29 research outputs found
Atomic Layer Deposition of Group 4 and 5 Transition Metal Oxide Thin Films : Focus on Heteroleptic Precursors
No full textThe atomic layer deposition process (ALD) is an alternative to the chemical vapour deposition (CVD) method that is universally appreciated for its unique advantages such as excellent repeatability, conformity and thickness control at the atomic level. ALD precursor chemistry has mainly been based on homoleptic compounds such as, but not limited to, metal halides, alkylamides or alkoxides. However, these precursors have drawbacks such as possible halide contamination and low thermal stabilities with respect to the alkylamides and alkoxides. Consequently, heteroleptic precursors were investigated as alternatives to the existing homoleptic counterparts, which have led to the development of several advantageous processes. Nevertheless, no thematic review dedicated to heteroleptic precursor and their properties exists and it seems that no coherent strategy has been adopted for the development of heteroleptic precursors.
This thesis gives a brief description of ALD and presents studies on the deposition of thin films of groups 4 and 5 metal oxide films using ALD. A description of the general ALD properties of homoleptic precursors in addition to a review on the thermal ALD of groups 4 and 5 metal oxides from heteroleptic precursors is provided. Trends in the properties of heteroleptic ALD precursors based on a literature review and new experimental data are discussed. Several novel heteroleptic compounds were evaluated for the ALD of thin films of TiO2, ZrO2, Nb2O5 and Ta2O5. The characteristics of these processes were evaluated and the film properties of these oxides were investigated by means of various characterization approaches. The effects of oxygen source, water or ozone, on the film growth characteristics and properties of ZrO2, Nb2O5, and Ta2O5, were also investigated. Mixed alkoxide-alkylamide and alkoxide-amidinate titanium compounds are liquid at room temperature. They are highly volatile, have excellent reactivity towards water and have high thermal stability. The deposited films exhibit high purity and conformability on high aspect ratio substrates. The growth of thin films of ZrO2 from a heteroleptic alkylamide-guanidinate zirconium precursor was notable in that the films grew in the high permittivity cubic phase and the ozone-based process had a high growth rate. Thin films of VOx were deposited from the homoleptic vanadium alkylamide precursor,vanadium tetraethylmethylamide. It was found that the structure and oxidation state of the films could be tuned from an amorphous mixture of VO2 and V2O5 to crystalline VO2 or V2O5. This was accomplished by simply exposing the films to heat treatment in different atmospheres, namely air or N2. Finally, alkylamide-imide precursors were investigated for the ALD of Nb2O5 and Ta2O5 thin films. These precursors are liquid at room temperature, and exhibited high thermal stabilities compared with the earlier known niobium and tantalum ALD precursors. The alkylamide-imide precursors studied had high volatility and excellent reactivity towards both water and ozone. The deposited films were smooth, uniform, and contained only low amounts of impurities.Atomikerroskasvatus (Atomic Layer Deposition, ALD) on ohutkalvojen kasvattamisessa käytettävä menetelmä, jonka ensisijaisia etuja ovat erinomainen toistettavuus ja konformaalisuus. Lisäksi menetelmällä kasvatettavien ohutkalvojen paksuutta voidaan kontrolloida atomitasolla. ALD-menetelmän lähtöaineina on käytetty tavallisesti homoleptisiä yhdisteitä. Homoleptisten lähtöaineiden käyttämisessä on kuitenkin haittapuolia, kuten esimerkiksi ohutkalvoihin mahdollisesti jäävät halidiepäpuhtaudet. Muista homoleptisten lähtöaineiden haittapuolista voidaan mainita homoleptisten alkyyliamidi- ja alkoksidilähtöaineiden heikko terminen pysyvyys. Homoleptisten lähtöaineiden korvaamista heteroleptisillä lähtöaineilla on tutkittu, mikä on johtanut useiden hyödyllisten prosessien kehittämiseen. Heteroleptisten yhdisteiden käyttämisestä ALD-lähtöaineina ei ole kuitenkaan tehty kattavaa tutkimusta, eikä uusien lähtöaineiden kehittämiselle ole tiettävästi luotu johdonmukaista suunnitelmaa.
Tässä väitöskirjassa esitellään lyhyesti sekä ALD-menetelmän yleisiä ominaisuuksia että homoleptisten lähtöaineiden hyödyntämistä ohutkalvojen kasvattamisessa ALD:n avulla. Heteroleptisten lähtöaineiden hyödyntämisestä ryhmien 4 ja 5 metallioksidiohutkalvojen kasvattamisessa esitetään kattavampi katsaus. Katsaus koostuu sekä kirjallisuuslähteistä että uusista kokeellisista tuloksista.
Kokeelliset tulokset koostuvat TiO2, ZrO2, Nb2O5 ja Ta2O5 ohutkalvojen kasvattamisessa käytettävien uusien heteroleptisten lähtöaineiden ominaisuuksista, sekä uusia lähtöaineita hyödyntävien kasvatusprosessien kartoittamisesta. Kasvatettujen metallioksidiohutkalvojen ominaisuuksia tutkittiin usealla eri menetelmällä. Lisäksi vertailtiin kahden eri happilähteen, veden ja otsonin, käyttämisen vaikutusta TiO2, ZrO2, Nb2O5 ja Ta2O5 ohutkalvojen kasvatusominaisuuksiin sekä itse metallioksidiohutkalvojen ominaisuuksiin.ei saavutettav
Nanometer-deep junctions with high doping concentration for Ge SDEs using solid-source doping and flash lamp annealing
No full textRole of the strain-rate tensor in turbulent scalar-transport modeling
No full textWe examine the geometric orientation of the subfilter-scale scalar-flux vector in homogeneous isotropic turbulence. Vector orientation is determined using the eigenframe of the resolved strain-rate tensor. The Schmidt number is kept sufficiently large so as to leave the velocity field, and hence, the strain-rate tensor, unaltered by filtering in the viscous-convective subrange. Strong preferential alignment is observed for the case of Gaussian and box filters, whereas the sharp-spectral filter leads to close to a random orientation. The orientation angle obtained with the Gaussian and box filters is largely independent of the filter-width and the Schmidt number. It is shown that the alignment direction observed numerically using these two filters is predicted very well by the tensor-diffusivity model. Further a-priori tests indicate poor alignment of the Smagorinsky and stretched vortex model predictions with the exact subfilter flux
Opracowanie metody LC/MS z zastosowanie ekstrakcji z użyciem mikrofal do oznaczania metadonu i jego głównego metabolitu (EDDP) w krwi pacjentów uczestniczących w programie metadonowym
No full textAtomic Layer Deposition of Groups 4 and 5 Transition Metal Oxide Thin Films: Focus on Heteroleptic Precursors
No full textSubject Doubling in Spoken French
No full textabstract: The purpose of this study is to explore the syntax and pragmatics of subject doubling in spoken French. Many prescriptivists have considered it a redundant and ungrammatical form, but over the years, it has gained more interest from syntacticians. It is widely acknowledged that dislocations involve topics, but the position of these structures is very disputed. Some linguists believe in base generation while others state there is movement. The status of subject clitics also comes into play and their role as arguments or agreement markers is crucial to understanding the issues at stake with a topic analysis. It is often argued that the clitics are undergoing a linguistic cycle whereby they lose their function of argument, and need to be reinforced by disjunct pronouns. In this study, I examined which analyses support my data and I attempted to determine what structures tend to be most dislocated by looking at the environment of the discourse in a corpus of spoken French.Dissertation/ThesisM.A. French 201
Electrical characteristics of P-type bulk Si fin field-effect transistor using solid-source doping with 1-nm phosphosilicate glass
No full textNanometer-deep junctions with high doping concentration for Ge SDEs using solid source doping and flash lamp annealing
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