The optical and structural properties of Er-doped Silicon oxide based thin films elaborated by RF magnetron sputtering were investigated as a function of annealing treatment. Atom Probe Tomography and Transmission electron microscopy were used to analyze the position of rare-earth ions as well as the phase separation occurring in the layer in order to provide a complete picture of the nanostructure. The emission properties of Er3+ ions were investigated using cathodoluminescence (CL) spectroscopy. The high doping level of Er ions in silicon oxide matrix leads to a phase decomposition of pure SiO2 and Er2Si2O7 phases with a nanostructure which is influenced by the annealing treatment. It results on different emission intensities in ultraviolet or infrared ranges. The relationship between the nanostructuration observed and the optical properties is discussed in regards of annealing treatment.

In this chapter, we will present a digest of the main materials science aspects of the controlled fabrication of 2D arrays of semiconducting (Si, Ge) nanocrystals (NCs) in metal oxide high-κ dielectric layers by using two promising techniques, namely magnetron-sputtering and Ultra Low Energy-Ion Beam Synthesis. In particular, the phase separation process as well as the problems related to humidity penetration or controlled oxidation processes are among the discussed topics. The different state-of-the-art tools for structural characterization will also be described. Finally, the associated electrical characterizations will be presented in order to evaluate the potential of such nanocomposite metal oxide layers for NC memory applications.

Many applications as optical spectroscopy, photothermal therapy, photovoltaics, or photocatalysis take advantage of the localized surface plasmon resonance of noble metal nanoparticles (NPs). Among them, AgNPs are multifunctional nano‐objects that can be used not only as efficient plasmonic antennae but also as electron reservoirs for charge transfer or ion reservoirs with strong biocide activity. Herein, the 10 years’ efforts on the safe‐by‐design synthesis of multifunctional nanocomposites consisting of 3D patterns of small AgNPs embedded in dielectrics are presented by coupling low‐energy ion implantation and stencil masking techniques. Their multifunctional coupling with different objects deposited on top of the dielectric surface is also presented through three examples. The twofold role of this single plane of AgNPs as the embedded plasmonic enhancer and charge carrier reservoir is first tested on few‐layer graphene deposited in specific areas at a controlled nanometer distance from the AgNPs. These buried AgNPs are also coupled to light emitters coimplanted in the dielectric matrix in specific regions, showing light emission enhancement. Finally, these AgNPs also provide an efficient biocide activity on green algae when submerged in water, with the amount of Ag + release simply controlled by the thickness of the silica cover layer.

Down converter SiN x :Yb 3+ /SiN x :Tb 3+ multilayers are deposited by reactive magnetron cosputtering with the objective of optimizing the interaction distance between Tb 3+ and Yb 3+ ions to favor a better light management in Si solar cells. Those Si‐based multilayers are developed to be compatible with the Si photovoltaic technology. The deposition parameters are optimized to enhance the emission of the Yb 3+ ions in the IR region. The emission efficiency of such multilayer structure is compared with a mixed RE SiN x :Tb 3+ ‐Yb 3+ layer evidencing a gain resulting from a better management of the Tb 3+ and Yb 3+ ions distance. At the end, we integrate the growth of such a multilayer in an industrial Si solar cell process and demonstrate the existence of a frequency conversion effect that is promising for the future increase of the Si solar cell efficiency.

2D networks of Si and Ag nanocrystals have been fabricated in the same SiO2 matrix by Ultra-Low-Energy Ion-Beam-Synthesis. Our synthesis scheme differs from a simple sequential ion implantation and its key point is the control of the matrix integrity through an appropriate intermediate thermal annealing. Si nanocrystal layer is synthesised first due to high thermal budget required for nucleation, while the second Ag nanocrystal plane is formed during a subsequent implantation due to the high diffusivity of Ag in silica. The aim of this work is to show how it is possible to overcome the limitation related to ion mixing and implantation damage to obtain double layers of Si-NCs and Ag-NCs with controlled characteristics. For this, we take advantage of annealing under slight oxidizing ambient to control the oxidation of Si-NCs and the Si excess in the matrix. The nanocrystal characteristics and in particular their position and size can be adjusted thanks to a compromise between the implantation energy, the implanted dose for both Si and Ag ions and the intermediate annealing conditions (atmosphere, temperature and duration).

We report an uncommon study of the insertion of distributions of both volume fraction and depolarization factors in the modeling of the plasmonic properties of implanted Ag nanoparticles (Ag-NPs) in a SiO2 layer when using spectroscopic ellipsometry (SE) characterization. The Ag-NPs were embedded in the SiO2 matrix by Ag+ ion implantation at various doses of 0.5 × 1016, 1 × 1016, 2 × 1016, and 5 × 1016 ions cm−2. The formation of the Ag-NPs in a host matrix of SiO2 was controlled by transmission electron microscopy (TEM). The Ag-NPs are self-organized in the layer, and their mean radius ranges between 2 and 20 nm. The optical properties of layers were extracted by modeling the SE parameters by taking into account the depth profile concentration of Ag-NPs. The mixture of SiO2 and Ag-NP inclusions was modeled as an effective medium according to the shape distributed effective medium theory (SDEMT). In addition to the optical responses, it is shown that this model enables the explanation of the impact of NP shape distribution on the plasmon band and provides precious information about the NP shape characteristics. A good agreement was obtained between ellipsometry and TEM results. The distribution of the volume fraction in the film was found to lead to a gradient of effective dielectric function which was determined by the SDEMT model. The effective dielectric function reveals distinct Ag plasmon resonance varying as the Ag+ ions dose is varied. The real part of the dielectric function shows a significant variation around the plasmon resonance in accordance with the Kramers-Kronig equations. All determined optical parameters by SDEMT are provided and discussed. We highlight that SE combined with SDEMT calculations can be considered as a reliable tool for the determination of the NP shape and volume fraction distributions without the need of TEM.

Hybrid systems based on silicon and silver nanocrystals (Si-NCs and Ag-NCs) are of considerable interest in photon conversion solar cells. Due to their plasmonic properties, Ag-NCs strongly increase the photoluminescence emission intensity of Si-NCs located in their vicinity, allowing, in principle, to solve the problem of their low emission yield. In this work, we have elaborated 2D networks of Ag-NCs and amorphous Si nanoparticles in a controlled way by using Ultra-Low-Energy Ion-Beam-Synthesis. In the proposed synthesis scheme, a 2D layer of Si-NCs is first obtained by implanting Si+ ions at ultra low energy (from 1 to 3 keV) in a SiO2 layer with subsequent high temperature thermal annealing. Then, Ag+ ions are implanted in the same matrix at energies between 3 and 10 keV and crystalline Ag-NCs are formed during the implantation step. Several configurations with either 2D arrays or a large band of Ag-NCs have been obtained following the Ag+ implantation energy. Enhancement of the PL emission from Si nanostructures, which is related to the presence of Ag-NCs, has been observed under specific arrangement of the two embedded subsystems. In this type of synthesis, a combination of physical phenomena including ion mixing, implantation damage, point defect, and thermal diffusion has been taken into account in order to explain and thus control the structural and the optical characteristics of the system.

Tb3+–Yb3+ co-doped SiNx down-conversion layers compatible with silicon Photovoltaic Technology were prepared by reactive magnetron co-sputtering. Efficient sensitization of Tb3+ ions through a SiNx host matrix and cooperative energy transfer between Tb3+ and Yb3+ ions were evidenced as driving mechanisms of the down-conversion process. In this paper, the film composition and microstructure are investigated alongside their optical properties, with the aim of maximizing the rare earth ions incorporation and emission efficiency. An optimized layer achieving the highest Yb3+ emission intensity was obtained by reactive magnetron co-sputtering in a nitride rich atmosphere for 1.2 W/cm2 and 0.15 W/cm2 power density applied on the Tb and Yb targets, respectively. It was determined that depositing at 200 °C and annealing at 850 °C lead to comparable Yb3+ emission intensity than depositing at 500 °C and annealing at 600 °C, which is promising for applications toward silicon solar cells.

Nowadays, silicon-based nanostructures attract great attention due to their wide functionality. However, in spite of a lot of efforts forwarded on the investigation of Si-based nanomaterials, additional research is still required in order to design their optical properties for optoelectronic, photovoltaic or memory applications. The structural disorder is one of the main issues that may reduce the efficiency of device operation in the applications area of every nanomaterial. Undoped and rare-earth (RE) doped Si-rich-SiO2 (SiOx) composite films and multilayers were recently investigated [1-3]. An efficient RE emission was achieved in Er- and, later, Nd-doped SRSO films due to an interaction of RE ions with Si-nanoclusters (Si-ncs). Although, a multilayer (ML) approach offers a precise control of Si-ncs distribution via a tuning of SRSO thickness, RE-doped SRSO-based MLs are not well addressed. This work presents the benefits of ML approach to achieve high efficiency and to control RE emission from Nd-doped SiOx/SiNx-based MLs grown by RF magnetron sputtering. Their properties were studied by means of XRD, TEM, PL and PL excitation methods versus deposition conditions, annealing treatment and ML design (doping, thickness of alternated sublayers (silicon oxide, nitride)). In each type of ML structures, either one or both sublayers were doped with Nd ions to investigate the effect of selective or full doping on PL emission. The results will be summarized and compared with those of Nd-doped SiOx/SiO2 MLs. It will be showed that comparable Nd PL emission can be obtained for both types of ML structures. Besides, fabrication approach allowed the PL emission to be achieved from as-grown samples. However, the highest Nd PL intensity was obtained after an annealing at about 700°C in nitrogen flow, whereas the formation of crystallized Si-ncs occurs at 1000-1100°C. The mechanism of Nd ions' excitation (i.e. an interaction with Si-ncs as well as with matrix defects, if any) will be discussed in details based on PL excitation spectra and PL life-time data. These results reveal potential photonic applications of Nd-doped MLs. This work was supported by French National Agency (ANR) through DAPHNES project. 1. Pratibha Nalini R., Khomenkova L., Debieu O., Cardin J., Dufour C., Carrada M., Gourbilleau F.,Nanoscale Research Letters, 7, 124 (2012). 2. Cueff S., Labbé C., Khomenkova L., Jambois O., Pellegrino P., Garrido B., Frilay C., Rizk R., Mater. Sci. Eng. B. 177, 725 (2012). 3. E. Talbot, R. Lardé, P. Pareige, L. Khomenkova, K. Hijazi, F. Gourbilleau, Nanoscale research letters 8, p.39 (8 pages) (2013).

Semiconductor nanowires have an excellent ability to trap, guide, scatter or absorb light thanks to the presence of specific resonant optical modes. The electromagnetic field-enhancement associated to such effects can be used to modify the luminescence of emitters positioned in the vicinity of the nanowire, as to plasmonic nano-antennas. We show that the photoluminescence of silicon nanocrystals embedded in silica can be enhanced by a factor of about 3 in the presence of a silicon nanowire on the silica surface. This could be the basis of a promising CMOS-compatible process to improve silicon-based light emitting devices. 2D maps of the nanocrystal photoluminescence exhibit different behaviors as function of laser polarization and can be related to the electric field intensity distribution in the nanowire near-field, where the Si-NCs layer is located. Preliminary results of nonlinear optics for imaging the local electric field are presented.

The structure and interface states of thin nanocomposite layers containing Si nanocrystals embedded in an amorphous nitride matrix have been analyzed by Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). The Si 2p core-level spectrum of the nanocomposite layer was deconvoluted by using five Gaussian-Lorentzian contributions corresponding to the different nitride states of Si. It was shown that the Si-ncs/Si3N4 interfaces formed during annealing are composed of a high density of Si2+ subnitrides. These subnitrides are more likely to be responsible for the shoulder at 494 cm(-1) on the Raman spectra. Considering the proportion of Si2+ subnitrides with respect to Si-0 states, an abrupt transition from the crystalline to the amorphous phase due to Si-2=N-Si bridge bonds is suggested.

We report on a comparative study between dielectric functions of Si nanoparticles (Si-NPs) obtained from Bruggeman effective medium approximation (BEMA), Maxwell-Garnett (MG), and a modified Maxwell-Garnett (MMG) models. Unlike BEMA and MG, a size-distribution dependent dielectric function of Si-NPs is considered in the introduced MMG model. We show that the standard deviation σ of a size distribution can be evaluated by analyzing the imaginary part of the dielectric functions of Si-NPs extracted from BEMA and MMG. In order to demonstrate this, several samples composed of Si-NPs embedded in silicon-rich silicon nitride are investigated by spectroscopic ellipsometry over the photon energy range varying between 2 and 4 eV. Assuming a lognormal size distribution of the Si nanoparticles, it is evidenced that the parameter σ ranges between 1.15 and 1.35. The values of size dispersion deduced by this methodology are in good agreement with TEM observations.

We compare the morphology and optical response of plasmonic nanostructures produced by pulsed laser deposition, consisting of a 2D distribution of Ag nanoparticles exposed to air or buried under an amorphous Al2O3 layer whose thickness is tuned in the 0.5 to 14 nm range. We observe that the covering process leads to drastic changes in Ag content, which are interpreted in terms of sputtering of Ag atoms promoted by the incoming Al ions. This Ag sputtering process is avoided as soon as the nanoparticles are embedded under a subnanometer-thick layer of amorphous Al2O3. Meanwhile, the spectral position of the nanoparticles’ characteristic surface plasmon resonance, measured immediately after the film growth, is not significantly affected by the deposition of the covering layer. Nevertheless, the resonance band associated with uncovered Ag nanoparticles has vanished after 12 months, as a result of their oxidation. Embedding the nanoparticles under a subnanometer-thick layer of amorphous Al2O3 is enough to avoi...

Semiconductor nanowires have an excellent ability to trap, guide, scatter, or absorb light for specific morphology-dependent resonant optical modes. The electromagnetic field enhancement associated with these modes could be used to modify the luminescence of emitters positioned in the vicinity of the nanowire, in a way similar to plasmonic nanostructures. We show that the photoluminescence of a single plane of silicon nanocrystals in silica, positioned at about 3 nm below the surface, can be enhanced by a factor of 2 to 3 in the presence of a silicon nanowire antenna on the silica surface. This could be the basis of a promising fully complementary metal oxide semiconductor compatible process to improve silicon-based light emitting devices, despite a lower enhancement compared to plasmonic nanostructures. Two-dimensional photoluminescence maps recorded for different polarization configurations (incident electric field parallel or perpendicular to the nanowire axis) exhibit different behaviors and can be related to the electric field intensity distribution in the near-field region of the nanowire, where the active silicon nanocrystal layer is located.

Plasma Immersion Ion Implantation (PIII) is a promising alternative to beam line implantation to produce a single layer of nanocrystals (NCs) in the gate insulator of metal-oxide semiconductor devices. We report herein the fabrication of two-dimensional Si-NCs arrays in thin SiO2 films using PIII and rapid thermal annealing. The effect of plasma and implantation conditions on the structural properties of the NC layers is examined by transmission electron microscopy. A fine tuning of the NCs characteristics is possible by optimizing the oxide thickness, implantation energy, and dose. Electrical characterization revealed that the PIII-produced-Si NC structures are appealing for nonvolatile memories. (C) 2013 AIP Publishing LLC.