The structure and photoluminescence of erbium-doped nanocrystalline silicon thin films produced by reactive magnetron sputtering

We have produced and studied undoped and erbium-doped nanocrystalline silicon thin films in order to evaluate the erbium influence on the film microstructure and how this correlates with the photoluminescence properties. Films were grown by reactive RF sputtering. For the doped films metallic erbium was added to the c-Si target. The structural parameters and the chemical composition of the different samples were investigated by X-ray in the grazing incidence geometry, Raman spectroscopy, ellipsometry and Rutherford Back Scattering. The effect of the nc-Si/SiOx matrix ,i.e., nc-Si volume fraction and the presence of SiO and/or SiO2 phases, on the erbium photoluminescence efficiency is discussed.(undefined

Photoluminescence of nc-Si:Er thin films obtained by physical and chemical vapour deposition techniques: The effects os microstructure and chemical composition

Erbium doped nanocrystalline silicon (nc-Si:Er) thin films were produced by reactive magnetron rf sputtering and by Er ion implantation into chemical vapor deposited Si films. The structure and chemical composition of films obtained by the two approaches were studied by micro-Raman scattering, spectroscopic ellipsometry and Rutherford backscattering techniques. Variation of deposition parameters was used to deposit films with different crystalline fraction and crystallite size. Photoluminescence measurements revealed a correlation between film microstructure and the Er3+ photoluminescence efficiency.FCT Project POCTI/CTM/39395/2001INTAS Project #03-51-648

Polycrystalline Diamond Characterisations for High End Technologies

Characterisations of polycrystalline diamond (PCD) coatings have routinely been done over the past three decades of diamond research, but there is less number of reports on some of its very unique properties. For example, diamond is the hardest known material and, in probing such hard surfaces with any indenter tip, it may lead to damage of the instrument. Due to such chances of experimental accidents, researchers have performed very few attempts in evaluating the mechanical properties of PCDs. In the present work, some of these very special properties of diamond that are less reported in the literature are being re-investigated. PCDs were characterised by photoluminescence (PL), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscope (TEM), and X-ray diffraction (XRD) techniques. The diamond surface was also polished to bring the as-grown micron level of surface roughness (detrimental for wear application) down to few hundreds of nanometer. The tribological properties of such polished and smooth surfaces were found to be appropriate for wear protective coating application. This chapter revisits some of the unreported issues in the synthesis and characterisation of PCD coatings grown on Si wafer by the innovative 915 MHz microwave plasma chemical vapour deposition (MPCVD) technique

Nanocrystal

We focused on cutting-edge science and technology of Nanocrystals in this book. "Nanocrystal" is expected to lead to the creation of new materials with revolutionary properties and functions. It will open up fresh possibilities for the solution to the environmental problems and energy problems. We wish that this book contributes to bequeath a beautiful environment and valuable resources to subsequent generations

Confining Metal-Halide Perovskites in Nanoporous Thin Films

Controlling size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum confined, inexpensive, solution derived metal halide perovskites offer narrow band, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, green-emitting materials cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability as the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy X-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next generation photonic devices

Visible and infrared photoluminescence from erbium-doped silicon nanocrystals produced by rf sputtering

Erbium-doped low-dimensional Si films with different microstructures were deposited by reactive magnetron sputtering on glass substrates by varying the hydrogen flow rate during deposition. Amorphous, micro- and nanocrystalline samples, consisting of Si nanocrystalls embedded in silicon-based matrices with different structures, were achieved with optical properties in the visible and IR depending on nanocrystalline fraction and matrix structure and chemical composition. Structural characterization was performed by X-ray diffraction in the grazing incidence geometry and Raman spectroscopy. The chemical composition was studied using RBS/ERD techniques. Spectroscopic ellipsometry was combined with the previous techniques to further re-solve the film microstructure and composition. In particular, the distribution along the film thickness of the volume fractions of nanocrystalline/amorphous silicon and SiOx phases has been obtained. In this contribution we discuss visible and infrared photoluminescence as a function of sample microstructure and of the oxygen/ hydrogen concentration ratio present in the matrix.FCT (POCTI/CTM/39395)INTAS Project #03-51-648

Nanostructured Si/SiO2 Quantum Wells

The motivation for developing light-emitting devices on an indirect transition semiconductor such as silicon has been widely discussed for Si/SiO2 nanostructures. In this chapter, we report on the fabrication of Si/SiO2 quantum-confined amorphous nanostructured films and their optical properties. The Si/SiO2 nanostructures comprising amorphous Si, SiO2, and Si/SiO2 multilayers are grown using ultrahigh vacuum radio frequency magnetron sputtering. Optical absorption coefficients of the Si/SiO2 nanostructures are evaluated with regard to tentative integrated Si thicknesses. Optical energy band gaps of the Si/SiO2 multilayer films are in accordance with the effective mass theory and described as E0 = 1.61 + 0.75d−2 eV at the Si layer-integrated thicknesses ranging from 0.5 to 6 nm. Quantum confinement effects in the Si/SiO2 nanostructures are inferred from optical transmittance and reflectance spectra. The rapid-thermal-annealed Si/SiO2 multilayer films demonstrate the intensified photoluminescence at ~1.45 eV due to the formation of nanocrystalline silicon. The temperature dependence of the nanocrystalline luminescence intensity shows the nonmonotonous behavior which is interpreted invoking the Kapoor model

Large-Scale Synthesis of Colloidal Si Nanocrystals and Their Helium Plasma Processing into Spin-On, Carbon-Free Nanocrystalline Si Films

This paper describes a simple approach to the large-scale synthesis of colloidal Si nanocrystals and their processing into spin-on carbon-free nanocrystalline Si films. The synthesized silicon nanoparticles are capped with decene, dispersed in hexane, and deposited on silicon substrates. The deposited films are exposed to nonoxidizing room-temperature He plasma to remove the organic ligands without adversely affecting the silicon nanoparticles to form crack-free thin films. We further show that the reactive ion etching rate in these films is 1.87 times faster than that for single-crystalline Si, consistent with a simple geometric argument that accounts for the nanoscale roughness caused by the nanoparticle shape