D. A. ZATSEPIN, S. KASCHIEVA, H. J. FITTING, E. Z. KURMAEV, S. N. SHAMIN

Nanosized heterostructures n-Si/SiO2 with different thicknesses of the oxide film (20, 500 nm) after implantation by Si+ ions with energies of 12 and 150 keV have been investigated using Si L2,3 X-ray emission spectroscopy. The n-Si/SiO2 samples under investigation were prepared in the form of plane_parallel plates 1×1 cm in size with an optical_quality surface. The thicknesses of amorphous SiO2 films formed on a massive silicon substrate were equal to 20 nm (sample no. 1 prepared by low_temperature oxidation of n-Si in a «dry» oxygen atmosphere) and 500 nm (sample no. 2 prepared by oxidation of n-Si in H2O vapors). Both samples were irradiated by a wide beam of Si+ ions (i.e., the beam diameter exceeded the sample sizes) with the energies E = 12 keV (sample no. 1; irradiation dose, 1×1016 Si+/cm2) and E = 150 keV (sample no. 2; irradiation dose, 5×1016 Si+/cm2) at the Research Center Rossendorf (Dresden, Germany). In both implantation processes, the ion current was approximately equal to 2-7 mA/cm2 and the temperature of the samples did not exceed 300 K. After the implantation, the sample with the silicon dioxide film 500 nm thick was annealed in a «dry» nitrogen at 1100 K atmosphere for 1 h. Sample no. 1 was not subjected to heat treatment. The Si L2,3 X-ray emission spectra (the 3d3s  2p1/2, 3/2 electronic transition) of the implanted samples and reference materials were recorded on a Spektrozond ultrasoft X-ray emission spectrometer with a high spatial (4 μm) and energy (E = 0.3 eV) resolution. The ion-beam modification of the interface has been revealed and studied for the heterostructure with a silicon dioxide thickness of 20 nm. An analysis of the Si L2,3 X-ray emission spectra has demonstrated that the Si+ ion implantation leads to the self-ordering of the structure of the initially amorphous SiO2 film 20 nm thick due to the effect of high doses. A mechanism of ion-beam modification of the insulator-semiconductor interface has been proposed. No substantial transformation of the atomic and electronic structures of the heterostructure with a silicon dioxide thickness of 500 nm has been revealed after the ion implantation