The formation of silicon nitride from trisilylamine and ammonia

Silane gas has been used for three decades as a precursor for plasma enhanced chemical vapour deposition processes but is unsustainable in the longer term due to the extremely hazardous nature of the compound. Alternative precursor materials have been proposed but have proved to be largely incompatible with the chemistry of the deposition process or the requirements of semiconductor process technology. One compound with the chemical and technological potential as a precursor for silicon nitride deposition is trisilylamine. Calculation of the Gibbs free energy change for the formation of silicon nitride from the reaction of trisilylamine and ammonia demonstrates that the reaction IS thermodynamically feasible as is the reaction involving silane with ammonia. The standard molar enthalpy of formation for trisilylamine was obtained from a semiempirical molecular orbital calculation while the standard molar entropy of formation was determined from spectroscopic data in the absence of a calorimetric value. Thermodynamic properties have been calculated for a range of aminated species using semi-empirical methods and entropy vs. molecular weight equations. These species are potential intermediates in a plasma discharge of trisilylamine and ammonia, with their successive combination leading to the deposition of a film of silicon nitride. Thermodynamic values for reactions involving the formation, propagation and termination of radical species of trisily lamine and ammonia have been determined and a mechanism is proposed for the deposition of silicon nitride films by plasma enhanced chemical vapour deposition. These results indicate that there is no thermodynamic barrier to the use of trisilylamine as a precursor with ammonia gas for the plasma enhanced deposition of silicon nitride films

Modular assembly with postponement to improve health, safety & productivity in construction

This paper presents the outcome of an engineering study as part of the design and development of a lean and agile construction system and in particular its supply chain component. This combines modular assembly with a postponement function to be tested on a case study project (not reported here), the objective of which is to improve health, safety and productivity for the company sponsoring the research. The contribution to research is the combination of countermeasures described in this paper that have been developed and incorporated into a wider construction system, in the same way that manufacturing has used this strategy with great success. Also, a further output is the development and use of an innovative method for assembling, transporting and installing mechanical and electrical modules, whereby modularization can be achieved with or without offsite manufacturing capability. The research forecasts a reduction of onsite labor of 35% compared to using traditional methods of construction, with less onsite operatives at risk of injury carrying out simpler assembly tasks within ergonomic mobile work cells. Further research is proposed to measure the benefits of the construction system following its implementation on a case study project

Toward Consistent Cross-Hauling Estimation for Input-Output Regionalization

Although the literature has provided steps in the right direction, conceptual shortcomings still exist in the cross-hauling adjustment methods that are currently being applied in the literature. This paper represents an attempt to 1) characterize the cross-hauling adjustment methods that exist in the literature; 2) identify the shortcomings that exist with the most widely applied method, CHARM; 3) provide an empirical analysis to tackle the notion of just how ubiquitous crosshauling is and the potential impact it has on input-output multiplier estimates; and 4) suggest directions for future conceptual and theoretical development that will lead to consistent cross-hauling measures for use

A Role for Regional Science in Analyzing Water Issues

The World Economic Forum has consistently ranked water crises as one of the top five most impactful issues facing humanity, alongside but not completely separate from issues such as climate change and natural disasters (World Economic Forum, 2019). A growing population and changing climate will only further stress the constrained water system. Acute and ongoing societal disruptions, caused by significant declines in the available quality and quantity of fresh water around the globe, underscore the importance of water to human life and a functional society. The papers in this special issue highlight the role that regional scientists can and should play in informed decision-making related to water at the local, regional, and national scale

Development and operation of the twin radio frequency single electron transistor for solid state qubit readout

Ultra-sensitive detectors and readout devices based on the radio frequency single electron transistor (rf-SET) combine near quantum-limited sensitivity with fast operation. Here we describe a twin rf-SET detector that uses two superconducting rf-SETs to perform fast, real-time cross-correlated measurements in order to distinguish sub-electron signals from charge noise on microsecond time-scales. The twin rf-SET makes use of two tuned resonance circuits to simultaneously and independently address both rf-SETs using wavelength division multiplexing (WDM) and a single cryogenic amplifier. We focus on the operation of the twin rf-SET as a charge detector and evaluate the cross-talk between the two resonance circuits. Real time suppression of charge noise is demonstrated by cross correlating the signals from the two rf-SETs. For the case of simultaneous operation, the rf-SETs had charge sensitivities of $\delta q_{SET1} = 7.5 \mu e/\sqrt{Hz}$ and $\delta q_{SET2} = 4.4 \mu e/\sqrt{Hz}$.Comment: Updated version, including new content. Comments most welcome: [email protected] or [email protected]

Analogy in Contact: Modeling Maltese Plural Inflection

Maltese is often described as having a hybrid morphological system resulting from extensive contact between Semitic and Romance language varieties. Such a designation reflects an etymological divide as much as it does a larger tradition in the literature to consider concatenative and non-concatenative morphological patterns as distinct in the language architecture. Using a combination of computational modeling and information theoretic methods, we quantify the extent to which the phonology and etymology of a Maltese singular noun may predict the morphological process (affixal vs. templatic) as well as the specific plural allomorph (affix or template) relating a singular noun to its associated plural form(s) in the lexicon. The results indicate phonological pressures shape the organization of the Maltese lexicon with predictive power that extends beyond that of a word\u27s etymology, in line with analogical theories of language change in contact

The Role of Regional Science in Shale Energy Development

The most recent boom in fossil fuel extraction is noteworthy through its extensive use of advanced technologies called hydraulic fracturing and horizontal drilling. The papers in this issue demonstrate the role that regional science can and should play in guiding policy, usefully complementing research from physical science and engineering disciplines that focuses on the important geological and environmental consequences of shale energy production. Furthermore, we underscore the need for expanding the traditional regional science focus in policy discussions pertaining to shale energy