Remote electricity actuation and monitoring mote

This work presents the design and evaluation of the REAM (Remote Electricity Actuation and Monitoring) node based around the modular Tyndall Mote platform. The REAM node enables the user to remotely actuate power to a mains power extension board while sampling the current, voltage, power and power factor of the attached load. The node contains a current transformer interfaced to an Energy Metering IC which continuously samples current and voltage. These values are periodically read from the part by a PIC24 microcontroller, which calculates the RMS current and voltage, power factor and overall power. The resultant values can then be queried wirelessly employing the Tyndall 802.15.4 compliant wireless module.

Farmers, agriculture and politics in the Irish Free State area, 1919-1936

Given the economic and social importance of agriculture in the early years of the Irish Free State, it is surprising that the development of organisations representing farmers has not received the attention it deserves from historians. While the issues of government agricultural policy and the land question have been extensively studied in the historiography, the autonomous response by farmers to agricultural policies and the detailed study of the farmers’ organisations has simply been ignored in spite of the existence of a range of relevant primary sources. Farmers’ organisations have only received cursory treatment in these studies; they have been presented as passive spectators, responding in a Pavlovian manner to outside events. The existing historiography has only studied farmers’ organisations during periods when they impinged on national politics, epecially during the War of Independence and the Economic War. Therefore chronological gaps exist which has led to much misinterpretation of farmers’ activities. This thesis will redress this imbalance by studying the formation and continuous development of farmers’ organisations within the twenty-six county area and the reaction of farmers to changing government agricultural policies, over the period 1919 to 1936. The period under review entailed many attempts by farmers to form representative organisations and encompassed differing policy regimes. The thesis will open in 1919, when the first national organisation representing farmers, the Irish Farmers’ Union, was formed. In 1922, the union established the Farmers’ Party. By the mid- 1920’s, a number of protectionist agricultural associations had been formed. While the Farmers’ Party was eventually absorbed by Cumann na nGaedheal, local associations of independent farmers occupied the resultant vacuum and contested the 1932 election. These organisations formed the nucleus of a new national organisation; the National Farmers’ and Ratepayers’ League. The agricultural crisis caused by both the Great Depression and the Economic War facilitated the expansion of the league. The league formed a political party, the Centre Party, to contest the 1933 election. While the Centre Party was absorbed by the newly-formed Fine Gael, activists from the former farmer organisations led the campaign against the payment of annuities and rates. Many of them continued this campaign after 1934, when the Fine Gael leadership opposed the violent resistance to the collection of annuities. New farmer organisations were formed to co-ordinate this campaign which continued until 1936, the closing point of the thesis.

Block copolymer self-assembly based device structures

This thesis investigated the block copolymer (BCP) thin film characteristics and pattern formation using a set of predetermined molecular weights of PS-b-PMMA and PS-b-PDMS. Post BCP pattern fabrication on the required base substrate a dry plasma etch process was utilised for successful pattern transfer of the BCP resist onto underlying substrate. The resultant sub-10 nm device features were used in front end of line (FEoL) fabrication of active device components in integrated circuits (IC). The potential use of BCP templates were further extended to metal and metal-oxide nanowire fabrication. These nanowires were further investigated in real-time applications as novel sensors and supercapacitors.

Synthesis & characterisation of group IV semiconducting nanowires

Semiconductor nanowires, particularly group 14 semiconductor nanowires, have been the subject of intensive research in the recent past. They have been demonstrated to provide an effective, versatile route towards the continued miniaturisation and improvement of microelectronics. This thesis aims to highlight some novel ways of fabricating and controlling various aspects of the growth of Si and Ge nanowires. Chapter 1 highlights the primary technique used for the growth of nanowires in this study, namely, supercritical fluid (SCF) growth reactions. The advantages (and disadvantages) of this technique for the growth of Si and Ge nanowires are highlighted, citing numerous examples from the past ten years. The many variables involved in this technique are discussed along with the resultant characteristics of nanowires produced (diameter, doping, orientation etc.). Chapter 2 outlines the experimental methodologies used in this thesis. The analytical techniques used for the structural characterisation of nanowires produced are also described as well as the techniques used for the chemical analysis of various surface terminations. Chapter 3 describes the controlled self-seeded growth of highly crystalline Ge nanowires, in the absence of conventional metal seed catalysts, using a variety of oligosilylgermane precursors and mixtures of germane and silane compounds. A model is presented which describes the main stages of self-seeded Ge nanowire growth (nucleation, coalescence and Ostwald ripening) from the oligosilylgermane precursors and in conjunction with TEM analysis, a mechanism of growth is proposed. Chapter 4 introduces the metal assisted etching (MAE) of Si substrates to produce Si nanowires. A single step metal-assisted etch (MAE) process, utilising metal ion-containing HF solutions in the absence of an external oxidant, was developed to generate heterostructured Si nanowires with controllable porous (isotropically etched) and non-porous (anisotropically etched) segments. In Chapter 5 the bottom-up growth of Ge nanowires, similar to that described in Chapter 3, and the top down etching of Si, described in Chapter 4, are combined. The introduction of a MAE processing step in order to “sink” the Ag seeds into the growth substrate, prior to nanowire growth, is shown to dramatically decrease the mean nanowire diameters and to narrow the diameter distributions. Finally, in Chapter 6, the biotin – streptavidin interaction was explored for the purposes of developing a novel Si junctionless nanowire transistor (JNT) sensor.

Development of food ingredients for modulation of glycemia

Starches are a source of digestible carbohydrate and are frequently used in formulated food products in the presence of other carbohydrates, proteins and fat. This thesis explored the effect of addition of neutral (Konjac glucomannan) or charged (milk proteins) polymers on the physical characteristics and digestion kinetics of waxy maize starch. The aim was to identify mechanisms to modulate the pasting properties and subsequent susceptibility to amylolytic digestion. Addition of αs- or β-caseinate protein fractions to waxy maize starch restricted granular swelling during gelatinisation, increasing granule integrity. It was shown that, while β-caseinate can adsorb to starch granules during pasting, αscaseinate can be absorbed into maize starch granules. The resultant effect was a reduction in granule size after heating, more intact granules and a subsequent decrease in starch digestion in vitro as determined by analysis of reducing sugars. The ability of αs-caseinate to reduce the level of amylolytic digestion was confirmed through in vivo pig (Teagasc, Moorepark) and human (University of Surrey, UK) trials. The scope of the thesis extended to the development of a new automated cell for attachment to a rheometer to measure digestion kinetics of starch-protein mixtures. In conclusion, the thesis offers new approaches to modulation of the physical characteristics of unmodified starch during gelatinisation and suggests that the type of protein and/or polysaccharide used in starch-based food systems may influence the ability of the food to modulate glycemia. This is an important consideration in the design of foods with positive health benefits.

Ab initio calculations of group 4 metallocene reaction mechanisms: atomic layer deposition and bond activation catalysis

Thin film dielectrics based on titanium, zirconium or hafnium oxides are being introduced to increase the permittivity of insulating layers in transistors for micro/nanoelectronics and memory devices. Atomic layer deposition (ALD) is the process of choice for fabricating these films, as it allows for high control of composition and thickness in thin, conformal films which can be deposited on substrates with high aspect-ratio features. The success of this method depends crucially on the chemical properties of the precursor molecules. A successful ALD precursor should be volatile, stable in the gas-phase, but reactive on the substrate and growing surface, leading to inert by-products. In recent years, many different ALD precursors for metal oxides have been developed, but many of them suffer from low thermal stability. Much promise is shown by group 4 metal precursors that contain cyclopentadienyl (Cp = C5H5-xRx) ligands. One of the main advantages of Cp precursors is their thermal stability. In this work ab initio calculations were carried out at the level of density functional theory (DFT) on a range of heteroleptic metallocenes [M(Cp)4-n(L)n], M = Hf/Zr/Ti, L = Me and OMe, in order to find mechanistic reasons for their observed behaviour during ALD. Based on optimized monomer structures, reactivity is analyzed with respect to ligand elimination. The order in which different ligands are eliminated during ALD follows their energetics which was in agreement with experimental measurements. Titanocene-derived precursors, TiCp*(OMe)3, do not yield TiO2 films in atomic layer deposition (ALD) with water, while Ti(OMe)4 does. DFT was used to model the ALD reaction sequence and find the reason for the difference in growth behaviour. Both precursors adsorb initially via hydrogen-bonding. The simulations reveal that the Cp* ligand of TiCp*(OMe)3 lowers the Lewis acidity of the Ti centre and prevents its coordination to surface O (densification) during both of the ALD pulses. Blocking this step hindered further ALD reactions and for that reason no ALD growth is observed from TiCp*(OMe)3 and water. The thermal stability in the gas phase of Ti, Zr and Hf precursors that contain cyclopentadienyl ligands was also considered. The reaction that was found using DFT is an intramolecular α-H transfer that produces an alkylidene complex. The analysis shows that thermal stabilities of complexes of the type MCp2(CH3)2 increase down group 4 (M = Ti, Zr and Hf) due to an increase in the HOMO-LUMO band gap of the reactants, which itself increases with the electrophilicity of the metal. The reverse reaction of α-hydrogen abstraction in ZrCp2Me2 is 1,2-addition reaction of a C-H bond to a Zr=C bond. The same mechanism is investigated to determine if it operates for 1,2 addition of the tBu C-H across Hf=N in a corresponding Hf dimer complex. The aim of this work is to understand orbital interactions, how bonds break and how new bonds form, and in what state hydrogen is transferred during the reaction. Calculations reveal two synchronous and concerted electron transfers within a four-membered cyclic transition state in the plane between the cyclopentadienyl rings, one π(M=X)-to-σ(M-C) involving metal d orbitals and the other σ(C-H)-to-σ(X-H) mediating the transfer of neutral H, where X = C or N. The reaction of the hafnium dimer complex with CO that was studied for the purpose of understanding C-H bond activation has another interesting application, namely the cleavage of an N-N bond and resulting N-C bond formation. Analysis of the orbital plots reveals repulsion between the occupied orbitals on CO and the N-N unit where CO approaches along the N-N axis. The repulsions along the N-N axis are minimized by instead forming an asymmetrical intermediate in which CO first coordinates to one Hf and then to N. This breaks the symmetry of the N-N unit and the resultant mixing of MOs allows σ(NN) to be polarized, localizing electrons on the more distant N. This allowed σ(CO) and π(CO) donation to N and back-donation of π*(Hf2N2) to CO. Improved understanding of the chemistry of metal complexes can be gained from atomic-scale modelling and this provides valuable information for the design of new ALD precursors. The information gained from the model decomposition pathway can be additionally used to understand the chemistry of molecules in the ALD process as well as in catalytic systems.

Crystallisation and crystal forms of carbohydrate derivatives

This thesis is focused on the synthesis and solid state analysis of carbohydrate derivatives, including many novel compounds. Although the synthetic chemistry surrounding carbohydrates is well established in the literature, the crystal chemistry of carbohydrates is less well studied. Therefore this research aims to improve understanding of the solid state properties of carbohydrate derivatives through gaining more information on their supramolecular bonding. Chapter One focuses on an introduction to the solid state of organic compounds, with a background to crystallisation, including issues that can arise during crystal growth. Chapter Two is based on glucopyranuronate derivatives which are understudied in terms of their solid state forms. This chapter reports on the formation of novel glucuronamides and utilising the functionality of the amide bond for crystallisation. TEMPO oxidation was completed to form glucopyranuronates by oxidation of the primary alcohol groups of glucosides to the carboxylic acid derivatives, to increase functionality for enhanced crystal growth. Chapter Three reports on the synthesis of glucopyranoside derivatives by O-glycosylation reactions and displays crystal structures, including a number of previously unsolved acetate protected and deprotected crystal structures. More complex glycoside derivatives were also researched in an aim to study the resultant supramolecular motifs. Chapter Four contains the synthesis of aryl cellobioside derivatives including the novel crystal structures that were solved for the acetate protected and deprotected compounds. Research was carried out to determine if 1-deoxycellodextrins could act as putative isostructures for cellulose. Our research displays the presence of isostructural references with 1-deoxycellotriose shown to be similar to cellulose III11, 1-deoxycellotetraose correlates with cellulose IV11 and 1-deoxycellopentose shows isostructurality similar to that of cellulose II. Chapter Five contains the full experimental details and spectral characterisation of all novel compounds synthesised in this project and relevant crystallographic information.

Exploring the physicochemical basis of cheese texture, rheology and functionality, with emphasis on cation-casein interactions

The physicochemical properties of cheese and milk gels are greatly influenced by molecular interactions between the casein proteins involving calcium. Novel experiments were designed to investigate the relationship between insoluble caseinbound cations and rheological properties of Cheddar cheese and rennet-induced milk gels. Cheddar cheese and rennet-induced milk gels were supplemented with Mg2+ or Sr2+ to compare their effects on their rheological properties to those previously reported in literature for Ca2+ supplementation. Sr2+ displayed behaviour similar to Ca2+ as observed by its ability to increase the rigidity of cheese and rennet milk gels and also decrease cheese meltability. Mg+2 had no influence on cheese rheological properties and was greatly inferior to Ca2+ and Sr2+ in its ability to increase rennet milk gel elasticity. Cheddar cheese was supplemented with the calcium-chelating salts trisodium citrate, disodium hydrogen phosphate or disodium EDTA, in an attempt to reduce the CCP content of cheese and thereby modify its rheological and functional properties. TSC and EDTA were successful in decreasing cheese CCP, whereas DSP caused an initial increase in CCP content. Cheddar cheese was supplemented with chlorides of iron, copper and zinc at salting to investigate the effects of concentrations of these elements in excess of those found innately or commonly in fortification studies, with emphasis on mineral equilibria changes and resultant alteration of rheological properties. Zinc addition was the only added metal that significantly influenced cheese rheological properties, leading to an increase in cheese rigidity and decreased cheese melt at elevated temperatures. Gum tragacanth was used as a fat-replacer in the manufacture of reduced-fat Cheddar cheese, in an attempt to improve the rheological, functional and sensory properties of reduced-fat Cheddar. Overall, the experimental work reported in this thesis generated new knowledge and theories about how casein-mineral interactions influence rheological properties of casein systems.

Networking protocols for long life wireless sensor networks

My original contribution to knowledge is the creation of a WSN system that further improves the functionality of existing technology, whilst achieving improved power consumption and reliability. This thesis concerns the development of industrially applicable wireless sensor networks that are low-power, reliable and latency aware. This work aims to improve upon the state of the art in networking protocols for low-rate multi-hop wireless sensor networks. Presented is an application-driven co-design approach to the development of such a system. Starting with the physical layer, hardware was designed to meet industry specified requirements. The end system required further investigation of communications protocols that could achieve the derived application-level system performance specifications. A CSMA/TDMA hybrid MAC protocol was developed, leveraging numerous techniques from the literature and novel optimisations. It extends the current art with respect to power consumption for radio duty-cycled applications, and reliability, in dense wireless sensor networks, whilst respecting latency bounds. Specifically, it provides 100% packet delivery for 11 concurrent senders transmitting towards a single radio duty cycled sink-node. This is representative of an order of magnitude improvement over the comparable art, considering MAC-only mechanisms. A novel latency-aware routing protocol was developed to exploit the developed hardware and MAC protocol. It is based on a new weighted objective function with multiple fail safe mechanisms to ensure extremely high reliability and robustness. The system was empirically evaluated on two hardware platforms. These are the application-specific custom 868 MHz node and the de facto community-standard TelosB. Extensive empirical comparative performance analyses were conducted against the relevant art to demonstrate the advances made. The resultant system is capable of exceeding 10-year battery life, and exhibits reliability performance in excess of 99.9%.

Atomic layer deposition of interface control layers for the fabrication of III/V MOS devices

The continued advancement of metal oxide semiconductor field effect transistor (MOSFET) technology has shifted the focus from Si/SiO2 transistors towards high-κ/III-V transistors for high performance, faster devices. This has been necessary due to the limitations associated with the scaling of the SiO2 thickness below ~1 nm and the associated increased leakage current due to direct electron tunnelling through the gate oxide. The use of these materials exhibiting lower effective charge carrier mass in conjunction with the use of a high-κ gate oxide allows for the continuation of device scaling and increases in the associated MOSFET device performance. The high-κ/III-V interface is a critical challenge to the integration of high-κ dielectrics on III-V channels. The interfacial chemistry of the high-κ/III-V system is more complex than Si, due to the nature of the multitude of potential native oxide chemistries at the surface with the resultant interfacial layer showing poor electrical insulating properties when high-κ dielectrics are deposited directly on these oxides. It is necessary to ensure that a good quality interface is formed in order to reduce leakage and interface state defect density to maximise channel mobility and reduce variability and power dissipation. In this work, the ALD growth of aluminium oxide (Al2O3) and hafnium oxide (HfO2) after various surface pre-treatments was carried out, with the aim of improving the high-κ/III-V interface by reducing the Dit – the density of interface defects caused by imperfections such as dangling bonds, dimers and other unsatisfied bonds at the interfaces of materials. A brief investigation was performed into the structural and electrical properties of Al2O3 films deposited on In0.53Ga0.47As at 200 and 300oC via a novel amidinate precursor. Samples were determined to experience a severe nucleation delay when deposited directly on native oxides, leading to diminished functionality as a gate insulator due to largely reduced growth per cycle. Aluminium oxide MOS capacitors were prepared by ALD and the electrical characteristics of GaAs, In0.53Ga0.47As and InP capacitors which had been exposed to pre-pulse treatments from triethyl gallium and trimethyl indium were examined, to determine if self-cleaning reactions similar to those of trimethyl aluminium occur for other alkyl precursors. An improved C-V characteristic was observed for GaAs devices indicating an improved interface possibly indicating an improvement of the surface upon pre-pulsing with TEG, conversely degraded electrical characteristics observed for In0.53Ga0.47As and InP MOS devices after pre-treatment with triethyl gallium and trimethyl indium respectively. The electrical characteristics of Al2O3/In0.53Ga0.47As MOS capacitors after in-situ H2/Ar plasma treatment or in-situ ammonium sulphide passivation were investigated and estimates of interface Dit calculated. The use of plasma reduced the amount of interface defects as evidenced in the improved C-V characteristics. Samples treated with ammonium sulphide in the ALD chamber were found to display no significant improvement of the high-κ/III-V interface. HfO2 MOS capacitors were fabricated using two different precursors comparing the industry standard hafnium chloride process with deposition from amide precursors incorporating a ~1nm interface control layer of aluminium oxide and the structural and electrical properties investigated. Capacitors furnished from the chloride process exhibited lower hysteresis and improved C-V characteristics as compared to that of hafnium dioxide grown from an amide precursor, an indication that no etching of the film takes place using the chloride precursor in conjunction with a 1nm interlayer. Optimisation of the amide process was carried out and scaled samples electrically characterised in order to determine if reduced bilayer structures display improved electrical characteristics. Samples were determined to exhibit good electrical characteristics with a low midgap Dit indicative of an unpinned Fermi level