Štěpán Potocký

Determination of temperature dependent parameters of zero-phonon line in photo-luminescence spectrum of silicon-vacancy centre in CVD diamond thin films

Abstract In this work we present a methodological approach to the temperature dependence of photoluminescence (PL) emission spectra of the silicon-vacancy centre in diamond thin films prepared by chemical vapour deposition. The PL spectra were measured in the temperature range of 11 - 300 K and used to determine the temperature dependence of the zero-phononline full-width at half-maximum and of the peak position. Experimental data were fitted by models of lattice contraction, quadratic electron-phonon coupling, homogeneous and inhomogeneous broadening. We found that the shift of peak position and peak broadening reflect polynomial dependence on temperature. Moreover, a proper setting of monochromator slits width is discussed with respect to line profile broadening.

Growth of carbon allotropes and plasma characterization in linear antenna microwave plasma CVD system

Growth of diamond coatings with tunable morphology and concurrent substrate catalyst pretreatment and further growth of carbon nanotubes were studied. The dependence of plasma parameters on gas composition was studied by Langmuir probe measurement. Grown diamond coatings and carbon nanotubes were characterized by scanning electron microscopy and Raman spectroscopy and correlated with process parameters. Well-defined nanocrystalline, polycrystalline, and porous diamond films were prepared. Concurrent substrate catalyst pretreatment and further growth of carbon nanotubes were shown.

Influence of substrate material on spectral properties and thermal quenching of photoluminescence of silicon vacancy colour centres in diamond thin films

Abstract Nanocrystalline diamond films with bright photoluminescence of silicon-vacancy colour centres have been grown using a microwave plasma enhanced CVD technique. The influence of substrate material (quartz, Al2O3, Mo and Si) on a reproducible fabrication of diamond thin films with Si-V optical centres is presented. Film quality and morphology are characterized by Raman spectroscopy and SEM technique. SEM shows well faceted diamond grains with sizes from 170 to 300 nm. The diamond peak is confirmed in Raman spectra for all samples. In the case of the quartz substrate, a redshift of the diamond peak is observed (≈3.5 cm−1) due to tension in the diamond film. The steady-state photoluminescence intensity was measured in the temperature range from 11 K to 300 K. All spectra consist of a broad emission band with a maximum near 600 nm and of a sharp zero phonon line in the vicinity of 738 nm corresponding to Si-V centres that is accompanied with a phonon sideband peaking at 757 nm. Activation energies for the thermal quenching of Si-V centre photoluminescence were determined and the effect of the substrate on photoluminescence properties is discussed too.

Uptake and intracellular accumulation of diamond nanoparticles – a metabolic and cytotoxic study

Diamond nanoparticles, known as nanodiamonds (NDs), possess several medically significant properties. Having a tailorable and easily accessible surface gives them great potential for use in sensing and imaging applications and as a component of cell growth scaffolds. In this work we investigate in vitro interactions of human osteoblast-like SAOS-2 cells with four different groups of NDs, namely high-pressure high-temperature (HPHT) NDs (diameter 18–210 nm, oxygen-terminated), photoluminescent HPHT NDs (diameter 40 nm, oxygen-terminated), detonation NDs (diameter 5 nm, H-terminated), and the same detonation NDs further oxidized by annealing at 450 °C. The influence of the NDs on cell viability and cell count was measured by the mitochondrial metabolic activity test and by counting cells with stained nuclei. The interaction of NDs with cells was monitored by phase contrast live-cell imaging in real time. For both types of oxygen-terminated HPHT NDs, the cell viability and the cell number remained almost the same for concentrations up to 100 µg/mL within the whole range of ND diameters tested. The uptake of hydrogen-terminated detonation NDs caused the viability and the cell number to decrease by 80–85%. The oxidation of the NDs hindered the decrease, but on day 7, a further decrease was observed. While the O-terminated NDs showed mechanical obstruction of cells by agglomerates preventing cell adhesion, migration and division, the H-terminated detonation NDs exhibited rapid penetration into the cells from the beginning of the cultivation period, and also rapid cell congestion and a rapid reduction in viability. These findings are discussed with reference to relevant properties of NDs such as surface chemical bonds, zeta potential and nanoparticle types.