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Abstract

The change of optical and structural properties of Ge nanoclusters in ZrO2 matrix have been investigated by spectroscopic ellipsometry versus annealing temperatures. Radio-frequency top-down magnetron sputtering approach was used to produce the samples of different types, i.e. single-layers of pure Ge, pure ZrO2 and Ge-rich-ZrO2 as well as multi-layers stacked of 40 periods of 5-nm-Ge-rich-ZrO2 layers alternated by 5-nm-ZrO2 ones. Germanium nanoclusters in ZrO2 host were formed by rapid-thermal annealing at 600-800 ∘C during 30 s in nitrogen atmosphere. Reference optical properties for pure ZrO2 and pure Ge have been extracted using single-layer samples. As-deposited multi-layer structures can be perfectly modeled using the effective medium theory. However, annealed multi-layers demonstrated a significant diffusion of elements that was confirmed by medium energy ion scattering measurements. This fact prevents fitting of such annealed structure either by homogeneous or by periodic multi-layer models.

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... Both surface topography 22 and in-depth microstructure 6 have been imaged, revealing a sponge-like structure with voids in many cases, e.g. for 50-300-keV self-ion bombardment 22 . Structural properties such as the size of crystals or the degree of amorphization can also be determined by optical methods 6,7,9,23 . Rutherford backscattering spectrometry (RBS) allows to reveal the degree of crystallinity, crystal structure (when combined with channeling) and the depth distribution of elements. ...
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... processor. So, Ge-NPs are formed at about 310 °C 30 in indium tin oxide (ITO), in the range of 800-1000 °C 31,32 in Al 2 O 3 or above 700 °C in ZrO 2 matrices 33 . Structures based on Ge-NPs deposited on glass or flexible substrates can be obtained using or not a thermal treatment during the deposition process [34][35][36] . ...
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In this paper spectroscopic ellipsometry is used to determine the dielectric function (refractive index) of three bulk materials: cubic zirconia (c-ZrO2), cubic magnesium oxide (c-MgO) and amorphous (vitreous) arsenic sulfide (a-As2S3) from 130 nm in the vacuum ultraviolet to 33 μ in the infrared. This work utilizes the very wide spectral coverage and sensitivity of modern spectroscopic ellipsometers to determine bulk optical properties of these materials over a wide spectral range. Ellipsometric psi and delta data at multiple angles of incidence were fit to extract the dielectric function of each material. Intensity transmission data were also acquired at normal incidence and fit simultaneously with the psi and delta data when possible. Including transmission data in the analysis greatly improves sensitivity to small absorption features. The ellipsometric delta data were very sensitive to surface quality. Therefore, it was very important to include surface roughness in all models to avoid non-physical absorption artifacts in the optical constants. The experimental data were fit in the transparent spectral range to determine the real part of the dielectric function and the surface roughness. Fixing the surface roughness then allows the optical constants to be determined by a direct fit for ε1 and ε2 at each measured psi-delta data point. Combinations of multiple Gaussian, Lorentz, and Tauc–Lorentz dispersion functions were then used to fit the experimental data. The different shapes of each function allow fitting a wide range of absorption features throughout the ultraviolet, visible and infrared spectral ranges. Combining multiple oscillator types provides a very flexible approach to fitting optical constants over a wide spectral range while simultaneously enforcing Kramers–Kronig consistency in the fitted optical constants.
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We have observed a unique damage structure, which forms within the amorphous phase, in ion‐implanted Ge above a certain ion dose. This structure, which represents a drastic alteration of the near‐surface morphology, is responsible for the adsorption of large quantities of C and O onto the surface of the implanted area. Results are presented of a systematic study of this effect and possible mechanisms for its information are discussed. Ion implantation conditions desirable for device applications are established and deleterious effects due to the presence of this damage upon both solid‐ and liquid‐phase epitaxial growth of the implanted layers are discussed.
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An in situ investigation of the growth of rf glow‐discharge amorphous germanium (a‐Ge:H) and silicon (a‐Si:H) films using fast real‐time spectroscopic phase‐modulated elipsometry is presented. The influence of the conditions of preparation is studied in both cases. The same behavior is obtained in a‐Ge:H and a‐Si:H films deposited in similar conditions. In particular, the initial stage of the growth can be described by a nucleation process in both cases, whatever the conditions of preparation. The incomplete coalescence of the nuclei leads to the formation of a surface roughness on a ∼40‐Å scale which is observed during film growth. In comparing real‐time ellipsometry measurements performed at different wavelengths, a correlation between the internuclei distance and the thickness of the surface roughness is observed. An enhancement of the surface mobility of the reactive species due to an increase of substrate temperature and/or ion‐bombardment energy results in an increase in the density of the nucleation centers. The influence of ion bombardment and gas pressure is discussed by comparing the growth of a‐Si:H film deposited in a rf discharge to the results of previous studies using a low‐pressure multipole plasma.
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The band gap and optical properties (dielectric functions and optical constants) of Ge thin films with various thicknesses below 50 nm, which were synthesized with electron beam evaporation technique, have been determined using spectroscopic ellipsometry and UV-visible spectrophotometry. The optical properties are well described with the Forouhi–Bloomer model. Both the band gap and optical properties show a strong dependence on the film thickness. For film thickness smaller than ∼10 nm , a band gap expansion is observed as compared to bulk crystalline Ge, which is attributed to the one-dimensional quantum confinement effect. However, a band gap reduction was observed for thickness larger than ∼10 nm , which is explained in terms of the amorphous effect in the Ge layers.
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Since the seventies a large number of computer methods have been developed for data analysis in Rutherford backscattering spectrometry (RBS). A short review of published computer methods for ion scattering is presented. The majority of programs can be divided into two categories: the interactive spectrum synthesis and the spectrum analysis codes. In this paper recent trends and problems in the area of spectrum simulation are presented. I demonstrate the main methods and approaches on our RBX computer program. The program can use any particle-target combination and beam energy between 100 keV and 10 MeV. The calculations and fitting methods of non-Rutherford scattering cross section are included. The contributions from electronic screening, the corrected Bohr straggling and the geometrical straggling are discussed. The useful techniques for extracting an accurate depth-concentration profile directly from RBS or ERDA spectrum are discussed. Some examples of the discussed methods are also given.
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A threshold-shifting, single transistor memory structure with fast read and write times and long retention time is described. The structure consists of a silicon field-effect transistor with nano-crystals of germanium or silicon placed in the gate oxide in close proximity of the inversion surface. Electron charge is stored in these isolated 2-5 nm size nano-crystals which are separated from each other by greater than 5 nm of SiO<sub>2</sub> and from the inversion layer of the substrate surface by less than 5 nm of SiO<sub>2</sub>. Direct tunneling of charge from the inversion layer and its storage in the nano-crystal causes a shift in the threshold voltage which is detected via current sensing. The nano-crystals are formed using implantation and annealing or using direct deposition of the distributed floating gate region. Threshold shift of 0.3 V is obtained in Ge-implanted devices with 2 nm of SiO<sub>2</sub> injection layer by a 4 V write pulse of 300 ns duration. The nano-crystal memories achieve improved programming characteristics as a nonvolatile memory as well as simplicity of the single poly-Si-gate process. The V<sub>T</sub> window is scarcely degraded after greater than 10<sup>9</sup> write/erase cycles or greater than 10<sup>5</sup> s retention time. Nano-crystal memories are promising for nonvolatile memory applications