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We report on the formation of self-organized structures in thin films of silicon-germanium (Si1-xGex) with 0.3

The grain boundary populations in laser crystallized polycrystalline silicon thin films are determined by electron microscope analysis, using electron backscattering contrast in the scanning electron microscope, and convergent beam electron diffraction in the transmission electron microscope. The grain boundary populations of the grains larger than 0.5 μm are dominated by first and second order twin boundaries. This result is found to be a general feature of laser crystallization independent of the experimental details of the laser crystallization process. Texture analysis of the laser crystallized poly-Si films shows that under certain experimental conditions a {111}-preferential orientation of the grains perpendicular to the substrate can be obtained. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Hybrid solar cells have been fabricated from solution processing of poly-(3-hexylthiophen-2,5-diyl) onto planar poly-crystalline thin film silicon (poly-Si) absorbers on glass. The poly-Si layers were prepared by laser crystallization. Methyl passivation of the poly-Si surface by a one-step grafting process via methyl-Grignard enabled open circuit voltages of up to 552 mV and an overall power conversion efficiency of 6.6% for this device type. The solar cell exhibited significant advantages compared to the wafer-based counterparts. The inverted device structure of the thin film cell lead to an enhancement of the quantum efficiency since the back side contacted cell had less light absorption and reflection losses due to the gold layer which was used as front contact for the c-Si-based hybrid solar cell. As a result, a photo current of 24.3 mA cm−2 was obtained for a 10 μm thin poly-Si layer on glass. Furthermore, the inverted device structure showed a pronounced increase in stability due to the much thicker gold back contact that reduces the diffusion of water and oxygen toward the polymer layer. After 3 months in ambient air, this type of solar cell operated with 86% of its initial efficiency. [ABSTRACT FROM AUTHOR]

Zinc oxide thin-films were grown on crystalline silicon employing magnetron sputtering and pulsed laser deposition. Bulk and interface properties were investigated using scanning electron microscopy, Raman backscattering, photoluminescence, and infrared spectroscopic ellipsometry. Sputter deposited ZnO samples reveal a large degree of disorder and an interface defect density of ≈1012 cm-2. A significant improvement of the structural quality is observed in samples grown by pulsed laser deposition. The bulk defect density is further reduced, when introducing monatomic oxygen during deposition. Simultaneously, the defect density at the ZnO/Si interface decreases by about a factor of five. Implications for devices containing ZnO/Si interfaces are discussed. [ABSTRACT FROM AUTHOR]

Macroscopic graphene films buried below amorphous and crystalline silicon capping layers are studied by Raman backscattering spectroscopy and Hall-effect measurements. The graphene films are grown by chemical vapor deposition on copper foil and transferred to glass substrates. Uncapped films possess charge-carrier mobilities of 2030 cm2/Vs at hole concentrations of 3.6 × 1012 cm-2. Graphene withstands the deposition and subsequent crystallization of silicon capping layers. However, the crystallinity of the silicon cap has large influence on the field-induced doping of graphene. Temperature dependent Hall-effect measurements reveal that the mobility of embedded graphene is limited by charged-impurity and phonon-assisted scattering. [ABSTRACT FROM AUTHOR]

The origin of the formation of {100} and {111} grain textures in polycrystalline silicon thin films prepared with multiple excimer laser shots at the super-lateral-growth crystallization regime is investigated in this study. Our results demonstrate that the type of texture formed is determined solely by the thickness of the silicon layer. At a critical value of 40 nm, a transition from {100} to {111} texture is observed with increasing layer thickness. It is therefore proposed that below this critical value, the texture formation is governed by surface energy anisotropy whereas above it, the kinetics of the solidification process predominate. [ABSTRACT FROM AUTHOR]