T. Friessnegg

Vacancy formation in (Pb,La)(Zr,Ti)O3 capacitors with oxygen deficiency and the effect on voltage offset

Vacancy-related defect profiles have been measured for La0.5Sr0.5CoO3/(Pb0.9La0.1)(Zr0.2Ti0.8)O3/La0.5Sr0.5CoO3 ferroelectric capacitors using a variable-energy positron beam. By varying the layer thickness and the postgrowth processing in a reducing ambient, a capacitor showing oxygen deficiency dominantly in the top electrode and one with deficiency in both electrodes were produced. The capacitor with an asymmetric defect profile showed a voltage offset polarization–voltage hysteresis loop, that with a symmetric distribution of vacancy-related defects showed no offset. These results are discussed in the context of current models for imprint.

Detection of oxygen vacancies in (Pb,La)(Zr,Ti)O3 thin film capacitors using positron annihilation

Abstract The detection of oxygen vacancies by positron annihilation techniques in selected perovskite-type oxide thin films is reviewed. The basic principles of this defect characterization method, applied to thin films, are introduced. The capability of the method is illustrated for ferroelectric Pb(Zr,Ti)O3 (PZT) and conducting oxide La(Sr,Co)O3 (LSCO) thin films. Its use in obtaining oxygen vacancy defect distribution profiles in La doped PZT (PLZT) capacitor structures, LSCO/PLZT/LSCO, exposed to different oxygen ambient process conditions, is also reviewed. The observed changes in the oxygen vacancy concentration are correlated with the polarization-voltage hysteresis loops measurements.

A study of vacancy-related defects in (Pb,La)(Zr,Ti)O/sub 3/ thin films using positron annihilation

The formation of vacancy-type defects in La-doped lead zirconate titanate (PLZT) thin films (Zr/Ti=20/80) was studied as a function of lanthanum doping and after cooling in an oxygen-reduced ambient. The changes in the Doppler-broadening S parameter are consistent with the progressive introduction of Pb-vacancies upon La-doping. Cooling of PLZT thin films with 0 and 10% La doping in 10/sup -5/ Torr oxygen partial pressure after growth exhibits an increase in the density of vacancy-type defects compared to films cooled in 760 Torr. It is proposed that the defects formed are likely cation-oxygen vacancy complexes.

Defect Identification in (La,Sr)CoO 3−δ Using Positron Annhiiilation Spectroscopy

Vacancy type defects in bulk La 1−x Sr x CoO 3−δ samples were investigated by positron lifetime spectroscopy. The effects of Sr-doping as well as the effect of oxygen deficiency were determined. Comparing the resolved lifetimes with calculated values permits defect identification.

OXYGEN DEFICIENCY AND VACANCY FORMATION IN LSCO/PLZT/LSCO CAPACITORS.

Vacancy type defects in La 0.5 Sr 0.5 CoO 3 /Pb 0.9 La 0.1 Zr 0.2 Ti 0.8 /La 0.5 Sr 0.5 CoO 3 capacitors were investigated by positron depth profiling. Post-growth annealing of the capacitor structure in oxygen deficient atmosphere exhibits the formation of vacancy type defects in all layers. A significant increase in open volume defects was found in the top and bottom electrode. The changes in the bottom electrode were studied more closely by etching off the top layer.

An investigation of vacancy-related defects in (Pb,La)(Zr,Ti)O/sub 3/ thin films using positron annihilation

The formation of vacancy-type defects in Pb/sub (1-x)/La/sub x/(Zr/sub 0.2/Ti/sub 0.8/)O/sub 3/ (PLZT) thin films was studied as a function of lanthanum doping x and after cooling in an oxygen reduced ambient. The Doppler-broadening S parameter indicates that Pb-vacancies are progressively introduced upon La-doping. Cooling of Pb(Zr/sub 0.2/Ti/sub 0.8/)O/sub 3/ and Pb/sub 0.9/La/sub 0.1/(Zr/sub 0.2/Ti/sub 0.8/)O/sub 3/ thin films in 10/sup -5/ Torr oxygen partial pressure after growth exhibits an increase in the density of vacancy type defects compared to films cooled in 760 Torr. It is proposed that the defects formed are lead-oxygen vacancy complexes.

The Influence Of The Incorporation And Desorption Of Ch n , Groups On The Defect Structure Of a-SiC:H Films

Changes in the defect structure in carbon rich a -SiC:H films deposited on various substrates using ditertiary butyl silane were investigated as a function of thermal treatment. Films grown at high deposition rates exhibit hydrogen trapped in voids. The incorporation of CH n , groups is thought to be the origin for these microvoids. With increasing annealing temperature the effusion of CH n , groups as determined by thermal desorption experiments promotes void growth which was studied using a variable energy positron beam. At annealing temperatures above 600 °C the films densify due to the breaking of C-H bonds and the formation of additional C-C bonds when the voids anneal out.