Serhiy Matichyn

STRONTIUM BISMUTH TANTALATE THIN FILM DEPOSITION BY LIQUID-DELIVERY MOCVD USING NOVEL LIQUID BISMUTH PRECURSORS

ABSTRACT Novel liquid bismuth precursors (triallylbismuth (Bi(CH2CH═CH2) and tributylbismuth (Bi(C4H9)3)) were tested for metalorganic chemical vapor deposition (MOCVD). Strontiumbis-pentaethoxy methoxyethoxy tantalate (Sr[Ta(OEt)5(OC2H4OMe)]2) was used as Sr-Ta source. The growth rates were ≤10 nm/h for triallylbismuth and for triphenylbismuth, ≤1000 nm/h for tributylbismuth, and ≤60 nm/h for Sr[Ta(OEt)5(OC2H4OMe)]2. The deposition rate of SBT was always lower than the rate of bismuth oxide. A decrease of the deposition pressure improved uniformity of the film thickness but reduced the deposition rate of the films. XPS depth profiling indicated more metallic bond characteristics of Ti, Sr, and Bi after ion bombardment.

CHARACTERISATION OF FERROELECTRIC PbZrXTi1-XO3 (PZT) THIN FILMS PREPARED BY LIQUID-DELIVERY METALORGANIC CHEMICAL VAPOR DEPOSITION

ABSTRACT A growth of leaf shape crystals was observed by SEM in the case of excess of Pb in the MOCVD grown films. Contrary, when the lead content was 20 at% or lower, the PZT-films were transparent and smooth. X-ray diffraction (XRD) measurements showed a presence of lead oxide phase additionally to the perovskite phase in the as-deposited PZT films. A pyrochlore phase began to form at an annealing temperature at 600°C. PZT films annealed at 520°C exhibit square hysteresis loop with peak Pr values of 60 μ C/cm2 and coercive voltage of 2 V.

ELECTRICAL CHARACTERIZATION OF ZIRCONIUM OXIDE LAYERS GROWN BY LIQUID DELIVERY MOCVD

ABSTRACT ZrO2 films were prepared on 150 mm (100) silicon substrates using liquid delivery MOCVD and Zirconium-tert-butoxide as precursor. The substrate temperature and the total process pressure were varied from 400°C to 500°C and from 1.5 mbar to 7.5 mbar, respectively. The surface roughness of the ZrO2 films was measured by atomic force microscopy (AFM). X-ray diffraction measurements (XRD) indicated the coexistence of monoclinic and cubic/tetragonal phases, whose ratio depended on the deposition temperature. The relative dielectric constant was calculated from the capacitance at strong accumulation. The values of the as grown layers were ranging from 14 for the thinnest layer up to 30 for the thickest layer. The density of interface states was determined from quasi-static CV-curves and admittance spectroscopy. Annealing decreased the interface trap density and the leakage current density but the measured dielectric constant was also lowered. After a temperature treatment at 800°C the best electrical properties were observed.

TRIBUTYLBISMUTH AS A LIQUID BISMUTH PRECURSOR IN AN AVD SYSTEM FOR STRONTIUM BISMUTH TANTALATE THIN FILM DEPOSITION

ABSTRACT In this study, tributylbismuth has been tested as a bismuth source for strontium bismuth tantalate (SBT) deposition using atomic vapor deposition (AVD) system. The effects of annealing temperature on the structural and electrical properties of deposited films were investigated. SBT films annealed at 750°C were crystallized in ferroelectric perovskite phase. Ferroelectric hysteresis loops of the SBT films have been measured, from which a remnant polarization of 3.5 μC/cm2 and a coercive voltage of 3 V of the crystallized SBT layer have been evaluated. SBT thin films annealed at 750°C also showed good fatigue properties. Fatigue was found to be about 4% after 109 cycles.