Sergey A. Dotsenko

Phase composition evolution of iron silicide nanocrystals in the course of embedding into monocrystalline silicon

Evgeniy A. Chusovitin, Dmitry L. Goroshko, Sergey A. Dotsenko, Alexander V. Shevlyagin, Nikolay G. Galkin and Anton K. Gutakovskii 1Institute of Automation and Control Processes FEB RAS, 5 Radio St., 690041 Vladivostok, Russia 2Far Eastern Federal University, School of Natural Sciences 8 Sukhanova St., 690950 Vladivostok, Russia 3Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia.

Mg2SixSn1-xheterostructures on Si(111) substrate for optoelectronics and thermoelectronics

Thin (50-90 m) non-doped and doped (by Al atoms) Mg2Sn0.6Si0.4 and Mg2Sn0.4Si0.6films with roughness of 1.9-3.7 nm have been grown by multiple deposition and single annealing at 150 °C of multilayers formed by repetition deposition of three-layers (Si-Sn-Mg) on Si(111) p-type wafers with 45 Ω-cm resistivity. Transmission electron microscopy has shown that the first forming layer is an epitaxial layer of hex-Mg2Sn(300) on Si(111) substrate with thickness not more than 5-7 nm. Epitaxial relationships:hex-Mg2Sn(300)|| Si(111), hex-Mg2Sn[001]|| Si[-112] and hex-Mg2Sn[030]||Si[110] have been found for the epitaxial layer. But inclusions of cub-Mg2Si were also observed inside hex-Mg2Sn layer. It was found that the remaining part of the film thickness is in amorphous state and has a layered distribution of major elements: Mg, Sn and Mg without exact chemical composition. It was established by optical spectroscopy data that both type films are semiconductor with undispersed region lower 0.18 eV with no= 3.59 ± 0.01, but only two direct interband transitions with energies 0.75-0.76 eV and 1.2 eV have been determined. The last interband transition has been confirmed by photoreflectance data at room temperature. Fourier transmittance spectroscopy and Raman spectroscopy data have established the formation of stannide, silicide and ternary compositions.

Optical properties of magic clusters formed in In/Si(111) and Cr/Si(111) systems

The optical properties of ultrasmall ordered indium and chromium quantum dots of identical size (magic clusters) in the In/Si(111) and Cr/Si(111) systems have been studied by differential reflection spectroscopy (DRS). Using the DRS data, the character of the magic clusters of each type has been elucidated. It is established that the magic clusters of chromium formed in the Cr/Si(111) system represent nanocrystals of chromium silicide (Cr/Si(111) is a reactive system featuring chemical interaction between the metal and the silicon substrate, which leads to silicide formation). The magic clusters of indium formed in the nonreactive In/Si(111) system represent a surface phase.

Formation of CrSi2 nanoislands on Si(111)7 × 7 and epitaxial growth of silicon overlayers in Si(111)/CrSi2 nanocrystallites/Si heterostructures

Low-energy electron diffraction and differential reflectance spectroscopy are used to study the self-formation of chromium disilicide (CrSi2) nanoislands on a Si(111) surface. The semiconductor properties of the islands show up even early in chromium deposition at a substrate temperature of 500°C, and the two-dimensional growth changes to the three-dimensional one when the thickness of the chromium layer exceeds 0.06 nm. The maximal density of the islands and their sizes are determined. The MBE growth of silicon over the CrSi2 nanoislands is investigated, an optimal growth temperature is determined, and 50-nm-thick atomically smooth silicon films are obtained. Ultraviolet photoelectron spectroscopy combined with the ion etching of the specimens with embedded nanocrystallites demonstrates the formation of the valence band, indicating the crystalline structure of the CrSi2. Multilayer epitaxial structures with embedded CrSi2 nanocrystallites are grown.