M. L. Thèye

Bio: M. L. Thèye is an academic researcher from Pierre-and-Marie-Curie University. The author has contributed to research in topics: Amorphous solid & Thin film. The author has an hindex of 12, co-authored 31 publications receiving 822 citations.

Investigation of the Optical Properties of Au by Means of Thin Semitransparent Films

Abstract: Both the real and imaginary parts of the dielectric constant of Au were accurately determined in the 0.5-6-eV range from measurements of the reflectance and transmittance of thin semitransparent films. The results obtained on well-crystallized films were in general agreement with previous data on bulk samples. They allowed a thorough analysis of the absorption spectrum of Au in terms of intra- and interband transitions. Deviations from the Drude theory were observed, and the values of the optical mass and relaxation time of the conduction electrons are discussed. The absorption edge was investigated very accurately. Further information on the absorption processes was also obtained by studying films with different crystallographic structures. In particular, the supplementary absorption often observed in Au below the absorption edge was shown to be due to impurities.

Structural, optical, and electrical characterization of improved amorphous hydrogenated germanium

Abstract: High‐quality amorphous hydrogenated germanium has been deposited using the diode rf glow discharge method out of a gas plasma of GeH4 and H2. The optical, electrical, and structural properties of this material have been extensively characterized. The optical and electrical properties are all consistent with material containing a low density of defect related states in the energy gap. In particular, this material has an ημτ=3.2×10−7 cm2/V, ratio of photocurrent to dark current of 1.3×10−1, and flux dependence of the photocurrent with γ=0.79 at 1.25 eV measured using photoconductivity, a μτ=4×10−8 cm2/V measured using time of flight, an Urbach energy of 51 meV and α at 0.7 eV of 8.3 cm−1 measured using photothermal deflection spectroscopy, a dangling bond spin density of 5×1016 cm−3 measured using electron spin resonance, photoluminescence with a peak energy position of 0.81 eV and full width at half maximum of 0.19 eV, an activation energy of 0.52 eV and σ0 of 6.1×103 (Ω cm)−1 measured using dark conductiv...

Influence of annealing on the hydrogen bonding and the microstructure of diamondlike and polymerlike hydrogenated amorphous carbon films

Abstract: The influence of hydrogen incorporation on the microstructure of hydrogenated amorphous carbon (a-C:H) films has been studied in detail by applying several complementary methods, i.e., elastic recoil detection analysis (ERDA), hydrogen evolution, and infrared absorption measurements, to two series of samples prepared by two different techniques, respectively representative of diamondlike and polymerlike a-C:H. The analysis of the changes of the infrared vibrational spectra over a large frequency range upon annealing at increasing temperatures up to 600 \ifmmode^\circ\else\textdegree\fi{}C allowed us to get insights into both the C-H and C-C bonding modifications.

Disorder effects and the optical properties of amorphous GaAs and GaP

Abstract: The optical properties of flash-evaporated amorphous GaAs and GaP thin films have been determined between 0.5 and 6.20 eV as a function of deposition conditions and heat treatments. The data obtained for stoichiometric samples of each compound are compared with each other and with similar data obtained earlier on evaporated amorphous Ge films. The effects of deviations from stoichiometry are also considered. These results are discussed and interpreted in relation to the results of complementary experiments, for example electrical conductivity. The nature of the defects responsible for the observed properties is discussed for both compounds, special attention being paid to the possibility of like-atom bonds.

Defect density and hydrogen bonding in hydrogenated amorphous silicon as functions of substrate temperature and deposition rate

Abstract: We present the results of a detailed investigation of hydrogen bonding and optical absorption in the 0.6–2 eV range for four series of hydrogenated amorphous silicon films (a-Si:H) deposited under four different plasma conditions and for substrate temperatures ranging from 100 to 300°C. We have found that, for each plasma condition, the subgap absorption shows a sharp decrease at a well defined temperature, which allows us to denne, for each series of samples, an equilibrium temperature T ED for defects above which the subgap absorption remains constant. A similar trend is observed for the structural properties of the films (hydrogen content, hydrogen bonding, optical gap and refractive index). However, for each series, the equilibrium temperature TED for the defects is about 50°C lower than the equilibrium temperature T ED for the hydrogen-related properties. Our results clearly show that the defect structure and the hydrogen-related structure of these a-Si: H samples do not follow the same subs...

Optical properties of metallic films for vertical-cavity optoelectronic devices.

Abstract: We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV

Abstract: We report values of pseudodielectric functions $〈\ensuremath{\epsilon}〉=〈{\ensuremath{\epsilon}}_{1}〉+i〈{\ensuremath{\epsilon}}_{2}〉$ measured by spectroscopic ellipsometry and refractive indices $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}=n+ik$, reflectivities $R$, and absorption coefficients $\ensuremath{\alpha}$ calculated from these data. Rather than correct ellipsometric results for the presence of overlayers, we have removed these layers as far as possible using the real-time capability of the spectroscopic ellipsometer to assess surface quality during cleaning. Our results are compared with previous data. In general, there is good agreement among optical parameters measured on smooth, clean, and undamaged samples maintained in an inert atmosphere regardless of the technique used to obtain the data. Differences among our data and previous results can generally be understood in terms of inadequate sample preparation, although results obtained by Kramers-Kronig analysis of reflectance measurements often show effects due to improper extrapolations. The present results illustrate the importance of proper sample preparation and of the capability of separately determining both ${\ensuremath{\epsilon}}_{1}$ and ${\ensuremath{\epsilon}}_{2}$ in optical measurements.

Long-range surface plasmon polaritons

Abstract: Long-range surface plasmon polaritons (LRSPPs) are optical surface waves that propagate along a thin symmetric metal slab or stripe over an appreciable length (centimeters). Vigorous interest in LRSPPs has stimulated a large number of studies over three decades spanning a broad topical landscape. Naturally, a good segment of the literature covers fundamentals such as modal characteristics, excitation, and field enhancement. But a large portion also involves the LRSPP in diverse phenomena, including nonlinear interactions, molecular scattering, fluorescence, surface-enhanced Raman spectroscopy, transmission through opaque metal films and emission extraction, amplification and lasing, surface characterization, metal roughness and islandization, optical interconnects and integrated structures, gratings, thermo-, electro- and magneto-optics, and (bio)chemical sensing. Despite the breadth and depth of the research conducted to date, much remains to be uncovered, and the scope for future investigations is broad. We review the properties of the LRSPP, survey the literature involving this wave, and discuss the prospects for applications. Avenues for further work are suggested.

Lasing in metallic-coated nanocavities

Abstract: Metallic cavities can confine light to volumes with dimensions considerably smaller than the wavelength of light. It is commonly believed, however, that the high losses in metals are prohibitive for laser operation in small metallic cavities. Here we report for the first time laser operation in an electrically pumped metallic-coated nanocavity formed by a semiconductor heterostructure encapsulated in a thin gold film. The demonstrated lasers show a low threshold current and their dimensions are smaller than the smallest electrically pumped lasers reported so far. With dimensions comparable to state-of-the-art electronic transistors and operating at low power and high speed, they are a strong contender as basic elements in digital photonic very large-scale integration. Furthermore we demonstrate that metallic-coated nanocavities with modal volumes smaller than dielectric cavities can have moderate quality factors.

Optical dielectric function of gold

Abstract: In metal optics gold assumes a special status because of its practical importance in optoelectronic and nano-optical devices, and its role as a model system for the study of the elementary electronic excitations that underlie the interaction of electromagnetic fields with metals. However, largely inconsistent values for the frequency dependence of the dielectric function describing the optical response of gold are found in the literature. We performed precise spectroscopic ellipsometry measurements on evaporated gold, template-stripped gold, and single-crystal gold to determine the optical dielectric function across a broad spectral range from 300 nm to 25 $\ensuremath{\mu}$m (0.05--4.14 eV) with high spectral resolution. We fit the data to the Drude free-electron model, with an electron relaxation time ${\ensuremath{\tau}}_{D}=14\ifmmode\pm\else\textpm\fi{}3$ fs and plasma energy $\ensuremath{\hbar}{\ensuremath{\omega}}_{p}=8.45$ eV. We find that the variation in dielectric functions for the different types of samples is small compared to the range of values reported in the literature. Our values, however, are comparable to the aggregate mean of the collection of previous measurements from over the past six decades. This suggests that although some variation can be attributed to surface morphology, the past measurements using different approaches seem to have been plagued more by systematic errors than previously assumed.