MOVPE growth and characterization of Al(Ga)N and InAlN/AlGaN quantum wells for UV LED applications

The study of III-nitride materials (InN, GaN and AlN) gained huge research momentum after breakthroughs in the production light emitting diodes (LEDs) and laser diodes (LDs) over the past two decades. Last year, the Nobel Prize in Physics was awarded jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for inventing a new energy efficient and environmental friendly light source: blue light-emitting diode (LED) from III-nitride semiconductors in the early 1990s. Nowadays, III-nitride materials not only play an increasingly important role in the lighting technology, but also become prospective candidates in other areas, for example, the high frequency (RF) high electron mobility transistor (HEMT) and photovoltaics. These devices require the growth of high quality III-nitride films, which can be prepared using metal organic vapour phase epitaxy (MOVPE). The main aim of my thesis is to study and develop the growth of III-nitride films, including AlN, u-AlGaN, Si-doped AlGaN, and InAlN, serving as sample wafers for fabrication of ultraviolet (UV) LEDs, in order to replace the conventional bulky, expensive and environmentally harmful mercury lamp as new UV light sources. For application to UV LEDs, reducing the threading dislocation density (TDD) in AlN epilayers on sapphire substrates is a key parameter for achieving high-efficiency AlGaNbased UV emitters. In Chapter 4, after careful and systematic optimisation， a working set of conditions, the screw and edge type dislocation density in the AlN were reduced to around 2.2×108 cm-2 and 1.3×109 cm-2 , respectively, using an optimized three-step process, as estimated by TEM. An atomically smooth surface with an RMS roughness of around 0.3 nm achieved over 5×5 µm 2 AFM scale. Furthermore, the motion of the steps in a one dimension model has been proposed to describe surface morphology evolution, especially the step bunching feature found under non-optimal conditions. In Chapter 5, control of alloy composition and the maintenance of compositional uniformity across a growing epilayer surface were demonstrated for the development of u-AlGaN epilayers. Optimized conditions (i.e. a high growth temperature of 1245 °C) produced uniform and smooth film with a low RMS roughness of around 2 nm achieved in 20×20 µm 2 AFM scan. The dopant that is most commonly used to obtain n-type conductivity in AlxGa1-xN is Si. However, the incorporation of Si has been found to increase the strain relaxation and promote unintentional incorporation of other impurities (O and C) during Si-doped AlGaN growth. In Chapter 6, reducing edge-type TDs is observed to be an effective appoach to improve the electric and optical properties of Si-doped AlGaN epilayers. In addition, the maximum electron concentration of 1.3×1019 cm-3 and 6.4×1018 cm-3 were achieved in Si-doped Al0.48Ga0.52N and Al0.6Ga0.4N epilayers as measured using Hall effect. Finally, in Chapter 7, studies on the growth of InAlN/AlGaN multiple quantum well (MQW) structures were performed, and exposing InAlN QW to a higher temperature during the ramp to the growth temperature of AlGaN barrier (around 1100 °C) will suffer a significant indium (In) desorption. To overcome this issue, quasi-two-tempeature (Q2T) technique was applied to protect InAlN QW. After optimization, an intense UV emission from MQWs has been observed in the UV spectral range from 320 to 350 nm measured by room temperature photoluminescence.

The Queen's College, Cork: its origins and early history, 1803-1858

This work examines the origins and early history of the Queen's College, Cork. Designedly there is as much stress on the origins as on the early history, for it is the contention of the work that the College was something more than a legislative mushroom. It was very much in the tradition of the civic universities which added an exciting new dimension to academic life in these islands in the nineteenth century. The first chapter surveys university practice and thinking at the opening of the century, relying exclusively on published sources. The second chapter is devoted specifically to the state of learning in Cork during the period, and makes extensive use of hitherto unpublished manuscript material in relation to the Royal Cork Institution. The third chapter deals with the highly significant evidence on education embodied in the Report of the Select Committee on Irish Education of 1838. This material has not previously been published. In chapter four an extended study is made of relevant letters in the manuscript correspondence of Sir Robert Peel - even the most recent authoritative biography has ignored this material. The remaining three chapters are devoted more specifically to the College, both in the formulation or policy and in its practical working. In chapter six there is an extended survey of early College life based exclusively on hitherto unpublished manuscript material in the College Archives. All of these sources, together with incidental published material, are set out at the end of each chapter.

An dátheangachas agus an t-aitheantas: déagóirí Éireannacha sa 21ú haois

Tugann an staidéar taighde aghaidh ar an dátheangachas i bPoblacht na hÉireann agus go háirithe ar thuairimí dhaoine óga dátheangacha sa 21ú haois. Is é cuspóir an staidéir ná iniúchadh a dhéanamh ar mheonta déagóirí Éireannacha dátheangacha i leith na Gaeilge agus a gcuid aitheantais mar dhéagóirí dátheangacha. Déanann an staidéar anailís ar mheonta daltaí a fhreastalaíonn ar iar-bhunscoileanna lán-Ghaeilge. Féachtar ar thuairimí tuismitheoirí, múinteoirí agus iar-scoláirí freisin. Is í príomhcheist an staidéir seo ná: Cad iad meonta déagóirí Éireannacha dátheangacha i leith teanga na Gaeilge agus cad iad a n-aitheantais mar Éireannaigh óga dátheangacha? Baineadh úsáid as modhanna cáilíochtúla idir agallaimh, agallamh grúpa, scríbhneoireacht phearsanta agus ríomhphoist chun eolas a bhailiú i scoil an staidéir cháis. Roghnaíodh modh cainníochtúil an cheistneora náisiúnta chun cur leis an eolas. Tugann an taighde le tuiscint go mothaíonn déagóirí Éireannacha dearfach faoi theanga na Gaeilge agus faoin a gcuid aitheantais mar dhaoine dátheangacha. Léiríonn torthaí an taighde gurb ionann teanga na Gaeilge dóibh agus seoid luachmhar a sholáthraíonn buntáistí, deiseanna agus féidearthachtaí dóibh. Maidir le cruthú aitheantais, chuaigh formhór na ndéagóirí i scoil an staidéir cháis i dtreo a ndá ghrúpa teangeolaíochta agus chruthaigh siad “linguistic brokerage” (Shenk, 2008) a tharraing a taobh Gaelach is Béarla le chéile. Mothaíonn formhór na ndéagóirí dátheangacha seo go bhfuil aitheantas amháin acu ach go bhfuil an dá theanga, an dá chultúr agus an dá pháirt dá saoil mar pháirt den gcomhaitheantas sin. Ach ba léir go raibh éagsúlachtaí i measc na rannpháirtithe freisin. Tacaíonn torthaí an taighde le gnéithe den litríocht ar a rinneadh athbhreithniú chun ról lárnach na teanga i gcruthú aitheantais an déagóra a léiriú. Cuireann an taighde seo leis an réimse toisc go soláthraíonn sé eolas luachmhar agus fiúntach faoin dátheangachas agus aitheantas i bPoblacht na hÉireann sa 21ú haois.

Mícheál Coimín agus a shaothar

Is é a chuirim romham a dhéanamh sa tráchtas seo ná eagar a chur ar shaothar liteartha Mhíchíl Coimín; file agus údar próis a bhí ag saothrú na litríochta i gCill Chorcoráin, Contae an Chláir san ochtú haois déag. D’éag sé sa bhliain 1760 nuair a bhí sé beagnach 90 bliain d’aois. Is féidir a rá go bhfuil an Coimíneach, ó thaobh chanóin litríocht na Gaeilge de i measc na mionscríbhneoirí, agus níl aon dabht faoi ach go bhfuil an-chuid de léitheoirí na Gaeilge sa lá atá inniu ann dall ar a chuid scríbhneoireachta. Tá cáil air mar údar ‘Laoi Oisín i dTír na n-Óg’ ach mar a léireofar sa tráchtas seo, tá gach cuma ar an scéal nárbh é a scríobh. Tá againn óna pheann dornán beag dánta agus dhá scéal rómánsaíochta (‘Eachtra Thoroilbh Mhic Stairn’ agus ‘Eachtra a Thriúr Mac’) a scríobh sé nuair a bhí an traidisiún sin próis ar an dé deiridh. Níl aon chuid dá shaothar ar fáil in eagráin a shásódh léitheoirí an lae inniu ná na critéir scolártha atá i bhfeidhm anois. Níor tháinig aon lámhscríbhinn, i lámh an Choimínigh, anuas chugainn agus dá bhrí sin bhí dúshlán áirithe ag baint leis an bpróiseas eagarthóireachta. Sa tráchtas rinne mé an suirbhé is iomláine go dtí seo ar a shaothar i dtraidisiún na lámhscríbhinní agus ar na scríobhaithe a rinne é a sheachadadh. Bhí sé mar aidhm agam teacht ar na lámhscríbhinní is údarásaí sa traidisiún d’fhonn eagráin a réiteach a bheadh dílis dá bhunshaothar. Chomh maith leis sin tabharfar cuntas ar a bheatha agus ar a chúlra liteartha, agus déanfar iniúchadh criticiúil ar a shaothar próis agus fileata.

College adjustment, depressive symptoms and peer support among undergraduate university students

Background: College adjustment is a developmental milestone that can be stressful and may lead to mental health problems such as depression. Support during this adjustment period is seen as essential, however it is unknown if informal peer support from fellow students has any impact on either college adjustment or depressive symptoms. Aim: To identify levels of social and personal college adjustment, depressive symptoms and peer support among students, and to examine the relationship between the variables. Design: A quantitative correlational design was used Instruments: Data were collected using two subscales of the Student Adaptation to College Questionnaire; the Centre for Epidemiology Depressive Symptoms Scale and a subscale of the Peer Support Evaluation Inventory. Sample: The sample consisted of 417, first (n=188), second (n=134) and fourth (n=94) year nursing and midwifery students from one University in Ireland. Findings: The findings indicated that 20% of participants were poorly personally adjusted and 9% poorly socially adjusted. Furthermore, 34% of participants experienced significant depressive symptoms. Most students had good levels of peer support. Statistically significant relationships were found between all key variables, the strongest of which were between personal adjustment and depressive symptoms and social adjustment and depressive symptoms. Differences in adjustment and depressive symptom scores were found based on year of study, with second year students experiencing more depressive symptoms and having poorer personal adjustment scores. Participants who had poor relationships with their father’s experienced greater depressive symptoms and had more difficulties personally and socially adjusting to college. The alcohol consumption of participants had a statistically significant correlation with college adjustment, depressive symptoms and peer support, with higher consumption having a positive impact on the variables.

Aspects of the biology of the parasite Bonamia ostreae with a view to gaining a greater understanding of how to alleviate its impact on the European flat oyster, Ostrea edulis.

The parasite Bonamia ostreae has decimated Ostrea edulis stocks throughout Europe. The complete life cycle and means of transmission of the parasite remains unknown. The methods used to diagnose B. ostreae were examined to determine sensitivity and reproducibility. Two methods, with fixed protocols, should be used for the accurate detection of infection within a sample. A 13-month study of two stocks of O. edulis with varying periods of exposure to B. ostreae, was undertaken to determine if varying lengths of exposure would translate into observations of differing susceptibility. Oyster stocks can maintain themselves over extended periods of time in B. ostreae endemic areas. To identify a well performing spat stock, which could be used to repopulate beds within the region, hatchery bred spat from three stocks found in the North sea were placed on a B. ostreae infected bed and screened for growth, mortality and prevalence of infection. Local environmental factors may influence oyster performance, with local stocks better adapted to these conditions. Sediment and macroinvertebrate species were screened to investigate mechanisms by which B. ostreae may be maintaining itself on oyster beds. Mytilus edulis was positive, indicating that B. ostreae may use incidental carriers as a method of maintaining itself. The ability of oyster larvae to pick up infection from the surrounding environment was investigated by collecting larvae from brooding oysters from different areas. Larvae may acquire the pathogen from the water column during the process of filter feeding by the brooding adult, even when the parents themselves are uninfected. A study was undertaken to elucidate the activity of the parasite during the initial stage of infection, when it cannot be detected within the host. A naïve stock screened negative for infection throughout the trial, using heart imprints and PCR yet B. ostreae was detected by in-situ hybridisation.

Béal Átha an Ghaorthaidh: logainmneacha agus dinnseanchas

Is é atá sa tráchtas ná staidéar ar logainmneacha agus dinnseanchas ceantair Ghaeltachta Bhéal Átha an Ghaorthaidh. Ins na léarscáileanna a cruthaíodh tá iarracht ar na logainmneacha a líonadh isteach chomh cruinn is ab fhéidir agus furasta iad a aimsiú mar go bhfuil iomlán an eolais ar leathanach amháin. Cuireadh leis an eolas seo trí úsáid foinsí béaloidis a bhain leis an gceantar nó baile fearainn agus is iad Páipéir Uí Dhonnchadha agus Cnuasach Bhéaloideas Éireann is mó a úsáideadh. Tá a lán eolas a bhailigh An tAth Ó Donnchadha faoin nGuagán scríte anseo agus tugann sé le fios a lán dúinn ar an áit agus imeachtaí na haimsire sin.

The endless search for SA: spiritual ideology in Hindustāni music

This dissertation centres on philosophical attitudes presented by North Indian classical musicians in relation to the concept and experience of rāga improvisation. In Hindustāni music, there is a dynamic tension ideology and pragmatism, devotion and entertainment, fixity and improvisational freedom, and cognition and visceral experience. On one hand, rāga is an embodied methodological template for the creation of music. On the other hand, rāga improvisation is conceptualised as a path to metaphysical experience and as an evocation of an ineffable divine presence. A masterful rendition of rāga is both a re-enactment of a systematic prescribed formula and a spontaneous flow of consciousness. This study presents these apparent dichotomies to highlight ideological concerns, while simultaneously contextualising philosophical idealism in relation to pragmatic realities. A central paradigm is the manner in which pragmatic concerns are elevated in status and given spiritual significance. The dissertation begins with a view into historical and religious context. The discussion continues with a speculative investigation positing co-relations between Hindustāni music and central tenets of Indian philosophy, considering how rāga improvisation may manifest as a philosophy of sound. The study then explores the concept of rāga, a modal and conceptual construct that forms the heart of Indian classical music. The final three sections ground the subject of spiritual ideology within the life experience of Hindustāni musicians: ‘Transmission’ looks at the learning and enculturation process, which encapsulates values intrinsic to the ethos of Hindustāni music culture. ‘Practice’ explores the discipline, science and experience of musical practice, revealing core ideological concerns connecting spirituality to musical experience; and ‘Performance’ examines the live presentation of rāga improvisation, and the relationship between music as ‘entertainment’ and music as ‘devotion’. Both ethnographic and musicological, this research is the culmination of various fieldtrips to India, extensive interviews with Hindustāni musicians, fifteen year’s sitār training, and the study of relevant musicological and philosophical texts.

Stair na Gaeilge i gContae Thiobraid Árann 1700-1901

Stair na Gaeilge i gCo. Thiobraid Árann i rith na tréimhse 1700-1901 atá á ríomhadh sa tráchtas seo. Tar éis a cúlra agus a comhthéacs a shuíomh i gCaibidil a hAon, déantar scríobhaithe an cheantair a áireamh, fara tráchtaireacht orthu, i gCaibidil a Dó. I gCaibidlí a Trí agus a Ceathair, féachtar ar thionchar na hEaglaisí Caitlicí agus Eaglais na hÉireann (i measc eaglaisí Protastúnacha eile) ar an dteangain. I gCaibidil a Cúig, faightear spléachadh ar ghnéithe éagsúla de shaíocht an chontae, ag tabhairt léargais ar tháirgí na scríobhaithe, ar leabhair a clóbhualadh sa réigiún, agus ar fhilí móra na háite, leithéidí Liam Daill Uí Ifearnáin, ag sonrú limistéir faoi leith, an t-oirdheisceart, mar shampla. Léirítear éifeacht na gcumann Gaelach agus na ndíograiseoirí iomadúla a bhain leo. Ábhar suime, leis, feidhm na Gaeilge sna cúirteanna dlí. Tugtar faisnéis i gCaibidil a Sé ar fhianaise cuairteoirí ar an Ghaeilge mar urlabhra i dTiobraid Árann. Is anseo chomh maith a deintear anailís ar Dhaonáirimh na mblianta 1861-1901, le mórchuid adhmaid á baint as ceann 1901 go háirithe. Breactar as ainmneacha sagart agus múinteoirí le Gaeilge, agus tráchtar ar aicmí suntasacha eile, na póilíní agus na saighdiúirí a raibh an teanga sin ina mbéal acu. Tugtar le chéile dá réir na snáithíní difriúla eolais ar an dúiche ar bhealach nár tharla cheana don gcontae casta fairsing seo le haghaidh na tréimhse atá idir lámha ag an saothar.

Na marbhnaí do Shéamas Óg Mac Coitir (1689-1720)

Go príomha, is tráchtas é seo a dhéanann staidéar ar ghné de litríocht iar-chlasaiceach na Gaeilge. Baineann sé go háirithe leis an sraith chaointe nó marbhnaí i bhfoirm véarsaíochta a cumadh do Shéamas Óg Mac Coitir (1689-1720), duine uasal Caitliceach ó Charraig Tuathail, Co. Chorcaí, nuair a ciontaíodh é in éigniú Elizabeth Squibb, bean de Chumann na gCarad; nuair a cuireadh pionós an bháis air; agus nuair a crochadh é i gCathair Chorcaí an 7 Bealtaine, 1720. Ó thaobh na staire de, scrúdaítear Clann Choitir mar shampla de theaghlach nár cheil a ndílseacht do chúis pholaitiúil na Stíobhartach agus a sheas an fód go cróga faoi mar a bhí a ngreim polaitiúil á dhaingniú ag an gCinsealacht Phrotastúnach ó dheireadh an 17ú haois amach. Tagraítear do sheicteachas na sochaí comhaimseartha agus don teannas idir an pobal Caitliceach agus an pobal Protastúnach ag an am. Déantar scagadh ar an véarsaíocht mar fhoinse luachmhar do dhearcadh míshásta an mhóraimh Chaitlicigh ar struchtúr polaitiúil chontae Chorcaí (agus na hÉireann) i dtosach an 18ú haois. Is feiniméan liteartha an dlús véarsaíochta seo a bhaineann go háirithe le traidisiún liteartha Chorcaí. Tá na dánta curtha in eagar agus aistriúchán go Béarla curtha ar fáil: is é seo croí an tráchtais. Tá an t-eagrán bunaithe ar scrúdú cuimsitheach ar thraidisiún na lsí; pléitear modheolaíocht na heagarthóireachta. Déantar iarracht ar na dánta a shuíomh sa traidisiún casta liteartha sa tráchtaireacht tosaigh; sa chuid eile den bhfearas scoláiriúil, scrúdaítear ceisteanna a bhaineann le cúrsaí teanga, foclóra, meadarachta agus stíle. Tá innéacsanna agus liosta foinsí le fáil i ndeireadh an tráchtais.

An túrscéal iar-nua-aoiseach sa Ghaeilge

Is éard atá curtha romham agam sa tráchtas seo ná an t-úrscéal iar-nua-aoiseach sa Ghaeilge a phlé; chun aitheantas a thabhairt don seánra mar rud ar leith; chun a fhréamhacha a aimsiú agus a thréithe sainiúla a léiriú. Féachaim anseo lena léiriú go bhfuil baint shainiúil ag an úrscéal iar-nua-aoiseach sa Ghaeilge le stair shochteangeolaíoch agus liteartha na hÉireann. Chruthaigh scríbhneoirí Béarla na hÉireann, ar nós Joyce, Beckett agus Flann O’Brien (Brian Ó Nualláin), cur chuige liteartha a raibh toradh ollmhór aige ar chúrsaí liteartha an domhain – go háirithe sa chomhthéacs (iar)-nua-aoiseach. Léireoidh mé gur tháinig an cur chuige seo chun cinn de bharr an choibhnis shainiúil atá ag muintir na hÉireann le teanga – coibhneas atá ginte i nguagacht faoin rud is teanga féin ann. Áitím gur eascair an ghuagacht seo as an athrú stádais – ó phríomhtheanga go mionteanga – a tharla don Ghaeilge. Áitím gur cruthaíodh feasacht ar fholús i bhféiniúlacht na tíre nuair a tharla an t-athrú sin agus go raibh tionchar ag an bhfeasacht seo ar litríocht na hÉireann – idir Ghaeilge agus Bhéarla. Is minic a fhéachann an túrscéal iar-nua-aoiseach, i ngach teanga ina gcleachtar a leithéid, le staidéar a dhéanamh ar na slite ina gcruthaítear brí sa saol trí theanga agus trí reacaireacht. Murab ionann is a mbíonn i gceist san úrscéal ‘traidisiúnta’ – an t-úrscéal ‘réadach’ mar a tuigtear leis – glacann iar-nua-aoiseachas leis go bhfuil solúbthacht agus saorgacht i ngach léiriú ar an mbrí seo. Léiríonn na húrscéalta atá faoi chaibidil sa tráchtas seo an-doimhneacht liteartha. Is saothair fhéinchomhfhiosacha agus mheitificseanúla iad a thaispeánann éiginnteacht i leith brí absalóidigh. Oibríonn siad mar léiriú ar fheidhm na teanga sa saol agus ar na slite ina gcruthaíonn gach reacaireacht a fírinne féin. Cé gur tréithe iar-nua-aoiseacha iad siúd, is tréithe iad chomh maith a bhaineann le stádas na mionteanga.