Mark R. DeGuire

Low temperature deposition of patterned TiO2 thin films using photopatterned self‐assembled monolayers

Patterned thin films of TiO2 were deposited from aqueous solution onto photopatterned self‐assembled monolayer (SAM) films on Si substrates. Regions of the SAM containing sulfonate surface functionality were created by the photo‐oxidation of initially deposited thioacetate groups through a mask. The nanocrystalline TiO2‐on‐SAM films were deposited selectively on the photolyzed regions of the SAM. The electrical properties of such films were assessed for potential microelectronic device applications. Current–voltage and capacitance–voltage measurements made on nonpatterned TiO2 films yielded values of relative permittivity ranging from 24 to 57, film resistivities of 1.0–1.5×109 Ω cm and breakdown voltages in excess of 1 MV/cm.

Synthesis of yttrium oxide thin films with and without the use of organic self-assembled monolayers

Thin Y-containing films have been deposited at 80 °C from aqueous solutions of YNO3⋅5H2O and urea on bare single crystal Si wafers, and on Si wafers coated with sulfonate-functionalized organic self-assembled monolayers. The as-deposited films are believed to be an amorphous yttrium basic carbonate and can be completely transformed at 600 °C in air to crystalline Y2O3. Capacitance–voltage measurements on these films showed good dielectric properties, with a relative permitivity of 18, more than a factor of four higher than that of SiO2.

Deposition of oxide thin films on silicon using organic self-assembled monolayers

Crystalline oxide thin films have been synthesized at low temperatures from aqueous liquid solutions. A key element of the approach is the use of organic self-assembled monolayers (SAMs) on the substrate to promote the growth of adherent inorganic films. A SAM is a close- packed, highly ordered array of long-chain hydrocarbon molecules, anchored to the substrate by covalent bonds. The terminating functional group on the SAM surface is chosen so as to initiate and help sustain the formation of the oxide film when the substrate is immersed in the oxide precursor solution. Synthesis, microstructural characterization, and properties of TiO2, ZrO2, SiO2, and Y2O3 films are surveyed. Crystalline films were formed either directly from solution, or through subsequent heat treatments at temperatures that in most cases were lower than typical sol-gel or vapor phase deposition processes. All depositions were from aqueous solutions onto single-crystal (100) silicon. The ability to produce patterned films on a micron scale has been demonstrated, taking advantage of the selective deposition characteristics towards different surface functional groups of the SAM. The role of the SAM in oxide film formation is discussed.

Spatial variations in a.c. susceptibility and microstructure for the YBa2Cu3O7−x superconductor and their correlation with room-temperature ultrasonic measurements

The spatial (within-sample) uniformity of superconducting behavior and microstructure in YBa2Cu30(7-x) specimens over the pore fraction range of 0.10 to 0.25 was examined. The viability of using a room-temperature, nondestructive characterization method (ultrasonic velocity imaging) to predict spatial variability was determined. Spatial variations in superconductor properties were observed for specimens containing 0.10 pore fraction. An ultrasonic velocity image constructed from measurements at 1 mm increments across one such specimen revealed microstructural variation between edge and center locations that correlated with variations in alternating-current shielding and loss behavior. Optical quantitative image analysis on sample cross-sections revealed pore fraction to be the varying microstructural feature.

Oxygen deficiency in cerium oxide under molten alkali carbonate

Abstract Pressed and sintered pure CeO 2 samples were exposed to molten (Li, K) 2 CO 3 for 350 and 500 h at 650°C. TEM and XRD studies after the exposure to molten carbonate showed the oxygen-deficient, ordered phases Ce 11 O 20 and Ce 6 O 11 to be present in these samples. Ce 11 O 20 was observed to re-oxidize in the microscope (3 × 10 −9 p o 2 −11 atm). Based on these observations, the oxygen activity of molten (Li, K) 2 CO 3 eutectic at 650°C was inferred to be at most 6 × 10 −29 atm.

The Effects of Seeding on the Formation of High-T c Bi-Pb-Sr-Ca-Cu-O Compounds

The effect of adding of Bi 1.80 Pb 1.33 Sr 1.87 Ca 2 Cu 3 O 2 seeds(the 37A phase) to the polycrystalline and glassy Bi-(Pb)-Sr-Ca-Cu-O materials was studied using XRD and SEM. The seeding effect was observed at 835 °C, 855 °C, and 870 °C in several compositions. Adding pre-synthesized 37A phase powder to a mixture of unreacted starting materials accelerates the formation of additional 37A phase.