Papers by Author: O.V. Naumova

Abstract: Properties of Si/buried oxide (BOX) systems with bonded interface in silicon-on-insulator (SOI) wafers were studied in this paper. Results show impact of the starting Si material - Czochralski (Cz) or float-zone (Fz) grown silicon on the electron mobility (μ_e) and BOX charge behavior in ultrathin SOI layers. In particular, there were found: 1) the μ_e ~ N_e^-0.3 dependencies at the electron density N_e in the range of 4х (10¹¹-10¹²) cm^-2 in accumulation Cz-SOI layers with the μ_e degradation when Si thickness decreases from 20 to 9 nm, and 2) the ~ N_e^-0.6 behavior of mobility with no degradation in Fz-SOI layers. Raman spectroscopy shows the structural modification of Cz-SOI layers. An origin of degradation of the electrical and structural properties for ultrathin SOI layer is discussed.

Abstract: In the present study, the pursued purposes were: (i) monitoring the electrical properties of silicon-on-insulator nanowires (SOI NWs), (ii) determination of surface treatments suitable for obtaining reproducible states on the surface of SOI NWs after their long-term storage, and (iii) identification of surface treatments suitable for regenerating the NW surface after protein (bovine serum albumin molecules) detection. It is shown that, during storage, with the passage of time a negative effective charge was accumulated on the surface of n-SOI NWs up to surface density Q_eff = (2-4)х10¹² cm^-2, while the interface states at the NW/SiO₂ interface underwent relatively slow depassivation. Treatments in H₂O₂ with subsequent treatments in HF can be used for removing organic contaminations from the NW surface and for regenerating the initial working state of SOI NWs after protein detection.

Abstract: Graphitic-diamond heterostructure may be very helpful not only for high frequency or power devices but also for new generation of electronic devices like single electron transistors or quantum computers operated at room temperature. The goal of our work was a formation of nanothin amorphous carbon or graphite layers with sp3 or sp2 hybridization inside the nitrogen doped synthetic monocristalline diamond by high dose hydrogen implantation. It was found that there is a “critical” dose of 50 keV hydrogen molecular ions equal to 4x1016 cm-2 above which an irreversible drop of the sheet resistivity in implanted layer occurs after annealing above 1000 oC. The nature of this conductivity was investigated and it was shown that variable range hopping mechanism of 3D conductivity dominates in investigated temperature interval. Four times higher value for the onset of this conductivity in comparison with “critical” dose for graphitization is explained by interaction of implantation induced defects with nitrogen atoms and surface defects.

Abstract: Electro-physical properties of metal-oxide-silicon (MOS) structures and MOS transistors, prepared in the top silicon layer of silicon-on-insulator (SOI) structures containing Ge nanocrystals in the buried SiO2 layers, have been studied. It was obtained that carrier accumulation in MOS structures depend on the direction of built-in electrical field in MOS structures. Accumulation of the excess negative charges in the case of p-channel transistors is associated with electron trapping on Ge nanocrystals synthesized in the buried dielectric. In the case of n-channel transistor, positive charge related to the Si/SiO2 interface or to the charged oxide is accumulated. The Ge atoms diffused to the SiO2/Si interface can stimulate the formation of the excess positive charge.