S.A. Dotsenko

An approach to growth of Fe-Si multilayers with controlled composition profile - A way to exchange coupled thin films

The growth, composition and structure of sandwich structures (Fe-rich layer/Si-rich layer/Fe-rich silicide layer) grown on a Si(111) surface were studied by a few complementary microscopic and spectroscopic techniques with high spatial resolution. Intermixing at the Fe/Si and Si/Fe interfaces is demonstrated. Fe-rich layers grown directly on the Si(111) surface are crystalline and have abrupt but rough interfaces at both sides. The succeeding layers are disordered and their interfaces are fuzzy. The distributions of Fe and Si within the layers are laterally non-uniform. The reproducible fabrication of thin non-magnetic silicide spacers of predetermined thickness is demonstrated. Sandwich structures with such spacers exhibit exchange coupling between ferromagnetic Fe-rich layers.

Structure and Optical Properties of Ca Silicide Films and Si/Ca3Si4/Si(111) Heterostructures

Thick, thin films and island of Ca silicide have been grown by Ca deposition onto 500 °C Si (111)7x7 substrates. The crystal structure of the grown layers strongly differs from the known Ca silicides (Ca2Si, CaSi, Ca5Si3, Ca14Si19, CaSi2). The phonon peaks at 389 and 416 cm-1 and the interband transition peaks (0.9-1.0, 1.3-1.7 and 2.0-2.5 eV) belongs to another silicide - Ca3Si4. Peculiarities of crystal, electronic, and phonon structure and optical properties of the grown Ca silicide films were measured by in situ and ex situ methods permit to state that the formed Ca silicide film has a composition Ca3Si4. Heterostructures with embedded Ca3Si4 films with different thicknesses have been formed atop the Ca3Si4 films by MBE and SPE at 500 °C. The observed density of pinholes with different sizes suggests the Si growth atop the Ca silicide follows a 3D mechanism. Photoluminescence was found first time in Si/Ca3Si4/Si (111) heterostructures.