Papers by Author: Ida E. Tyschenko

Abstract: Hydrogenated Si nanocrystals were performed by high-dose (51017 cm-2) low-energy (24 keV) H+ ion implantation of silicon-on-insulator (SOI) layers. The formation of the nanocrystalline phase was observed in the as-implanted samples and in those annealed at the temperature of 200-400o C. Both the Raman shift and the broadening of the phonon peak corresponded to Si nanocrystals with the diameters ranging from ~2 to ~3 nm. The room-temperature photoluminescence (PL) peaked at 1.58 - 1.64 eV was observed at room temperature. The PL peak energy corresponded to the energy of quantum confined exciton in the Si nanocrystals with the diameters mentioned above. The PL intensity had the bell-shaped dependence on the measurement temperature and had its maximum near 150 K. The estimated thermal activation energy of the PL was about 12.1 meV and was in good accordance with the singlet-triplet splitting energy of the exciton states.

Abstract: The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator (SOI) structures are studied. It is shown that no germanium nanocrystals are formed in the buried SiO2 layer of the SOI structure as a result of annealing at the temperature of 1100° C. The implanted Ge atoms segregate at the Si/SiO2 bonding interface. In this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. It is found that the slope of the drain–gate characteristics of the back metal-oxide-semiconductor (MOS) transistors, prepared in the Ge+ ion implanted structures, increases. This effect is attributed to the grown hole mobility due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface.

Abstract: The behavior of Sb and In atoms embedded into silicon-on-insulator structure (SOI) near the bonding interface was investigated as a function of annealing temperature. Two kinds of the ionimplanted SOI structures were prepared. First kind of the structures contained the buried SiO2 layer implanted with In+ and Sb+ ions near the top Si/SiO2 interface. In second kind, the ion-implanted regions were placed on each side of the bonding interface: Sb+ ions were implanted into Si film; In+ ions were implanted into SiO2 layer. Rutherford backscattering spectrometry (RBS) and crosssectional high-resolution electron microscopy (XTEM) were employed to study the properties of the prepared structures. The formation of InSb nanocrystals was observed within the SiO2 bulk from first kind of the SOI structures as annealing temperature increased to 1100o C. In the case of the double side implanted SOI structures, an increase in annealing temperature to 1100o C was accompanied by the up-hill diffusion of In atoms from the SiO2 bulk toward the bonding interface and by the endotaxial growth of InSb nanocrystals on the top Si/SiO2 interface. It was concluded from the experimental results that Sb atoms were the nucleation centers of InSb phase.

Abstract: Cavity effect on the room-temperature (RT) photoluminescence (PL) from emitting centers in the top silicon layer of silicon-on-insulator (SOI) structure has been studied. The lightemitting centers were produced by the implantation of H+ ions and subsequent annealing at the temperatures Ta = 450-1000 oC for 5 h in an Ar ambient under pressure P = 1 - 1.2×104 bar. It has been obtained that annealing under hydrostatic pressure higher than 6 kbar prevented the outdiffusion of hydrogen in the form of gas bubbles, which took place after annealing at Ta≥600 oC under atmospheric conditions. Absence of micro-pores and gas bubbles in the top surface region creates the conditions to retain the mirror quality of the SOI/air interface. A wavelength-selective effect of the formed cavity on visible PL has been observed from the H+ ion implanted SOI structures annealed under pressure of 12 kbar. The cavity enhancement of PL emission for 23-40 times has been found at the wavelength of 515 and 560 nm.

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.

Abstract: The properties of Si and Ge nanocrystals with uniformly strained Si-Si and Ge-Ge bonds have been studied. The strained Si and Ge nanocrystals were produced by the implantation of Ge+ or Si+ ions in thermally grown SiO2 films subsequently annealed under hydrostatic pressure ranging from 1 bar to 12 kbar. Correlation between the formation of the hydrostatically strained nanocrystals and the features of the photoluminescence spectra has been observed. The obtained results are discussed in terms of broadening energy gap between the levels of electron states of the hydrostatically strained nanocrystals. This effect brings about direct radiative recombination.