Photon-Assisted Electron Transmission through a Quantum Point Contact

The theory of coherent photon-assisted electron transmission through a one-dimensional smooth barrier is successfully used to model the results of measuring the terahertz photoconductivity of a tunneling point contact in a two-dimensional electron gas. For this barrier in a deeper tunneling mode, photon steps in the curve of the transmission coefficient versus initial electron energy were found. Their position is determined by the terahertz photon energy.     

Luminescence of Spatially Ordered Self-Assembled Solitary Ge(Si) Nanoislands and their Groups Incorporated into Photonic Crystals

Semiconductors - The luminescence properties of arrays of spatially ordered self-assembled solitary Ge(Si) nanoislands and their groups, including those embedded in two-dimensional photonic...     

Control of Electron-Beam Surfacing-Process Parameters Using Current Signals of the Wire and Article

This paper presents a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors. The main metal-transfer modes are specified that are observed with a change of the energy-input rate. The importance of the solved problem for additive technologies is shown. A scheme of experimental investigations carried out at the ELA-15I apparatus is given, and the obtained oscillograms are presented. The relation of the characteristics of the registered signals with the operation modes of the equipment and transfer parameters is shown. It is noted that, with a change of only the filler-wire feed rate, a changeover from drop metal transfer to the scattering mode can be triggered. The possibility of detecting the mode of appearance of the shot metal, as well as emergency modes related with stopping the filler-wire feed or excessive increase of its feed rate, is substantiated. The influence of the plasma processes on the registered signals in the developed scheme is analyzed, and it is also shown that, to reduce the influence of these processes, it is necessary to decrease the resistance of the measuring circuit. Photographs of the process corresponding to the certain oscillogram intervals are given.     

Self-Organization of Ge(Si) Nanoisland Groups on Pit-Patterned Si(100) Substrates

Semiconductors - Space-arranged arrays of pits on Si(001) substrates were prepared using electron-beam lithography and plasma chemical etching. The positions of pits were arrange to the square and...     

Carbon-stimulated self-organization of Ge nanoislands during molecular beam epitaxy of Ge/CaF<Subscript>2</Subscript>/Si(111) heterostructures

The self-organization of germanium nanoislands on the surface of calcium fluoride was studied using atomic-force microscopy and reflection electron diffraction. A Ge/CaF₂/Si(111) structure was grown by molecular beam epitaxy. The surface of the calcium fluoride film was modified by submonolayer carbon coverage to stimulate the formation of germanium nanoislands. The parameters of an array of nanoislands were found to depend on the coverage.     

Initial stages of gold adsorption on silicon stepped surface at elevated temperatures

Experimental study performed by ultrahigh vacuum reflection electron microscopy and atomic force microscopy reveals step instability on Si(111) surface during gold deposition at elevated temperatures (higher than 900°C). Our results show that transformations of regular atomic steps into the system of step bunches and vice versa depend on the gold coverage and direction of the electrical current heating the sample. The mechanism and conditions of the surface morphology transformations are discussed. The text was submitted by the authors in English.     

Proximity effects in formation of photonic crystals by lithographic methods

Proximity effects in formation of photonic crystals in the form of ordered arrays of holes of similar radii close to 100 nm by methods of electron beam lithography are considered. The coefficients of the proximity function characterizing the contribution of back-scattered and secondary electrons to the exposure dose are experimentally determined. It is demonstrated that the minimum standard deviation from the mean radius of the elements in the array is provided by means of the proximity effect correction with the use of experimentally obtained coefficients and an iterative equation with an increased contribution of back-scattered electrons.     

Ordered Arrays of Ge(Si) Quantum Dots Incorporated into Two-Dimensional Photonic Crystals

Semiconductors - Two different approaches to the integration of self-assembled Ge(Si) quantum dots into two-dimensional photonic crystals are considered. One approach includes the synthesis of an...     

The effect of high-temperature annealing on the stability of the structure and properties of welded joints in tungsten single crystals with planar and axial geometry

The results of experimental studies of the effect of high-temperature treatment on the stability of the substructure, crystallography and mechanical properties of welded joints in tungsten single crystals with planar and axial geometry are presented. The main task of the study was to obtain data on the possibility of producing monohedral tubes of tungsten single crystals with a stable structure (ρ = 10⁵–10⁶ cm^?2), with permissible misorientation angles at the sub-boundaries (θ < 3°) in the central part of the welded joint and strength characteristics (σ_bend of the weld metal should be higher than or equal to σ_bend of the parent metal), suitable for service of these components at working temperatures (up to 2500 °C). The methods for producing pipes with the required homogeneous orientation of the side (working) surface made of a single crystal tungsten ingot are described.