A general approach toward shape-controlled synthesis of silicon nanowires.

Controlling the morphology, electronic properties, and growth direction of nanowires (NWs) is an important aspect regarding their integration into devices on technologically relevant scales. Using the vapor-solid-solid (VSS) approach, with Ni as a catalyst and octachlorotrisilane (Si(3)Cl(8), OCTS) as a precursor, we achieved epitaxial growth of rectangular-shaped Si-NWs, which may have important implications for electronic mobility and light scattering in NW devices. The process parameters were adjusted to form cubic α-NiSi(2) particles which further act as the shaping element leading to prismatic Si-NWs. Along with the uncommon shape, also different crystallographic growth directions, namely, [100] and [110], were observed on the very same sample. The growth orientations were determined by analysis of the NWs' azimuths on the Si (111) substrates as well as by detailed transmission electron microscopy (TEM) and selected area electron diffraction (SAED) investigations.

Subeutectic synthesis of epitaxial Si-NWs with diverse catalysts using a novel Si precursor.

The applicability of a novel silicon precursor with respect to reasonable nanowire (NW) growth rates, feasibility of epitaxial NW growth and versatility with respect to diverse catalysts was investigated. Epitaxial growth of Si-NWs was achieved using octochlorotrisilane (OCTS) as Si precursor and Au as catalyst. In contrast to the synthesis approach with SiCl(4) as precursor, OCTS provides Si without the addition of H(2). By optimizing the growth conditions, effective NW synthesis is shown for alternative catalysts, in particular, Cu, Ag, Ni, and Pt with the latter two being compatible to complementary metal-oxide-semiconductor technology. As for these catalysts, the growth temperatures are lower than the lowest liquid eutectic; we suggest that the catalyst particle is in the solid state during NW growth and that a solid-phase diffusion process, either in the bulk, on the surface, or both, must be responsible for NW nucleation.

Intraoperative localization of intestinal arteriovenous malformation.

Intestinal arteriovenous malformation (AVM) is an uncommon cause of gastrointestinal hemorrhage and is difficult to diagnose. Selective visceral angiography is essential to make the diagnosis and to localize the lesion. We treated two patients in whom AVMs of the small intestine were located by means of arteriography and intraoperative selective mesenteric venous pressure and PO2 measurements. The local venous return from an intestinal AVM is characterized by elevated venous pressure and PO2 levels compared with the venous drainage of adjacent normal intestine.

Transhepatic dilatation of choledochoenterostomy strictures.

During the last seven years percutaneous transhepatic biliary drainage (THD) was used in 13 patients to relieve obstructive jaundice caused by postsurgical stricture. Nine patients had internal drainage with dilatation, and external drainage alone was feasible or available in 4 patients. Of these 4, 2 had further reconstructive surgery without lasting results, jaundice was not completely relieved in 1 because of biliary cirrhosis, and 1 died in hepatic coma from sclerosing cholangitis. Eight patients treated with internal drainage and dilatation became asymptomatic with normal serum bilirubin values; the ninth patient, with biliary cirrhosis and portal hypertension, improved only moderately.