Due to the fast expansion and development in the optical communication industry, the demand for the film quality has correspondingly increased. Ion beam sputter deposition (IBSD) achieves the lowest loss, but low throughput. In our Lab., E-beam system was used for CaO, MgO and Cr2O3 evaporation on the circumference of the Cr:YAG crystal fiber. Although the substrate was heated to around 275oC, the thin film didn¡¦t achieve low loss and high laser-induced damage threshold film. Adding ion-beam assisted deposition (IAD) system to enhance the thin film energy and packing density is the main theme of this thesis. The thesis mainly focuses on the characteristics of TiO2 and SiO2 thin film based on E-beam with IAD system. Spectrometer analyzer and Macleod software were used to calculate the refractive index and extinction coefficient. ESCA (electron spectroscopy for chemical analyzer) was adopt to measure the thin film composition of Ti, Si, O. SEM (scanning electron microscope) was used to observe the thin film quality. Low loss and high laser-induced damage threshold thin film are the goal of the present research. With optimized parameters, the refractive index of TiO2 film was achieved to be 2.51 at 500 nm, and the extinction coefficient was less than 2x10-4. The refractive index of SiO2 film can be achieved to be 1.466 at 500 nm, and the extinction coefficient was less than 1x10-4. An HR (R>99.83%) coating at 1233 nm was successfully demonstrated by the IAD deposition system.

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This thesis is divided into three main parts dealing with ion beam assisted deposition. In the first part there is a brief description of the IBAD chamber at Institute of Physical Engineering of BUT. There is also a detailed description of control of the IBAD apparatus during deposition. Next part deals with measuring of deposition rates of ion sputtering in order to refine deposition of thin layers. Last part deals with planned and already finished changes that should improve quality and speed of thin layers deposition. Changes include the option of covering the substrate holder, change of the entry flange, design of new insertion chamber with multifunctional substrate holder and the option to control the deposition by computer.

No description available.

The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy <100 eV) is capable to modify the characteristics of the growing film without generating a large number of irradiation induced defects. The nitrogen ion beam assisted molecular beam epitaxy (ion energy <25 eV) is used to deposit GaN thin films on (0001)-oriented 6H-SiC substrates at 700 C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality.

Orientador: Fernando Alvarez / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-09T10:47:17Z (GMT). No. of bitstreams: 1 ParedezAngeles_PabloJenner_D.pdf: 4194390 bytes, checksum: 8881d83ee8bcb5a5ad4bfb23b7ff1028 (MD5) Previous issue date: 2007 / Resumo: Nesta tese são apresentados os efeitos nas propriedades estruturais, eletrônicas e de emissão eletrônica por efeito de campo elétrico induzidos pela incorporação de nitrogênio em nanoestruturas de carbono. As nanoestruturas de carbono contendo nitrogênio foram preparadas por pulverização catódica (sputtering) de um alvo de grafite assistido, ou não, por um feixe iônico. A técnica permite atuar sobre os parâmetros de deposição induzindo mudanças nas propriedades estruturais, eletrônicas e de emissão eletrônica por efeito de campo elétrico. O papel do hélio na formação de nanoes-truturas de carbono contendo nitrogênio foi também explorado, mostrando que o gás nobre promove maior incorporação de nitrogênio. Isto é provavelmente devido à relativa alta condutividade térmica que apresenta o hélio, propriedade que modifica a cinética do crescimento das nanoestruturas. O estudo realizado permitiu entender o mecanismo de formação das nanoestruturas, mostrando que primeiramente o carbono alcança as partículas de Ni por difusão até a saturação do metal, iniciando a formação das camadas grafíticas sobre a partícula de Ni, camadas que foram observadas por microscopia eletrônica de transmissão de alta resolução. O estudo mostra, também, que os parâmetros importantes que controlam a incorporação de nitrogênio no material são a pressão parcial de nitrogênio na câmara de deposição, assim como a energia do feixe de íons assistindo a deposição.Foram estudadas três séries de amostras preparadas em atmosferas controladas. Na primeira série foi utilizado um feixe de íons de nitrogênio como feixe de assistência, e na segunda, uma mistura composta por duas espécies iônicas, íons de nitrogênio e hidrogênio. Com o auxilio da espectroscopia de elétrons fotoemitidos por raios-X observou-se a incorporação de nitrogênio nos filmes. A microscopia de força atômica revelou a presença de estruturas do tipo domo, distribuídas de maneira uniforme na superfície das amostras, apresentando uma densidade média de ~3×10 9 domos/cm 2as da primeira série, e ~1.4×10 9 domos/cm 2as da segunda série. Tanto a distribuição como a forma seguem o padrão estabelecido pelos precursores utilizados na preparação das nanoestruturas, i.e., ilhas de níquel que agem ao mesmo tempo como catalisadores e como suporte para as nanoestruturas. Na terceira série, as nanoestruturas foram crescidas sobre um filme de nitreto de titânio, depositado sobre substratos de Si, pulverizando um alvo de grafite em atmosferas de nitrogênio e hélio-nitrogênio. A densidade dos domos encontrada para esta série foi de ~5.3×10 10 domos/cm 2 . Os espectros Raman das três séries apresentam as bandas G e D, o que indica a presença estruturas grafíticas com distorções representadas pela banda D. A incorporação de nitrogênio ocasiona o alargamento da banda G e aumento da razão das intensidades das bandas D e G, respectivamente, indicando uma redução da ordem estrutural com a incorporação de Nitrogênio. Finalmente, para as três séries de amostras, fez-se também um estudo das propriedades de emissão eletrônica por efeito de campo elétrico. A emissão é predominantemente por tunelamento quântico (as curvas de densidade de corrente vs campo elétrico seguem o modelo de Fowler-Nordheim) e dependem da concentração de nitrogênio assim como do processo usado na preparação das amostras / Abstract: The subject of this thesis is establishing a link among the synthesis, structures, and field emission properties for nanostructured carbon materials containing nitrogen. The materials were prepared by ion beam assisted deposition and ion beam sputtering. The carbon material was obtained sputtering an ultra pure graphite target by an argon ion beam. The method allows controlling the deposition parameters to induce changes in the structural, electronic, and field emission properties. Also, the role of helium on the carbon containing nitrogen nanostructures was investigated. The remarkable thermal conductance of He modifying the growing kinetics was also studied. An important goal of the work was to elucidate the mechanism of the nanostructures formation. It was found that, at first, the carbon atoms reach the Ni particles saturating the metal particle, and then, the formation of stacked graphene starts on the metal particles. The graphene layers were observed by high resolution transmission electron microscopy. The results show that mainly two parameters control the nitrogen incorporation, namely, the deposition chamber nitrogen partial pressure and the energy of the nitrogen ion beam assisting the growth. Three sample series prepared in controlled atmospheres were studied. The first series was prepared assisting the growth with a nitrogen ion beam and, the second series by a nitrogen-hydrogen ion beam. The third sample series were prepared by ion beam sputtering on silicon substrate by sequentially depositing titanium nitride thin film, nanometric nickel particles and carbon. The carbon containing nitrogen nanostructures were grown in nitrogen and helium-nitrogen atmospheres. X-ray photoelectron spectroscopy analysis indicates nitrogen incorporation and it depends predominantly on the ion beam energy or on the nitrogen partial pressure. Atomic force microscopy reveals dome-like structures uniformly distributed on the surface of the samples, with ~3×10 9 domes/cm 2 for the first series, ~1.4×10 9 domes/cm 2 for the second, and ~5.3×10 10 domes/cm 2 for the third. Both distribution and shape follow the Ni island pattern, i.e. the Ni islandsact both as a catalytic and uphold. The three samples series were also analyzed by Raman spectros-copy, showing a defined G bands around 1593 cm -1 indicating the presence of graphitic structures. Also, are observed D bands indicating structural disorder. The disorder increases with the augment of the nitrogen content, as is shown by the augment of the D and G intensities ratio. Finally, the field emission properties of the three series were studied and the electron emission depends on the growing conditions in general, and on the nitrogen content in particular. The results show that the emission is predominantly by quantum tunneling and the current density vs. electric field curves follow the Fowler-Nordheim model / Doutorado / Física / Doutor em Ciências

The aim of this thesis is a systematic study of physical properties of magnetic multilayered nanostructures. Namely it include multilayered spin valves NiFe/Cu/Co with magnetic anisotropy iduced by magnetic field applied during the deposition. Induced magnetic anisotropy influences exchange interactions between magnetic layers and so it gives the possibility to control magnetic properties of nanolayers. This is important for applications in MRAM, magnetoresistive read heads and spin-transfer-torque devices. Magnetooptic spectroscopy and Kerr effect hysteresis loop measurement were used as effective probe techniques. Secondly we examinated Ar3+ rf sputtering influence on multilayer interface quality level. We found out, that Ar3+ irradiation during deposition process has a possitive effect on interface quality.

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No description available.