No description available.

For many years, electrochemically deposited polypyrrole has found application in a host of technologically significant areas. Popular applications include use in rechargeable batteries, electrochromic displays and artificial muscles. However, perhaps the most significant application of polypyrrole is as a gas sensing material. The relatively low selectivity of polypyrrole has led to it seldom being used as a 'stand alone' sensor; the ease by which the properties of polypyrrole may be subtly modified during electrochemical deposition (resulting in subtly different sensor responses) makes it ideally suited for incorporation into sensing 'arrays'. The level of understanding concerning the growth dynamics and structural characteristics of electrochemically deposited polypyrrole was poor prior to the commencement of the work presented; this thesis describes research undertaken in order to elucidate the properties of this material. As variation of the dopant group used during electrochemical deposition has been shown to result in significant structural and operational variations, the work presented focuses on polypyrrole doped with sodium benzene sulfonate (benzene sulfonic acid, sodium salt). The effects of deposition parameter variation have been studied (such as deposition potential and dopant concentration); repeatable relationships were found between deposition parameters and [a] sensor electrical conductivity, and [b] the surface morphology of the films formed. The influence of sensor substrate design is also considered; dissimilarities were found between the consistency and resistance temporal stability of elements deposited on simple 'boot' electrodes and interdigital microelectrodes. A significant proportion of the work presented concerns the study of the macrostructure of electrochemically deposited polypyrrole films. Several novel structural features have been presented, all of which have been documented in the scientific press. These include: The formation of 'tendrillar' morphology (as opposed to the commonly observed polypyrrole 'nodular' morphology) during electrochemical deposition from aqueous electrolyte. Tendril formation has been shown to be the result of the accumulation of impurities at the advancing growth face; a model has been presented which relates impurity accumulation to tendrillar polymer morphology; Demonstration of the evolution of gas at the polymer/substrate interface during aqueous electrolytic deposition. It is suggested that gas evolution is the result of the catalysed disassociation of the (aqueous) supporting electrolyte, and shown that the production of gas at the substrate/polymer interface results in the formation of discrete pockets, the positions of which relate strongly to the positions of nodules on the upper film surface. Demonstration of the recrystallisation of ionic dopant trapped within the polymer films during maturation. Dopant recrystallisation has been verified by SEM and ED AX; crystal growth has been demonstrated by XRD.Finally, the microstructures of a range of subtly different polypyrrole films have been considered. Repeatable relationships were observed between deposition potential, electrolyte solution concentration and microstructure. Characteristic features of X-Ray diffractograms have been related to the theoretical spacing between adjacent pyrrole rings (=3.6A), we believe for the first time.

No description available.

Chloride, bromide, pyridinium and quinolinium homologues of 4-(N- hexadecylpyridinium-4-ylmethylidene-amino)-2,6-dichlorophenolate have been investigated in solution, Langmuir and Langmuir-Blodgett films. Techniques including spectroscopy, surface potential measurement, quartz crystal microbalance, surface plasmon resonance, atomic force microscopy, reectometry and X-ray diffraction have been used to characterise these molecular systems. In solution, solvatochroism was observed and Benisi-Hildebrand analysis revealed dimeric aggregation. Langmuir monolayers were compressed at the air/water interface and chromophore rotation was observed by surface potential measurement. Langmuir- Blodgett monolayers showed lm-thickness dependence on the deposition-pressure. Monolayer thicknesses between 6-24Ä were measured using SPR and molecular areas between 40-l25Ä2 were measured using a quartz crystal microbalance. Both the molecular/s/area)and monolayer thicknesses were deposition-pressure dependent. The high tilt phases were visually distinguishable from the low tilt phases using atomic force microscopy, The compounds showed phase behaviour that was predominantly alike for the bromide and chloride homologues but different for the pyridinium and quinolinum homologues. Multilayer Y-type films of the merocyanine dyes were analysed using reectometry and deposition-pressure dependent thicknesses were found. Alternate layer structures of NLO-active hemicyanine amphiphiles were used to achieve homogeneous. orientation ordering using active and inactive spacer layers. Ordering was achieved but the optical efficiency was reduced by high proportions of inactive material and interlayer dipole formation. Double chained hemicyanine molecules were used to form Z-type structures and subsequent layers were found to significantly interdigitate. Different chain lengths were found to interdigitate by the length of the shortest chain. Gas detection experiments were undertaken on the quinolinium, dichloro merocyanine using three optical geometries. The absorption method showed slow switching and poor sensitivity. The Kretschmann SPR geometry showed high sensitivity and rapid switching. The grating SPR geometry showed rapid switching but was less sensitive than the ATR method. Protonation of the monolayers was investigated using hydrochloric acid gas, acetic acid vapour and stearic acid immobilised within the lm.

This paper presents an integrated column-type micro thermoelectric cooler (£g-TEC) constructed with serial connected p-type antimony-tellurium (Sb2Te3) and n-type bismuth-tellurium (Bi2Te3) micro pillars deposited by electrochemical deposited technology. To optimize the power factor, density and uniformity of the TE films and to enhance the reproducibility of £g-TEC device, a cathode with tunable rotary speed and with accurate current controller has been designed in the electroplating system of this research. The electroplating deposited Bi2Te3 and Sb2Te3 with an average thickness of 8 £gm, are connected using Cr/Au layers at the hot junctions and cold junctions. The measured Seebeck coefficient and electrical resistivity are -86 £gV/K and 16 £g£[-m for Bi2Te3 films after annealed at 250¢XC, and are 68 £gV/K and 30 £g£[-m for Sb2Te3 films after annealed at 200¢XC. The optimized power factors of the n-type (2.64¡Ñ10-4 W/K2m) and p-type (2.64¡Ñ10-4 W/K2m) telluride compounds have been demonstrated in this paper. Under 5 volts driven, the integrated £g-TEC device shows average cooling achieved is about 1.3 ¢XC.

No description available.

In order to resolve the Al void formation originated from the severe stress issues in dynamic random access memory (DRAM), double-deposited-aluminum (DDA) layer process was proposed. This novel metallization process can be effectively and simply performed with the native oxide such as Al 2 O 3 between upper and lower Al metal layer by ex-situ deposition technique. We could effectively control the Al void by adapting the DDA layers with different grain structure. From this novel metallization process, we have confirmed the optimal thickness of Al barrier metal to 100Å to be free from Al voids, which makes it possible to improve the static refresh characteristics of DRAM by 17%.

No description available.

No description available.

Approximately 1500 km (43%) of the strategic Scottish trunk road network drainage asset takes the form of Highway Filter Drains (HFDs). However, despite their popularity, they are prone to clogging, therefore they have an estimated operational life-cycle of ten-years. This research was undertaken to investigate the complex inter-relationship between catchment characteristics, road dynamics and the physical characteristics of the road to establish the key factors that govern the generation and spatial variability of Road-Deposited-Sediment (RDS). The aim being to establish the impact RDS Particle Size Distribution (PSD) has on clogging and the operational life-cycle of HFDs. The research adopted an integrated approach, incorporating: (i) a Field Study to investigate RDS PSD grading envelopes across the Scottish trunk road network, (ii) a HFD Field Survey (HFD-FS) to investigate the current condition of HFDs across a range of catchments, (iii) a HFD Field Study to establish whether, or not, graded stone PSD envelopes comply with specification requirements when first placed in the trench, (iv) 3 HFD Field Studies to assess the level of risk of system failure through evaluating the causes and quantifying the individual, cumulative and influencing factors which contribute to the evolution of clogging in HFDs, and (v) a Field Study utilising Ground Penetrating Radar data to explore why stratified (clogged) layers evolve within some HFDs. Based on the results of this research, design and maintenance procedures were then identified to improve the performance of HFDs. Results established that Scottish trunk roads operate under variable catchment characteristics and road dynamics, with the condition and specification of the road surface, volume of traffic, road geometry, number of running lanes and adjacent land use governing the generation and spatial variability of RDS. Five of the nine trunk road RDS PSD profiles shared a peak particle diameter of 425 μm, two had a peak of 600 μm, one had a peak of 1180 μm and one resulted in a peak of 2120 μm. Particles >1000 μm were mostly mineral or asphalt and it was shown that there is a direct link between the factors that govern the generation and spatial variability of RDS and those that govern the evolution of clogging and actual operational life-cycle of HFDs. The HFD-FS revealed that 69% were assigned Filter Drain Condition Index ratings of 3 or below, which identifies these as having exceeded the ten-year estimated operational life-cycle. 94% of those deemed to have reached the end of their operational life-cycle were over-the-edge (OTE) HFDs, which supports the assertion that pre-treatment would increase their operational life-cycle. Results also established that introducing a kerb-line and gully-pots or grass-strip between the road and the HFD significantly reduced the indices of particle size composition d50 and d90 and percentage of RDS retained at depths spanning 0 - 400 mm, compared to OTE HFDs with comparable catchment characteristics and road dynamics. Based on these results, the operational life-cycle of HFDs with a kerb-line and gully-pots and OTE HFDs with a grass-strip can be expected to exceed twenty-years, if catchment characteristics and road dynamics are representative of those in this study. This research also identified that compacting Type B graded stone with ‘heavy vibrating machinery’ during construction could potentially contribute to clogging. It was also established that HFD harrowing may exacerbate clogging because the process of disintegrating the cake-layer mobilises an otherwise rigid and compacted RDS mass and this is more likely to penetrate deeper into the HFD and inundate the HFD during a storm event. These findings indicate that current HFD construction and maintenance practice could have a detrimental impact on the effective operational life-cycle of HFDs. Overall, this research study has demonstrated that there are considerable uncertainties related to PSD grading envelopes and percentage of RDS migrating from roads to HFDs. It is clear therefore that one of the most notable findings of this research is that given the scale of strategic trunk road networks, assuming a single HFD operational life-cycle profile, for a trunk road or trunk road network, is highly unlikely to be representative of a HFD at the local level. It follows then that the widely accepted estimated ten-year operational life-cycle for HFDs, does not reflect the actual operational life-cycle of HFDs.