Search

Dislocations are basic crystal defects and represent one-dimensional native nanostructures embedded in a perfect crystalline matrix. Their structure is predefined by crystal symmetry. Two- dimensional, self-organized arrays of such nanostructures are realized reproducibly using specific preparation conditions (semiconductor wafer direct bonding). This technique allows separating dislocations up to a few hundred nanometers which enables electrical measurements of only a few, or, in the ideal case, of an individual dislocation. Electrical properties of dislocations in silicon were measured using MOSFETs as test structures. It is shown that an increase of the drain current results for nMOSFETs which is caused by a high concentration of electrons on dislocations in p-type material. The number of electrons on a dislocation is estimated from device simulations. This leads to the conclusion that metallic-like conduction exists along dislocations in this material caused by a one-dimensional carrier confinement. On the other hand, measurements of pMOSFETs prepared in n-type silicon proved the dominant transport of holes along dislocations. The experimentally measured increase of the drain current, however, is here not only caused by an higher hole concentration on these defects but also by an increasing hole mobility along dislocations. All the data proved for the first time the ambipolar behavior of dislocations in silicon. Dislocations in p-type Si form efficient one-dimensional channels for electrons, while dislocations in n-type material cause one- dimensional channels for holes.

Silica nanotubes and silica nanohelices were obtained by thermolysis of silicon tetraacetate in nanoporous alumina in the presence of amphiphilic block copolymer soft templates. Silica preferential...

Multiple internal reflection spectroscopy (MIRS) was applied to analyse atomic bonds at deep (500 μm) interfaces of directly bonded Si/Si wafer pairs. It is shown that under the conditions used the polarized spectra contain information only about the interface layer a few nanometers thick. Examples are given of analysing the Si-H- and SiO-H vibration modes and bands of undissociated water in interfaces of bonded hydrophobic and hydrophilic wafer pairs, respectively, after annealing at temperatures between 200 and 1100 °C. Variations of the bonding behaviour (especially caused by alterations of the Si-H bonds) are discussed.

Pulsed laser deposition is described as a technique for the synthesis of multilayers showing X- ray optical quality. The state of the art is characterized by results that demonstrate a development of the instrument basis superior to that of conventional PLD systems. Multilayers of the Ni/C, Mo/Si- and W/C-types prove the versatility of the method and the output of layer stack characterization by HREM, SPM, XD, AES, XPS, ellipsometry and image processing ensures a high quality with regard to stack regularity, layer homogeneity and interface smoothness.

The structure and chemistry of interfaces of directly bonded Si/Si wafer pairs after annealing at 1100°C were investigated by secondary ion mass spectroscopy (SIMS), multiple internal reflection spectroscopy (MIRS), and high resolution electron microscopy (HRTEM). Si–O, SiO–H, and Si–H x bonds are shown to be the main atomic bonds at the interfaces of bonded hydrophilic wafer pairs, whereas Si–Si and Si–H x bonds are dominant at interfaces of bonded hydrophobic wafer pairs. For bonded hydrophobic wafer pairs a frequency shift of the Si–H x modes suggest that fluorine is probably present in Si–F···H–Si configurations. Strongly oriented SiO–H modes detected in bonded hydrophobic wafer pairs appear to be related to oxide islands at the interface.