Orientadores: Lisandro Pavie Cardoso, Rossano Lang Carvalho / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T10:35:30Z (GMT). No. of bitstreams: 1 CalligarisdeAndrade_Guilherme_M.pdf: 21575111 bytes, checksum: b393b34194bc7dab77ca356bced5b375 (MD5) Previous issue date: 2014 / Resumo: O alto controle e reprodutibilidade envolvidos nas técnicas de implantação e de irradiação iônica fazem com que elas sejam muito utilizadas por permitir modificação estrutural de semicondutores, possibilitando, por exemplo, a geração de defeitos estruturais que atuam como centros de recombinação radiativa de portadores para aplicação em eficientes dispositivos emissores de luz baseados em Silício. Igualmente necessária é a caracterização estrutural desses materiais modificados, como os sistemas provenientes de engenharia de defeitos, promovendo um correto e abrangente entendimento que irá contribuir para a otimização dos seus processos de síntese. Nesse contexto, e motivados por resultados recentes, o presente trabalho visa aplicar técnicas de raios-X com boa resolução no estudo de defeitos gerados pelos processos de implantação e irradiação em dois sistemas distintos baseados em Silício. O primeiro sistema, em que amostras de Si(001) foram implantadas com Fe+ e irradiadas com Au++, mostrou uma forte absorção na região de UV (maior para a amostra implantada e irradiada) durante seus estudos preliminares de reflectância óptica UV-Vis. O segundo, em que amostras de Si(001) implantados com Xe+ e submetidas a posterior tratamento térmico de 600, 700 e 800 ºC/30 min, foi motivado por trabalhos do grupo de pesquisa do Laboratório de Implantação Iônica - UFRGS, em que íons de He e Ne produziram nanobolhas no Silício monocristalino. Foram utilizadas as técnicas de Refletividade de Raios-X (XRR), Difração de Raios-X com Incidência Rasante (GIXRD), além de varreduras no espaço recíproco Q-scans e Mapeamentos do Espaço Recíproco (RSM) que utilizam geometria de alta resolução. Também foram realizadas varreduras Renninger e mapeamentos ?:?, ângulos incidente (?) e azimutal (?) acoplados, da Difração Múltipla de Raios-X (XRMD) utilizando Radiação Sincrotron. A Fluorescência de Raios-X (XRF) e a Microscopia Eletrônica de Transmissão (TEM) também foram utilizadas como técnicas complementares. Os resultados do primeiro sistema (Fe+/Au++) para a XRR distinguiu as diferentes regiões geradas pelos processos de implantação/irradiação de íons. A análise das amostras implantada e irradiada e a apenas irradiada foi feita: i) por medidas de Q-scan para a reflexão (004) e mostrou a contribuição de uma região distorcida (RD) na direção normal à superfície com a? = 5,4235(4) Å, com perfil diferente para cada uma delas; ii) por RSM e mostrou contribuições diferentes no padrão de intensidade, na direção QX (direção paralela), para essas mesmas amostras; iii) por mapeamentos ?:? da XRMD na exata condição de 4-feixes (000)(002)(1 1 1)(1 13) e mostrou a ocorrência inédita, para este sistema, de um pico de reflexão híbrida coerente (CHR) do tipo substrato/camada (SL), envolvendo o caminho (1 13)S + (11 1)L . Os resultados do segundo sistema (Xe+) para medidas de: i) RSM e ii) Q-scans com a reflexão assimétrica (113) da amostra como-implantada mostraram a contribuição dos defeitos pontuais gerados pela implantação. Nas amostras tratadas termicamente mostraram a recristalização da rede do Si com o tratamento térmico (direção perpendicular), além de evidenciar a formação de uma região tensionada com a? = 5,425(2) Å (800 ºC/30 min); iii) mapeamento ?:? mostraram o aumento da densidade de defeitos com a temperatura de recozimento, tanto pelo espalhamento difuso no caso 3-feixes (000)(002)(1 11) , quanto pela ocorrência de extinção primária no caso 4-feixes (000)(002)(1 1 1)(1 13) . Imagens de seção transversal (TEM) em associação com análise elementar por Espectroscopia de Energia Dispersiva (EDS) confirmaram a presença de nanodefeitos, possivelmente do tipo {111} e {113}, e a formação de nanobolhas de Xe, que por sua vez devem ser os responsáveis pela tensão compressiva observada por RSM / Abstract: The high reproducibility and control involved in ion implantation and irradiation techniques, makes them to be widely used to allow structural modification of semiconductors, enabling, for instance, the generation of structural defects that act as radiative recombination centers of carriers for application in efficient Silicon-based light emitting devices. Equally necessary is the structural characterization of these modified materials, such as engineered-defects systems, promoting an accurate and comprehensive understanding that will contribute to the optimization of their synthesis processes. In this framework, and motivated by recent results, the present work intends to apply highresolution X-ray techniques on the study of the defects created by ion implantation/irradiation process into two distinct Silicon-based systems. The first system consists of Fe+-implanted and/or Au++-irradiated Si(001) samples that exhibited a significant absorption increase on the UV region during preliminary studies of its UV-Vis optical reflectance. The second system consists of Xe+- implanted Si(001) samples thermally treated at 600, 700, and 800 ºC/30 min, that was motivated by previous works from Laboratório de Implantação Iônica ¿ UFRGS in which He and Ne ions have produced nanobubbles in a Silicon matrix. The X-ray techniques, such as Reflectivity (XRR), Grazing Incidence (GIXRD), and also Qscans on reciprocal space and Reciprocal Space Mappings (RSM), under high-resolution geometry, were all used in the measurements. Furthermore, Renninger scans and X-Ray Multiple Diffraction (XRMD) ?:? mappings, for coupled incident (?) and azimuthal (?) angles, were also applied with synchrotron radiation. X-Ray Fluorescence (XRF) and Transmission Electron Microscopy (TEM) were employed as complementary techniques. For the first system (Fe+/Au++), XRR results were able to distinguish the distinct regions generated by the ion implantation/irradiation process. The analysis of the implanted-and-irradiated sample, as well as the just irradiated sample was made by: i) Q-scans of the (004) reflection and exposes the contribution of a Distorted Region (RD) in the out-of-plane direction with a? = 5.4235(4) Å, which has a different profile for each sample; ii) RSM that reveals distinct QX (inplane direction) intensity profiles for each sample; iii) ?:? mapping of the XRMD at the exact condition of the (000)(002)(111)(113) 4-beam case that exhibited an unprecedented occurrence, for this system, of a Coherent Hybrid Reflection (CHR) peak involving the substrate/layer (SL) S (1 13) + L (11 1) path. The results of the second system (Xe+) for the measurements of: i) RSM and ii) Q-scans using the asymmetric (113) reflection of the as-implanted sample showed the contributions of the implantation-induced point defects. The annealed samples have exposed the Si lattice recrystallization (out-of-plane profile), in addition to demonstrating the formation of a strained region with a? = 5.425(2) Å (800 ºC/30 min); iii) ?:? mappings showed an increase of defects density for higher temperature annealed samples by both the diffuse scattering in the (000)(002)(111) 3-beam case, as the occurrence of primary extinction for the (000)(002)(111)(113) 4-beam case. The presence of both {111} and {113} defects, as well as Xe nanobubbles formation, were confirmed by cross-section TEM images in association with elemental analysis by Energy Dispersive Spectroscopy (EDS), indicating that the later one is responsible for the compressive strain observed by RSM measurements. Combined cross-section TEM images and Energy Dispersive Spectroscopy (EDS) results have confirmed the presence Xe nanobubbles, which should be responsible for the compressive strain observed by RSM measurements, as well as the formation of the {111} and {113} nanodefects / Mestrado / Física / Mestre em Física

Real-time coherent Grazing-Incidence Small-Angle X-ray Scattering was used to investigate the average kinetics and the fluctuation dynamics during self-organized ion beam nano-patterning of two semiconductor surfaces: silicon at room temperature and germanium heated above its recrystallation temperature. For silicon nano-patterning, initially flat samples at room temperature were bombarded by a broad collimated beam of 1keV Ar+ and Kr+ ions at 65° polar angle, leading to the amorphization of the ion-irradiated surfaces and the spontaneous formation of nanoscale ripples. The temporal evolution of the average X-ray scattering intensity shows the evolution of average kinetics, while the fluctuation dynamics can be investigated by correlation of X-ray speckles. The surface behavior at early times can be explained within a linear theory framework. The transition away from the linear theory behavior is observed in the dynamics since the intensity correlation function quickly evolves into a compressed exponential decay on length scales corresponding to the peak wavelength and a stretched exponential decay on shorter length scales. The correlation times for silicon nano-patterning are maximum at the ripple wavelengths while they are smaller at other wavelengths. This has notable similarities and differences with the phenomenon of de Gennes narrowing. Overall, this dynamics behavior is found to be consistent with the simulations of a nonlinear growth model by Harrison et al. Following the formation of self-organized nano-ripples, they move across the surface. Homodyne X-ray alone cannot detect the motion, but because of the gradient of ion flux across the sample, we were able to measure in-situ the corresponding ripple velocity gradient by cross-correlating speckles and tracking their movements. For germanium nano-patterning at an elevated temperature, flat germanium samples kept at 300°C were bombarded by 1keV Ar+ ions at normal incidence. Unlike the case when surfaces are amorphizated during room temperature bombardment, the crystalline nano-pattern formation occurs mainly due to a surface instability caused by the Ehrlich-Schwoebel barrier. By using a linear theory analysis on the X-ray scattering intensities in the early times, we measured the contribution of the Ehrlich-Schwoebel barrier to the crystalline nano-patterning kinetics.

Ce travail a pour but d'implémenter des procédés d’implantation ionique pour des cellules solaires à hétérojonctions de silicium (SHJ) afin d'en simplifier le procédé de fabrication ou d’en augmenter les performances.Nous avons d'abord étudié le procédé pour réaliser le dopage des couches de silicium amorphe hydrogéné (a-Si:H). Par ce nouveau procédé, il est possible de réaliser des dopages localisés de manière simple, à travers des masques, ce qui peut permettre une diminution des coûts de fabrication de certains types de cellules SHJ comme les cellules à contacts interdigités à l'arrière. Les implantations de phosphore et de bore ont été étudiées, pour la réalisation de dopage respectivement de type n et p. Les comportements et les conclusions sont très différents pour ces deux types de dopage. Le phosphore étant plus lourd que le bore, il est possible de l'implanter dans des couches très minces sans endommager fortement l'interface avec le silicium cristallin, mais la création très importante de défauts dans le a-Si:H, résistant à des recuits post-implantation, conduit à de fortes dégradations des propriétés électriques du a-Si:H, et il n'a pas été possible d'atteindre des niveaux de conductivité suffisants. Au contraire, pour le bore, conformément à des résultats de la littérature, les atomes sont activés plus facilement par un recuit post-implantation grâce à la forte diminution de la concentration de défauts localisés. Cependant, le bore, implanté plus profondément, atteint e plus facilement l'interface, ce qui nécessite des recuits à plus haute température pour guérir les défauts d'interface. Néanmoins, pour des couches de a-Si:H de l'ordre de 25 nm, nous avons pu trouver des conditions technologiques permettant d'obtenir des propriétés comparables à celles obtenues par le procédé classique de dépôt de (p) a Si:H assisté par plasma, à savoir des valeurs élevées de conductivités du a-Si:H (10-4 Ω-1cm-1) et de passivation d’interface (i VOC > 700 mV).Une deuxième partie de ce travail est consacrée à l’étude d’une nouvelle cellule, dite à homo hétérojonction de silicium (HHJ) comprenant un homo-émetteur additionnel (p+) c-Si à l’hétéro-interface côté émetteur. Le but est d’améliorer la passivation de l’interface afin d’augmenter le rendement de la cellule. Des simulations numériques ont mis en évidence une augmentation de FF de la cellule HHJ, que nous avons pu attribuer à une meilleure passivation par effet de champ et à une diminution de la résistance globale du a-Si:H due à des modifications des courbures de bandes. Elles ont aussi montré la nécessité d’un homo-émetteur suffisamment mince et fortement dopé (5×1018 cm-3). De ce fait, nous avons utilisé le procédé d’implantation ionique pour développer des profils de bore adéquats et avons pu vérifier expérimentalement que l'incorporation de la couche de (p+) c-Si permet la diminution de la résistance de contact et l'amélioration de la passivation de l'interface (i) a-Si:H/(p+) c-Si par effet de champ lorsque la concentration de bore en surface n'est pas trop importante. Ces deux améliorations ont pu être concrétisées dans la réalisation de cellules présentant une amélioration du facteur de forme et de meilleurs rendements de conversion par rapport à des cellules SHJ de référence. Cette réalisation constitue la première preuve de concept pour les cellules de type HHJ. / This work aims at investigating the use of ion implantation to process silicon heterojunction solar cells (SHJ) in order to improve the ratio of cost to produced power (€/Wp) of the cells either by cost reduction due to manufacturing simplification or by increase of the cell performance.A first part of the work consists in doping hydrogenated amorphous silicon (a-Si:H) layers by ion implantation. Using hard masks, doping of localized regions required in cell architectures like interdigitated back contact cells can thus be easily achieved at lower cost. Both boron and phosphorus implantation have been studied for p- and n-type doping, respectively. These two types behave very differently. Phosphorous being heavier than boron, very shallow implantation can be achieved on thin a-Si:H layers onto crystalline wafers without damaging the interface. However very high defect densities are created in a-Si:H which cannot be annealed out by post-implantation annealing treatments. Therefore it was not possible to reach conductivity values suitable for solar cell applications. For B implantation, consistently with previous work, the activation of B atoms has been achieved upon annealing thanks to a decrease of localized bandgap states. Also, boron can penetrate deeper and reach high concentration at the a-Si:H/c-Si interface, which requires higher temperature annealing compared to P implantation to recover a good interface passivation quality. Nevertheless, for a-Si:H layers of about 25 nm process conditions allowing similar properties to PECVD-doped (p) a-Si:H deposition (i.e. conductivity of 10-4 Ω-1cm-1 and interface passivation allowing i-VOC > 700 mV) have been obtained.A second study is dedicated to the study of a new cell concept, named silicon homo-heterojunction (HHJ) which comprise an additional homo-emitter (p+) c-Si at the emitter interface. The goal is to improve the interface passivation in order to increase the cell efficiency. Numerical simulations have evidenced an improved fill factor in this cell that is attributed to a field effect passivation improvement and a decrease in series resistance related to band bending changes in the a-Si:H layers. The need of sufficiently shallow and strongly doped (> 5×1018 cm-3) emitter has also been evidenced. Therefore, ion implantation has been used to develop suitable boron profiles and both the increase in fill factor and the decrease in contact resistances have been obtained when the boron surface concentration is not too high. These improvements have been validated by processing HHJ solar cells that exhibit a fill factor improvement and an improved efficiency compared to SHJ cells. This achievement is a first proof of concept of the HHJ architecture.

No description available.

In diesem Report wird eine Niederenergie-Implantationskammer (NEI-Kammer) beschrieben, die im Forschungszentrum Rossendorf entwickelt und aufgebaut wurde. Die Kammer ermöglicht es, die Implantation von Ionen bei niedrigen Energien (< 30 keV) mit einer Implantationsanlage für mittlere Energien durchzuführen. In der Kammer werden der Ionenstrahl, den der Implanter liefert, auf die erwünschte niedrige Energie abgebremst. Dazu wird ein elektrostatisches Bremslinsensystem eingesetzt, das auf einem neuartigen Prinzip basiert. Das System besteht aus einer Sammellinse und einer Zerstreuungslinse, wobei die Öffnungsfehler beider Linsen entgegengesetzte Vorzeichen besitzen und sich gegenseitig kompensieren. Dadurch ist es möglich, Wafer gebräuchlicher Größe bei geringer Energie mit hoher Dosishomogenität zu implantieren. Die NEI-Kammer ist insbesondere für Forschungseinrichtungen eine vorteilhafte Lösung, da sie eine wesentlich kostengünstigere und flexiblere Alternative zur Anschaffung einer Niederenergie-Implantationsanlage darstellt.

Image charge detection is a non-perturbative pre-detection approach for deterministic ion implantation. Using low energy ion bunches as a model system for highly charged single ions, we experimentally studied the error and detection rates of an image charge detector setup. The probability density functions of the signal amplitudes in the Fourier spectrum can be modelled with a generalised gamma distribution to predict error and detection rates. It is shown that the false positive error rate can be minimised at the cost of detection rate, but this does not impair the fidelity of a deterministic implantation process. Independent of the ion species, at a signal to-noise ratio of 2, a false positive error rate of 0.1% is achieved, while the detection rate is about 22%

Silicates analogous to cosmic dust were synthesized, modified, and analyzed utilizing ion-beam techniques with Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD). Silicate dust is a common constituent in interstellar space, with an estimated 50% of dust produced in the stellar winds of M class Asymptotic Giant Branch (AGB) stars. Silicate dust acts as a surface upon which other chemicals may form (water ice for example), increasing significance in the cosmochemistry field, as well as laboratory astrophysics. Silicate formation in the stellar winds of AGB stars was simulated in the laboratory environment. Three sequential ion implantations of Fe-, MgH2-, and O- with thermal annealing were used to synthesize a mixture appropriate to silicate dust in the surface layers of a p-type Si substrate. Post implantation He+ irradiation was shown to preferentially induce crystalline formation in the analogue prior to thermal annealing. This effect is believed to originate in the ion-electron interaction in the Si substrate. The effects of ionization and ion energy loss due to electronic stopping forces is believed to precipitate nucleation in the amorphous media. For annealing temperatures of 1273 K, predominant quartz formation was found in the substrate, whereas lower annealing temperatures of 1000 K formed enstatite without post-implantation He+ irradiation, and olivine with He+ irradiation. Post annealed crystalline phase modification was investigated via x-ray diffraction and elemental compositions were investigated utilizing RBS. Finally, the interdiffusion of Fe and Mg at temperatures of 900-1100 K was investigated with RBS, and activation energies for interdiffusion were extracted for the transition from amorphous to crystalline phase in the silicate analogues. Fe had an interdiffusion energy of 1.8 eV and Mg 1.5eV. The produced analogues have similar properties to those inferred from infrared spectroscopy of the stellar winds of M-class AGB stars with an oxygen-rich outflow. This work established a method of silicate production using ion beam modifications, explored He+ irradiation effects in the annealed structures, and derived interdiffusion activation energies for Fe and Mg in the amorphous structure. Grain sizes were <100 nm with the observed formation of quartz, enstatite, and olivine.

No description available.

No description available.

No description available.