Structural defects in CdTe

This thesis is primarily concerned with the characterisation of the native defects present in CdTe crystals grown from the vapour phase using two different methods. The principal characterisation techniques used were TEM, SEM and etching/optical microscopy. Crystal defects in bulk CdTe are of great importance since this material is in demand as a substrate for the epitaxial growth of Cd(_x)Hg(_1-x)Te for use in large area infra-red imaging devices. Large single crystals grown using the 'Durham' technique invariably contain first order twin boundaries lying on {111} planes and these are of the 'ortho'-type. Twin boundaries on other planes were characterised using the coincidence site lattice models of twin boundaries in sphalerite which were developed during this work. First order lateral twin boundaries lying on {511}-{111}, {112}-{112}, {001}-{221} and {110}-{114} and second order twin boundaries lying on {111}-{115} {114}-{114} and {22l}-{22l} are discussed. Twinning in CdTe is thought to be due to post-growth stress rather than to a growth phenomenon. The dislocations which are present in crystals grown by the 'Durham’ method are predominantly concentrated into well-formed arrays which are sometimes associated with other crystal defects. These arrays were shown by EBIC studies to be electrically active and the average sub-grain dimension was found to be ~ 150 µm. It is thought that the arrays form as a result of dislocation polygonisation during the latter stages of growth. Precipitates, which were identified as being comprised of Te, are found in the bulk of the crystals although they are more often seen on twin boundaries. The relationship between boundary type and the density of precipitates is discussed. Sub-grain boundaries and precipitates were also examined in a small number of CdTe crystals which had been grown by a modified 'Piper-Polich' technique. The differences between the defects in this material and those in CdTe crystals grown by the 'Durham' method are fully explained in terms of the differences in the crystal growth conditions employed in the two techniques. Networks of dislocations in Cd(_0.95) Zn(_0.0 5) Te crystals grown by the 'Durham' technique were also investigated. A mechanochemical polishing machine which was developed during the course of this work and which is capable of producing high quality chemically polished surfaces is described. Also the use of chemical etchants to determine the crystallographic polarity of {111} oriented surfaces is clarified. Important features of this work include; the development of coincidence site lattice models of first order lateral and second order twin boundaries in the sphalerite structure and the thorough characterisation of these boundaries in as-grown CdTe crystals, and the comparison of the sub-grain boundaries and precipitates present in material grown from the vapour phase by two different techniques

Towards the ‘Big Society’: What role for neighbourhood working? Evidence from a comparative European study

Under the New Labour government, the neighbourhood emerged prominently as a site for policy interventions and as a space for civic activity, resulting in the widespread establishment of neighbourhood-level structures for decision-making and service delivery. The future existence and utility of these arrangements is now unclear under the Coalition government's Big Society proposals and fiscal austerity measures. On the one hand, sub-local governance structures might be seen as promoting central-to-local and local-to-community devolution of decision-making. On the other, they might be seen as layers of expensive bureaucracy standing in the way of bottom-up community action. Arguably the current value and future role of these structures in facilitating the Big Society will depend on how they are constituted and with what purpose. There are many local variations. In this paper we look at three case studies, in England, France and the Netherlands, to learn how different approaches to neighbourhood working have facilitated and constrained civic participation and action. Drawing on the work of Lowndes and Sullivan (2008) we show how the achievement of civic objectives can be hampered in structures set up primarily to achieve social, economic and political goals, partly because of (remediable) flaws in civic engagement but partly because of the inherent tensions between these objectives in relation to issues of spatial scale and the constitution and function of neighbourhood structures. The purpose of neighbourhood structures needs to be clearly thought through. We also note a distinction between 'invited' and 'popular' spaces for citizen involvement, the latter being created by citizens themselves. 'Invited' spaces have tended to dominate to date, and the Coalition's agenda suggests a fundamental shift to 'popular' spaces. However we conclude that the Big Society will require neighbourhood working to be both invited and popular. Citizen participation cannot always replace local government - sometimes it requires its support and stimulation. The challenge for local authorities is to reconstitute 'invited' spaces (not to abolish them) and at the same time to facilitate 'popular' spaces for neighbourhood working.Big Society, local government, neighbourhood, neighbourhood management, community

Control of grain size in sublimation-grown CdTe, and the improvement in performance of devices with systematically increased grain size

A method to control the grain size of CdTe thin films deposited by close space sublimation using chamber pressure is demonstrated. Grain diameter is shown to increase in the pressure range 2–200 Torr, following the linear relationship D (?m)=0.027×P (Torr)+0.90. A mechanism is proposed to explain the dominance of the 111 preferred orientation in the small-grained, but not the large-grained films. For a series of CdTe/CdS solar cells in which the only variable was grain size, the performance parameters were seen to increase from 0.54% (0.94 ?m grains) up to a plateau of 11.3% (?3.6 ?m grains). This corresponds to the point at which the series resistance is no longer dominated by grain boundaries, but by the contacts

Materialism and Well‑Being Revisited: The Impact of Personality

Although the negative link between materialism and well-being has been confirmed by results from many empirical studies, mechanisms underlying this association still remain partially unexplained. The issue is addressed in this article in two ways. Firstly, the nature of the components of materialism is examined, and secondly—the article demonstrates that personality (particularly neuroticism and narcissism) is one of the important factors linking materialism and well-being. The article presents the results of three empirical studies, in which three main assumptions were verified—that the components of materialism, i.e. acquisition centrality, acquisition as a pursuit of happiness and possession-defined success, have dissimilar impacts on well-being, that materialists with high and low levels of neuroticism and narcissism differ with regard to well-being, and that neuroticism and narcissism mediate the relationship between materialism and well-being. The studies were based on self-reports and utilized well-known, established questionnaire measures of materialism, personality and well-being. The results showed that each component of materialism was associated with well-being in a slightly different way. Of the three possession-defined happiness was the strongest predictor of all aspects of well-being examined and the centrality component was not associated with any of them. Materialists with a high level of neuroticism and low level of grandiose narcissism experienced diminished well-being in comparison to materialism with a low level of neuroticism and high level of grandiose narcissism. Neuroticism and grandiose narcissism were both significant mediators, acting contrary to each other—neuroticism lowered well-being, whereas grandiose narcissism elevated it

Deconstructing materialism – towards a better understanding of its connections with well-being

According to the most popular conceptualization of materialism by Richins and Dawson it consists of three components: acquisition centrality, acquisition as the pursuit of happiness and possession -defined success. They are usually combined and an overall indicator of materialism is used commonly in various studies. In the article the three components are examined separately. Differences in their nature are revealed in a theoretical analysis, whereas in two empirical studies the ways they connect with well -being are presented. The results show that the overall materialism explains much less variance of well -being than the three components taken separately. Of the three the possession- -defined happiness is the most detrimental to all aspects of well -being. The possession -defined success does not connect with well -being at all. Finally, acquisition centrality elevates hedonic and psychological well -being. The conclusion is that the modest effect of materialism on well -being, usually identified in various studies, is probably at least partly due to conflicting forces existing within the construct

Fast scholarship is not always good scholarship: relevant research requires more than an online presence.

Blogging and social media are tools to facilitate engagement, but are they in danger of being treated as ends in themselves? Catherine Durose and Katherine Tonkiss argue for more awareness on how the research process can democratise knowledge. Rather than quickly responding to recent events, scholars should look towards sustained engagement with the participants of research and those affected by it

The structure of goal contents revisited : a verification of the model in polish samples

The article presents an attempt to confirm the circumplex structure of goal contents, identified in 15 cultures around the world (Grouzet et al., 2005), in nine Polish samples. The procedure followed steps from the original study and included testing the assumed 11-factor goal structure and the two-dimensional circular organization of the goal contents. None of the analyses showed outcomes that would explicitly confirm the results attained in the original study. The CFA showed rather poor fits. Results of the MDS generally supported the assumption about the two-dimensional goal contents structure, however ipsative distance analysis reproduced only one of the two assumed dimensions. Finally, although the CIRCUM analysis showed in principle that in the Polish sample the organization of goal contents on the circumference was quite similar to original, the RMSEA indicated poor fit. Methodological and conceptual reasons for the replication failure are analyzed and discussed

The expansion of arms-length government is not necessarily at odds with democratic accountability

How democratic is arms-length government? Catherine Durose, Jonathan B. Justice and Chris Skelcher argue that those who consider it to be an undemocratic phenomenon over-simplify, and make the case for assessing the question in a more citizen and community focussed manner

Nanowire and core-shell-structures on flexible Mo Foil for CdTe solar cell applications

CdTe films, nanowires, film-nanowire combinations and CdS-CdTe core-shell structures have been fabricated in a preliminary survey of growth methods that will generate structures for PV applications. Selectivity between film, nanowire and film plus nanowire growth was achieved by varying the pressure of N2 gas present during Au-catalysed VLS growth of CdTe, on either Mo or Si substrates. Metamorphic growth of CdTe nanowires on sputtered CdTe films, deposited on glass substrates, was demonstrated. Coating of CdTe nanowires with CBD CdS gave conformal coverage whereas coating with MOCVD (Cd,Zn)S yielded highly crystallographic dendritic growth on the wires

Intrinsic - Extrinsic - Transcendent. A triarchic model of goal contents: introduction and validation

The article refers to an 11-factor circumplex model of goal contents introduced by Grouzet et al., which suggested a consistent structure of goals allocated within two dimensions: extrinsic–intrinsic and self-transcendent–physical. A previous study showed a rather poor fit of this model in a Polish context. Therefore using data from the aforementioned replication project in Study I we re-examined the structure and found a triarchic configuration more adequately fitting existing data. This new model was further tested in Study II. To find an adequate factor structure of life goals measured by the Polish version of the Aspiration Index in Study I we ran exploratory and confirmatory factor analyses in three groups of 1,762 people in total. To check psychometric characteristics of the developed AI-23 questionnaire we conducted Study II on a group of 319 students. The analyses revealed a new structure of the Aspiration Index consisting of scales related to seven life goals connected with three general groups of goals: intrinsic, extrinsic and transcendent. Results of confirmatory factor analysis, convergent and divergent validation, internal consistency and test–retest reliability allowed AI-23 to be treated as an effective tool to measure life goals. The results suggest a triarchic organization of goal contents, with self-transcendent goals supplementing well-established theoretical categories of intrinsic and extrinsic goals