Magnetotransport in graphene on silicon side of SiC

We have studied the transport properties of graphene grown on silicon side of SiC. Samples under study have been prepared by two different growth methods in two different laboratories. Magnetoresistance and Hall resistance have been measured at temperatures between 4 and 100 K in resistive magnet in magnetic fields up to 22 T. In spite of differences in sample preparation, the field dependence of resistances measured on both sets of samples exhibits two periods of magneto-oscillations indicating two different parallel conducting channels with different concentrations of carriers. The semi-quantitative agreement with the model calculation allows for conclusion that channels are formed by high-density and low-density Dirac carriers. The coexistence of two different groups of carriers on the silicon side of SiC was not reported before.Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of Physics: Conference series" as a contribution to the proceedings of the 20th International Conference on "High Magnetic Fields in Semiconductor Physics", HMF 2

Safety of Simultaneous Resections of Colorectal Cancer and Liver Metastases

Liver resection is the only potentially curative method for patients with colorectal cancer metastases and 5-year survival rates are 20% – 40%. Simultaneous resection of colorectal cancer and synchronous liver metastases has been recommended if minor hepatectomy is indicated. The purpose of this paper is to analyze the treatment of hepatic colorectal secondaries and to assess the safety of simultaneous and delayed liver resections and relations of morbidity to the extensiveness of hepatectomy and perioperative factors. Analyzed were 21 patients with liver metastases from colorectal cancer operated between 1997 and 1999 in the Clinical Hospital »Sestre milosrdnice«. Operating time for simultaneous colorectal and liver resections was not significantly longer compared to liver resections alone. No significant difference in complication rate was found after simultaneous procedures and liver resection alone (38% vs. 31%). Complication rate after major liver resections was not significantly greater than after minor resections (38% vs. 31%). No statistically significant differences were found in operation time and blood replacement between patients who developed postoperative complications and those who did not. In conclusion, simultaneous resections of primary colorectal cancer and liver metastases may be considered safe. Morbidity rates are not significantly different from those after liver resections alone, nor depend significantly upon the extensiveness of liver resection, providing that the operation time and blood loss are within the range observed in this study

Single-Source, Solvent-Free, Room Temperature Deposition of Black γ-CsSnI₃ Films

The presence of a non-optically active polymorph (yellow-phase) competing with the optically active polymorph (black $\gamma$-phase) at room temperature in CsSnI3 and the susceptibility of Sn to oxidation, represent two of the biggest obstacles for the exploitation of CsSnI3 in optoelectronic devices. Here room-temperature single-source in vacuum deposition of smooth black $\gamma$ - CsSnI3 thin films is reported. This has been done by fabricating a solid target by completely solvent-free mixing of CsI and SnI2 powders and isostatic pressing. By controlled laser ablation of the solid target on an arbitrary substrate at room temperature, the formation of CsSnI3 thin films with optimal optical properties is demonstrated. The films present a band gap of 1.32 eV, a sharp absorption edge and near-infrared photoluminescence emission. These properties and X-ray diffraction of the thin films confirmed the formation of the orthorhombic (B-$\gamma$) perovskite phase. The thermal stability of the phase was ensured by applying in situ an Al2O$_3$ capping layer. This work demonstrates the potential of pulsed laser deposition as a volatility-insensitive single-source growth technique of halide perovskites and represents a critical step forward in the development and future scalability of inorganic lead-free halide perovskites.Comment: Accepted by Advanced Materials Interfaces, 16 pages, 4 figures, and supplemen

Light trapping in thin-film solar cells measured by Raman spectroscopy

In this study, Raman spectroscopy is used as a tool to determine the light-trapping capability of textured ZnO front electrodes implemented in microcrystalline silicon (mu c-Si:H) solar cells. Microcrystalline silicon films deposited on superstrates of various roughnesses are characterized by Raman tnicro-spectroscopy at excitation wavelengths of 442 nm, 514 nm, 633 nm, and 785 nm, respectively. The way to measure quantitatively and with a high level of reproducibility the Raman intensity is described in details. By varying the superstrate texture and with it the light trapping in the mu c-Si:H absorber layer, we find significant differences in the absolute Raman intensity, measured in the near infrared wavelength region (where light trapping is relevant). A good agreement between the absolute Raman intensity and the external quantum efficiency of the pc-Si:H solar cells is obtained, demonstrating the validity of the introduced method. Applications to thin-film solar cells, in general, and other optoelectronic devices are discussed. (C) 2014 AIP Publishing LLC