INTC-2012-005/INTC-P-275-ADD-1 - CERN Document Server

Relative emission (arb. units)
Sn 2+
Sn 4+
-6 -4 -2 0 2 4 6
Velocity (mm/s)
Fig. 3: 119 Sn Mössbauer spectra obtained after implantation of 119 In into a ZnO single crystal held at the
temperatures indicated. The total dose is ~10 10 119 In/cm 2 per measurement.
At low temperatures, some of the Sn is observed in the expected 2+ state, but at elevated
temperatures, Sn 4+ is observed. This is in contradiction with the results obtained with 57 Mn,
where one finds that above room temperature and for fluence < 10 11 cm -2 , Fe occupies regular
lattice sites and is observed as Fe 2+ by simple replacement of Zn 2+ . Similar results were
obtained in -Al2O3 and MgO. One straightforward explanation of this finding is that the
relatively large In ion cannot simply exchange the metal ion, and hence is in a site with a
charge compensating metal vacancy as the next nearest neighbour.
This result and its interpretation is of fundamental importance for several reasons:
(1) 111 In is commonly used as a probe for perturbed angular correlation (PAC)
experiments (see e.g. [Dogra09] and references therein). It is often assumed that the
probe upon annealing occupies regular substitutional sites. Our results suggest that
this assumption is not necessarily correct, and it would be of interest to be able to
investigate this in more detail.
(2) In + N co-doping of ZnO has been suggested as a method to obtain p-type doping in
ZnO [Ye09]. If we prove that In implanted into ZnO does not lead to a simple
replacement of Zn, it might help in a further theoretical and/or experimental
endeavour to use such co-doping
Although the quality of the 119 In beam in 2011 was below usefulness, we were able to
generate one spectrum after implantation in ZnSe.
6
476 K
300 K
95 K