Conformal oxide coating of Carbon Nanotubes

The International Roadmap for Ferroelectric Memories requires three-dimensional integration of high-dielectric materials onto metal interconnects or bottom electrodes by 2010. We report the first integration of high-dielectric oxide films onto carbon nanotube electrodes with an aim of ultra-high integration density of FeRAMs (Tb/in2).Comment: 4 pages, 3 figure

Ultrasonic intensification as a tool for enhanced microbial biofuel yields

peer-reviewedUltrasonication has recently received attention as a novel bioprocessing tool for process intensification in many areas of downstream processing. Ultrasonic intensification (periodic ultrasonic treatment during the fermentation process) can result in a more effective homogenization of biomass and faster energy and mass transfer to biomass over short time periods which can result in enhanced microbial growth. Ultrasonic intensification can allow the rapid selective extraction of specific biomass components and can enhance product yields which can be of economic benefit. This review focuses on the role of ultrasonication in the extraction and yield enhancement of compounds from various microbial sources, specifically algal and cyanobacterial biomass with a focus on the production of biofuels. The operating principles associated with the process of ultrasonication and the influence of various operating conditions including ultrasonic frequency, power intensity, ultrasonic duration, reactor designs and kinetics applied for ultrasonic intensification are also described

Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound ─ morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) ─ are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm−2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics

Dielectric relaxation in antiferroelectric multigrain PbZrO<SUB>3</SUB> thin films

Antiferroelectric materials are found to be good alternative material compositions for high charge storage devices and transducer applications. Lead zirconate (PZ) is a room temperature antiferroelectric material. Thin films of PZ with various thicknesses were deposited by excimer laser ablation technique on Pt coated Si-substrates at a substrate temperature of 300°C and, subsequently, post annealed at 650° C. The antiferroelectric nature of PZ thin films was studied over a temperature range 30-250° C. Effect of thickness on the net dielectric constant was studied in detail and the calculated interfacial dielectric layer thickness is 0.1 nm approximately, with a bulk dielectric constant of 222 at 100 kHz. Impedance and electric modulus formalisms were employed in order to gain an insight of the microstructural details of multigrain thin films. A comprehensive study on relaxation mechanism revealed that the Maxwell-Wagner type polarization is the basic relaxation phenomenon in the multigrain PZ thin films, due to the presence of multiple grain and grain boundaries across the film thickness. The activation energies from the interior grain relaxation and ac conductivity studies were 0.631 and 0.563 eV, respectively. These activation energies were attributed to the excitation of the charge carriers from a set of shallow traps and/or oxygen vacancies present at an average depth of 0.5-0.6 eV from the bottom of the conduction band

Antiferroelectric thin films for MEMs applications

Antiferroelectric compositions have many potential applications in energy conversion and microelectromechanical systems. Electric field induced phase transitions between ferroelectric and antiferroelectric phases were studied in antiferroelectric lead zirconate and modified lead zirconate titanate stannate family thin films for various smart system applications. Thin films of various antiferroelectric thin film compositions such as PbZrO3, Nb-and La-modified Lead Zirconate Titanate Stannate were processed by pulsed excimer laser ablation technique. Dielectric, hysteresis, pyroelectric and switching properties were studied in detail for a new generation of functional materials. A comparative study of functional properties is presented with these antiferroelectric compositions in comparison with the conventional ferroelectric compositions

Study of La-modified antiferroelectric PbZrO<SUB>3</SUB> thin films

Dielectric and DC electrical properties of antiferroelectric lead zirconate and La-doped lead zirconate thin films deposited using a pulsed excimer-laser ablation technique were studied in detail. Increased La dopant concentration in pure lead zirconate thin films reduced the dielectric maximum and Curie temperature. At 9 mol.% of La in pure lead zirconate, the dielectric transition temperature reduced to room temperature. A gradual change from antiferroelectric to paraelectric through ferroelectric phases was observed with the addition of La to pure lead zirconate. The DC electrical properties of pure lead zirconate and the effect of donor addition on leakage current properties were studied. Correlation between the macroscopic changes observed in the charge transport mechanisms, microscopic defect chemistry and charge-carrier trapping phenomenon was examined in detail

Antiferroelectric lead zirconate thin films by excimer laser ablation

Utilization of antiferroelectric thin films was proposed for high charge storage capacitors and transducer applications. The volume changes that are associated with the AFE⇒FE and FE ⇒ AFE phases are high enough to use them in MEMs device technology. Lead zirconate was the first identified antiferroelectric compound with a reported dielectric phase transition temperature of ~230° C. In this article, deposition of lead zirconate thin films by a pulsed excimer laser ablation technique is reported. The antiferroelectric nature of the lead zirconate thin films were confirmed by the presence of double hysteresis loop in polarization vs. applied electric field response as well as double butterfly behavior in capacitance vs. voltage characteristics. The variations in the polarization hysteresis with temperature were elucidated in detail. The switching times between the field induced FE and AFE phases (backward switching) were studied at various applied electric fields

Study of AC electrical properties in multigrain antiferroelectric lead zirconate thin films

Antiferroelectric lead zirconate (PZ) thin films were deposited by excimer laser ablation technique on Pt-coated Si substrates. Antiferroelectric thin film compositions are potential candidates for high charge storage and microelectromechanical systems. The antiferroelectric nature in PZ thin films was confirmed by means of double hysteresis behaviour in polarisation vs. applied electric field and double butterfly response in capacitance vs. applied voltage measurements. The maximum spontaneous polarisation observed was 37 &#181; C/cm2 with zero remnant polarisation at an applied electric field of 225 kV/cm. PZ thin films showed a polycrystalline multigrain structure and detail comprehensive study of dielectric relaxation and ac electrical properties were carried out

Backward switching phenomenon from field forced ferroelectric to antiferroelectric phases in antiferroelectric PbZrO<SUB>3</SUB> thin films

Antiferroelectric materials (example: lead zirconate and modified lead zirconate stannate), in which a field-induced ferroelectric phase transition is feasible due to a small free energy difference between the ferroelectric and the antiferroelectric phases, are proven to be very good candidates for applications involving actuation and high charge storage devices. The property of reverse switching from the field-induced ferroelectric to antiferroelectric phases is studied as a function of temperature, applied electric field, and sample thickness in antiferroelectric lead zirconate thin films deposited by pulsed excimer laser ablation. The maximum released charge density was 22 &#181; C/cm2 from a stored charge density of 36 &#181; C/cm2 in a 0.55 &#181; thick lead zirconate thin film. This indicated that more than 60% of the stored charge could be released in less than 7 ns at room temperature for a field of 200 kV/cm. The content of net released charge was found to increase with increasing field strength, whereas with increasing temperature the released charge was found to decrease. Thickness-dependent studies on lead zirconate thin films showed that size effects relating to extrinsic and intrinsic pinning mechanisms controlled the released and induced charges through the intrinsic switching time. These results proved that antiferroelectric PZ thin films could be utilized in high-speed charge decoupling capacitors in microelectronics applications

Field-induced dielectric properties of laser ablated antiferroelectric (Pb<SUB>0.99</SUB>Nb<SUB>0.02</SUB>)(Zr<SUB>0.57</SUB>Sn<SUB>0.38</SUB>Ti<SUB>0.05</SUB>)<SUB>0.98</SUB>O<SUB>3</SUB> thin films

Niobium-modified lead zirconate stannate titanate antiferroelectric thin films with the chemical composition of (Pb0.99Nb0.02)(Zr0.57Sn0.38Ti0.05)0.98O3 were deposited by pulsed excimer laser ablation technique on Pt-coated Si substrates. Field-induced phase transition from antiferroelectric to ferroelectric properties was studied at different fields as a function of temperature. The field forced ferroelectric phase transition was elucidated by the presence of double-polarization hysteresis and double-butterfly characteristics from polarization versus applied electric field and capacitance and voltage measurements, respectively. The measured forward and reverse switching fields were 25 kV/cm and 77 kV/cm, respectively. The measured dielectric constant and dissipation factor were 540 and 0.001 at 100 kHz, respectively, at room temperature