Cost-effective processing of dairy whey permeates is important to the environment and economics of the agriculture industry in Canada. Bioconversion of whey permeates is an attractive means of obtaining value-added adjuncts with improved nutritional and functional properties. In the past, cost-effective technologies to recover additional value from whey permeates at a low cost were lacking. Currently, such a technological platform is now feasible with the introduction of new modern bioconversion technologies that incorporate batch or continuous bioreactors, and use ultra- and nano-filtration membranes for the separation of whey permeate components. In this dissertation, a novel processing methodology is described. This methodology, which is a desirable configuration for food manufacturers includes a stirred batch nanomembrane bioreactor equipped with a crossflow nanomembrane and offers lactose bioconversion with an immobilized biocatalyst, product separation, and biocatalyst recovery in a batch operation. The major focus of this research was on: a) the development of a new analytical methodology for carbohydrate measurement during the lactose bioconversion process, b) the selection, testing and integration of highly selective nanomembranes to separate the desired substrates, whey permeate carbohydrates, from the reaction mixture, and c) the production of a stable and highly active and specific immobilized biocatalyst. Noticeably, this methodology was designed, developed and tested for the bioconversion of lactose, but could also be used for the bioconversion of other carbohydrate feedstocks. The food industry in Canada needs an integrated approach to achieve complete lactose reclamation and use. This research project offers such a solution. The research described in this dissertation presents an integrated model of a stirred batch bioreactor that may support not only current, but also future research, and may economically impact the development and bioconversion of whey permeates containing lactose. This may lead to the development of a continuous processing methodology for low cost recovery of lactose from whey permeates and simultaneous conversion to value-added products. / Bioresource and Food Engineering

No description available.

Submitted by Ricardo Magno Lopes da Silva (ricardo.magnolopes@gmail.com) on 2019-01-23T12:18:26Z No. of bitstreams: 1 Dissertação_Ricardo Magno Lopes da Silva.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2019-01-24T12:27:59Z (GMT) No. of bitstreams: 1 silva_rml_me_bauru.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) / Made available in DSpace on 2019-01-24T12:27:59Z (GMT). No. of bitstreams: 1 silva_rml_me_bauru.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) Previous issue date: 2018-12-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A técnica de autoenrolamento de nanomembrana foi utilizada neste trabalho para a fabricação de capacitores ultracompactos (UCCap), permitindo a caracterização de filmes finos de materiais orgânicos e híbridos. O método é conhecido como roll-up, e consiste na formação de uma nanomembrana tensionada, elaborada a fim de produzir estruturas autosustentadas, que promovem o enrolamento do sistema ao serem libertadas de um substrato, determinando uma arquitetura em 3D. Neste trabalho, a tecnologia de nanomembranas foi utilizada com o objetivo de determinar as propriedades elétricas e dielétricas, sob diferentes temperaturas, de camadas de moléculas semicondutoras (CoPc, CuPc e F16CuPc) e de camadas de estruturas híbridas metal-orgânicas (HKUST-1). A caracterização desses materiais em nanoescala foi possível por meio de sua incorporação em UCCap. Os dispositivos foram caracterizados por medidas de espectroscopia de impedância e corrente elétrica. Em filmes finos das ftalocianinas (= 5 nm) na temperatura ambiente (≈ 296 K), foram encontrados valores de 2,1 ± 0,5 para a constante dielétrica da CoPc (kCoPc), 3,1 ± 0,6 para a CuPc (kCuPc) e 1,2 ± 0,6 para F16CuPc (kF16CuPc). As propriedades elétricas / dielétricas dos filmes das ftalocianinas foram analisadas sob diferentes temperaturas e filmes de CoPc foram explorados na presença de campos magnéticos aplicados com valores de magnitude entre - 500 e + 500 mT. As camadas de HKUST-1 incorporadas ao UCCap possibilitaram a determinação do valor de 3,2 ± 1,6 para sua constante dielétrica (kHKUST-1) à ≈ 296 K. Os valores encontrados para os materiais estudados como camada dielétrica em capacitor no estado-sólido são condizentes com valores encontrados na literatura, determinados nas mesmas condições de temperatura a partir de outros métodos de caracterização. O alto valor de incerteza do cálculo se deve ao pequeno espaço amostral utilizado até então. Foi constatado que a estratégia relatada consiste em uma metodologia adequada para determinação de algumas propriedades de filmes finos orgânicos e híbridos, com potencial para aplicação no estudo de outros materiais em escalas nanométricas. / The rolled-up nanomembrane-based technique was used in this work to the manufacture of ultracompact capacitors (UCCap), allowing the characterization of thin films of organic and hybrid materials. The method, known as roll-up, consists in the formation of a strained nanomembrane, elaborated in order to produce self-supported structures that promote the winding of the system when released from a substrate, determining a 3D architecture. In this work, the nanomembrane technology was used to determine the electrical and dielectric properties, for different conditions of temperatures, in layers of semiconductor molecules (CoPc, CuPc and F16CuPc) and layers of hybrid metal-organic structures (HKUST-1). The characterization of these materials at nanoscale was possible by their incorporation into UCCap. Current-voltage and impedance spectroscopy measurements were used to characterize the devices. For thin films of the phthalocyanines (= 5 nm) at room temperature (≈ 296 K), values of 2,1 ± 0,5 were found for CoPc dielectric constant (kCoPc), 3,1 ± 0,6 for CuPc (kCoPc) and 1,2 ± 0,6 for F16CuPc (kF16CoPc). The electrical / dielectric properties of the phthalocyanine films were analyzed under different temperatures and CoPc films were screened in the presence of applied magnetic fields with magnitude values between - 500 and + 500 mT. The HKUST-1 layers incorporated into the UCCap allowed the determination of a value of 3,2 ± 1,6 for its dielectric constant (kHKUST-1) at ≈ 296 K. The values found for the materials studied as dielectric layer of a solid-state capacitor are consistent with values found in literature, determined in the same temperature conditions yet by other characterization methods. The high uncertainty value of the calculation is due to the small number of samples explored until then. It was verified that the reported strategy consists an adequate methodology for determination of some properties of organic and hybrid thin films, with potential for application in the study of other materials in nanometric scales. / 88882.143501/2017-01

Submitted by Paula Andreia Petrini (paula.petrini@yahoo.com.br) on 2018-05-02T16:19:17Z No. of bitstreams: 1 2018_Dissertação_MS_Paula_Petrini_final.pdf: 4085214 bytes, checksum: da32a03d5bb301af130de6f96b52316f (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-05-03T12:28:49Z (GMT) No. of bitstreams: 1 petrini_pa_me_bauru.pdf: 4085214 bytes, checksum: da32a03d5bb301af130de6f96b52316f (MD5) / Made available in DSpace on 2018-05-03T12:28:49Z (GMT). No. of bitstreams: 1 petrini_pa_me_bauru.pdf: 4085214 bytes, checksum: da32a03d5bb301af130de6f96b52316f (MD5) Previous issue date: 2018-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conhecido como o ramo da ciência que utiliza camadas moleculares ativas para agregar novas funcionalidades a dispositivos, a eletrônica molecular apresenta propostas promissoras para o futuro. Uma classe de pequenas moléculas semicondutoras que vem sendo explorada devido ao seu potencial na fabricação de diferentes dispositivos é a das ftalocianinas de cobre (CuPc). Entretanto, poucos trabalhos presentes na literatura relatam a relação entre a características elétricas dos filmes orgânicos e sua espessura em nanoescala. Tal fato é explicado pela dificuldade na deposição de contatos elétricos sobre as camadas moleculares, dado que os métodos atualmente empregados podem vir a danificá-las. Nesse contexto, essa dissertação apresenta a fabricação de um capacitor hibrido ultracompacto (h-Cap) constituído por metal / óxido dielétrico / camada molecular / Metal como uma plataforma para acessar as propriedades elétricas de camadas moleculares. Utilizando como a camada metálica a combinação de filmes finos de ouro, titânio e cromo, óxido de alumínio (Al2O3) para o dielétrico e filmes finos de CuPc como camadas moleculares, os h-Caps são fabricados a partir da técnica roll-up. Para a deposição dos filmes metálicos foi utilizado a técnica de evaporação térmica por feixe de elétrons, a técnica de deposição por camada atômica foi utilizada para a deposição do Al2O3 e pôr fim a técnica de deposição por evaporação por filamento resistivo para as camadas moleculares de CuPc. As características geométricas e estruturais dos h-Caps foram obtidas utilizando microscópios ópticos e eletrônico de varredura. Para a caracterização topográfica do filme de CuPc foi utilizado um microscópio de força atômica. Quanto a caracterização elétrica, foram realizadas medidas de corrente-tensão nos dispositivos, com a finalidade de obter os parâmetros de transportes. A resposta dielétrica do dispositivo foi avaliada utilizando a técnica de espectroscopia de impedância de modo a fornecer medidas de capacitância-frequência, permitindo relacionar a espessura e a constante dielétrica do filme de CuPc (kCuPc). Para os filmes de CuPc entre 5 a 20 nm foi obtido o valor de kCuPc = 4,5 ± 0,5, mostrando que a técnica proposta é uma excelente alternativa para caracterização dielétrica de camadas ultrafinas de semicondutores orgânicos. / Known as the branch of science that uses active molecular layers to add new functionality to devices, molecular electronics presents promising proposals for the future. A class of small semiconductor molecules being exploited due to its potential in the manufacture of different devices is that of copper phthalocyanines (CuPc). However, few papers in the literature report the relationship between the electrical characteristics of organic films and their thickness at the nanoscale. This fact is explained by the difficulty in the deposition of electrical contacts on the molecular layers, since the methods currently used may damage them. In this context, this dissertation presents the fabrication of an ultracompact hybrid capacitor (h-Cap) consisting of metal / dielectric oxide / molecular layer / metal as a platform to access the electrical properties of molecular layers. Used as the metallic layer is the combination of thin films of gold, titanium and chromium, aluminum oxide for the dielectric and thin films of CuPc as molecular layers, the h-Cap are formed from the roll-up technique. For the deposition of the metallic films was used the thermal evaporation technique by electron beam, the technique of deposition by atomic layer was used for the deposition of Al2O3 and finally the technique of deposition by evaporation by resistive filament for the molecular layers of CuPc . The geometric characteristics of the h-Caps were obtained using optical and scanning electron microscopes. For the topographic characterization of the CuPc film was used to an atomic force microscope. As for the electrical characterization, current-voltage measurements, the h-Caps were evaluated as a function of CuPc thickness (5 to 50 nm) in order to extract their transport parameters. The dielectric response of the device was evaluated using the impedance spectroscopy technique to provide capacitance-frequency measurements, making it possible to relate the thickness and dielectric constant of the CuPc film (kCuPc). For the CuPc films between 5 and 20 nm, the value of kCuPc = 4.5 ± 0.5 was obtained, showing that the proposed technique is an excellent alternative for the dielectric characterization of ultrafine layers of organic semiconductors.

We report the fabrication of Ni2.7Mn0.9Ga0.4/InGaAs bilayers on GaAs (001)/InGaAs substrates by molecular beam epitaxy. To form freestanding microtubes the bilayers have been released from the substrate by strain engineering. Microtubes with up to three windings have been successfully realized by tailoring the size and strain of the bilayer. The structure and magnetic properties of both, the initial films and the rolled-up microtubes, are investigated by electron microscopy, X-ray techniques and magnetization measurements. A tetragonal lattice with c/a = 2.03 (film) and c/a = 2.01 (tube) is identified for the Ni2.7Mn0.9Ga0.4 alloy. Furthermore, a significant influence of the cylindrical geometry and strain relaxation induced by roll-up on the magnetic properties of the tube is found. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

The combination of strain engineering, lithography, thin film deposition and etching techniques is an elegant approach to create single microtubes and well-defined arrays of magnetic microtubes. In this work we have successfully shown that strain engineering techniques developed for rolled-up nanomembranes can be applied to magnetic materials and material combinations. To obtain sufficiently strained nanomembranes, different substrates and sacrificial layers in combination with the magnetic layers were used. Careful tuning of the etching parameters ensured a controlled roll-up process without damage or oxidation of the magnetic layer. Additionally, rolled-up nanomembranes were further integrated in a highly parallel fashion on chip, by development and application of multi-step fabrication procedures. Based on the prepared rolled-up magnetic structures and their planar counterparts we have performed a comprehensive study of their magnetic properties, mainly under the influence of magnetic field, strain and temperature. The role of the special cylindrical or curved geometry and their impact on the magnetic properties was outlined and explained based on our understanding. Moreover, the magnetic properties were also discussed in relationship to other influencing material parameters, e.g. composition, crystallographic structure, and surface effects. The first experimental magnetization study on rolled-up InGaAs/Fe3Si heterostructures was presented. It was demonstrated for tube arrays that the change in the geometry from a planar film to the cylindrical shape has a significant effect on the magnetization behavior. A deeper study provided insight into the magnetic switching behavior of single tubes and arrays. Rolled-up Au/Co/Au tubes and showed that in addition to shape anisotropy, magnetostrictive anisotropy due to the anisotropic stress release can inverse the magnetization direction. Exchange coupling at ferromagnetic/antiferromagnetic interfaces due to partial oxidation of Co was observed at low temperatures. The results suggest possibilities to tune magnetic properties by controlling the tube dimensions and careful control of thin film growth parameters. The cylindrical shape, the layer thickness the number of rotations and the type of magnetic material are proven to have a strong influence on the magnetic domain patterns and magnetization behavior. Therefore, Ni/Fe tubes have been studied by means of magneto optical Kerr effect. It was found that the magnetization reversal in rolled-up tubes with 1.2 and 2.5 windings occurs via nucleation and propagation of magnetic domain walls. On the other hand, we have demonstrated for rolled-up Au/Co tubes that a certain magnetic layer thickness is required to observe magnetic stripe domains. In another experiment performed with magnetic force microscopy, rolled-up Co/Pt nanomembranes with magnetic domains radially aligned due to perpendicular anisotropy, which behaves as radially polarized cylindrical magnets, were achieved. Moreover, we have demonstrated an elegant approach to create compact MR devices based on rolled-up Co/Cu-ML nanomembranes. We have shown the magnetization behavior and the MR magnitude in comparison to the corresponding planar structures. The influence of number of Co/Cu bilayers, non-magnetic spacer layer, interface roughness and multiple windings on MR was discussed. Our fabrication method can be applied to the most common magnetic materials. Certainly, further optimization of MR towards application as magnetic sensor or magneto-fluidic sensors can be achieved by change of Co/Cu-layer thickness, increase of rolling length and reduced spacer layer thickness. Finally, we have shown a fabrication route to realize freestanding tubes based on Ni-Mn-Ga alloys grown by molecular beam epitaxy on GaAs substrates. The evolution of structural and magnetic properties induced by roll-up was investigated in detail and showed a pronounced influence of crystallographic orientation and strain state of the Ni-Mn-Ga alloys. These insights are fundamental in order to realize thin nanomembranes and freestanding three-dimensional FSMA structures with defined composition for smart applications as compact actuators and microsensors. Consequently, rolled-up magnetic nanomembranes offer a great chance in reducing the size of electronic components and can bring several functionalities to the device. These facts make rolled-up tubes highly attractive for the detection, stimulation and manipulation of small objects, such as ions, molecules, cells and particles. It is expected in the future, that magnetic lab-in-a-tube systems will further account in analysis of microfluidic systems. On the other hand, rolled-up structures significantly contribute to the field of shapeable magnetoelectronics.

The combination of modern self-assembly techniques with well-established top-down processing methods pioneered in the electronics industry is paving the way for increasingly sophisticated devices in the future[1]. Nanomembranes, made from a variety of materials, can provide the necessary framework for a diverse range of device structures incorporating wrinkling, buckling, folding, and rolling of thin films[2, 3]. Over the past decade, an elegant symbiosis of bottom-up and top-down methods has been developed, allowing the fabrica- tion of hybrid layer systems via the controlled release and rearrangement of inherently strained layers [4]. Self-assembled rolled-up structures[4, 5] have become increasingly at- tractive in a number of fields including micro/nano uidics[6], optics[7](including metama- terial optical fibers[8]), Lab on a Chip applications[9], and micro- and nanoelectronics[10]. The use of such structures for microelectronic applications has been driven by the versatility in contacting geometries and the abundance of material combinations that these devices offer. By allowing devices to expand in the third dimension, certain obstacles that inhibit 2D structuring can be overcome in elegant ways. Similarly, recent progress in nanostructured superconducting electronic structures has been receiving increased attention[11]. The advancement of such devices has been mo- tivated by their use in quantum computation[12], high sensitivity radiation sensors[13], precision voltage standards[14] and superconducting spintronics[15] to name a few. Combining semiconductor with superconductor materials to create new hybrid geometries is advantageous because it adds the functionalities of the semiconductor, including high charge carrier mobilities, gating possibilities, and refined processing technologies. The main focus of the work presented in this thesis is the development of new methods for controlling strain behavior and its applications toward novel semiconduc- tor/superconductor heterostructures based on nanomembranes. More specifically, the goal is to integrate inherently strained semiconductor layer structures with superconducting materials to create innovative electronic devices by the controlled releasing and rearrangement of thin films. By rolling up pre-patterned semiconductor/superconductor layers, device geometries have been realized that are not feasible using any other technique. In this way, superconducting hybrid junctions, or Josephson junctions, have been created and their basic properties investigated. The Josephson effect, and junctions displaying this quantum coherent behavior, have found many essential uses in diverse areas of science and technology. Many research groups around the world are involved in finding new materials and fabrication methods to tune the properties and structure of such Josephson devices further[11]. The inclusion of semi- conductors, for example, allows for a greater control of the charge carrier density within the junction area, thus allowing for "transistor-like" behavior in these superconducting devices. By rolling up the superconductor contacts using a strained semiconductor as scaffolding, the fabrication of hybrid nano-junctions is simplified drastically, removing the need for complicated processing steps such as electron-beam or nano-imprint lithography. Furthermore, the technique allows many nanometer-sized devices to be created in parallel on a single chip which has the advantage that it can be scaled up to full-wafer processing. First, post-growth processing techniques of epitaxial layers are developed in order to extend the control of hybrid device fabrication. Here, three unique concepts for controlling the rolling behavior of strained semiconductor nanomembranes are presented. First an optical method for inhibiting the rolling of the strained layers is described. Next, a selective etching method for destroying the inherent strain within the semiconductor layer is introduced. Finally, a method by which the strain gradient across a trilayer stack is altered in situ during rolling is presented. Next, the fabrication of a hybrid nanomembrane-based superconducting device is presented. Various experimental details of the fabrication process are analyzed, and the electronic properties of the completed device are investigated. The devices created here highlight the fabrication process in which nanometer-sized structures are created using self-assembly techniques and standard microelectronics fabrication methods, presenting a new method to circumvent more complicated processing techniques. References [1] G. M. Whitesides and B. Grzybowski. Self-assembly at all scales. Science 295, 2418{2421 (2002). [2] Y. G. Sun, W. M. Choi, H. Q. Jiang, Y. G. Y. Huang and J. A. Rogers. Controlled buckling of semiconductor nanoribbons for stretchable electronics. Nature Nanotechnology 1, 201{207 (2006). [3] O. G. Schmidt and K. Eberl. Nanotechnology - Thin solid films roll up into nanotubes. Nature 410, 168 (2001). [4] O. G. Schmidt, C. Deneke, Y. Nakamura, R. Zapf-Gottwick, C. Mller and N. Y. Jin-Phillipp. Nanotechnology { Bottom-up meets top-down. Advanced Solid State Physics 42, 231 (2002). [5] V. Ya. Prinz, V. A. Seleznev, A. K. Gutakovsky, A. V. Chehovskiy, V. V. Preobrazhenskii, M. A. Putyato and T. A. Gavrilova. Free-standing and overgrown InGaAs/GaAs nanotubes, nanohelices and their arrays. Physica E 6, 828 (2000). [6] D. J. Thurmer, C. Deneke, Y. F. Mei and O. G. Schmidt. Process integration of microtubes for uidic applications. Applied Physics Letters 89, 223507 (2006). [7] R. Songmuang, A. Rastelli, S. Mendach and O. G. Schmidt. SiOx/Si radial superlattices and microtube optical ring resonators. Applied Physics Letters 90, 091905 (2007). [8] E. J. Smith, Z. W. Liu, Y. F. Mei and O. G. Schmidt. Combined surface plasmon and classical waveguiding through metamaterial fiber design. Nano Letters 10, 1{5 (2010). [9] G. S. Huang, Y. F. Mei, D. J. Thurmer, E. Coric and O. G. Schmidt. Rolled-up transparent microtubes as two-dimensionally confined culture scaffolds of individual yeast cells. Lab on a Chip 9, 263{268 (2009). [10] C. C. B. Bufon, J. D. C. Gonzalez, D. J. Thurmer, D. Grimm, M. Bauer and O. G. Schmidt. Self-assembled ultra-compact energy storage elements based on hybrid nanomembranes. Nano Letters 10, 2506{2510 (2010). [11] G. Katsaros, P. Spathis, M. Stoffel, F. Fournel, M. Mongillo, V. Bouchiat, F. Lefloch, A. Rastelli, O. G. Schmidt and S. De Franceschi. Hybrid superconductor-semiconductor devices made from self-assembled SiGe nanocrystals on silicon. Nature Nanotechnology 5, 458{464 (2010). [12] Y. J. Doh, J. A. van Dam, A. L. Roest, E. P. A. M. Bakkers, L. P. Kouwenhoven and S. De Franceschi. Tunable supercurrent through semiconductor nanowires. Science 309, 272{275 (2005). [13] F. Giazotto, T. T. Heikkila, G. P. Pepe, P. Helisto, A. Luukanen and J. P. Pekola. Ultrasensitive proximity Josephson sensor with kinetic inductance readout. Applied Physics Letters 92, 162507 (2008). [14] S. P. Benz. Superconductor-normal-superconductor junctions for programmable voltage standards. Applied Physics Letters 67, 2714{2716 (1995). [15] Y. C. Tao and J. G. Hu. Superconducting spintronics: Spin-polarized transport in superconducting junctions with ferromagnetic semiconducting contact. Journal of Applied Physics 107, 041101 (2010).

Orientadores: Christoph Friedrich Deneke, Eduardo Granado Monteiro da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-25T16:50:29Z (GMT). No. of bitstreams: 1 MercesSilva_Leandrodas_M.pdf: 8926273 bytes, checksum: 010f49f410852b0ba0278adfc3e091fa (MD5) Previous issue date: 2014 / Resumo: Nanomembranas livres são definidas como filmes ultrafinos constituídos por metais, óxidos ou semicondutores, com espessuras nanométricas e vastas áreas superficiais. São obtidas em geral por um processo de subcorrosão seletiva de uma camada de sacrifício, cujo papel é liberá-las gradualmente, permitindo que o relaxamento da energia elástica nelas armazenada aconteça de maneira controlada, garantindo a integridade final das estruturas. Neste trabalho, nanomembranas livres de Si suportadas por um substrato de SOI foram utilizadas como substratos complacentes para o crescimento de ilhas de InAs em uma câmara de MBE. Além disso, nanomembranas metálicas tensionadas (Ag/Ti/Cr/Ag) foram utilizadas na obtenção de microtubos metálicos enrolados. Análises detalhadas da morfologia das amostras, das estruturas das ilhas e dos microtubos, do strain em ambos os sistemas e de suas possíveis aplicações foram realizadas. A microscopia eletrônica de varredura mostrou que as estruturas permaneceram íntegras após as deformações. A microscopia de força atômica revelou uma baixa densidade de ilhas no topo das nanomembranas de Si. Ademais, possibilitou o aperfeiçoamento de parâmetros superficiais das nanomembranas metálicas e o enrolamento de microtubos com diâmetros pré definidos, garantindo convergência com o modelo analítico. Técnicas de difração de raios X e modelagem por elementos finitos foram utilizadas para elucidar os estados de strain observados em ambas as estruturas. As simulações das curvaturas do substrato complacente de Si e do microtubo metálico sugeriram, respectivamente, um gradiente de strain dependente da posição lateral de cada ilha na nanomembrana e coeficientes de strain constantes nas nanomembranas de Ti e Cr. Finalmente, cálculos envolvendo elasticidade contínua sugeriram que para uma nanomembrana de Si com espessura adequada, o InAs pode transferir strain suficiente para possibilitar o crescimento epitaxial coerente. Ainda, medidas de espectroscopia Raman em moléculas auto organizadas de 1-octadecanethiol, adsorvidas em Ag e aprisionadas entre as paredes dos microtubos metálicos, sugeriram que tal sistema pode ser utilizado como um dispositivo SERS para self-assembled monolayers / Abstract: Freestanding nanomembranes (NMs) are defined as metallic, semiconductor or oxide ultrathin films with nanometer thickness and macroscopic surface areas. In general, they are obtained by a process of selective underetching of a sacrificial layer, whose role is gradually release them, allowing relaxation of their stored elastic energy in a controlled way, ensuring integrity of the final structure. In this work, freestanding edge-supported Si nanomembranes are used as compliant substrate to the InAs growth on a SOI substrate in a MBE chamber. Furthermore, strained metallic nanomembranes (Ag / Ti / Cr / Ag) are used to obtain rolled-up metallic microtubes. A detailed analysis of sample morphology, InAs island and metallic microtube structure, strain on both systems and their possible applications is carried out. Scanning electron microscopy shows the structures stay intact during and after deformation. Atomic force microscopy reveals a lower island density on the top of the freestanding membranes. Moreover, it allowed optimizing the surface parameters of the strained metallic membranes, rolling-up tubes with pre-defined diameters and ensuring convergence with the proposed analytical model. X-ray diffraction and finite element modeling is used to elucidate the observed strain states in both structures. The bending simulations of compliant Si substrate and rolled up metallic microtube suggest, respectively, a lateral strain distribution depending on the island position on the freestanding membrane and a constant strain distribution on the Ti/Cr strained NMs. Finally, continuous elasticity calculations suggest that for a Si nanomembrane with adequate thickness, the InAs can transfer enough strain to enable coherent epitaxial growth. In addition, Raman spectroscopy measurements of 1-octadecanethiol self-assembled molecules adsorbed on an Ag nanomembrane and trapped between the microtube Ag walls suggest the system could be used as a SERS sensor for self-assembled monolayers / Mestrado / Física / Mestre em Física

Rechargeable lithium-ion batteries are now attracting great attention for applications in portable electronic devices and electrical vehicles, because of their high energy density, long cycle and great convenience. For new generations of rechargeable lithium-ion batteries, they applied not only to consumer electronics but also especially to clean energy storage and hybrid electric vehicles. Therefore, further breakthroughs in electrode materials that open up a new important avenue are essential. Graphite, the most commonly used commercial anode material, has a limited reversible lithium intercalation capacity (372 mAh g-1). In this regard, tremendous efforts have been made towards even further improving high capacity, excellent rate capability, and cycling stability by developing advanced anode materials. This work focuses on the lithium storage properties of nickel oxide (NiO) and germanium (Ge) nanomembranes anodes mainly fabricated by electron-beam evaporation. Specifically, NiO is selected for conversion-type material because of high theoretical specific capacity of 718 mAh g-1 and easily obtained material. The resultant curved NiO nanomembranes anodes exhibit ultrafast power rate of 50 C (1 C = 718 mA g-1) and good capacity retention (721 mAh g-1, 1400 cycles). Remarkably, multifunctional Ni/NiO hybrid nanomembranes were further fabricated and investigated. Benefiting from the advantages of the intrinsic architecture and the electrochemical catalysis of metallic nickel, the hybrid Ni/NiO anodes could be tested at an ultrahigh rate of ~115 C. With Ge as active alloying-type material (1624 mAh g-1), the effect of the incorporated oxygen to the lithium storage properties of amorphous Ge nanomembranes is well studied. The oxygen-enabled Ge (GeOx) nanomembranes exhibit improved electrochemical properties of highly reversible capacity (1200 mAh g-1), and robust cycling performance.

Li-O2 batteries have attracted world-wide research interest as an appealing candidate for future energy supplies because they possess the highest energy density of any battery technology. However, such system still face some challenges for the practical application. One of the key issues is exploring highly efficient cathode materials for Li-O2 batteries. Here, a rolled-up technology associated with other physical or chemical methods are applied to prepare architectural nanomembranes for the cathode materials in Li-O2 batteries. The strain-release technology has recently proven to be an efficient approach on the micro/nanoscale to fabricate composite nanomembranes with controlled thickness, versatile chemical composition and stacking sequence. This dissertation first focuses on the synthesis of trilayered Pd/MnOx/Pd nanomembranes. The incorporation of active Pd layers on both sides of the poor conductive MnOx layer commonly used in energy storage systems greatly enhances the conductivity and catalytic activity. Encouraged by this design, Pd nanoparticles functionalized MnOx-GeOy nanomembranes are also fabricated, which not only improve the conductivity but also facilitate the transport of Li+ and oxygen-containing species, thus greatly enhancing the performance of Li-O2 batteries. Similarly, Au and Pd arrays decorated MnOx nanomembranes act as bifunctional catalysts for both oxygen reduction reaction and oxygen evolution reaction in Li-O2 batteries. Moreover, by introducing hierarchical pores on the nanomembranes, the performance of Li-O2 batteries is further promoted by porous Pd/NiO nanomembranes. The macropores created by standard photolithography facilitate the rolling process and the nanopores in the nanomembranes induced by a novel template-free method supply fast channels for the reactants diffusion. In addition, a facile thermal treatment method is developed to fabricate Ag/NiO-Fe2O3/Ag hybrid nanomembranes as carbon-free cathode materials in Li-O2 batteries. A competing scheme between the intrinsic strain built in the oxide nanomembranes and an external driving force provided by the metal nanoparticles is introduced to tune the morphology of the 3D tubular architectures which greatly improve the performance by providing continuous tunnels for O2 and electrolyte diffusion and mitigating the side reactions produced by carbonaceous materials.