Raman spectroscopy of ZnTe-based nanowires grown by MBE *
|Wojciech Szuszkiewicz 1, Jean-Francois Morhange 2, Elżbieta Janik 1, Wojciech Zaleszczyk 1, Grzegorz Karczewski 1, Tomasz Wojtowicz 1|
1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
ZnTe and Zn1-xMnxTe nanowires (NWs) with a mixed crystal composition up to x = 0.6, grown on GaAs substrates by catalytically enhanced molecular beam epitaxy (MBE), have been investigated by Raman scattering. As it has been demonstrated previously [1,2], in the whole composition range the NWs crystallize in the zinc-blende structure with their axis (<111> direction) aligned along the <111> direction of the GaAs substrate, independently of the crystallographic orientation of this substrate. Their diameters vary in the range from 30 to 70 nm, and their typical length is 1000 nm.
Raman scattering was achieved in resonant condition with the excitation energy close to the direct energy gap of the material. The accumulation of Raman spectra was possible because of weak enough intensity of luminescence near this energy. The intensity of Raman signal was such that it was possible to observe up to three phonon replicas (2LO and 3LO) even on a single NW. The dependence of the Raman spectra on the Mn composition shows the typical behavior of bulk Zn1-xMnxTe alloy, which confirm the incorporation of Mn2+ ions on the cation substitutional sites of the ZnTe matrix of the NWs. For the composition range x < 0.2 the high crystalline quality of the investigated mixed crystal NWs, characterized by the width of the observed Raman structures, is comparable to that corresponding to pure ZnTe NWs [1,2]. The crystalline quality of NWs slightly degrades when the Mn content rises above 20%. This degradation can be attributed to an increasing number of defects or stacking faults in the mixed crystal NWs with higher compositions.
 E. Janik et al., Appl. Phys. Lett. 89, 133114 (2006).
 E. Janik et al., Nanotechnology 18, 475606 (2007).
* The research was partially supported by the Ministry of Science and Higher Education (Poland) through grants No N507 030 31/0735 and N515 015 32/0997, and by the Foundation for Polish Science through subsidy 12/2007.
Presentation: Invited oral at E-MRS Fall Meeting 2008, Symposium J, by Wojciech Szuszkiewicz
See On-line Journal of E-MRS Fall Meeting 2008
Submitted: 2008-05-12 21:52 Revised: 2009-06-07 00:48