Hydrogenated amorphous silicon (a-Si:H) has recently proved to be a suitable base material for the synthesis of silicon nanowires (SiNWs) by metal-assisted chemical etching (MACE). The etching procedure on this material shows an extraordinary sensitivity to slight compositional changes and, although dopant influence on the process has been previously addressed, little is known on the role of hydrogen. In this article, we have studied the behavior of MACE on a-Si:H films with different hydrogen contents and bond configurations. As-grown films were studied by Raman spectroscopy, Fourier transform infrared spectroscopy, and ion beam analysis to obtain a complete description of the material composition. Additionally, these results were further correlated with the morphology and characteristics of the obtained SiNWs, showing that the material stability under MACE is reduced as the bond configuration is shifted from monohydrides to polyhydrides. The effect of bond configuration has an extraordinary importance regarding the material application, as it is intrinsically related to the content of hydrogen, which simultaneously controls the optical properties of the material. This study proves that bond configuration also affects the nanostructuration, which should be considered in future devices based on this material.

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Keywords:Laser firing Laser processing Heterojunction Solar cell Surface treatment One of the key steps to achieve high efficiencies in amorphous/crystalline silicon photovoltaic structures is to design low-ohmic-resistance back contacts with good passivation in the rear part of the cell. A well known approach to achieve this goal is to use laser-flred contact (LFC) processes in which a metal layer is fired through the dielectric to define good contacts with the semiconductor. However, and despite the fact that this approach has demonstrated to be extremely successful, there is still enough room for process improvement with an appropriate optimization. In this paper, a study focused on the optimal adjustment of the irradiation parameters to produce laser-fired contacts in a-Si:H/c-Si heterojunction solar cells is presented. We used samples consisting of crystalline-silicon (c-Si) wafers together with a passivation layer of intrinsic hydrogenated amorphous silicon (a-Si:H(i)) deposited by plasma-enhanced chemical deposition (PECVD). Then, an aluminum layer was evaporated on both sides, the thickness of this layer varied from 0.2 to 1 u,m in order to identify the optimal amount of Al required to create an appropriate contact. A q-switched NdiYVCu laser source, A. = 532 nm, was used to locally fire the aluminum through the thin a-Si:H(i)-layers to form the LFC. The effects of laser fluences were analyzed using a comprehensive morphological and electrical characterization.