De invloed van complexvorming op het elektronische spectrum van uranyl: een computationele studie.

Een computationele studie van het elektronische spectrum van het uranylion en verschillende uranylcomplexen met kleine liganden, zoals chloride, nitraat, fluoride, water en aceton, wordt gepresenteerd. Multiconfigurationele perturbatietheorie (CASSCF/CASPT2) werd gebruikt en, voor het spectrum van uranyl en uranyltetrachloride, ook tijdsafhankelijke DFT. Zowel scalaire relativistische effecten als spin-orbitaalkoppeling werden in rekening gebracht. De elektronische spectra werden berekend voor geometrieën geoptimaliseerd met DFT of, voor uranyl en uranyltetrachloride, met CASPT2. Voor de laagst gelegen aangeslagen toestanden, afkomstig van transities vanuit het bindende sigma.u-orbitaal naar het niet-bindende delta.u- of pi.u-orbitaal, is de volgorde dezelfde voor alle beschouwde complexen (CASSCF/CASPT2): a Pi.g < a Delta.g < a Phi.g < b Delta.g < b Phi.g < a Gamma.g < c Delta.g < c Phi.g. De berekende excitatie-energieën komen tot op 1000 cm-1 overeen met experimentele waarden uit UV/VIS-spectra en liggen voor de verschillende complexen dicht bij elkaar. Voor het vrije uranylion daarentegen, waarvan geen experimenteel spectrum beschikbaar is, vinden we Delta.g (sigma.u -&gt; phi.u) als laagste aangeslagen toestand, in plaats van Pi.g (sigma.u -&gt; delta.u). Bovendien zijn de berekende excitatie-energieën beduidend lager voor uranyl dan voor de complexen (ongeveer 3000 cm-1 voor uranyltetrachloride). Dat wijst op een significant effect van de aanwezigheid van een equatoriaal ligandveld op de excitatie-energieën. De chemische aard van de liganden is minder bepalend. Voor de oscillatorsterkte zijn aanzienlijke verschillen gevonden tussen de beschouwde complexen. De symmetrie van de complexen speelt daarin een belangrijke rol. Toch werd de opvallende intensiteit in het experimentele spectrum van uranyltrinitraat, gewoonlijk toegeschreven aan de elektrisch-dipool-toegelaten overgang Sigma.g -&gt; Delta.g, niet bevestigd door de huidige berekeningen. Ook werd in geen enkel van de spectra berekend voor de intermediaire uranylchloridecomplexen in aceton de experimentele intensiteit teruggevonden. De excitatie-energieën uit de berekeningen met tijdsafhankelijke DFT zijn duidelijk minder nauwkeurig dan de CASPT2-resultaten en sterk afhankelijk van de gebruikte functionaal. Enkel de SAOP-functionaal geeft waarden in de buurt van de experimentele energieën. De eerste resultaten met spin-orbitaalkoppeling tonen, net als de CASSCF/CASPT2-resultaten, een verandering van de laagst gelegen aangeslagen toestand van uranyl door de coördinatie van chlorideliganden.status: publishe

Electronic spectrum of UO22+ and [UO2Cl4](2-) calculated with time-dependent density functional theory

The electronic spectra of UO22+ and [UO2Cl4](2-) are calculated with a recently proposed relativistic time-dependent density functional theory method based on the two-component zeroth-order regular approximation for the inclusion of spin-orbit coupling and a noncollinear exchange-correlation functional. All excitations out of the bonding sigma(+)(u) orbital into the nonbonding delta(u) or phi(u) orbitals for UO22+ and the corresponding excitations for [UO2Cl4](2-) are considered. Scalar relativistic vertical excitation energies are compared to values from previous calculations with the CASPT2 method. Two-component adiabatic excitation energies, U-O equilibrium distances, and symmetric stretching frequencies are compared to CASPT2 and combined configuration-interaction and spin-orbit coupling results, as well as to experimental data. The composition of the excited states in terms of the spin-orbit free states is analyzed. The results point to a significant effect of the chlorine ligands on the electronic spectrum, thereby confirming the CASPT2 results: The excitation energies are shifted and a different luminescent state is found. (C) 2007 American Institute of Physics.status: publishe

Influence of the ion bombardment of O₂ plasmas on low-k materials

In this study, special tests were devised in order to investigate the influence of ion bombardment on the damage induced in low-k dielectrics by oxygen plasmas. By placing a sample that suffered a lot of ion bombardment and one which suffered little ion bombardment simultaneously in the same plasma, it was possible to verify that ion bombardment in fact helped to protect the low-k film against oxygen plasma induced damage. Exhaustive analyses (ellipsometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, porosimetry, capacitance–voltage (C–V) measurements, water contact angle analysis) show that ion bombardment induced the formation of a denser top layer in the film, which then hampered further penetration of active oxygen species deeper into the bulk. This was further confirmed by other tests combining capacitively and inductively coupled plasmas. Therefore, it was possible to conclude that, at least for these plasmas, ion bombardment may help to reduce plasma induced damage to low-k materials

Fabrication of a CMOS-based Imaging Chip with Monolithically Integrated RGB and NIR Filters

Recent developments in multispectral cameras have demonstrated how compact and low-cost spectral sensors can be made by monolithically integrating filters on top of commercially available image sensors. In this paper, the fabrication of a RGB + NIR variation to such a single-chip imaging system is described, including the integration of a metallic shield to minimize crosstalk, and two interference filters: a NIR blocking filter, and a NIR bandpass filter. This is then combined with standard polymer based RGB colour filters. Fabrication of this chip is done in imec’s 200 mm cleanroom using standard CMOS technology, except for the addition of RGB colour filters and microlenses, which is outsourced

Effect of UV-wavelength on Hardening Process of Porogen-containing and Porogen-free Ultra-low-k PECVD Glasses

The ITRS scaling of ultra-large-scale integrated circuits requires mechanically robust materials with low k-value. Low-k materials recently used in the Cu/low-k integration scheme have k-values between 2.5 and 3.0. One of the limiting factors in further reduction of k-value is mechanical robustness, since major way to decrease k-value is increasing the material porosity. The PECVD low-k deposition of ultra low-k films uses a porogen-based approach. The matrix material is deposited by oxidation of alkylsilanes in a plasma-enhanced chemical vapor deposition (PECVD) process. The porogen molecules, usually cyclic hydrocarbons, are introduced into a SiOCH film by co-deposition with the matrix material. To create porosity, the porogen is removed from the films using UV-assisted-thermal curing. The porogen molecules are photo-dissociated by UV-light with the formation of volatile hydrocarbons and non-volatile carbon-rich residues (porogen residue) [1]. We showed recently that SiOCH glasses with improved mechanical properties and ultra-low-k value could be obtained by controlled decomposition of the porogen molecules prior to the UV-hardening step [2]. The controlled removal of porogen can be performed by H2-based afterglow plasma treatment of PECVD film [1,2]. In this work we study the effect of narrow band 172 nm and broadband >200 nm UV-sources in the new curing scheme of the PECVD dielectrics. The data are compared with the PECVD films fabricated in the conventional UV-curing scheme. The effect of both 172 nm and >200 nm UV-sources is comparable for porogen-containing conventional PECVD films. However, the porogen-free films cured with 172 nm UV-source shows approximately twice as higher Young’s modulus of 6.64 GPa (k100kHz ~ 2.2, 44% open porosity) than those cured with >200 nm UV with YM of 3.38 GPa (k100kHz ~ 2.0, 48% open porosity). The mechanical properties, optical properties 150 nm - 800 nm, dielectric constants at 100 kHz and 4 GHz, porosities and pore size distributions, bonding structure are presented. The impact of porogen on optical characteristic and therefore on photochemical UV-hardening mechanism is discussed. The achieved mechanical properties are explained on a basis of the percolation of rigidity theory and random network concepts. References [1] A. M. Urbanowicz, K. Vanstreels, D. Shamiryan, S. De Gendt and M. Baklanov, Electrochem. Solid State Lett., 12, H292 (2009). [2]Urbanowicz, K. Vanstreels, P. Verdonck, D. Shamiryan, S. De Gendt and M. R. Baklanov, 107 (7), J. Appl. Phys. (2010).http://www2.avs.org/symposium/AVS57/pdfs/techprog.pdfstatus: publishe

Lanthanide(III)-induced conversion of 12-metallacrown-4 to 5-metallacrown-5 complexes in solution

The conversion of 12-metallacrown-4 complexes with copper(II) in the central cavity to 15-metallacrown-5 complexes with lanthanide(iii) ions in the central cavity upon addition of trivalent lanthanide ions was analysed in solution by electrospray ionisation mass spectrometry (ESI-MS), absorption spectrophotometry, circular dichroism and proton NMR spectroscopy. In all cases, copper(II) ions were the ring metals. The lanthanide-induced shifts of the proton resonances in the NMR spectra of different lanthanide (m)-containing 15-metallacrown-5 complexes with tyrosinehydroximate ligands were studied. The dynamics of ligand exchange of alpha-aminohydroximate-based lanthanide (iii) -containing 15-metallacrown-5 complexes were studied in methanol solutions. The ring structure of the 12-metallacrown-4 complex that acts as starting compound for the formation of the 15-metallacrown-5 complexes was optimized by DFT methods using alanine-hydroximate as a model ligand.status: publishe

Reliability challenges for barrier/liner system in high aspect ratio through silicon vias

The reliability results for barrier/liner systems in different high aspect ratio (5 x 50 µm) through silicon vias (TSV) are presented. Quite a few factors can influence the TSV barrier/liner reliability performance, including the TSV trench etch process, the oxide liner material/thickness, etc. The challenges for more advanced TSV technology nodes (e.g. 3 x 40 µm) are also discussed and possible solutions are proposed.status: publishe