ABSTRACT
The arrays of metallic nanowires are considered as promising precursors for 1D semiconductor nanostructures after appropriate treatment at temperatures close to the melting point. Therefore the melting behaviour of the metallic structures in oxide templates is a key parameter for the subsequent conversion process. The present paper focuses on understanding of the effect of mechanical stress generated during heating on the melting point of the metal nanowires deposited into the pores of anodic alumina. Extremely high local compressive stress appears due to the difference in the thermal coefficients of the oxide template and nanowires inside the pores. The effect of the composite structural parameter that may be related to the concentration of nanowires on the melting temperature has been investigated. A numerical model predicting the melting point has been developed for composites with indium, tin, and zinc nanowires. The simulation results obtained using the suggested model were compared with the experimental data.
ABSTRACT
For the quantitative characterization of atomic ordering in the transition region between crystalline and amorphous materials we have previously described a method based on averaging HREM images along the interface, simulation of averaged images with the use of the averaged projected potential approximation and determination of the atom arrangement by means of an iterative matching procedure for high-resolution focus series. In order to study mesoscopic properties of crystal induced ordering a fully quantitative procedure is developed in this work. For this purpose, the width of the averaging region is defined as a compromise providing necessary accuracy of calculations and desirable locality of characterization of the atom distribution. Fluctuations of the obtained atom distribution on the amorphous side of the interface are estimated by means a of special Monte-Carlo simulation technique. As a result, distribution functions obtained from different regions can be quantitatively compared and statistically significant differences can be identified and related to the atomic structure. The method is applied to investigate the near interfacial atom order at the interface between atomically flat crystalline Si(111) and amorphous Ge. It is shown that significant variations in the atomic density distribution occur on a 5-10nm scale for germanium atoms in the second and third atomic layer lying parallel to the interface.
ABSTRACT
For the analysis of images of homogeneous crystalline-amorphous interfaces we propose to average them along the interface obtaining the averaged interface image or the averaged intensity profile. Due to averaging, contrast components with the periodicity of the crystalline area of the image are extracted. Thus, the contrast features originating from the random overlap of the projected potentials of atoms in the amorphous layer are suppressed. It is shown that averaged images can be simulated by the multi-slice method using the novel approach to model the near interfacial amorphous structure by its mean atomic density distribution in front of the crystalline boundary. The crystalline structure is represented by its known atomic positions. We apply the proposed method to the investigation of the near interfacial short-range order in the c-Si/ a-Ge crystalline-amorphous interface.
