ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012) P 17
OBSERVATION OF EXTREMELY SLOW ORDERING EFFECTS IN Co-IMPLANTED ZnO
E. Dynowska1∗, W. Paszkowicz1, P. Aleshkevych1, L. G ladczuk1, W. Szuszkiewicz1, S. M¨uller2, C. Ronning3, and W. Caliebe4
1Institute of Physics, Polish Academy of Sciences, al. Lotnik´ow 32/46, 02–668 Warszawa, Poland
2II. Physikalisches Institut, Universit¨at G¨ottingen, Friedrich-Hund-Platz 1, 37077 G¨ottingen, Germany
3Institut f¨ur Festk¨orperphysik, Universit¨at Jena, Max-Wien-Platz 1, 07743 Jena, Germany
4Hasylab at DESY, Notkestr. 85, D–22603 Hamburg, Germany Keywords: synchrotron radiation, X-ray diffraction, ZnO, implantation, cobalt
∗e-mail : dynow@ifpan.edu.pl
The partial substitution of the nonmagnetic Zn ions in ZnO by magnetic transition metal (TM) ions (Fe, Mn, Co and Ni) was predicted to be a way to- wards room temperature ferromagnetism. One of the methods for the incorporation of TM into ZnO is ion implantation. However, for recovering the radiation-damaged ZnO lattice, post-implantation annealing is needed. In the case of relatively high TM doses such annealing can cause the formation of secondary phase precipitates which may have in- teresting magnetic properties as noted in Ref. [1].
In previous reports [1]-[3] we described the re- sults of studies of TM containing ZnO layers formed by implantation of TM ions (TM = Mn, Fe, Co and Ni) into ZnO single crystals, with intentional atomic ratio x = TM/(Zn+TM+O) of 0.04 to 0.16, annealed at 700◦C [1] and 900◦C [1, 2], respectively.
In this presentation we concentrate on the structural aspects of those studies with special consideration of ZnO sample implanted with Co (x = 0.16) annealed at 900◦C in air for 15 – 30 min.
The X-ray structural characterization was per- formed using synchrotron radiation at the W1.1 beamline at DESY-Hasylab. The monochromatic X-ray beam of wavelength λ = 1.54056 ˚A was used. Magnetization measurements were made with a superconducting quantum interference device (SQUID) at temperatures 5 and 300 K.
The results of the first measurements performed with the use of synchrotron radiation in 2008 were presented in [1, 2]. According to the cited re- sults, the existence of secondary phases ZnMn2O4, ZnFe2O4 and Ni0.8Zn0.2O was confirmed for the samples implanted with Mn, Fe and Ni, respectively.
In the case of Co-implanted samples, the X-ray diffraction did not reveal any secondary phase.
However, the measurements cyclically repeated during two years for the Co-implanted crystal, with a period of about 6 months revealed that new rela- tively strong reflections appear and grow with elaps- ing time (for Mn, Fe and Ni implanted samples, no time evolution is observed). The observed new diffraction peaks indicate a development of a new,
monocrystalline or quasi-monocrystalline phase in the implanted area. The lattice planes of this phase (with spacing 10.747 ˚A) are oriented in parallel to the (0001) planes of ZnO host. This means that new, oriented phases form not only for Mn, Fe, and Ni implanted ZnO, but also for Co implanted ZnO.
The difference is that for Co-implanted ZnO, the phase formation process is very slow, in the month timescale. Generally, the presence of a set of diffrac- tion peaks from an oriented layer does not allow unambiguous identification of a phase. Neverthe- less, the attempts of understanding of the implanted layer structure led to finding a possible solution of the problem, which will be presented and discussed.
Acknowledgments: This work was supported by the European Community — Research Infrastructure Ac- tion under the FP6 “Structuring the European Research Area” Programme (through the Integrated Infrastruc- ture Initiative “Integrating Activity on Synchrotron and Free Electron Laser Science,” Contract RII3-C-2004- 506008) and by the Polish Ministry of Science and Higher Education from founds for science for 2009 – 2012 years, under a research project (0809/B/T02/2009/37).
References
[1] M. Schumm, M. Koerdel, S. M¨uller, C. Ronning, E. Dynowska, Z. Go lacki, W. Szuszkiewicz, J. Geurts, “Secondary phase segregationin heavily transition metal implanted ZnO,” J. Appl. Phys.
105 (2009) 083525.
[2] E. Dynowska, W. Szuszkiewicz, C. Ziereis, J. Geurts, S. M¨uller, C. Ronning, J. Doma- gala, P. Romanowski, W. Caliebe, “Structural studies of heavily transition metal implanted ZnO,”
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[3] J. Geurts, M. Schumm, M. Koerdel, C. Ziereis, S. M¨uller, C. Ronning, E. Dynowska, Z. Go lacki, W. Szuszkiewicz, “Annealing effects and generation of secondary phases in ZnO after high-dose transi- tion metal implantation,” Phys. Stat. Sol. B 247 (2010) 1249.
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