Speaker
A.C. Marques
(Centro de Física Nuclear da Universidade de Lisboa, Portugal)
Description
Strontium-titanate is a perovskite ceramic material, which is of interest, e.g.,
for future devices based on metal-oxide Si heterostructures such as high-k field
effect transistors. The electrical, optical and magnetic properties of SrTiO3 can
be modified by the incorporation of dopants. For instance, transition metal doped
SrTiO3 has been considered as a candidate for a room-temperature ferromagnetic
semiconductor [1]. Ion implantation might thus represent an attractive approach for
doping, especially in cases where the solubility of dopants is limited and they
cannot be introduced during growth. However, very little is known about the
fundamental question whether implants are incorporated on proper lattice sites in
SrTiO3 (substitutional Sr, substitutional Ti and substitutional O sites, regular
interstitial sites or randomly dispersed). This can be studied with the emission
channelling technique, which unambiguously identifies and quantifies the impurity
lattice site location.
Results for implanted 111Ag in SrTiO3 perovskite are reported to illustrate the EC
technique capabilities. Electron channeling patterns were measured around several
crystalline directions following in-situ-vacuum annealing up to 900ºC. It is shown
that in the as-implanted state, Ag occupies several lattice sites and upon
annealing, most of Ag goes to near-substitutional Sr sites [2], while for instance
Fe is to a large extent incorporated on Ti substitutional sites.
In addition, a short description of a new data readout technology for electron Si
pad detectors with a strong impact on the applications of the EC technique will be
presented. The new technology improves the detection efficiency of very low energy
conversion electrons below 40keV, and at the same time, allows very high readout
count rates up to tens of kHz. These facts will broaden the range of available
elements for EC studies, in particular, by using short-lived isotopes, already next
year. Perspectives about the near future of the EC technique at ISOLDE-CERN will be
given.
[1] S.J. Pearton, W.H. Heo, M. Ivill, D.P. Norton, and T. Steiner, Semicond. Sci.
Tech. 19 (2004) R59-74.
[2] A.C. Marques, U. Wahl, J.G. Correia, E. Rita and J.C. Soares, “Lattice location
and perturbed angular correlation studies of implanted Ag in SrTiO3”, accepted by
Nucl. Instr. And Meth B (2005).
Primary author
A.C. Marques
(Centro de Física Nuclear da Universidade de Lisboa, Portugal)
Co-authors
E. Rita
(Centro de Física Nuclear da Universidade de Lisboa, Portugal)
J.C. Soares
(Centro de Física Nuclear da Universidade de Lisboa, Portugal)
J.G. Correia
(Instituto Tecnológico e Nuclear, Sacavém, Portugal)
U. Wahl
(Instituto Tecnológico e Nuclear, Sacavém, Portugal)
