This thesis explores the feasibility of high power impulse magnetron sputtering (HiPIMS) to synthesize hydrogenated amorphous carbon (a-C:H) thin films in Ar-hydrocarbon ambient and the relationship between process parameters, gas phase composition and film properties. To this purpose a stable process based on HiPIMS and direct current magnetron sputtering (DCMS) has been developed. Four series of amorphous carbon thin films were deposited by hybrid HiPIMS-DCMS and pure DCMS processes at 15 mTorr pressure using different Ar-acetylene compositions and a substrate bias from 0 to -350 V. The effect of Ar-acetylene compositions and depositions processes on the film properties was investigated by characterizing the films using scanning electron microscopy (SEM), x-ray reflectometry (XRR), nanoindentation and elastic recoil detection analysis (ERDA). Moreover the process characterization was done by recording the optical emission spectrum and current and voltage waveforms of the hybrid HiPIMS-DCMS discharge. The characterization of the films revealed that the hybrid HiPIMS-DCMS process is a powerful tool for controlling the amorphous carbon film properties such as density, deposition rate, hardness and hydrogen content.

In the process of sputtering, what a system operator concerns are the sputtering rate, target utilization, and substrates uniformity. All of them are influenced by variables such as electromagnetic environment, chamber temperature, and pressure. In thin film manufacturing, targets bombarded by ions will sputter atoms to the substrates in order to make thin films; therefore, when a certain target zone is extensively bombarded by ions, target surface will become thinner. In general, when certain part of the target is penetrated, it is no longer usable while utilization rate only from 30 to 50 percent. It causes considerable waste and relatively higher costs. As a result, the objective of this study is to enhance target utilization and the sputtering rate through appropriate adjustment in the structure of the existing DC Magnetron Sputtering System (MSS). Since, the magnetic field distribution in the chamber will be appropriately adjusted inside the DC MSS with extra iron annulus and active compensation magnetizations being added. However, in order to get the better structural refinement of DC MSS it needs a thorough design and management based on Taguchi Method. Then, based on such structural adjustment, electron trajectories on top surface of targets can be conveniently controlled, and target erosion patterns and the number of ions bombarding the target will be indirectly controlled. It will, as a result, achieve the objective of this study by enhancing not only the target utilization efficiency but the sputtering rate.

Sputtering is a physical vapor deposition (PVD) process used to create thin films, i.e very thin layers of material. To form compounds, such as oxides and nitrides, it may be beneficial to add a reactive gas to the process which is known as reactive sputtering. This thesis focuses on the simulation of the reactive sputtering process and, more specifically, the effect of the process pressure. Two models have been developed. A Monte Carlo model simulates the distribution of sputtered material throughout the chamber. It is based on the binary collision model with initial conditions acquired from simulations in TRIM. The hard-sphere potential is used as interaction potential in the scattering calculations. The effect of the process pressure is studied for two different elements, sulfur and tungsten. It is found that the distribution of material is heavily influenced by the pressure. A high pressure gives a more diffusion-like distribution compared to a low pressure. As the pressure is increased the deposited material’s energy distribution is found to be shifted towards lower energies until it reaches the energy of thermalized atoms. The second model developed is an extended Berg model that incorporates the effect of redeposition of sputtered material on the target, implantation of reactive ions in the target and preferential sputtering. Using simulations the effect of these extensions is discussed. It is found that an increased pressure may eliminate the hysteresis region which has been observed experimentally. Finally an outline is presented on how the two models can be unified into a Berg-model that takes the non-uniform distribution of sputtered material into account.

No description available.

O uso de magnetismo em sensores, transdutores e, principalmente, em mídias de gravação magnética, atinge uma escala de investimento no mercado global de bilhões de dólares anualmente. Essas aplicações tecnologicas, atualmente, apontam para usos do magnetismo na escala nanoscópica, por meio da miniaturização de dispositivos magnéticos sensores e transdutores; em gravação magnética através da nanoestruturação das unidades básicas de armazenamento; ou, ainda, na medicina pelo uso de nanopartículas magnéticas como carregadores de drogas medicinais ou como elementos aquecedores por meio da radiação em radiofrequência. Neste trabalho, adotamos uma abordagem top-down. Partimos de objetos magnéticos microscópicos e buscamos progressivamente reduzir a sua escala espacial visando atingir a escala nanoscópica. Produzindo objetos com formato regular e simples, como quadrados, discos e triângulos produzidos por litografia de feixe de elétrons e método lift-off, a partir de filmes finos produzidos por Magnetron Sputtering. Utilizando como elemento de estudo Metais de Transição (MT) e Terras Raras (TR). A estequiometria e espessura dos filmes finos de Tb-Fe foram obtidas com análise de RBS. Já a análise magnética dos filmes finos de Tb-Fe foram obtidas por técnicas de VSM e SQUID. O que possibilitou averiguar que as amostra com a proporção de Tb variando entre 22% e 36% possuem uma anisotropia magnética perpendicular bem definida e possuem um ordenamento sperimagnético. Através do microscópio de força magnética observamos a formação de domínios magnéticos do tipo bolha irregular nos filmes finos de Tb-Fe. Utilizando o microscópio eletrônico de varredura e o SNOM-MO foi possível analisar a morfologia dos micro-objetos produzidos. Os resultados mostram uma eficácia na preparação de estruturas com dimensões maiores que 2 µm, com altura de aproximadamente 50 nm. Fazendo-se necessário um estudo mais preciso para obtenção de amostra com dimensões abaixo desta dimensão. / The use of magnetism in sensors, transducers and, mainy, in magnetic recordable media reaches a total investment of billions of dollars annually in the markets worldwide. These applications in technology are currently being focused toward the uses of magnetism in the nanoscopic scale, by shrinking the magnetic sensor devices and transducers. Also, in magnetic recordings by the nanostructuration of basic storage units or - going even further - in the use of nanomagnetic particles in Medicine such as drug delivery or heating elements by radiofrequency radiation. In this paper, we take a \"top-down\" approach. We start with microscopic magnetic objects and seek progressively reduce its spatial scale in order to reach the nanoscale. Producing objects with regular and simple format, such as squares, triangles and discs produced by electron beam lithography and lift-off method, The thin films were based on transition metal and rare earth elements. The thickness and stoichiometry of thin films of Tb-Fe were meadured with RBS analysis. The analysis of the Tb-Fe magnetic thin films were obtained by techniques VSM and SQUID. The sample with the ratio of Tb ranging between 22% and 36% have a well-defined perpendicular magnetic anisotropy and have a sperimagnetic behavior. Through the magnetic force microscopy we observed the formation of magnetic domain structure of the \"irregular bubble\" type. Using scanning electron microscope and the SNOM-MO was possible to analyze the morphology of the produced micro-objects. The results show that efficiency in the preparation of structures with dimensions larger than 2 microns, and a height of approximately 50 nm. This result exposes the need for a more investigation in order to produce samples with smaller dimension.

Filmes finos de óxido de nióbio têm sido usados em muitas aplicações tecnológicas. Existem pelo menos três óxidos estáveis de nióbio: NbO, NbO2 e Nb2O5 e cada um deles tem propriedades específicas. O Nb2O5 é a forma termodinamicamente mais estável e apresenta propriedades físicas e químicas únicas, como alto índice de refração, band gap largo, excelente estabilidade química e resistência à corrosão, baixa absorção óptica no campo da luz visível até regiões próximas ao infra-vermelho, sendo amplamente utilizados como filtros de interferência óptica de alta qualidade. Neste trabalho foram depositados filmes de óxido de nióbio por meio da técnica de sputtering reativo sobre substratos de silício e borossilicato. Os filmes finos foram obtidos com vazão de oxigênio variando entre 15 e zero sccm. O objetivo deste trabalho foi a caracterização das propriedades ópticas dos filmes. Foram avaliados o índice de refração e a espessura pela técnica de elipsometria, o band gap pelo método de Tauc e a razão atômica e a densidade superficial por meio de Espectrometria de Retroespalhamento Rutherford (RBS). Foram obtidos espectros de transmitância e refletância por Espectrofotometria UV/Vis/NIR e o coeficiente de extinção foi calculado pelo método de Hong. Todos estes parâmetros são importantes para aplicação em dispositivos ópticos. Nos filmes depositados com vazão de oxigênio de 15 sccm foi observado que o índice de refração aumenta com o aumento da espessura dos filmes e que o composto formado foi Nb2O5. Para uma vazão de 2,0 sccm foi encontrado o composto NbO2 e o filme apresentou alta absorção ótica. Os resultados sugerem que outros óxidos de nióbio ou nióbio metálico foram incorporados nos filmes conforme o fluxo de oxigênio foi diminuído. Foi observada uma relação direta entre a diminuição da vazão de oxigênio durante a deposição e um aumento da quantidade de nióbio nos filmes, acompanhados de um aumento do índice de refração e da densidade superficial. / Niobium oxide thin films have been used in many technological applications. There are at least three stable niobium oxides: NbO, NbO2 and Nb2O5 and each one has specific properties. The Nb2O5 is the most stable thermodynamically form having unique physical and chemical properties such as high refractive index, wide band gap, excellent chemical stability and corrosion resistance, low optical absorption in the field of visible light to near the infrared regions, being widely used as high quality optical interference filters. In this work niobium oxide thin films were deposited by reactive sputtering technique on silicon and borosilicate substrates. The films were obtained by using oxygen flow rates varying from 15 up to zero sccm. The objective of this work was the optical characterization of niobium oxide films. The refractive index and the thickness were evaluated by ellipsometry technique, the band gap by TAUC method and the atomic ratio and the surface density by means of Rutherford backscattering spectrometry (RBS). Spectral transmittance and reflectance spectrophotometry by UV / Vis / NIR curves were obtained and the extinction coefficient was calculated by the method of Hong. All of these parameters are important for application in optical devices. In the films deposited with oxygen flow of 15 sccm it was observed that the refractive index increases with increasing thickness of the films and analyzes indicated that Nb2O5 forms for when a flow rate of 15 sccm is used. For a flow rate of 2.0 sccm it was found NbO2 and a high optical absorption. As the flow of oxygen used in the deposition of the films was decreased, there were signs that were incorporated in the films other oxides of niobium or niobium metal itself. A direct relationship between decreased of oxygen flow during deposition and a increase in niobium quantity in the films, accompanied by an increase in the refractive index and surface density was observed.

Atualmente, nanopartículas (NPs) são utilizadas em todos os ramos da tecnologia. Suas promissoras aplicações envolvem entre outros, o campo dos sensores e transdutores, mídia de gravação magnética, carreadores magnéticos de drogas medicinais. Com o objetivo de produzir NPs pelo método físico, um gerador de nanopartículas foi adaptado usando um dos canhões do sistema de magnetron sputtering, baseando-se no método de agregação gasosa. Com o gerador somos capazes de produzir NPs de diversos materiais e codepositá-las em matrizes dielétricas ou metálicas. Neste trabalho apresentamos o desenvolvimento da metodologia para a produção de nanopartículas de materiais magnéticos duros, usando alvos de SmCo5, Sm2Co17, Nd2Fe17B, FePt e CoPt. Investigamos a influência dos parâmetros de deposição (pressão, fluxo de gás e potência de sputtering), tipo de substrato e a existência de buffer e/ou codeposição, na obtenção das propriedades estruturais e magnéticas desejadas para esses materiais. As NPs produzidas são analisadas magneticamente pelo VSM e SQUID, sua morfologia e tamanho por TEM e SEM, a sua estequiometria pelo RBS, e a sua estrutura cristalina por XRD, a fim de obter nano-ímãs de alta anisotropia magnética. Da caracterização morfológica, através de microscopia eletrônica, encontramos para as NPs produzidas e estudadas diâmetros entre 5 e 17 nm. Através de análises de RBS obtemos para composição das NPs que as mesmas possuem estequiometria diferente dos alvos usados. Estudos estruturais e magnéticos mostram que para Sm-Co, Fe-Pt e Co-Pt é possível obter NPs cristalinas e com coercividade da ordem de 1 kOe. / In the recent years, nanoparticles (NPs) are being in all fields of technology. Their promising applications involve among others, the field of sensors and transducers, magnetic recording media, magnetic carriers of medicinal drugs. Aiming to produce NPs by physical method, a generator of nanoparticles was adapted using a system of guns \"magnetron sputtering\", based on the aggregation gas method. With the generator we are able to produce NPs with different types of material. In this work, we present the development of the methodology for the production of nanoparticles of hard magnetic materials, using targets of SmCo5, Sm2Co17, Nd2Fe17B, FePt and CoPt. We investigated the influence of the deposition parameters (pressure, gas flux and sputtering power), substrate type and the existence of the buffer and/or codeposition layers, to obtain the desired structural and magnetic properties for the nanoparticles. The produced NPs were magnetically analyzed by VSM and SQUID, the morphology and size by TEM and SEM, the stoichiometry by RBS and the crystal structure by XRD. The main objective of this work is to obtain nano-magnet with high magnetic anisotropy. Through the morphological characterization by electron microscopy, we found for NPs produced and studied have diameters between 5 and 17 nm. Through RBS analysis we have obtained the composition of the NPs, and also that they have different stoichiometry in relation to the used targets. Structural and magnetic studies have show that for Sm-Co, Fe-Pt and Co-Pt it is possible to obtain crystalline NPs with coercive field around 1 kOe.

No description available.

No description available.

Abstract A modified thermal spike model initially proposed to account for defect formation in metals within the high heavy ion energy regime is adapted for describing the sputtering of Bi thin films under MeV Kr ions. Surface temperature profiles for both the electronic and atomic subsystems have been carefully evaluated versus the radial distance and time with introducing appropriate values of the Bi target electronic stopping power for multi-charged Kr15+ heavy ions as well as different target physical proprieties like specific heats and thermal conductivities. Then, the total sputtering yields of the irradiated Bi thin films have been determined from a spatiotemporal integration of the local atomic evaporation rate. Besides, an expected non negligible contribution of elastic nuclear collisions to the Bi target sputtering yields and ion-induced surface effects has also been considered in our calculation. Finally, the latter thermal spike model allowed us to derive numerical sputtering yields in satisfactorily agreement with existing experimental data both over the low and high heavy ion energy regions, respectively, dominated by elastic nuclear collisions and inelastic electronic collisions, in particular with our data taken recently for Bi thin films irradiated by 27.5 MeV Kr15+ heavy ions. An overall consistency of our model calculation with the predictions of sputtering yield theoretical models within the target nuclear stopping power regime was also pointed out.