In this paper, we report on the deposition of amorphous silicon (a-Si:H) films at ultra-high growth rate (11-60 nm/s) by means of the expanding thermal plasma technique, followed by solid-phase crystallization (SPC). Large-grain (similar to 1.5 mu m) polycrystalline silicon was obtained after SPC of high growth rate (similar to 25 nm/s) deposited a-Si:H films. The obtained results are discussed by taking into account the impact of the a-Si:H microstructure parameter R* as well as of its morphology, on the final grain size development. (C)@en

We have found that controlled Ar ion bombardment enhances the degradation of a-Si:H based surface passivation of c-Si surfaces. The decrease in the level of surface passivation is found to be independent on the ion kinetic energy (7¿70 eV), but linearly proportional to the ion flux (6×1014¿6×1015¿ions¿cm¿2¿s¿1). This result suggests that the ion flux determines the generation rate of electron¿hole pairs in a-Si:H films, by which metastable defects are created at the H/a-Si:c-Si interface. Possible mechanisms for the ion induced generation of electron¿hole pairs are discussed.@en

Insight into the oxidation mechanism of microcrystalline silicon thin films has been obtained by means of Fourier transform infrared spectroscopy. The films were deposited by using the expanding thermal plasma and their oxidation upon air exposure was followed in time. Transmission spectra were recorded directly after deposition and at regular intervals up to 8 months after deposition. The interpretation of the spectra is focused on the Si¿Hx stretching (2000¿2100 cm¿1), Si¿O¿Si (1000¿1200 cm¿1), and OxSi¿Hy modes (2130¿2250 cm¿1). A short time scale (<3 months) oxidation of the crystalline grain boundaries is observed, while at longer time scales, the oxidation of the amorphous tissue and the formation of O¿H groups on the grain boundary surfaces play a role. The implications of this study on the quality of microcrystalline silicon exhibiting no post-deposition oxidation are discussed: it is not sufficient to merely passivate the surface of the crystalline grains and fill the gap between the grains with amorphous silicon. Instead, the quality of the amorphous silicon tissue should also be taken into account, since this oxidation can affect the passivating properties of the amorphous tissue on the surface of the crystalline silicon grains.@en

In this work, the expanding thermal plasma chemical vapor deposition in combination with radio frequency magnetron sputtering is used to deposit dielectric/metal multi-layers with controlled size and density of nanoparticles. The multi-layer structure serves the purpose of increasing the nanoparticle number density, without changing the metal particle size, shape and the interparticle distance. The possibility of independently tuning and, therefore, controlling the nanoparticle size and number density allows developing surface plasmon resonance-based deep-colored coatings. The influence of the number of layers, metal surface area coverage, and thickness of the dielectric layer on the multi-layer nanostructure and on the developed color is presented here in detail. The nanoparticle size and distribution have been measured by transmission electron microscopy. Rutherford back-scattering and infra-red transmission spectroscopy have been used to determine the metal surface coverage and the film chemistry, respectively. Optical properties of the nano-composite layers have been investigated by UV-VIS spectroscopy and exhibit an increase in amplitude of the plasmon absorption spectra at a fixed plasmon resonance frequency with an increase in the number of layers.@en

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 SiH(x) 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.@en

In this paper, a hybrid system consisting of metal nano-particles dispersed on the surface of a dielectric layer is presented: a remote Expanding Thermal Plasma CVD system is used for the deposition of the inorganic (i.e. SiO2) layers from hexamethyldisiloxane/oxygen mixtures in combination with an rf magnetron sputtering tool for the deposition of metallic (i.e. gold) nanoparticles on top of the SiO2 layers. The optical properties of the Au/SiO2 layers have been investigated by means of UV-VIS-NIR variable angle spectroscopic ellipsometry. Rutherford backscattering and transmission electron microscopy were used to determine the film density, the nanoparticle size and its distribution, respectively. The uniform distribution of gold nanoparticles on the surface of the SiO2 layers allows obtaining red- to blue- colored coatings as a consequence of the shift of the surface plasmon resonance band to higher wavelengths, caused by an increase in size of nanoparticles and metal surface coverage.@en