Vitreous SiO2 thin films thermally grown onto Si wafers were bombarded by Au ions with energies from 0.005 to 11.1 MeV/u and by ions at constant velocity (0.1 MeV/u A197u, T130e, A75s, S32, and F19). Subsequent chemical etching produced conical holes in the films with apertures from a few tens to ∼150 nm. The diameter and the cone angle of the holes were determined as a function of energy loss of the ions. Preferential track etching requires a critical electronic stopping power Seth∼2 keV/nm, independent of the value of the nuclear stopping. However, homogeneous etching, characterized by small cone opening angles and narrow distributions of pore sizes and associated with a continuous trail of critical damage, is only reached for Se>4 keV/nm. The evolution of the etched-track dimensions as a function of specific energy (or electronic stopping force) can be described by the inelastic thermal spike model, assuming that the etchable track results from the quenching of a zone which contains sufficient energy for melting. The model correctly predicts the threshold for the appearance of track etching Seth if the radius of the molten region has at least 1.6 nm. Homogeneous etching comes out only for latent track radii larger than 3 nm.

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Magnetization dynamic response of coupled and uncoupled spin valves with structure NiFe(20nm)/Cu(tCu)/NiFe(20nm)/IrMn(10nm) is probed using broadband ferromagnetic resonance absorption measurements. The coupling intensity between the free and pinned layers is tailored by varying the Cu thickness tCu. Broadband spectra exhibit two resonant modes for each value of applied field. It is observed that the coupling among NiFe layers modifies the amplitude of the absorption peaks and also the shape of the dispersion relations for each mode, which becomes particularly distorted at the anti-parallel magnetization state. The observed phenomena is well described by applying a semianalytical model that properly takes into account the coupling interactions and allows an efficient numerical calculation of the absorption peak amplitudes, and the dispersion relation shapes.

This work presents an approach for the estimation of the adsorbed mass of 1,5-diaminopentane (cadaverine) on a functionalized piezoelectrically driven microcantilever (PD-MC) sensor, using a polynomial developed from the characterization of the resonance frequency response to the known added mass. This work supplements the previous studies we carried out on the development of an electronic nose for the measurement of cadaverine in meat and fish, as a determinant of its freshness. An analytical transverse vibration analysis of a chosen microcantilever beam with given dimensions and desired resonance frequency (> 10 kHz) was conducted. Since the beam is considered stepped with both geometrical and material non-uniformity, a modal solution for stepped beams, extendable to clamped-free beams of any shape and structure, is derived and used for free and forced vibration analyses of the beam. The forced vibration analysis is then used for transformation to an equivalent electrical model, to address the fact that the microcantilever is both electronically actuated and read. An analytical resonance frequency response to the mass added is obtained by adding simulated masses to the free end of the beam. Experimental verification of the resonance frequency response is carried out, by applying known masses to the microcantilever while measuring the resonance frequency response using an impedance analyzer. The obtained response is then transformed into a resonance frequency to the added mass response polynomial using a polynomial fit. The resulting polynomial is then verified for performance using different masses of cantilever functionalization solution. The functionalized cantilever is then exposed to different concentrations of cadaverine while measuring the resonance frequency and mass of cadaverine adsorbed estimated using the previously obtained polynomial. The result is that there is the possibility of using this approach to estimate the mass of cadaverine gas adsorbed on a functionalized microcantilever, but the effectiveness of this approach is highly dependent on the known masses used for the development of the response polynomial model.

a b s t r a c tWe investigate the structural and magnetic properties, and the magnetization dynamics in Ni 81 Fe 19 /Pt multilayer systems grown onto rigid and flexible substrates. The structural characterization shows evidence of a superlattice behavior, while the quasi-static magnetization characterization reveal a weak magnetic anisotropy induced in the multilayers. The magnetization dynamics is investigated through the magnetoimpedance effect. We employ a theoretical approach to describe the experimental magnetoimpedance effect and verify the influence of the effective damping parameter on the magnetization dynamics. Experimental data and theoretical results are in agreement and suggest that the multilayers present high effective damping parameter. Moreover, our experiments raise an interesting issue on the possibility of achieving considerable MI% values, even for systems with weak magnetic anisotropy and high damping parameter grown onto flexible substrates.

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RESUMONo custo de produção de uma célula solar, a lâmina de silício representa da ordem de 50 % do valor final do dispositivo. Para reduzir os custos, vem sendo proposta a diminuição das espessuras atuais de 180-200 µm para 100-120 µm. Embora o silício tipo p seja o mais usado na fabricação de células solares, este material é suscetível à degradação devido à interação boro-oxigênio. Os dispositivos fabricados em lâminas de Si tipo n, dopadas com fósforo não apresentam tal degradação e têm potencial de obtenção de altas eficiências devido ao maior tempo de vida dos portadores de carga minoritários. O objetivo deste trabalho é apresentar o desenvolvimento de células solares n + np + fabricadas sobre lâminas de silício Cz (Czochralski) com 100 μm de espessura. Foram fabricados dispositivos finos com a estrutura n + np + e comparados com os dispositivos n + pp + fabricados em lâminas convencionais. A eficiência média alcançada foi de (14,6 ± 0,4) % e o dispositivo mais eficiente atingiu 15,3 %. O maior valor de eficiência ficou abaixo do obtido com estruturas n + pp + de 200 μm de espessura, quando atingiu-se uma eficiência de 16,2 %. O principal parâmetro que reduziu a eficiência das células finas foi o fator de forma, que alcançou um valor máximo de 0,748. Embora a eficiência seja menor com as lâminas finas, obteve-se uma baixa relação massa/potência, de 1,5 g/W, valor que é aproximadamente 53 % inferior ao obtido quando foram usadas lâminas espessas tipo p. Palavras-chave:Células solares; Lâminas de silício finas; Silício tipo n. ABSTRACTIn the solar cell production cost, the silicon wafer represents roughly 50 % of the final value of the device. To lower the costs, the reduction of the current wafer thickness from 180-200 µm to 100-120 µm has been proposed. Although the p-type silicon is used to manufacture solar cells, it is susceptible to degradation due to boron-oxygen interaction. The devices manufactured in n-type silicon wafers doped with phosphorus do not present such degradation and has the potential of achieving higher efficiencies due to the larger minority charge carrier lifetime. The aim of this work is to present the development of n + np + solar cells fabricated in Cz silicon wafers 100 μm thick. Thin devices were manufactured with the n + np + structure and compared to n + pp + devices manufactured in standard thick wafers. The average efficiency of (14.6 ± 0.4) % was achieved and the most efficient device reached 15.3%. The efficiency was lower than obtained with n + pp + thick devices, which presented 16.2 %. The main parameter that reduced the efficiency of thin cells was the fill factor, which reached a maximum value of 0.748. Although the efficiency reached by thin n-type devices was worse than thick p-type ones, the former achieved a low mass/power ratio of 1.5 g/W, which is approximately 53 % lower than that obtained from thick p-type devices.