Le but de cette thèse était d’étudier la dynamique de croissance par pulvérisation par plasma RF magnétron des couches minces à base d’oxyde de zinc destinées à des applications électroniques, optoélectroniques et photoniques de pointe. Dans ce contexte, nous avons mis au point plusieurs diagnostics permettant de caractériser les espèces neutres et chargées dans ce type de plasmas, notamment la sonde électrostatique, la spectroscopie optique d’émission et d’absorption, ainsi que la spectrométrie de masse. Par la suite, nous avons tenté de corréler certaines caractéristiques physiques de croissance des couches de ZnO, en particulier la vitesse de dépôt, aux propriétés fondamentales du plasma. Nos résultats ont montré que l’éjection d’atomes de Zn, In et O au cours de la pulvérisation RF magnétron de cibles de Zn, ZnO et In2O3 n’influence que très peu la densité d’ions positifs (et donc la densité d’électrons en supposant la quasi-neutralité) ainsi que la fonction de distribution en énergie des électrons (populations de basse et haute énergie). Cependant, le rapport entre la densité d’atomes d’argon métastables (3P2) sur la densité électronique décroît lorsque la densité d’atomes de Zn augmente, un effet pouvant être attribué à l’ionisation des atomes de Zn par effet Penning. De plus, dans les conditions opératoires étudiées (plasmas de basse pression, < 100 mTorr), la thermalisation des atomes pulvérisés par collisions avec les atomes en phase gazeuse demeure incomplète. Nous avons montré que l’une des conséquences de ce résultat est la présence d’ions Zn+ suprathermiques près du substrat. Finalement, nous avons corrélé la quantité d’atomes de Zn pulvérisés déterminée par spectroscopie d’émission avec la vitesse de dépôt d’une couche mince de ZnO mesurée par ellipsométrie spectroscopique. Ces travaux ont permis de mettre en évidence que ce sont majoritairement les atomes de Zn (et non les espèces excitées et/ou ioniques) qui gouvernent la dynamique de croissance par pulvérisation RF magnétron des couches minces de ZnO. / The goal of this thesis was to study the growth dynamics of zinc oxide based thin films by RF magnetron sputtering plasmas for advanced electronic, optoelectronic, and photonic applications. In this context, we have developed several diagnostics to characterize neutral and charged species in such plasmas, in particular electrostatic probe, optical emission and absorption spectroscopy, as well as plasma sampling mass spectrometry. Afterward, we have tried to correlate specific physical characteristics of as-grown ZnO thin films, in particular the deposition rate, to fundamental plasma properties. Our results have shown that the ejection of Zn, In and O atoms during the RF magnetron sputtering of Zn, ZnO and In2O3 targets does not significantly influence the number density of positive ions (and thus the electron density assuming quasi-neutrality) as well as the electron energy distribution function (populations of low and high energy). However, the ratio of the number density of metastable argon atoms (3P2) to the electron density decreases with increasing concentration Zn atoms; a feature that can be ascribed to Penning ionization of RF sputtered Zn atoms. Furthermore, over the range operating conditions examined in this study (low-pressure plasmas), the thermalization of sputtered atoms by collisions with atoms in the gas phase remains incomplete. We have shown that one of the consequences of this result is the presence of suprathermic Zn+ ions near the target. Finally, we have correlated the quantity of sputtered Zn atoms determined by optical emission spectroscopy with the deposition rate of ZnO thin films measured by spectroscopic ellipsometry. This set of data lead us to the conclusion that mainly Zn atoms (and not excited and/or ionic Zn species) govern the growth dynamic of ZnO-based thin films during magnetron sputtering in argon RF plasmas.

[pt] Um espectrômetro de massa por tempo-de-vôo 252Cf-PDMS foi empregado para a realização de três atividades: a) o aperfeiçoamento do espectrômetro com a instalação de novos dispositivos; b) a análise da emissão secundária de agregados iônicos por um alvo de LiF; c) a análise da fragmentação em vôo de íons positivos (LiF)nLi+ metaestáveis. O aperfeiçoamento do espectrômetro consistiu: i) na blindagem elétrica do detector start para aumentar a sua estabilidade; ii) na caracterização de dois pares de placas defletoras já existentes; iii) na instalação de um novo tipo de detector sensível à posição com anodo multi-fios, e iv) no projeto e na instalação de uma lente Einzel para aumentar a transmissão de íons secundários entre a amostra e o detector. A emissão secundária de agregados iônicos por um filme de LiF policristalino, bombardeado por fragmentos de fissão de ~ 60 MeV foi analisada através da técnica tempo-de-vôo (TOF). O detector sensível à posição recém instalado permite o emprego da técnica XY-TOF para analisar distribuições angulares de íons Li e dos agregados (LiF)nLi+. Determinaram-se as distribuições angulares dos agregados com n = 0 a 3, através de medidas simultâneas de suas velocidades axiais e radiais, evento por evento. A vida media de íons metaestáveis (LiF)nLi+* é determinada fazendo uso da configuração do espectrômetro e especialmente do comprimento do tubo de vôo livre. Após serem emitidas, as espécies iônicas metaestáveis monocarregadas são aceleradas por um campo elétrico da ordem de 2 kV/mm, e conduzidas a uma região de campo externo nulo, onde podem se dissociar espontaneamente em um fragmento iônico e outro neutro. Para facilitar a analise dos dados, impede-se a detecção do fragmento iônico através de um filtro eletrostático. Foram analisados os agregados iônicos com n = 1 a 5. Encontrouse que os valores das vidas medias estão na faixa de 30 a 100 ns. Discute-se também a detecção de espécies neutras produzidas por colisão de agregados (LiF)nLi+ com moléculas de gás residual. / [en] A 252Cf-PDMS time-of-flight mass spectrometer was used for the accomplishment of three activities: a) improvement of the spectrometer by introducing new devices; b) analysis of the LiF cluster ion secondary emission; c) analysis of the (LiF)nLi+ metastable íon fragmentation, in flight. The spectrometer improvement consists of: i) the shielding of the start detector to increase its stability, ii) the characterization of two existing deflecting- plate pairs, iii) the installation of a new type of position-sensitive delay line detector for secundary ions, and iv) the project and manufacture of a Einzel lens to increase the transmission of the secondary íons between the sample and the detector. The secondary cluster ion emission of policrystalline LiF, induced by the impact of fission fragments (60 MeV), is analyzed by the time-of-flight technique (TOF). The new position sensitive delay-line detector allows the use of the XY-TOF technique to analyze angular distributions of Li ions and (LiF)nLi+ clusters. Event by event, their axial and radial velocities are measured simultaneously, allowing the angular distributions measurement of clusters with n = 0 to 3. Mean lives of metastable clusters are determined through the measurement of the detection rate dependence on the target bias. After been emitted, the monocharged metatable ions are acelerated by a 2 kV/mm electric field towards a field-free region, where they can spontaneously dissociateinto two fragments, one ion and another neutral. To facilitate the data analysis, it is avoided the detection of ionic fragments by placing an electrostatic filter in front of the detector. Mean lives values of 30 to 100 ns are determined for ionic clusters with n = 1 to 5. The production of neutral species by collision of the (LiF)nLi+ clusters with the gas molecules is also discussed.

The DART ion source was introduced in 2005 at the ASMS Sanibel Conference and immediately afterward Professor Sparkman was contemplating of a way to get our lab this revolutionary mass spectrometry ionization technique. It did not take long because it was delivered to the Pacific Mass Spectrometry Facility in August 2006 and I was able to being using and learning the technique. The ion source creates excited state helium metastables (2 3 S) with an ionization potential of 19.8 eV are created by a glow discharge at atmospheric pressure. The metastables are sent through an optional heater, to aid in desorption, enter the open-air to directly ionize your sample or ionize reagent species to react with the analyte molecules. The most observed ionization mechanism is the formation of protonated molecules from a proton-transfer reaction between the analyte and protonated water clusters. The limited to no sample preparation with the "soft" ionization provide very quick identification of intact organic ions in or on various types of matrices. When the DART is coupled to a high resolving power instrument, such as the JEOL AccuTOF, accurate masses and accurate isotope ratios are assigned to aid in the determination of unknown elemental compositions. This research discusses the formation of the metastable species and how they are used to produce analyte and reagent ions within the open-air sample gap of the DART-mass spectrometer interface. A description of the fundamentals on the operation including real time visualization of the fluid dynamics and confirmation of the formation of a hydroxyl radical in the proposed formation of the protonated water clusters, along with applications developed in the Pacific Mass Spectrometry Facility will also be discussed. These include cleavage, desorption, and ionization of solid-phase peptides, desorption of aqueous metal ions using a heated wire filament and the increased ion transmission with the Vapur interface using metal coated glass tube for the transfer tube.