Resistive switching behaviour of non-stoichiometric SrTiO 3 -thin films
An investigation with respect to ferroelectric antisite-defects

The cause of resistive switching in off-stoichiometric SrTiO 3 -thinfilms (STO)
is investigated. Resistive switching in Sr-deficient thinfilms has previously been
ascribed to the migration of oxygen vacancies (V O ) and V O -filaments. Nev-
ertheless, recent theoretical works suggest, that Sr-deficiency in STO-thinfilms
favours the emergence of ferroelectric Ti-antisite-defects, where a Ti-atom oc-
cupies a vacant Sr-position. Due to the difference in size, the Ti-atom is off-
centered. This supposedly induces a local dipole and ferroelectric properties.
The resulting polarisation charges also affect the barrier height between a fer-
roelectric and an applied electrode. Polarisation reversal therefore influences
the electrical resistance. This effect is particularly relevant in ferroelectric thin-
films, since electrical conductance is contributed by tunneling electrons. Tun-
neling current is higher and more sensitive to the change of polarisation charges,
enabling resistive switching over up to four orders of magnitude. Like this, Sr-
deficient STO-thinfilms have a potential to be used as devices in resistive data
storage and memristors. To elucidate the possible connection between ferroelec-
tric and resistive switching, in-situ time resolved X-ray diffraction experiments
under an oscillating electric field are carried out, while current and voltage are
measured. The hysteresis-behaviour of the maximum diffraction intensity as a
function of voltage is used to monitor the ferroelectric switching of antisite Ti-
atoms. The latest results from XRD and electrical investigations are presented.