Scanning mid-IR-laser microscopy: an efficient tool for materials studies in silicon-based photonics and photovoltaics

A method of scanning mid-IR-laser microscopy has recently been proposed for the investigation of large-scale electrically and recombination-active defects in semiconductors and non-destructive inspection of semiconductor materials and structures in the industries of microelectronics and photovoltaics. The basis for this development was laid with a wide cycle of investigations on low-angle mid-IR-light scattering in semiconductors. The essence of the technical idea was to apply the dark-field method for spatial filtering of the scattered light in the scanning mid-IR-laser microscope together with the local photoexcitation of excess carriers within a small domain in a studied sample, thus forming an artificial source of scattering of the probe IR light for the recombination contrast imaging of defects. The current paper presents three contrasting examples of application of the above technique for defect visualization in silicon-based materials designed for photovoltaics and photonics which demonstrate that this technique might be an efficient tool for both defect investigation and industrial testing of semiconducting materials.Comment: DRIP-

Nucleation of Ge quantum dots on the Si(001) surface

A direct observation of nucleation of Ge hut clusters formed by ultrahigh vacuum molecular beam epitaxy is reported for the first time. The nuclei of the pyramidal and wedge-like clusters have been observed on the wetting layer blocks and found to have different structures. The growth of the clusters of both species goes on following different scenarios: Formation of the second atomic layer of the wedge-like cluster results in rearrangement of its first layer. Its ridge structure does not replicate the structure of the nucleus. The pyramidal cluster grows without phase transitions. The structure of its vertex copies the structure of the nucleus. The wedge-like clusters contain point defects on the triangular faces and have preferential directions of growth along the ridges. The derived structure of the {105} facet corresponds to the PD model. The critical epinucleation phenomenon may be responsible for hut formation.Comment: 6 pages, 6 figures; Fig. 4e has been improved; additional explanations have been added. To appear in Phys. Rev.

Finding mesoscopic communities in sparse networks

We suggest a fast method to find possibly overlapping network communities of a desired size and link density. Our method is a natural generalization of the finite-$T$ superparamegnetic Potts clustering introduced by Blatt, Wiseman, and Domany (Phys. Rev. Lett. v.76, 3251 (1996) and the recently suggested by Reichard and Bornholdt (Phys. Rev. Lett. v.93, 21870 (2004)) annealing of Potts model with global antiferromagnetic term. Similarly to both preceding works, the proposed generalization is based on ordering of ferromagnetic Potts model; the novelty of the proposed approach lies in the adjustable dependence of the antiferromagnetic term on the population of each Potts state, which interpolates between the two previously considered cases. This adjustability allows to empirically tune the algorithm to detect the maximum number of communities of the given size and link density. We illustrate the method by detecting protein complexes in high-throughput protein binding networks.Comment: 8 pages, 2 figure, typos corrected, 1 figure adde

Some peculiarities of burnt birch wood pyrolysis

The results of thermal analysis of sound and burnt birch wood samples were compared. An attempt was made to establish a connection between the type of the TG, DTG and DSC curves and the mechanism of wood pyrolysis. The dependence of the exothermic effect of the pyrolysis process on the oxygen content in the original wood is shown. © 2019 IOP Publishing Ltd. All rights reserved

The forming factors of high values of superconducting transition temperature Tc in 3d-Transition metal compounds. I. The main groups of known superconductors

The review of modern known groups of superconductors is presented. The main classification rule is the type of chemical bonding. The factors of forming superconducting transition temperature are impurities and the external pressure. © 2013 Elmira Yuryeva and Anatoliy Yuryev