Thin films of lithium tantalate have been deposited by RF sputtering on RuO2- or SiO2-coated silicon substrates. Two electrical contact configurations have been used. The first configuration is a thin capacitor with an RuO2 buried electrode and a gold, nickel or RuO2 upper electrode. The second configuration has recourse to RuO2 interdigitated electrodes fabricated by a photolithographic process. Ferroelectric hysteresis measured with a Sawyer-Tower circuit shows a spontaneous polarization in the range of 20 mu C/cm(2) and an electric coercive field of 3 kV/cm. The dynamic pyroelectric response has been measured as a function of frequency at various temperatures. From 100 Hz to 1 kHz at room temperature, the pyroelectric current and voltage responses are 12 mu A/W and 18 V/W, respectively. The device with interdigitated electrodes shows a higher response due to a larger pyroelectric coefficient. The effects of the poling process have also been investigated and significant improvements of the pyroelectric response have been obtained.

Conducting thin films of RuO 2 were grown at temperatures down to 623K on glass by metalorganic chemical vapor deposition (MOCVD). Tris-trifluoroacetylacetonate-ruthenium(III) (Ru(tfa) 3 ) served as precursor. Smooth, specular and well adherent films were deposited, if the reaction gas contained water. The films were investigated by X-ray diffraction, SEM, and fourprobe resistivity measurement. Growth kinetics were also studied by in situ ellipsometry. The results are compared with films prepared by d.c. reactive sputtering before and after annealing. The properties of the MOCVD films, in particular the resistivity (ρ down to 72 μΩcm), are comparable to CVD films deposited at much higher temperatures and sputtered films after high temperature annealing.

Lithium tantalate thin films have been prepared by reactive rf sputtering from a ceramic target. The films deposited on RuO 2 -coated silicon at room temperature are initially amorphous. The films were crystallized by annealing in an oxygen flow at various temperatures using two processes. In the first process, the samples were annealed for one hour and in the second they were subjected to rapid thermal annealing (RTA) for 45 seconds. X-ray diffraction shows that in both cases, crystallization starts above 500°C. Transmission electron microscopy reveals that films subjected to RTA contain significant amounts of inter- and intragrain porosity as 8 nm bubbles. The composition depth profile of the films has been determined by secondary ion mass spectrometry. The influences of deposition and annealing parameters on the film microstructure and composition are discussed.