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A Annalisa Branca

Bio: A Annalisa Branca is an academic researcher from Eindhoven University of Technology. The author has contributed to research in topics: Grain size & Amorphous carbon. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

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TL;DR: In this paper, the effect of the microstructure of remote plasma-deposited amorphous silicon films on the grain size development in polycrystalline silicon upon solid-phase crystallization is reported.
Abstract: In this paper the effect of the microstructure of remote plasma-deposited amorphous silicon films on the grain size development in polycrystalline silicon upon solid-phase crystallization is reported. The hydrogenated amorphous silicon films are deposited at different microstructure parameter values R* (which represents the distribution of SiHx bonds in amorphous silicon), at constant hydrogen content. Amorphous silicon films undergo a phase transformation during solid-phase crystallization and the process results in fully (poly-)crystallized films. An increase in amorphous film structural disorder (i.e., an increase in R*), leads to the development of larger grain sizes (in the range of 700-1100 nm). When the microstructure parameter is reduced, the grain size ranges between 100 and 450 nm. These results point to the microstructure parameter having a key role in controlling the grain size of the polycrystalline silicon films and thus the performance of polycrystalline silicon solar cells.

23 citations


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TL;DR: A new deformation-induced nanostructure was observed by transmission electron microscopy, consisting of an amorphous phase, a new tetragonal phase, slip bands, twinning superlattices, and a single crystal, providing new insights for potential applications in transistors, integrated circuits, diodes, solar cells, and energy storage systems.
Abstract: Nanostructures in silicon (Si) induced by phase transformations have been investigated during the past 50 years. Performances of nanostructures are improved compared to that of bulk counterparts. Nevertheless, the confinement and loading conditions are insufficient to machine and fabricate high-performance devices. As a consequence, nanostructures fabricated by nanoscale deformation at loading speeds of m/s have not been demonstrated yet. In this study, grinding or scratching at a speed of 40.2 m/s was performed on a custom-made setup by an especially designed diamond tip (calculated stress under the diamond tip in the order of 5.11 GPa). This leads to a novel approach for the fabrication of nanostructures by nanoscale deformation at loading speeds of m/s. A new deformation-induced nanostructure was observed by transmission electron microscopy (TEM), consisting of an amorphous phase, a new tetragonal phase, slip bands, twinning superlattices, and a single crystal. The formation mechanism of the new phase was elucidated by ab initio simulations at shear stress of about 2.16 GPa. This approach opens a new route for the fabrication of nanostructures by nanoscale deformation at speeds of m/s. Our findings provide new insights for potential applications in transistors, integrated circuits, diodes, solar cells, and energy storage systems.

176 citations

Journal ArticleDOI
TL;DR: The HC@c-Si@a-Si anodes showed an excellent cycle retention of 97.8% even after 200 cycles at a 1 C discharge/charge rate and the LiCoO₂/HC@ c-Si @ a-Si full-cell showed excellent rate capability and very stable long-term cycle.
Abstract: Nanocrystalline Si (c-Si) dispersed in amorphous Si (a-Si) encapsulating hard carbon (HC) has been synthesized as an anode material for fast chargeable lithium-ion batteries. The HC derived from natural polysaccharide was coated by a thin a-Si layer through chemical vapour deposition (CVD) using silane (SiH4) as a precursor gas. The HC@c-Si@a-Si anodes showed an excellent cycle retention of 97.8% even after 200 cycles at a 1 C discharge/charge rate. Furthermore, a high capacity retention of ∼54% of its initial reversible capacity at 0.2 C rate was obtained at a high discharge/charge rate of 5 C. Moreover, the LiCoO2/HC@c-Si@a-Si full-cell showed excellent rate capability and very stable long-term cycle. Even at a rate of 10 C discharge/charge, the capacity retention of the LiCoO2/HC@c-Si@a-Si full-cell was 50.8% of its capacity at a rate of 1 C discharge/charge and showed a superior cycle retention of 80% after 160 cycles at a rate of 1 C discharge/charge.

45 citations

Journal ArticleDOI
TL;DR: In this article, the hydrogen plasma passivation of thin film polycrystalline silicon (pc-Si) was investigated in conjunction with plasma texturing process to make efficient heterojunction solar cells.

20 citations

Journal ArticleDOI
TL;DR: A low-temperature, rapid means of a-Si:H crystallization based on high-density hydrogen plasma, integrating the three processes of hydrogen insertion, etching, and diffusion is reported to elucidate the hydrogenation depth evolution and the crystallization mechanism.
Abstract: Being a low-cost, mass-production-compatible route to attain crystalline silicon, post-deposition crystallization of amorphous silicon has received intensive research interest. Here we report a low-temperature (300 °C), rapid (crystallization rate of ~17 nm/min) means of a-Si:H crystallization based on high-density hydrogen plasma. A model integrating the three processes of hydrogen insertion, etching, and diffusion, which jointly determined the hydrogenation depth of the excess hydrogen into the treated micrometer thick a-Si:H, is proposed to elucidate the hydrogenation depth evolution and the crystallization mechanism. The effective temperature deduced from the hydrogen diffusion coefficient is far beyond the substrate temperature of 300 °C, which implies additional driving forces for crystallization, i.e., the chemical annealing/plasma heating and the high plasma sheath electric field. The features of LFICP (low-frequency inductively coupled plasma) and LFICP-grown a-Si:H are also briefly discussed to reveal the underlying mechanism of rapid crystallization at low temperatures.

18 citations