A. M. Svetlichnyi

Comparative characteristics of the Raman scattering spectra of graphene films on conductive and semi-insulating 6H-SiC substrates

The raman scattering (RS) spectra of graphene on semi-insulating and conductive 6H-SiC substrates formed by preliminary and additional annealing of silicon carbide at various temperatures are studied. The degree of perfection of the graphene films and sizes of its clusters are estimated. It is shown that the temperature of additional annealing in the case of conductive substrates should be higher than that for semi-insulating substrates to obtain graphene layers with the same structural perfection.

Characterization of field-emission cathodes based on graphene films on SiC

The properties of a point field-emission cathode representing a structure in the form of a silicon carbide tip coated with a thin graphene film are assessed. For the point cathode with the graphene coating, the current–voltage characteristics are constructed in the Fowler–Nordheim coordinates; the work functions φ of the point cathode are calculated by their slope. The possibility of forming heavily doped n+-SiC on the point surface by the sublimation of low-threshold field emission cathodes with low threshold electric fields and field-emission currents is shown.

Morphology and optical properties of titanium-doped porous silicon carbide layers

The effect of rapid thermal annealing (RTA) in oxygen on the properties of titanium-doped porous silicon carbide (por-SiC) layers has been studied. The data on the surface morphology and the photoluminescence (PL) spectra show that the high-temperature diffusion annealing is accompanied by the formation of titanium silicides, by an increase in the grain size of the material, and by the emergence of pores on the surface of the por-SiC-Ti sample. The results of PL measurements are consistent with data on the phase composition and the surface morphology of the samples. It is established that RTA leads to modification of the titanium-doped por-SiC structure.

Effect of microwave annealing on silicon dioxide/silicon carbide structures

The methods of atomic force microscopy and optical absorption spectroscopy are applied to study the effect of microwave treatment on the properties of SiO2/SiC structures obtained by rapid thermal annealing and conventional thermal oxidation in steam. From the variation of the sample optical density with total time of microwave treatment, it is concluded that the structures prepared by rapid thermal annealing are more stable against microwave radiation. It is shown that long-term microwave treatment flattens the oxide film surface at the nanolevel regardless of the method of silicon carbide oxidation.

Characterization of porous silicon carbide according to absorption and photoluminescence spectra

The results of the atomic-force microscopy, optical-absorption spectroscopy, and photoluminescence spectroscopy of porous silicon carbide (por-SiC) produced by anodic etching are reported. Analysis of the data shows that the cubic SiC phase is lacking in the porous layer and the photoluminescence signal from por-SiC at the excitation photon energy hνex ≤ Eg appears due to the formation of radiative centers associated with impurity atoms and surface defects produced upon anodic etching of the sample and subsequent treatment to uncover the pores.

Reduction in absorption in quartz/Si, quartz/Si/SiO2, and SiC/Si/SiO2 structures on laser treatment

The effect of laser radiation on the optical absorption spectra of the quartz/Si, quartz/Si/SiO2, and SiC/Si/SiO2 systems is studied. The effects of modification of the transparency of the structures are clarified.

Field emission properties of pointed cathodes based on graphene films on SiC

Electrical properties of low-threshold field emission cathodes produced by growth nanocluster graphene films on the pointed surface of heavily doped n+SiC by sublimation epitaxy have been considered. The quality of the graphene coating has been assessed based on the morphological studies and Raman spectroscopy. Using the volt–ampere characteristics the work function from a pointed cathode with graphene coating was calculated (∼ 0.76 eV). Such a low value of the work function is explained on the assumptions that the graphene film has the nanocluster nature and the sources of the field emission are graphene nanoclusters.

Laser-annealing-induced features of the Raman spectra of quartz/Si and glass/Si structures

The effect of laser radiation on the characteristics of amorphous silicon films on glassy or quartz substrates are studied by Raman spectroscopy. It is established that an increase in the laser-treatment power yields a phase transition from amorphous silicon to nanocrystalline silicon. The variation in the relation between the nanocrystalline and amorphous silicon fractions in the films is described in the context of the critical impact model.

Formation of titanium oxide films on the surface of porous silicon carbide

The influence of rapid thermal annealing (RTA) on the properties of a titanium film on the surface of porous silicon carbide is considered. It is shown that an increase in the RTA temperature to 900°C stabilizes the phase composition of the forming titanium oxide over the film, which is identified as rutile. Due to the formation of titanium oxide nanoclusters under the action of RTA, an additional photoluminescence band arises near 2.5 eV. Based on Auger spectrometry data, a multilayer model to calculate the optical parameters of titanium oxide films covering porous silicon carbide is suggested.

Planar nanosized field emission cathodes on the basis of graphene/semi-insulating silicon carbide fabricated by focused ion beam

We investigate the field emission properties of planar graphene structures with nanosized interelectrode distance. The graphene was obtained by thermal decomposition of silicon carbide in vacuum. Planar field emission structures on the basis of graphene on semiinsulating SiC were fabricated by using focused ion beam. We have performed current-voltage measurement on graphene/SiC field emission cathodes. The planar field emission structures showed a threshold voltage less than 1 V.