Tynne filmer av multiferroisk BiFeO3

I dette arbeidet er det for første gang deponert tynne filmer av α-Bi2O3 med ALD. Det er undersøkt tre forskjellige forløpere for vismutoksider: BiPh3 (Ph = fenyl), Bi(OtBu)3 (OtBu = tert-butoksy) og Bi(thd)3 (thd = 2,2,6,6-tetrametyl-2,5-heptadionato) og det er oppnådd selvbegrensende vekst med Bi(thd)3. BiPh3 er vist å være uegnet som forløper for deponering av tynne filmer av både binære og komplekse vismutoksider med ALD. Bi(OtBu)3 er syntetisert for bruk som forløper, men denne er vist å dekomponere allerede ved 65 oC, som er for lavt til å kunne benyttes i praksis. I arbeidet med denne forløperen ble strukturen til Bi(OtBu)3 bestemt med røntgendiffraksjon, dette er det første alkoksidet som kun inneholder vismut som er strukturbestemt. Bi(thd)3 er syntetisert som forløper og vist å være den første thd-forløperen til ALD som er egnet til å deponere film med vann som oksygenforløper. Filmene er deponert på glass, silisium, 012- og 001-orientert Al2O3. På alle substrater som er undersøkt har filmene sterk preferert orientering i 012-retningen og viser fibertekstur. Filmer som er deponert på Al2O3-substrater viser også ordning i fiberretningen. In-situ-eksperimenter har vist en dekomponering på overflaten, men denne er sannsynliggjort at kommer fra reaksjon med forløperens eget krystallvann. Dette arbeidet presenterer også forsøk på deponering av blandinger av vismut- og jernoksider. Det er påvist en etsningsreaksjon av jernoksidoverflater og den syntetiserte Bi(thd)3 forløperen. Det er sannsynliggjort at etsningen også har opphav i reaksjonen mellom Bi(thd)3 og krystallvannet til forløperen som danner frie Hthd-ligander i gassfase, og de frie ligandene er tenkt å etse jernoksidet

Atomic layer deposition of thin films containing alkali metals

This thesis presents experimental work on thin films of different compounds containing lithium, sodium or potassium has been synthesized by atomic layer deposition (ALD). The overall motivation for this work has been to develop materials and methods to improve lithium ion battery technology by using ALD. A cathode in a lithium ion battery should have a long operating life, be environmentally benign and have high capacity and power density. Vanadium oxides are popular as cathodes in lithium ion batteries due to their relative low price and potentially high capacity. Most studies of vanadium oxide cathodes shows relatively short lifetime of the cathode or relatively fast cathodes. In this work a high power thin film cathode of V2O5 for lithium ion batteries has been developed. The cathode is deposited by ALD using VO(thd)2 and ozone, which displays a rather peculiar type of ALD-growth. This peculiar growth is studied in detail, and the optical properties of these films are investigated. The films have an unusually rough surface, and it was found that a 10nm thick film deposited at 235ºC consisted of individual nano particles. The 10 nm thick cathode has been shown to endure more than 4000 dischargecycles at 120C and almost 1600 cycles while staying within 80% of the original capacity. The same cathode was also shown to sustain discharge rates of 960C which corresponds to a discharge in 3.75s. The power density obtained in this work bridges the gap between super capacitors and batteries and the combination of long lifetime and high discharge rate is not found previously for thin film batteries of V2O5. ALD of lithium containing materials has attracted widespread interest the last few years. The number of known precursors for lithium has grown, but the complete picture is still not understood. Therefore lithium hexamethyldisilazane (LiHMDS) is explored as a precursor for ALD of lithium compounds. The precursor is shown successful in deposition of Li3N, Li2CO3 and LiNbO3. The deposition of Li3N may be an important step to deposit solid electrolytes and the deposition of Li2CO3 proved to be important for proving the growth of oxides using this precursor. When comparing the growth of Li3N and Li2CO3 it was found significant difference in the surface chemistry. The LiNbO3-films were shown to be ferroelectric with an unusually high coercive field. It proved possible to deposit epitaxial LiNbO3 on single crystal substrates of LaAlO3 and Al2O3 and the orientation of the films could be controlled by the orientation of the substrate. A milestone in atomic layer deposition of lithium compounds would be to deposit a full battery. In order to realize this, a lithiated cathode material must be deposited. The cathode material LiMn2O4 was also studied in this work. It was discovered that the amount of lithium in the deposited films is more or less independent of the number lithium cycles to manganese cycles. It is hypothesized that the ligand of the lithium precursor reduces the manganese and the lithium is intercalated into the manganese oxide. This is a new approach to ALD of lithium compounds and the term film body controlled lithium deposition is used to describe the mechanism. The use of LiHMDS is also attempted in deposition of LiMn2O4, with no success. Sodium and potassium are among the few elements in the periodic table which are not yet used in ALD. Sodium and potassium are relatively similar to lithium and exploring the deposition of these elements will hopefully shed new light on the deposition of lithium compounds. Many oxides of sodium and potassium also have piezo- and ferroelectric properties, and the sodium ion battery is predicted to be a way to combat lithium shortage. Atomic layer deposition of sodium and potassium oxides is reported for the first time in this thesis. Six different precursors are investigated and evaluated and precursors for sodium and potassium. The initial study was performed by depositing sodium and potassium aluminates, in order to evaluate the precursors. The process for the aluminates was found to scale up to the 200mm wafer scale. The precursors were found to work in a large temperature window and react with both water and ozone, thus proving to relatively flexible and possible to combine with most known ALD-processes. Further development into deposition of sodium based ferroelectrics then explored by deposition of sodium tantalate and sodium niobate

Risikostyring : analyse av LOS-programmets metode for usikkerhetsstyring i et helhetlig styringsperspektiv

Denne utredningen har som formål å beskrive og analysere LOS-programmets metode for usikkerhetsstyring i et helhetlig styringsperspektiv, med fokus på hvordan de tilfredsstiller normene satt gjennom regelverk for økonomistyring i staten. Foruten kravene som stilles til risikostyring og intern kontroll, gir ikke regelverket noen nærmere anvisning om hvordan dette skal utformes eller gjennomføres i statlige virksomheter. Som et resultat av dette utga Senter for statlig økonomistyring (SSØ) i 2006 metodedokumentet ”Risikostyring i staten – håndtering av risiko i mål- og resultatstyringen”. Dette dokumentet danner sammen med teorien og LOS-programmets metode for usikkerhetsstyring utgangspunktet for å beskrive og analysere LOS-programmets metode for usikkerhetsstyring i et helhetlig styringsperspektiv. I kapittel 5 fokuseres det på de normene som blir stilt til statlige virksomheter gjennom regelverket for økonomistyring i staten. Som det fremkommer gjennom analysen settes det normer til at alle statlige virksomheter skal styres gjennom mål- og resultatstyring og risikostyring. Videre fokuserer analysen i dette kapitlet på hvilke faktorer som kompliserer normene i statlige virksomheter. Analysen avdekker at for normen mål- og resultatstyring er det tildelingsbrevets form, prosessene i mål- og resultatstyringen, og kostnadsfokuset som er de kompliserende faktorene. For normen knyttet til risikostyring er det SSØs manglende fokus på muligheter som kompliserer i forhold til teoriens metode for helhetlig risikostyring. Utredningen tar for seg LOS-programmet i Forsvaret og programmets DVU enhet som et praktisk eksempel. Analysen i kapittel 6 drøfter først hvordan DVU enhetens mål- og resultatstyring tar hensyn til de kompliserende faktorene, før LOS-programmets metode for usikkerhetsstyring analyseres opp mot henholdsvis teorien og SSØs anbefalte metode. Det fremkommer gjennom analysen at LOS-programmet og SSØs metode er ulike med tanke på hvordan de vurderer de identifiserte usikkerhetene og hvilke risikostyringsstrategier som benyttes. Videre fremkommer det at LOS-programmet og teoriens metode er ulike med tanke på hvordan de vurderer de identifiserte usikkerhetene og hvilke risikostyringsstrategier som finnes i metodene. Gjennom analysene i kapittel 7 identifiseres først ulike brukere av DVU enhetens usikkerhetsrapport, før bruken av rapporten analyseres. De viktigste funnene er at det utarbeides en felles rapport til de ulike brukerne, men de ulike brukerne etterspør ulik informasjon. Dette resulterer i at de ulike brukerne ikke alltid finner informasjonen i usikkerhetsrapporten like relevant. I kapittel 8 trekkes utredningens konklusjoner på bakgrunn av analysen i de tre foregående kapitlene. Hovedkonklusjonen som trekkes er at LOS-programmets metode for usikkerhetsstyring tilfredsstiller kravet fra regelverket for økonomistyring i staten. Metoden oppfyller i hovedsak alle de viktigste antakelsene/prinsippene presentert gjennom teorien for å oppnå suksess med risikostyringen, men LOS-programmets DVU enhet lykkes bare delvis i å integrere usikkerhetsstyringen i mål- og resultatstyringen

Optical Properties of Vanadium Pentoxide Deposited by ALD

Nanostructures of V₂O₅ find important technological applications in optics, catalysis, and lithium ion batteries. Their optical properties and surface roughness are important parameters in these respects. Here we report on atomic layer deposition (ALD) of V₂O₅ using the β-diketonate VO­(thd)₂ and ozone as precursors. In this work, X-ray diffraction, AFM, ellipsometry, and UV–vis-spectroscopy are used to show that the crystallographic orientation, optical properties, band gap, and surface roughness of the derived films are correlated and can be varied by controlling deposition temperature and film thickness. The band gap of the samples varies between 2.70 and 2.35 eV. The observed growth rate varies between 0.1 to 1 Å/cycle depending on deposition temperature and the number of cycles. This large variation in growth rate provides an interesting case of ALD growth, which can be rationalized in terms of a geometric crystal growth model

Atomic layer deposition of ferroelectric LiNbO3

The ferroelectric and electro-optical properties of LiNbO3 make it an important material for current and future applications. It has also been suggested as a possible lead-free replacement for present PZT-devices. The atomic layer deposition (ALD) technique offers controlled deposition of films at an industrial scale and thus becomes an interesting tool for growth of LiNbO3. We here report on ALD deposition of LiNbO3 using lithium silylamide and niobium ethoxide as precursors, thereby providing good control of cation stoichiometry and films with low impurity levels of silicon. The deposited films are shown to be ferroelectric and their crystalline orientations can be guided by the choice of substrate. The films are polycrystalline on Si (100) as well as epitaxially oriented on substrates of Al2O3 (012), Al2O3 (001), and LaAlO3 (012). The coercive field of samples deposited on Si (100) was found to be ∼220 kV cm−1, with a remanent polarization of ∼0.4 μC cm−2. Deposition of lithium containing materials is traditionally challenging by ALD, and critical issues with such deposition are discussed

Atomic layer deposition of sodium and potassium oxides: evaluation of precursors and deposition of thin films

Thin films of sodium and potassium oxides have for the first time been deposited using atomic layer deposition. Sodium and potassium complexes of tert-butanol, trimethylsilanol and hexamethyldisilazide have been evaluated as precursors by characterising their thermal properties as well as tested in applications for thin film depositions. Out of these, sodium and potassium tert-butoxide and sodium trimethylsilanolate and hexamethyldisilazide were further tested as precursors together with the Al(CH3)3 + H2O/O3 process to form aluminates and together with ozone to form silicates. Sodium and potassium tert-butoxide and sodium trimethylsilanolate showed self-limiting growth and proved useable at deposition temperatures from 225 to 375 or 300 °C, respectively. The crystal structures of NaOtBu and KOtBu were determined by single crystal diffraction revealing hexamer- and tetramer structures, respectively. The current work demonstrates the suitability of the ALD technique to deposit thin films containing alkaline elements even at 8′′ wafer scale

Room-temperature plasma-enhanced atomic layer deposition of ZnO : Film growth dependence on the PEALD reactor configuration

Room-temperature plasma-enhanced atomic layer deposition (PEALD) of ZnO was studied by depositing the films using diethylzinc and O2 plasma from inductively-coupled plasma (ICP) and capacitively-coupled plasma (CCP) plasma source configurations. The CCP-PEALD was operated using both remote and direct plasma. It was observed that the films deposited by means of remote ICP and CCP were all highly oxygen rich, independently on plasma operation parameters, but impurity (H, C) contents could be reduced by increasing plasma pulse time and applied power. With the direct CCP-PEALD the film composition was closer to stoichiometric, and film crystallinity was enhanced. The ZnO film growth was observed to be similar on silicon, polycarbonate and poly(methyl methacrylate) substrates, but changes in polymer surface morphology indicate plasma-induced damage during the deposition due to exposure to ion bombardment when direct plasma was applied.peerReviewe