The thesis describes some aspects of the aqueous solution chemistry of chlororuthenate(III) and chlorocarbonylruthenate(III or II) complexes including their reactivity toward carbon monoxide. This led to the synthesis and characterisation of a polymeric complex [HRu(CO)₃][sub n], which is formally a Ru(I) derivative. The use of these ruthenium complexes for activating CO catalytically was studied, especially for the carbonylation of amines. The [HRu(CO)₃][sub n] polymer was characterised by microanalysis, infra-red and high-field ¹H n.m.r. , and its chemistry In donor solvents in which it was soluble. The polymer may be formed by reductive carbonylation of chloro complexes of Ru[sup II], Ru[sup III](CO), Ru[sup II] (CO), Ru[sup II] (C0)₂ and Ru[sup II]CO)₃, and stoichiometric evidence suggests processes such as: [chemical reactions 1 to 4]. Increasing acidity and chloride concentration inhibit the reductive carbonylation process, which likely requires simultaneous coordination of cis CO and OH ligands. Reactions (1) - (4) are accompanied by formation of smaller amounts of low valent ruthenium complexes including Ru₃(CO)₁₂, which could result from a reductive carbonylation process such as [chemical reaction 5] or via 'combination' of Ru[sup I] and Ru[sup -I] species. Evidence is presented for reaction (5) starting with CsRu(CO)₃Cl₃. Reductive carbonylation 2- of Ru(CO)₂Cl₄⁻² (reaction (4)) shows autocatalytic gas uptake plots, indicating catalysis of the reaction via a Ru(0) or Ru(I) intermediate. The kinetics for the carbonylation of piperidine to N-formyl piperidine catalysed by each of the complexes [HRu(CO)₃][sub n], [Ru(CO)₂(OAc)(pip)]₂, and CsRu(CO)₃Cl₃, have been studied under mild conditions. Mechanisms are proposed to explain the observed kinetics and in each case a tricarbonyl monomeric species appears to be the active catalyst. A CO insertion reaction in a Ru(CO)₃ (pip)[sub x] intermediate must be involved. A scheme such as (6) e.g. [chemical reaction 6] requires a hydride shift, likely metal activated. Alternatively, piperidine could behave as a proton acceptor with the reaction proceeding via a carbamoyl intermediate (reaction (7)). [chemical reaction 7] Both [HRu(CO)₃][sub n] and CsRu(C0)₃Cl₃ carbonylate piperidine in a stoichiometric reaction in the absence of CO, and in the case of the cesium salt evidence suggests the following reactions: [chemical reactions 8-9] Only secondary amines were carbonylated effectively. Attempts to isolate and characterise ruthenium complexes via the reactions [HRu(CO)₃][sub n] or CsRu(C0)₃Cl₃with piperidine proved frustrating, although one complex isolated from the polymer reaction is thought to be H₂Ru₂(CO)₄(pip)₃, and an oxygenated solution of [HRu(CO)₃][sub n] in piperidine yielded a complex which analysed well for [HRu(CO)₂(pip)]₂•0₂. / Science, Faculty of / Chemistry, Department of / Graduate

archives@tulane.edu / 1 / Kristina Martinez

Cyclic voltammetry experiments were performed to compare the electrodeposition characteristics of bismuth on ruthenium. Two types of electrodes were used for comparison: a Ru shot electrode (polycrystalline) and a thin film of radio-frequency sputtered Ru on a Ti/Si(100) support. Experiments were performed in 1mM Bi(NO3)3/0.5M H2SO4 with switching potentials between -0.25 and 0.55V (vs. KCl sat. Ag/AgCl) and a 20mV/s scan rate. Grazing incidence x-ray diffraction (GIXRD) determined the freshly prepared thin film electrode was hexagonally close-packed. After thermally oxidizing at 600°C for 20 minutes, the thin film adopts the tetragonal structure consistent with RuO2. a hydrated oxide film (RuOx?(H2O)y) was made by holding 1.3V on the surface of the film in H2SO4 for 60 seconds and was determined to be amorphous. Underpotential deposition of Bi was observed on the metallic surfaces and the electrochemically oxidized surface; it was not observed on the thermal oxide.

As the semiconductor industries are moving beyond 22 nm node technology, the currently used stacked Ta/TaN diffusion barrier including a copper seed will be unable to fulfill the requirements for the future technologies. Due to its low resistivity and ability to perform galvanic copper fill without a seed layer, ruthenium (Ru) has emerged as a potential copper diffusion barrier. However, its crystallization and columnar nanostructure have been the main cause of barrier failures even at low processing temperatures (300 oC -350 oC). In this study, we have proposed and evaluated three different strategies to improve the performance of the ultrathin Ru film as a diffusion barrier for copper. The first study focused on shallow surface plasma irradiation/amorphization and nitridation of 5 nm Ru films. Systematic studies of amorphization and nitrogen incorporation versus sample bias were performed. XPS, XRD and RBS were used to determine the physico-chemical, crystallization and barrier efficiency of the plasma modified Ru barrier. The nitrogen plasma surface irradiation of Ru films at substrate bias voltage of -350 V showed an improved barrier performance up to 400 oC annealing temperatures. The barrier barely started failing at 450 oC due mainly to nitrogen instability. The second study involved only amorphization of the Ru thin film without any nitrogen incorporation. A low energy ion beam irradiation/amorphization on Ru thin film was carried out by using 60 KeV carbon ions with different irradiation doses. The irradiation energy was chosen high enough so that the irradiation ions pass through the whole Ru thin film and stop in the SiO2/Si support substrate. The C-ion fluence of 5×1016 atoms/cm2 at 60 KeV made the Ru film near amorphous without changing its composition. XRD and RBS were used to determine the relationship between crystallization and barrier efficiency of the carbon irradiated Ru barrier. The amorphized Ru film showed an improved barrier performance up to 400 oC annealing temperatures similar to the plasma nitrided Ru films. The barrier barely began to fail at 450 oC due mainly to crystallization. The third study focused on a study of Al doping of nitrided Ru thin films and their crystallinity with the aim of obtaining a completely amorphous Ru based barrier and stable nitridation. The addition of 4% Al and 14% of nitrogen in Ru produced a near amorphous film. Nitrogen in the film remained stable until the annealing temperature of 450 oC for 10 min in N2 atmosphere. Crystallization growth of the film was inhibited until 450 oC. At 500 oC, the crystallization of the Ru films barely started, but the degree of its crystallization is minimal. The Ru-Al-N film was demonstrated to be an effective diffusion barrier for copper until the annealing temperature of 450 oC and began to fail at 500 oC. The Al doping was shown to stabilize the nitrogen in the Ru thin film barrier inhibiting its crystallization and leading to improved diffusion barrier performance and a gain in processing temperatures of 150 oC -200 oC over the as prepared pure Ru thin film barriers.

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The novel compound [Ru(bpy)(dpb)–(PFâ )â was synthesized, in a manner similar to the literature synthesis of [Ru(bpy)(dpq)â (PFâ )â . For the sake of completeness, the related analogs, [Ru(bpy)â (dpb)](PFâ )â , [Ru(bpy)â (dpq)](PFâ )â and [Ru(bpy)(dpq)â ](PFâ )â were also synthesized. Alumina adsorption chromatography was used for purification purposes. Liquid secondary ion mass spectroscopy was used to confirm identity of compounds. The new compound contained 1% electroactive impurity as determined by OSWV. Spectroelectrochemical studies were conducted with both a bulk H-cell and a ~0.2 mm pathlength, optically transparent thin layer electrode (OTTLE) cell. High reversibility (a 99%) is possible with dilute solutions (ca 10⠻⠴ M) and the OTTLE cell as compared to ca 50% with the H-cell. Spectroelectrochemical data supported the following electronic transitions for the new compound [Ru(bpy)(dpb)â ](PFâ )â : (1) the Ru (dÏ ) â dpb MLCT at 552 nm, (2) a d â d at 242 nm, a bpy Ï â Ï * at 285 nm. (3) The location of the Ru (dÏ ) â bpy MLCT peak is obscured by shoulders from 390-420 nm. (4) The strong peak at 316 nm may be dpb Ï â Ï â *, the location of the lower energy intraligand dpb Ï â Ï â * is uncertain. Upon oxidation of the metal center, no LMCT was observed within the UV-VIS range. This is in direct contrast to the results of Gordon et al. This author hypothesizes that their LMCT found in the visible region was actually the result of incomplete electrochemical conversion and that a LMCT should be seen in the NIR. The spectroelectrochemical properties of [Ru(bpy)(dpq)â ](PFâ )â were also presented for the first time. These results indicated that the 256 nm transition was d â d and not bpy Ï â Ï â * as suggested by Rillema et al. / Master of Science

The kinetics for the bridge-to-chelate isomerization of the dppe ligand in H4Ru4(CO)10(dppe) have been investigated by UV-vis and NMR spectroscopies over the temperature range of 308-328 K. The isomerization of the ligand-bridged cluster 1,2-H4Ru4(CO)10(dppe) was found to be reversible by 31P NMR spectroscopy, affording a Keq = 15.7 at 323 K in favor of the chelating dppe isomer. The forward (k1) and reverse (k-1) first-order rate constants for the reaction have been measured in different solvents and in the presence of ligand trapping agents (CO and PPh3). On the basis of the activation parameters and reaction rates that are unaffected by added CO and PPh3, a sequence involving the nondissociative migration of a phosphine moiety and two CO groups between basal ruthenium centers is proposed and discussed. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligands dppbz proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(dppbz) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C4H4]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(dppbz) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(dppbz), molecular structure of both the isomers have been determined by X-ray crystallography. The kinetics for the ligand isomerization has been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-343 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Ortho metalation of one of the phenyl groups associated with the dppbz ligand is triggered by near-UV photolysis of the chelating cluster 1,1-Os3(CO)10(dppbz). The triosmium cluster 1,2-Os3(CO)10(MeCN)2 reacts with the diphosphine ligand 3,4­bis(diphenylphosphino)-5-methoxy-2(5)H-furanone (bmf) at 25 ºC to give the bmf-bridged cluster 1,2-Os3(CO)10(bmf). Heating 1,2-Os3(CO)10(bmf) leads to an equilibrium with the chelating isomer 1,1-Os3(CO)10(bmf). The molecular structure of each isomer has been crystallographically determined, and the kinetics for the isomerization has been investigated by UV-vis and 1H NMR spectroscopy. The reversible nature of the diphosphine isomerization has been confirmed by NMR measurements, and the forward (k1) and reverse (k-1) first-order rate constants for the bridge-to-chelate isomerization have been determined. Thermolysis of the SEQ CHAPTER h r 11,1-Os3(CO)10(bmf) cluster (>110 ºC) leads to regiospecific activation of C-H and P-C bonds, producing the hydrido clusters HOs3(CO)9[µ-PPh2C=C{PPh(C6H4)} CH(OMe)OC(O)] and the benzyne clusters HOs3(CO)8(μ3-C6H4)[µ-PPhC=C(PPh2)CH(OMe)OC(O)]. The hydride and benzyne clusters, which exist as a pair of diastereomers, have been fully characterized in solution by IR and NMR spectroscopy, and the molecular structure of one benzyne cluster (major diastereomer) has been determined by X-ray crystallography.

Ion Implantation of ruthenium ions into a silicon substrate followed by a high temperature anneal (known as Ion Beam Synthesis) has been used for the first time to fabricate three wafers, under the following conditions. 1. 5.67 X 1016 Ru+ cm-2, beam heated 2. 4.25 X 1016 Ru+ cm-2, heated to ~ 600°C 3. 1.27 X 1017 Ru+ cm-2, heated to ~ 600°C All wafers contained precipitates of the orthorhombic semiconducting silicide of ruthenium, Ru2Si3. No other phase was identified. The samples exhibited a complicated microstructure, with 16 different orientation variants identified, and a high degree of disorder (~ +11% strain). The first optical measurements ever carried out on this material are reported here. Absorption measurements in transmittance yielded a direct band gap, in the region of ~ 0.9eV, 0.87eV, and 0.92eV for wafers 1, 2, and 3 respectively. No discernible variation of band gap magnitude with measurement temperature was found. Upon sequential annealing, the direct band gap magnitude remained constant up to ~ 650°C after which it shifted to above that of silicon, possibly due to a change in microstructural disorder as the precipitates increase in size. This observation was confirmed by several single step anneals at various temperatures above 650°C. No photoluminescence was observed in any of the samples.