N. A. Feoktistov

Raman Investigation of Different Polytypes in SiC Thin Films Grown by Solid-Gas Phase Epitaxy on Si (111) and 6H-SiC Substrates

Raman spectroscopy was applied to investigate a series of SiC films grown on Si and 6H-SiC substrates by a new method of solid gas phase epitaxy. During the growth characteristic voids are formed in Si at the SiC/Si interface. Raman peak position, intensity and linewidth were used to characterize the quality and the polytype structure of the SiC layers. A large enhancement in the peak intensity of the transverse optical and longitudinal optical phonon modes of SiC is observed for the Raman signal measured at the voids. In addition, scanning electron microscopy and atomic force microscopy were used to investigate the surface morphology of SiC layers.

Micro-Raman Mapping of 3C-SiC Thin Films Grown by Solid-Gas Phase Epitaxy on Si (111).

A series of 3C-SiC films have been grown by a novel method of solid–gas phase epitaxy and studied by Raman scattering and scanning electron microscopy (SEM). It is shown that during the epitaxial growth in an atmosphere of CO, 3C-SiC films of high crystalline quality, with a thickness of 20 nm up to few hundreds nanometers can be formed on a (111) Si wafer, with a simultaneous growth of voids in the silicon substrate under the SiC film. The presence of these voids has been confirmed by SEM and micro-Raman line-mapping experiments. A significant enhancement of the Raman signal was observed in SiC films grown above the voids, and the mechanisms responsible for this enhancement are discussed.

Optical properties of diamond films grown by MPCVD method with alternating nanodiamond injection

Transparent polycrystalline diamond films with grain size ranging from a few tens to hundreds of nanometres were prepared on fused silica substrate by Microwave Chemical Plasma Vapour Deposition method (MPCVD). The new technique, called alternating nanodiamonds injection, was applied for substrate pretreatment. It was demonstrated that nanodiamonds injected on fused silica substrate serve as nucleation centres and make possible an increase in nucleation density to 1010 cm-2. The influence of MPCVD parameters such as methane concentration, total pressure and substrate temperature on the crystalline structure and optical properties of diamond films were investigated by using micro-Raman spectroscopy and scanning electron microscopy, transmittance and reflectance measurements in the wavelength range of 400-1000 nm. Under appropriate MPCVD parameters, diamond films with optical transmission ~70% from 650 to 1000 nm and high content of diamond phase were fabricated.

Nanodiamond Injection into the Gas-Phase During CVD Diamond Film Growth

We describe a way of combining, in the same technological cycle, the nanodiamond particle injection from a suspension and the growth of diamond films by microwave plasma chemical vapor deposition (MPCVD). The breaking of injected nanodiamond aggregates into particles of about 100 nm in size when they hit a substrate provides a nucleation density over 1010 cm−2. The films produced from a CH4+H2 mixture with a periodic injection of ND particles during the film growth are found to consist of diamond nanocrystallites with the traces of sp2 -hybridized carbon on them.

Emitting a-SiOx(Er) films and a-SiOx(Er)/a-Si:H microcavities doped with Er by remote magnetron sputtering technique

We have developed the technique of growing amorphous a-SiO(x)(Er) films and a-SiO(x)(Er)/a-Si:H multilayer structures based on spatially separating the processes of the decomposition of an oxygen-silane gas mixture in an rf glow discharge plasma and remote magnetron sputtering of an Er target. This approach allows us to control independently the film deposition rate, the Er-ion concentration and its depth distribution in the film. Time-resolved photoluminescence measurements have shown that films and planar microcavities with an Er-doped active layer exhibit internal quantum efficiency for Er ion emission of ∼75%. The method that we suggest is a way of producing effectively emitting microcavity structures, in which the distribution profile of emission centers coincides with that of the electromagnetic field in individual layers of the structure.

New luminescence lines in nanodiamonds obtained by chemical vapor deposition

The spectral characteristics of the photoluminescence lines detected for nanodiamonds obtained by the reactive ion etching of diamond particles in oxygen plasma, deposited by chemical vapor deposition on a silicon substrate, are studied. At room temperature, narrow lines are observed in the visible and infrared spectral regions, with a full width at half-maximum in the range of 1–2 nm at an almost complete absence of a broadband photoluminescence background signal. At decreasing temperature, the lines narrowed to 0.2–0.6 nm at T = 79 K, and the minimum line width was 0.055 nm at T = 10 K. With increasing temperature, the narrow lines shifted to the long-wavelength region of the spectrum, and their intensity decreased.

Amorphous silicon-carbon based p-i-n structures for electron flux conversion

A study of the collection efficiency of electron-hole pairs in amorphous silicon-carbon based p-i-n structures under keV electron irradiation is presented. a-Si:C:H films have been prepared by a conventional RF plasma deposition technique. A scanning electron microscope in the spot-mode regime was used for electron irradiation of our structures. The current-voltage characteristics and spectral dependence of the short-circuit current were measured. A numerical current transport model was used for simulation and the energy of the electron-hole pair creation Eeh = 7-8eV was determined.