This study is focused on the properties of the diamond lattice before and after implantation. The diamond lattices with nitrogen-vacancy centres have very exciting properties and they can be used in a plethora of applications from quantum sensing to biomarkers. Characteristic transmission, scattering and photoluminescence of diamond lattice with nitrogen-vacancy centres (NV-) were studied through different techniques at different temperatures. The luminescence of the synthesised diamonds was studied at a 532nm excitation wavelength and recorded in the range of 500-1100nm. Since its intensity decreases with decreasing the number of nitrogen-vacancy centres. Also, we analysed the luminescence depend on the functional groups attached to the diamond surface.
Raman spectroscopy studies provide interesting results about the phonon confinement effect, structure composition and homogeneity of the material and information about the functional groups attached above the diamond surface. Raman spectra depend on the structure, purity, sp3/sp2 ratio, crystal size and surface chemistry. With increasing sp3 carbon content the intensity of the diamond peak increases, while the D-band in the Raman spectra weakens. Also, we analysed the shifts in the energy and linewidth of the diamond peak in the Raman spectra.
The recent development of novel super-resolution imaging techniques coincides with the efforts to synthesize optically bright and stable biomarkers. In the future, we can use the differently doped nanodiamond fluorophores as biomarkers for sensing and bioimaging.
In this work we study Ge structures grown on silicon substrates. We use photoluminescence and photoreflectance to determine both direct and indirect gap of Ge under tensile strain. The strain is induced by growing the Ge on an InGaAs buffer layer with variable In content. The band energy levels are modeled by a 30 band k·p model based on first principles calculations. Characterization techniques show very good agreement with the calculated energy values.
Here we describe a uniform diameter, direct bandgap Ge1-xSnx alloy nanowires, with a Sn incorporation up to 9%, the fabricated through a conventional catalytic bottom-up growth paradigm employing innovative catalysts and precursors. Optical characterization by means of temperature dependent photoluminescence is used to identify transition point from indirect to direct badgap of GeSn nanowires.
In this work we study Ge transistor structures grown on silicon substrate. We use photoluminescence to determine the band gap of Ge under tensile strain. The strain is induced by growing Ge on an InGaAs buffer layer with variable In content. The band energy levels are modeled using a 30 band k·p model based on first principles calculations. Photoluminescence measurements show a reasonable correspondence with calculated values of the band energies.
Tunable tensile-strained germanium (epsilon-Ge) thin films on GaAs and heterogeneously integrated on silicon (Si) have been demonstrated using graded III-V buffer architectures grown by molecular beam epitaxy (MBE). epsilon-Ge epilayers with tunable strain from 0% to 1.95% on GaAs and 0% to 1.11% on Si were realized utilizing MBE. The detailed structural, morphological, band alignment and optical properties of these highly tensile-strained Ge materials were characterized to establish a pathway for wavelength-tunable laser emission from 1.55 μm to 2.1 μm. High-resolution X-ray analysis confirmed pseudomorphic epsilon-Ge epitaxy in which the amount of strain varied linearly as a function of indium alloy composition in the InxGa1-xAs buffer. Cross-sectional transmission electron microscopic analysis demonstrated a sharp heterointerface between the epsilon-Ge and the InxGa1-xAs layer and confirmed the strain state of the epsilon-Ge epilayer. Lowtemperature micro-photoluminescence measurements confirmed both direct and indirect bandgap radiative recombination between the Γ and L valleys of Ge to the light-hole valence band, with L-lh bandgaps of 0.68 eV and 0.65 eV demonstrated for the 0.82% and 1.11% epsilon-Ge on Si, respectively. The highly epsilon-Ge exhibited a direct bandgap, and wavelength-tunable emission was observed for all samples on both GaAs and Si. Successful heterogeneous integration of tunable epsilon-Ge quantum wells on Si paves the way for the implementation of monolithic heterogeneous devices on Si.