S. Levichev

Charge trapping properties and retention time in amorphous SiGe/SiO2 nanolayers

In this paper, we report on the electrical properties of metal–oxide–semiconductor (MOS) capacitors containing a well-confined 8 nm-thick SiGe amorphous layer (a-SiGe) embedded in a SiO2 matrix grown by RF magnetron sputtering at a low temperature (350 ◦ C). Capacitance–voltage measurements show that the introduction of the SiGe layer leads to a significant enhancement of the charge trapping capabilities, with the memory effect and charge retention time larger for hole carriers. The presented results demonstrate that amorphous floating-gate SiGe layers embedded in SiO2 may constitute a suitable alternative for memory applications. (Some figures may appear in colour only in the online journal)

Mn-doped ZnO nanocrystals embedded in Al2O3: structural and electrical properties

We report on the structural and electrical properties of Mn-doped ZnO/Al(2)O(3) nanostructures produced by the pulsed laser deposition technique. Grazing incidence small angle x-ray scattering (GISAXS) and Rutherford backscattering spectrometry revealed the multilayered structure in as-deposited samples. Annealing of the nanostructures was shown to promote the formation of nanocrystals embedded in the Al(2)O(3) matrix, as was evidenced by GISAXS and high resolution transmission microscopy. Particle-induced x-ray emission analysis showed a doping of 8 at.% Mn in ZnO. Grazing incidence x-ray diffraction and Raman spectroscopy demonstrated that the nanocrystals have the pure wurtzite ZnMnO crystalline phase. Resonant Raman scattering displayed an increase of intensity of the 1LO mode as well as broadening of the 2LO mode related to the size effect. Capacitance-voltage measurements showed carrier retention with a voltage shift higher than those reported for similar systems.

Investigation of photoelectrical properties of CdSe nanocrystals embedded in a SiO2 matrix

CdSe nanocrystals (NCs) embedded in SiO2 thin films were prepared using RF-magnetron co-sputtering. The average NC size was estimated to be 18 nm. The dark and photocurrent temporal dependences have been measured as a function of the magnitude of applied voltage (50?150 V). Annealing the samples seems to improve the photoconductivity (~10?12 ??1) that increases with the film thickness and slightly changes under the bias voltage. Furthermore, the photovoltage measurements showed that a concentration of CdSe in the range of 27 mol% leads to the generation of a photovoltaic signal up to 5 V at 400 ?W cm?2. These results demonstrate the potential of silica films with embedded CdSe NCs for photovoltaic applications.

THERMAL STABILITY OF ENERGY-EMISSION FROM CdTe NANOCRYSTALS EMBEDDED IN SiO2 THIN FILMS

CdTe-doped SiO2 thin films were produced by RF magnetron co-sputtering technique. Presence of CdTe nanocrystals inside the silica matrix was confirmed by Raman spectroscopy and grazing incidence X-ray diffraction. The samples demonstrate size dependent photoluminescence. Temperature dependent photoluminescence measurements were carried out in the temperature range 15–295 K and revealed energy-emission thermal stability. This feature can be usefully applied in a production of light-emitting diodes with wavelength stability in a wide temperature range.