Controlled Transformation of Electrical, Magnetic and Optical Material Properties by Ion Beams

Key circumstance of radical progress for technology of XXI century is the development of a technique which provides controllable producing three-dimensional patterns incorporating regions of nanometer sizes and required physical and chemical properties. Our paper for the first time proposes the method of purposeful direct transformation of the most important substance physical properties, such as electrical, magnetic, optical and others by controllable modification of solid state atomic constitution. The basis of the new technology is discovered by us effect of selective atom removing out of thin di- and polyatomic films by beams of accelerated particles. Potentials of that technique have been investigated and confirmed by our numerous experiments. It has been shown, particularly, that selective atom removing allows to transform in a controllable way insulators into metals, non-magnetics into magnetics, to change radically optical features and some other properties of materials. The opportunity to remove selectively atoms of a certain sort out of solid state compounds is, as such, of great interest in creating technology associated primarily with needs of nanoelectronics as well as many other "nano-problems" of XXI century.Comment: 22 pages, PDF, 9 figure

Formation of Ge-Sn nanodots on Si(100) surfaces by molecular beam epitaxy

The surface morphology of Ge0.96Sn0.04/Si(100) heterostructures grown at temperatures from 250 to 450°C by atomic force microscopy (AFM) and scanning tunnel microscopy (STM) ex situ has been studied. The statistical data for the density of Ge0.96Sn0.04 nanodots (ND) depending on their lateral size have been obtained. Maximum density of ND (6 × 1011 cm-2) with the average lateral size of 7 nm can be obtained at 250°C. Relying on the reflection of high energy electron diffraction, AFM, and STM, it is concluded that molecular beam growth of Ge1-xSnx heterostructures with the small concentrations of Sn in the range of substrate temperatures from 250 to 450°C follows the Stranski-Krastanow mechanism. Based on the technique of recording diffractometry of high energy electrons during the process of epitaxy, the wetting layer thickness of Ge0.96Sn0.04 films is found to depend on the temperature of the substrate

Ge/Si Quantum Dots Superlattices Grown at Different Temperatures and Characterized by Raman Spectroscopy and Capacitance Measurements

Ge/Si heterostructures with Ge self-assembled quantum dots (SAQDs) grown at various temperatures by molecular beam epitaxy were investigated using resonant Raman spectroscopy and capacitance measurements. The occurrence of quantum confinement effects was confirmed by both techniques. For the structures grown at low temperatures (300 − 400 • C), the SAQDs optical phonon wavenumbers decrease as the Raman excitation energy is increased; this is an evidence of the scattering sensitivity to the size of the SAQDs and to the inhomogeneity in their sizes. However, the opposite behavior is observed for the SAQDs grown at higher temperatures, as a consequence of the competition between the phonon localization and internal mechanical stress effects. The E 1 electronic transition of the Ge in the SAQDs was found to be shifted towards higher energies as compared to bulk Ge, due to biaxial compressive stress and to the electronic confinement effect present in the structures. The intermixing of Si atoms in the quantum dots was found to be much more significant for the sample grown at higher temperatures. The capacitance measurements, besides confirming the existence of the dots in these structures, showed that the deepest Ge layers lose their 0D signature as the growth temperature increases

Absorption of Terahertz Radiation in Ge/Si(001) Heterostructures with Quantum Dots

The terahertz spectra of the dynamic conductivity and radiation absorption coefficient in germanium-silicon heterostructures with arrays of Ge hut clusters (quantum dots) have been measured for the first time in the frequency range of 0.3-1.2 THz at room temperature. It has been found that the effective dynamic conductivity and effective radiation absorption coefficient in the heterostructure due to the presence of germanium quantum dots in it are much larger than the respective quantities of both the bulk Ge single crystal and Ge/Si(001) without arrays of quantum dots. The possible microscopic mechanisms of the detected increase in the absorption in arrays of quantum dots have been discussed.Comment: 9 pages, 4 figures; typos correcte

MicElec1_05KarasevLO

Abstract -Si(111) 7 × 7 films are grown by MBE on clean (111) diamond surfaces. It is shown that the film structure can be controlled in real time by varying the substrate temperature and Si flux. Modes of growth are identified that provide Si films of higher crystalline quality