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While dielectric/metal/dielectric (DMD) multilayer thin films have raised considerable interest as transparent and conductive electrodes in various optoelectronic devices, the knowledge of optical characteristics of thin metallic layers integrated in such structures is still rather approximate. The multispectral surface plasmon resonance characterization approach described in this work precisely aims at providing a rigorous methodology able to accurately determine the optical constants of ultra-thin metallic films. As a practical example, the refractive index and extinction dispersion curves of 8 to 25 nm-thick silver layers have been investigated. As a result, their extreme dependence on the layer thickness is highlighted, in particular in a thickness range close to the critical threshold value (~10nm) where the silver film becomes continuous and its electrical conductance/optical transmittance ratio particularly interesting. To check the validity of the revisited Ag layers constant dispersion curves deduced from this study, they were introduced into a commercial optical model software to simulate the behavior of various optoelectronic building blocks from the simplest ones (DMD electrodes) to much more complex structures [full organic light emitting device (OLED) stacks]. As a result, a much better prediction of the emission spectrum profile as well as the angular emission pattern of top-emitting OLEDs is obtained. On this basis, it is also shown how a redesign of the top encapsulation thin film of OLEDs is necessary to better take benefit from the advanced DMD electrode. These results should particularly interest the micro-OLED display field where bright and directive single color pixel emission is required. [ABSTRACT FROM AUTHOR]

Germanium nanocrystals were prepared by a nanocluster source and characterized by photoluminescence and spectroscopic photometry methods. The optical measurements were carried out in order to estimate the effective bandgap of the Ge nanocrystals. Both Mie theory and the quantum confinement theory were applied to interpret the extracted absorption data. We found that the quantum confinement theory enables to explain the nanocrystal size and the host matrix dependence of the nanocrystal bandgap. On the other hand, the photoluminescence measurements have not allowed to confirm the bandgap evaluated from absorption data. This is explained as due to the dominant effect of the recombination at the nanocrystals surface. [ABSTRACT FROM AUTHOR]

Copper nanoparticles (NPs) were synthesized by inert-gas condensation of a sputtered metallic vapor using a dedicated commercial reactor. By controlling the time of residence of NPs in the carrier gas phase via the tuning of the collision path length, Cu NPs were produced. They exhibit various and well controlled diameters (3–10 nm) and a relatively narrow size dispersion. On the basis of these experimental results, a detailed modeling of NP nucleation and growth based on the classical nucleation theory was developed. It takes into account the peculiar geometry and thermal profile of the NP reactor. The simulated curves, calculated by a MATLAB® program developed for that purpose, exhibit a good qualitative agreement with experiment. Moreover, they highlight the role of process parameters and the strong influence of the reactor temperature profile on the NP size distribution. In the future, such calculations could be used for the optimization of the NP source design in order to increase its efficiency and reproducibility. [ABSTRACT FROM AUTHOR]

Presents a study that examined calcium fluoride thin films deposited on various substrates by radio frequency sputtering of a hot-pressed calcium-fluoride target in a pure argon plasma. Use of load-locked sputtering equipment; Background on thin films of magnesium fluoride and alkaline earth metal fluorides; Deposition rate of calcium fluoride films.

In this study, the synthesis of Ge nanoparticles by a physical vapour deposition (PVD) nanocluster source has been investigated. We typically obtain Ge nanoparticles with a mean diameter between 4 and 9 nm. The microstructure of Ge nanoparticles was widely studied by high resolution transmission electron microscopy, energy filtered transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The main result is the capability of the PVD process to synthesize well crystallized Ge nanocrystals at room temperature and without any post thermal annealing. It was found from Raman analysis that these room temperature deposited nanoparticles are composed of a Ge crystalline core and a sub-nm thick amorphous Ge shell. A low temperature annealing (450 °C) during 1 h under vacuum leads to the reorganization of the surface atoms while longer annealing seems to promote the formation of a Ge oxide shell around the nanoparticles. [ABSTRACT FROM AUTHOR]

Despite the technological importance of metal/Si multilayer structures in microelectronics, the interface reactions occurring during their preparation are not yet fully understood. In this work, the interface intermixing in Mo/Si multilayer coatings has been studied with respect to their preparation conditions. Various samples, prepared at room temperature with different Mo deposition rates (0.06–0.43  Å  s -1 ) and a constant Si rate, have been investigated by detailed TEM observations. Contrary to the Si-on-Mo interface where no evidence of chemical intermixing could be found, the Mo-on-Si interface presents a noticeable interface zone whose thickness was found to noticeably decrease (from 4.1 to 3.2  nm) when increasing the Mo deposition rate. Such intermixing phenomena correspond to diffusion mechanisms having coefficients ranging from 0.25  ×  10 -15 to 1.2  ×  10 -15   cm 2   s -1 at room temperature. By assuming a diffusion mechanism mainly driven by Mo–Si atomic exchanges to minimize the surface energy, the diffusion dependence with Mo deposition rate has been successfully simulated using a cellular automaton. A refined simulation including Mo cluster formation is also proposed to explain the scenario leading to the full crystallization of Mo layers. [ABSTRACT FROM AUTHOR]

We investigated the possibility of using physical vapour deposited Ge nanocrystals (NCs) in optoelectronic devices such as solar cells. We have prepared p-i-n heterojunctions based on p+-doped Si substrate/undoped Ge NCs/ZnO:Al layer stacks and their optoelectronic properties were characterised. Under light, the generation of photo-carriers from the Ge NCs themselves was demonstrated. The photovoltaic behaviour of the p-i-n structure was also highlighted, with a measured Voc of 224 mV compared to 580 mV in theory. The discrepancy between theory and experiment was discussed on the basis of TEM observations, optical and carrier generation measurements as well as modelling. [ABSTRACT FROM AUTHOR]

A technique to probe defects buried inside extreme ultraviolet (EUV) masks has been implemented using a dark-field microscopy detection setup. Specific samples have been fabricated to evaluate the sensitivity of this technique. They consist of silicon oxide gratings of a few nanometers height, coated with 40 layer pairs of molybdenum–silicon. We observed images with a good contrast on samples with defects as low as 3 nm. However, the imaging mechanism of scanning dark-field microscopy is not linear and can produce image distortions. Conditions of correct imaging have been analyzed, and simulations have been performed that show good agreement with the experimental data. This work opens the way for a better understanding of the capability of at-wavelength inspection technique for EUV mask. [ABSTRACT FROM AUTHOR]

Extreme ultraviolet lithography (EUVL) mask is a complex multilayer stack, fabricated with electron-beam lithography. Detailed understanding of the scattering events and energy loss mechanism of the electron beam within this stack is mandatory due to the high accuracy requirements of the fabrication process. Simulation of electron-beam lithography is performed incorporating the details of the mask material-stack and the metrological information of the final layout is quantified. The effect of the Mo–Si multilayer of the EUVL mask blank on the deposited energy in the resist film is investigated. Simulation of complex layout containing features of various sizes down to 100 nm reproduced experimental metrology trends on the fine features of the layout. [ABSTRACT FROM AUTHOR]