Structural and electrical characterization of strontium bismuth tantalate (SBT) thin films

Ferroelectric strontium bismuth tantalate (SBT) thin films were deposited by thermal metalorganic chemical vapour deposition (MOCVD) onto a complex layered Pt/IrO₂/Ir/Ti(Al)N substrate. A study of ultra-violet (UV)-assisted rapid thermal processing (RTP) annealing strategies of the SBT thin films was performed. The influence of UV irradiation temperature and annealing atmosphere on the crystallinity of the deposited films was evaluated using both microstructural and electrical analysis techniques. A UV-RTP strategy in an oxygen atmosphere above 400 °C, followed by a furnace treatment at 700 °C, provided an optimum remnant polarization figure of merit.     

Laser polymerization-based novel lift-off technique

The fabrication of microstructures by two-photon polymerization has been widely reported as a means of directly writing three-dimensional nanoscale structures. In the majority of cases a single point serial writing technique is used to form a polymer model. Single layer writing can also be used to fabricate two-dimensional patterns and we report an extension of this capability by using two-photon polymerization to form a template that can be used as a sacrificial layer for a novel lift-off process.A Ti:sapphire laser, with wavelength 795 nm, 80 MHz repetition rate, 100 fs pulse duration and an average power of 700 mW, was used to write 2D grid patterns with pitches of 0.8 and 1.0 μm in a urethane acrylate resin that was spun on to a lift-off base layer. This was overcoated with gold and the grid lifted away to leave an array of gold islands.The optical transmission properties of the gold arrays were measured and found to be in agreement with a rigorous coupled-wave analysis simulation.     

Thin tantalum pentoxide films deposited by photo-induced chemical vapor deposition using an injection liquid source

We report the growth of thin tantalum pentoxide films on Si (100) by ultraviolet-assisted injection liquid source (UVILS) chemical vapor deposition (CVD) at low temperatures (200-350 °C). This new technique combines the intense radiation from an excimer lamp (5=222 nm) with a novel injection liquid source capable of delivering precisely controllable quantities of a liquid metalorganic precursor into the CVD chamber. The composition and optical properties of the oxides were determined using a variety of standard characterization methods. After optimization of the deposition parameters, the best layers were incorporated into simple MOS test structures to enable electrical characterization. Refractive index values of 2.09ǂ.07, fixed oxide charge content of <5᎒¹⁰ cm^-2, breakdown fields higher than 2 MV/cm and dielectric constant values of 18-24 were readily achievable in the as-deposited films. These properties compare favorably with those for layers prepared by conventional thermal-CVD at significantly higher temperatures of 500 °C.