Papers by Jean-eric Bourée
Revue de physique appliquée, 1987
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Canadian Journal of Chemistry, 1970
The free radicals •Mn(CO)5 and •Co(CO)4 have been produced by the pyrolysis of Mn2(CO)10 and Co2(... more The free radicals •Mn(CO)5 and •Co(CO)4 have been produced by the pyrolysis of Mn2(CO)10 and Co2(CO)8 in graphite flow reactors. The effusing molecular beams from these reactors were analyzed mass spectrometrically. Evidence is presented for the following equilibria[Formula: see text]From the temperature dependence of the equilibrium constants, enthalpy changes of 24.9 ± 2 and 14.5 ± 2 kcal/mole, respectively, have been obtained. These enthalpy changes give D(Mn—Mn) = 21 ± 3 kcal/mole and D(Co—Co) = 13 ± 3 kcal/mole, which substantiate the earlier literature values based on electron impact measurements.
MRS Proceedings, 1998
Electronic properties of polymer-like hydrogenated amorphous carbon films, grown in a RF-assisted... more Electronic properties of polymer-like hydrogenated amorphous carbon films, grown in a RF-assisted microwave plasma reactor, have been studied using optical absorption and photoluminescence spectroscopies. Using a Forouhi-Bloomer parametrization of π-π* transitions, two regimes are evidenced for increasing C atom density : a decrease of the optical gap Eππ* at constant (H/H+C) content attributed to sp2C clustering, followed by some H elimination with minor changes in Eππ* due to cross-linking of polymer chains. The photoluminescence efficiency in the visible range (peak at ≈ 2.3 eV) is found to decrease over four orders of magnitude at the onset of the cross-linking regime. This quenching is attributed to stress-induced non-radiative centers.
MRS Proceedings, 1997
ABSTRACTPolysilicon N-channel TFT have been hydrogenated using the H2 dissociation on a hot tungs... more ABSTRACTPolysilicon N-channel TFT have been hydrogenated using the H2 dissociation on a hot tungsten filament. A post-annealing realized at the optimal temperature of 300°C is necessary to obtain interesting electrical TFT characteristics. Different TFT's sizes and geometries have been processed. The analysis of their characteristics shows that hydrogen preferentially diffuses through silicon oxide layer. The enhancement of the current in the ON-state shows that hydrogen atoms have passivated silicon oxide gate / polysilicon interface traps. The important reduction of the dependency of the OFF-state current with the reverse gate voltage shows that hydrogen atoms have passivated grain boundary traps near the interface in the channel region and in the drain sheet resistance region then reducing the trapped carrier emission.
Journal of Non-Crystalline Solids, 1998
Ž. Ž Polymer-like hydrogenated amorphous carbon a-C:H films containing increasing concentrations ... more Ž. Ž Polymer-like hydrogenated amorphous carbon a-C:H films containing increasing concentrations of Si atoms up to 12. Ž. at.% have been grown using a dual-mode plasma microwave and radiofrequency plasma enhanced chemical vapor Ž deposition reactor with low ion energies. X-ray emission and X-ray photoelectron spectroscopies giving respectively Si 3p. states and the total valence band states have been used to probe the electronic structure. Complementary information on the local bonding have been obtained from the Si 2p and C 1s core levels. These results show that the Si bonding environments are consistent with Si-C units. The influence of the tetrahedrally bonded Si atoms on the C atom local environment is 4 basically explained by a topological effect rather than a change in the C hybridization.
Journal of Applied Physics, 1998
Polymer-like hydrogenated amorphous carbon (a-C:H) films have been grown in a dual-plasma [radio ... more Polymer-like hydrogenated amorphous carbon (a-C:H) films have been grown in a dual-plasma [radio frequency (rf)–microwave (MW)] reactor using butane as a carbon precursor and different mixtures (H2–Ar or He–Ar) in the MW plasma in order to vary the atomic hydrogen flux impinging on the growing film. Decreasing the rf power (i.e., the energy of ion bombardment on a-C:H) or increasing the H atom flux both result in a wide band gap H-rich polymer-like a-C:H network. Nuclear techniques have been combined with UV-visible ellipsometry to determine the stoichiometry, density and growth rate of a-C:H films as a function of the plasma parameters. Parametrization of UV-visible optical properties allows to monitor the changes in the optical parameters (optical gap and density of π states) attributed to the formation of structural units containing C=C double bonds. C–H bonds observed by in situ infrared ellipsometry have been used to investigate the role of ions in the growth processes (densifi...
Journal of Applied Physics, 2002
Hydrogenated amorphous carbon and carbon nitride films (a-C1−xNx:H) have been synthesized from me... more Hydrogenated amorphous carbon and carbon nitride films (a-C1−xNx:H) have been synthesized from methane, acetylene, or acetylene–nitrogen precursor gases using a high density electron cyclotron resonance plasma. The deposition and etching rates, along with the film stoichiometry, density, Raman signature of the sp2 phase, and optical and transport properties, have been studied as a function of plasma parameters (microwave power and negative bias of the substrate). While low-density H-rich carbon films have been grown from methane for ion energies up to 200 eV, films grown using acetylene have been obtained at high deposition rate (1.1 nm s−1) with H content below 25 H at. % and density of 2.0 g cm−3, which makes them interesting as electronic materials. For dense carbon nitride alloys, the maximum (N/N+C)=0.35 is limited by the vanishing growth rate, which results from ion-assisted chemical etching mechanisms. A larger N2 plasma etching rate related with lower film density is observe...
Journal De Physique, 1975
Perovskite solar cells (PSCs) research is an intense field that could benefit from every availabl... more Perovskite solar cells (PSCs) research is an intense field that could benefit from every available research tool. Synchrotron tools have played an important role in fundamental and applied research for decades. Many synchrotron-based hard X-ray tools are already providing effective feedback to the PSC research community. With several fourth-generation light sources up and running or under development, this contribution will continue to impact every aspect of scientific advancement including PSC research. Arguably, the contribution of soft X-rays in PSC research is relatively limited. In view of the developments in the synchrotron world and the fact that a multimethod approach, combining laboratory-based techniques as well as synchrotron-based techniques, is necessary to provide constructive feedback to the PSC community we present here a collection of arguments and procedures with the aim of highlighting the use of soft X-ray scanning transmission X-ray microscopy (STXM). Some aspec...
HAL (Le Centre pour la Communication Scientifique Directe), 1995
A study of the fabrication of thin-film silicon solar cells in the p-i-n superstrate diode config... more A study of the fabrication of thin-film silicon solar cells in the p-i-n superstrate diode configuration on plastic substrates at a temperature of 150 ºC, using different absorbing i-layers, is presented. A typical solar cell structure in this work comprises the following successive layers: PEN/GZO/p/buffer/i/n/metal. GZO is a transparent conductive window layer made of Zinc Oxide doped with Gallium and buffer is a high-bandgap ~10 nm-thick amorphous silicon layer. Flexible solar cells deposited entirely by radio-frequency plasma enhanced chemical vapour deposition on PEN had a conversion efficiency of 5.0%, JSC = 11.2 mA/cm2, and VOC = 0.830 V. Similar solar cells on PEN but with the i-layer deposited by hot-wire chemical vapor deposition had efficiency 4.53%, JSC = 12.7 mA/cm2, and VOC = 0.699 V. Based on the spectral response of the solar cells and on their I-V characteristics under different light levels, it is concluded that the efficiency of the devices is limited by recombination in the i-layer and by losses in the long wavelength part of the spectrum. Devices fabricated on PEN and on Asahi-U glass have comparable characteristics. However, the best fill factor obtained on PEN is 55.6% whereas on glass it is 60.1%. Nanocrystalline solar cells on PEN have high JSC (17.2 mA/cm2) but very poor FF (32.7%).
SiOxCy monolayers or stacked multilayers have been deposited at low temperature using a low frequ... more SiOxCy monolayers or stacked multilayers have been deposited at low temperature using a low frequency (100 kHz) plasma-enhanced chemical vapor deposition reactor associated or not with a plasma treatment. An innovative test based on transformation of lithium with oxygen and water vapor has been used to assess the permeation barrier properties of the films. Effects on the permeability of barrier thickness, of a specific argon plasma treatment during the growth process and of the number of grown interfaces are successively studied. A physical explanation of the effect of the plasma treatment is proposed.
Thin Solid Films, 2001
This paper is a synthesis of the work performed in LPICM-Palaiseau on the catalytic chemical vapo... more This paper is a synthesis of the work performed in LPICM-Palaiseau on the catalytic chemical vapor deposition (Cat-CVD) process. First of all, some technological problems, such as increasing the filament lifetime, have been solved, which were necessary for the stability and homogeneity of the silicon layers deposited. A study was then conducted on the main deposition parameters in order to deposit dense microcrystalline silicon layers (as compared with amorphous silicon) at low substrate temperature (-3008C) and to try to clarify the possible mechanisms of growth. For the first aspect of this study, a specific procedure based on the variation of dilution of silane in hydrogen during deposition has been put forward, allowing simultaneous preparation of a dense microcrystalline layer and removal of the initial amorphous layer, thus favoring electronic transport across the whole layer. UV-visible ellipsometry, as well as time-resolved microwave conductivity, has been used to confirm these hypotheses. Using the variable dilution process, some unoptimized n-i-p microcrystalline silicon solar cells have been realized on TCO-coated Corning glass substrates, the AM1.5 efficiency being 4.6%. For the second aspect, mechanistic reactions have been approached via an in situ Fourier-transform phase-modulated infrared ellipsometry analysis, which allowed attribution of the stretching vibration at 2000 cm to hydrogen, as in bulk amorphous silicon, and that at 2100 cm to hydrogen at the interface y1 y1 of microvoids (porous microcrystalline silicon). This analysis confirmed that the layers deposited by the variable dilution process were microcrystalline from the substrate surface, but with a significant amorphous phase in the bulk. Results issued from this study coupled with those from other groups have been simply interpreted in terms of gas precursors different from the precursors invoked in plasma-enhanced chemical vapor deposition processes.
Materials Science Forum, 2004
Silica and Ge-doped silica films have been deposited in a recently developed matrix distributed e... more Silica and Ge-doped silica films have been deposited in a recently developed matrix distributed electron cyclotron resonance (MDECR) reactor. Process parameters were optimized in order to obtain films with low hydrogen content at a low substrate temperature keeping a high deposition rate. The choice of silane injection system is shown to be of crucial importance for the deposition of high quality material. Injection of silane near the surface resulting in increase of its local partial pressure allows to obtain films with a low OH adsorption independently of silane flow i.e. growth rate. Conversely, in the case of uniform distribution of silane in the reactor volume (well-mixed reactor), the hydrogen content increases with silane flow. Under optimal conditions, silica films with a low adsorption at the communication wavelengths have been deposited at rates up to 70 nm/min at temperatures lower than 150°C. Non-absorbing oxynitride films with refractive indices ranging from 1.46 to 1.81 have been obtained. Ge-doped silica was deposited using a mixture of 2% GeH4 in H2 as a dopant gas. Germanium content, refractive index and adsorption coefficient of the films have been studied as a function of process parameters. The results show that the MDECR concept can be a technology of choice for the deposition of waveguide structures for integrated optical components.
Materials Science and Engineering: B, 2000
Hot-wire chemical vapour deposition (HW-CVD) is a well-known technique to deposit amorphous silic... more Hot-wire chemical vapour deposition (HW-CVD) is a well-known technique to deposit amorphous silicon with high deposition rates from the decomposition of silane and hydrogen gases. By changing the hydrogen and silane flow rates, it is possible to observe a transition from amorphous silicon (a-Si:H) to microcrystalline silicon (mc-Si:H). In this study, structural and electrical properties of layers deposited as a function of silane concentration in the gas are presented. Ellipsometry and X-ray diffractometry have been used to assess the structure of the films. Steady-state photoconductivity, steady-state photocarrier grating, and modulated photocurrent experiments have been carried out to characterise both majority and minority carrier transport properties. Finally, the addition of phosphine and diborane in the reactor allows the deposition of n-and p-type layers with conductivities up to 10 and 1 s cm − 1 , respectively, making possible the realisation of HW-CVD solar cells.
Surface and Coatings Technology, 2014
Easily degradable organic photovoltaic (OPV) devices based on flexible polymer substrates require... more Easily degradable organic photovoltaic (OPV) devices based on flexible polymer substrates require barrier films exhibiting extremely low permeation rates for water vapor. We report the barrier properties of hard/ soft alternating layer structures where a soft PMMA layer is sandwiched between two hard SiN x layers. The interfaces between the hard/soft layers hinder the propagation of pinholes from one single-layer to the other and thus have an effect on the overall barrier properties of the whole system. We focus our attention on the effect of increasing number of interfaces on the final barrier properties. The encapsulation barrier properties of these layers are assessed using the electrical calcium test. A minimum water vapor transmission rate (WVTR) of~2 × 10 −4 g/m 2 •day is reported for 7 hard/soft interfaces, which has also high potential for flexible barrier applications.
Solid State Phenomena, 1996
Thin Solid Films, 2009
Fifth international conference on hot-wire CVD (Cat-CVD) process This is the fifth in the series ... more Fifth international conference on hot-wire CVD (Cat-CVD) process This is the fifth in the series of hot-wire chemical vapor deposition (HWCVD) (or catalytic CVD) conferences held for the purpose of exchanging information and highlighting research advances in this expanding technology. The first conference was held in Kanazawa, Japan in November 2000, and was organized and hosted by Prof. Hideki Matsumura. Succeeding conferences have since been held biannually in Denver, USA, hosted by Dr. Harv Mahan, in Utrecht, the Netherlands, hosted by Prof. Ruud Schropp, then in Takayama, Japan, hosted by Prof. Shuichi Nonomura, and the most recent gathering was in Cambridge, USA, hosted by Prof. Karen Gleason. The next conference is scheduled to be held in Palaiseau, France, in September 2010. While some attrition has occurred amongst the original conference participants, new researchers have continued to join the HWCVD field, enabling conference participation to remain at relatively constant levels. In the present conference, 80 papers were presented, with 110 researchers from 15 countries in attendance. Fifty-three papers, approved by the review process, are included in this volume of Thin Solid Films.
Thin Solid Films, 2008
The structure and the transport properties of microcrystalline silicon films prepared by hot-wire... more The structure and the transport properties of microcrystalline silicon films prepared by hot-wire/catalytic chemical vapor deposition (HWCVD/ Cat-CVD), using different dilution ratios of silane in hydrogen, were investigated. Spectroscopic ellipsometry analysis revealed an increase in the thickness of amorphous incubation layer formed before nucleation and a reduction of the void volume fraction when hydrogen dilution decreases. Thus, a specific microcrystalline silicon film growth process was proposed, based on a variable dilution of silane in hydrogen. For films prepared in such conditions, the formation of the incubation layer was inhibited, which led to a drastic improvement in carrier transport along the growth direction as proved by the diffusion-induced time-resolved microwave conductivity data.
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Papers by Jean-eric Bourée