[en] For a few years now, it has been possible to dope GaN layers using molecular beam epitaxy (MBE) growth. This aims to use the wide band gap semiconductors as hosts to rare earth ions and exploit the sharp emission lines from atomic shell transitions. It was shown that the whole visible spectrum can be covered by addressing different exited states of various rare earth ions. It is also suspected that as in some systems like Si(nano)/SiO₂, the energy coupling could involve defects. In this work, we carry out TEM and HREM analysis on MBE doped GaN layers grown on metal organic chemical vapour deposition (MOCVD) GaN templates. Er concentrations of 1, 6, and 16 at.% were subsequently measured by wavelength dispersive X-ray (WDX) in an electron probe. We discuss the results on the spatial distribution of the rare earth atoms at a nanometer scale

[en] Thulium ions were implanted into metal organic chemical vapour deposition (MOCVD) grown GaN films with different fluences at implantation temperatures of 20, 400 and 500 deg. C. Subsequent annealing of the samples was performed in a rapid thermal annealing apparatus. The lattice damage introduced by the implantation and the effect of post-implant annealing were investigated with the Rutherford backscattering (RBS)/channelling technique. We observe that implantation at 500 deg. C considerably reduces the induced lattice damage and increases the amorphisation threshold. The lattice-site location of the implanted ions was determined by performing detailed channelling measurements for the <0 0 0 1> and <1 0 1-bar1> crystal directions. The results show that Tm ions mainly occupy substitutional Ga-sites directly after implantation and after annealing. The optical properties of the ion-implanted GaN films have been studied by room temperature cathodoluminescence (CL) measurements. Well-defined emission due to intra-4f shell transitions of the Tm³⁺ ions are observed in the blue spectral range at 477 nm and in the near infra-red (IR) at 804 nm

[en] Europium was implanted into GaN through a 10 nm thick epitaxially grown AlN layer that protects the GaN surface during the implantation and also serves as a capping layer during the subsequent furnace annealing. Employing this AlN layer prevents the formation of an amorphous surface layer during the implantation. Furthermore, no dissociation of the crystal was observed by Rutherford backscattering and channeling measurements for annealing temperatures up to 1300 deg. C. Remarkably, the intensity of the Eu related luminescence, as measured by cathodoluminescence at room temperature, increases by one order of magnitude within the studied annealing range between 1100 and 1300 deg. C

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[en] CdSe nanocrystals (NCs) are synthesized by the single source precursor thermal method. The use of a temperature ramp allows to obtain faster elaboration and smaller nano-particles in size. A cross-disciplinary study between chemical analyses and physical techniques provides consistent data for these small size NCs. Joint mass spectroscopy, transmission electron microscopy and optical spectrometry techniques give a coherent picture about average size and size dispersion of the NCs, as well as their optical spectral response in correlation with their size via quantum confinement effects.