Spectroscopic and phase-stabilisation properties of pure and rare-earth ions activated ZrO2 and HfO2
Failid
Kuupäev
2010-05-17T12:04:39Z
Autorid
Ajakirja pealkiri
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Kirjastaja
Abstrakt
Laia keelutsooniga pooljuht- ja dielektrikmaterjalid on olulisel kohal mitmetes kaasaegsetes valgustus- ja elektroonikarakendustes. Tänu nendele materjalidele on osutunud võimalikuks mitmete luminofoorvalgustite (sh. valged LED-lambid), tahkislaserite ja innovaatiliste mikroelektroonika lahenduste väljatöötamine.
Tingituna valdkonna olulisusest on tahkisefüüsikud tegelenud ligikaudu pool sajandit aktiivselt nii antud materjalide valmistamise, rakenduslike aspektide selgitamise kui ka fundamentaalteaduslike probleemidega.
Antud teadustöö raames on uuritud kahe viimasel ajal järjest enam rakendusi leidva laia keelutsooniga oksiidmaterjali — ZrO2 ja HfO2 — optilisi ja struktuurseid omadusi. Tingituna nimetatud ainete võimalike modifikatsioonide mitmesusest ja struktuuri keerukusest on hoolimata juba läbi viidud teaduslikest uurimistöödest viimastega siiski seotud mitmeid üheselt lahendamata ja rakendusi pärssivaid probleeme. Nende hulgas on olulisel kohal kristallstruktuuri defektide (peamiselt hapniku vakantside) ja erinevate optiliselt aktiivsete haruldaste muldmetalli lisandite ja valguse poolt indutseeritud laengukandjate vaheline energiaülekanne ning samuti rakenduslikult rohkem huvi pakkuvate mittetasakaaluliste kristallifaaside lisanditega stabiliseerimise tingimused.
Töös antakse põhjalik võrdlev ülevaade erinevatel meetoditel valmistatud ZrO2 ja HfO2 spektroskoopilistest ja faasistabilisatsiooni iseärasustest. Lähemalt vaadeldakse haruldaste muldmetalliooni lisandite energiaülekande mehhanisme oksiidis ning kirjeldatakse viimaste energeetilist paiknemist põhiaine tsoonide suhtes. Samuti kirjeldatakse uudset muldmetallioonide kiirgusspektrite peenstruktuuri analüüsil põhinevat kristallifaasi detektsiooni meetodit, mida kasutatakse kristallifaasi määramiseks nii mikro- kui nanoskaalas.
Wide band-gap materials are rather important in many contemporary lighting and electronic applications. Such materials contribute to a number of recent advances in lighting (incl. white LED-lamps) and solid state lasers as well as to novel designs in microelectronic device manufacturing. Because of the high interest in the field of applications, systematic studies concerning the preparation, technological adaption and fundamental properties of these materials have been carried out for almost half a century. In the current work mostly two wide-gap oxides — ZrO2 and HfO2 — have been studied. Regardless of the amount of work already done, many questions about some specific properties of these oxides are still only speculatively described. Important among those are questions of intrinsic defects (mainly oxygen vacancies) and energy transfer mechanisms between light-induced charge carriers and both intrinsic and optically active rare-earth dopant. Decisive is the role of dopant ions to the stabilisation of tehnologically more attractive metastable crystal phases. As a result of the work a comparative spectroscopic and phase stabilisation study of differently prepared ZrO2 and HfO2 was conducted. A closer look is given to the energy transfer mechanisms between light-induced charge carriers and rare earth defects and the energetic placement of rare-earth ions’ energy levels with respect to the energy bands of the host matrices. Additionally, a novel method was introduced and applied to probe the crystal phase in micro- and nanoscale by analysing the spectral fine structure of rare-earth ions’ photoluminescence.
Wide band-gap materials are rather important in many contemporary lighting and electronic applications. Such materials contribute to a number of recent advances in lighting (incl. white LED-lamps) and solid state lasers as well as to novel designs in microelectronic device manufacturing. Because of the high interest in the field of applications, systematic studies concerning the preparation, technological adaption and fundamental properties of these materials have been carried out for almost half a century. In the current work mostly two wide-gap oxides — ZrO2 and HfO2 — have been studied. Regardless of the amount of work already done, many questions about some specific properties of these oxides are still only speculatively described. Important among those are questions of intrinsic defects (mainly oxygen vacancies) and energy transfer mechanisms between light-induced charge carriers and both intrinsic and optically active rare-earth dopant. Decisive is the role of dopant ions to the stabilisation of tehnologically more attractive metastable crystal phases. As a result of the work a comparative spectroscopic and phase stabilisation study of differently prepared ZrO2 and HfO2 was conducted. A closer look is given to the energy transfer mechanisms between light-induced charge carriers and rare earth defects and the energetic placement of rare-earth ions’ energy levels with respect to the energy bands of the host matrices. Additionally, a novel method was introduced and applied to probe the crystal phase in micro- and nanoscale by analysing the spectral fine structure of rare-earth ions’ photoluminescence.
Kirjeldus
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