nature and it is difficult to make
them p-type (in fact, ZnO still remains n-type). My work is a study of different centres in
both materials, intrinsical and substitutional candidates for acceptors (p-type cond.).
About the technique: ODMR
Optically detected magnetic resonance is a method which belongs to the category
"solid state spectroscopy". It can be very mighty but isn't seen often these days. It
traces the optical effects caused by defects in crystal structure back to the origin.
Description of ODMR
- D.M. Hofmann, A. Hofstaetter, F. Leiter, H. Zhou, F. Henecker,
B.K. Meyer, S.B. Orlinski, J. Schmidt, P.G. Baranov
"Hydrogen: a relevant shallow donor in Zinc Oxide"
Phys. Rev. Lett. 88 (4), 045505 1-4 (2002)
- F.H. Leiter, H.R. Alves, A. Hofstaetter, D.M. Hofmann, B.K. Meyer
The Oxygen Vacancy as the Origin of a Green Emission in Undoped ZnO
Physica status solidi (b) 226, No.1, R4-R5 (2001)
- B. K. Meyer, D. M. Hofmann, F. H. Leiter, D. Meister, M. Topf, and H. Alves
"Defects in undoped and Mg-doped GaN and AlGaN"
Mat. Sci. Eng. B82, 77 (2001)
- H. Alves, A. Hofstaetter, F. Leiter, B.K. Meyer, N.G. Romanov,
R. Novotny, and M.V. Korzhik
"Green emitting Molybdate complexes in PbWO4 - results of an ODMR study"
Radiation Measurements 33, 641 (2001)
- F. Leiter, H. Zhou, F. Henecker, A. Hofstaetter, D.M. Hofmann, and B.K. Meyer
"Magnetic resonance experiments on the green emission in undoped ZnO crystals"
Physica B 308 - 310, 908 (2001)
- D. M. Hofmann, B. K. Meyer, H. Alves, F. Leiter, W. Burkhardt,
N. Romanov, Y. Kim, J. Krüger, and E. R. Weber
"The red (1.8 eV) luminescence in epitaxially grown GaN"
Phys. Stat. Sol. (a), 180, 261 (2000)
- D. M. Hofmann, B. K. Meyer, F. Leiter, W. v. Förster, H. Alves, N. Romanov,
H. Amano, and I. Akasaki
"Optical transitions of Mg acceptors in GaN"
Jap. Appl. Phys. Lett. 38, 1422 (1999)
- D. M. Hofmann, W. Burkhardt, F. Leiter, W. Förster, H. Alves,
A. Hofstaetter, K. Meyer, N. G. Romanov, H. Amano, and I. Akasaki
"Mg acceptors in GaN: Dependence of the g-anisotropy on the
Physica 43 B 273-274, (1999)
- F.H. Leiter, D.M. Hofmann, A. Hofstaetter, B.K. Meyer, and S.I. Nikitin
"Optically detected magnetic resonance on Cr3+ centres in KZnF3"
Solid State Commun. 108, 625 (1998)