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Silicon nitride (SiNx, x ∼ 1) thin films were deposited by chemical vapor deposition on silicon oxide (SiO2) substrates by combining controlled pulses of the precursor 1,3,5-tri(isopropyl)cyclotrisilazane (TICZ, C9H27N3Si3) with a continuous ammonia (NH3) plasma. This plasma-assisted pulsed CVD (PPCVD) process enables the integration of the nanoscale thickness and uniformity control achieved in atomic layer deposition with the efficiency of plasma-enhanced CVD (PE-CVD). TICZ was selected because it is a nonpyrophoric stable liquid with a high vapor pressure (∼133 Pa at 70 °C) and could act as a single source for SiNx with both high Si and N contents. An optimized PPCVD process window was identified consisting of a substrate temperature of 350 °C, a TICZ pulse of ≤0.2 s, and a TICZ purge pulse ≥10 s in a continuous direct NH3 plasma at a NH3 flow rate and a power of 40 SCCM and 3000 W, respectively. The as-deposited films were analyzed by x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS analysis confirmed the absence of any C inclusion and demonstrated the existence of the 1:1 Si:N ratio. In situ, real-time ellipsometry measurements indicated that SiNx growth occurred in a typical PE-CVD regime. They also yielded an as-grown SiNx average refractive index of ∼1.75.

Transparent conductive oxides (TCOs) are a group of materials that have good electrical conductivity, high visible and low near infrared (NIR, 790–2500 nm) transparencies. They are widely used in flat-panel displays, thin film solar cells and low-emissivity windows. The current material that dominates over 90% of the TCO market is tin doped indium oxide (ITO), which has superior electrical and optical properties. However, the two issues of ITO are the high cost of indium as well as its incomplete coverage of blockage in the NIR range, especially in the 790–1100 nm range that contains nearly 60% of the NIR solar irradiance. For decades, ZnO has been considered as a potentially low-cost replacement for ITO. But even after years of empirical explorations, the conductivity of the doped ZnO films are still not as good as ITO in many cases. The lack of fundamental studies such as the understandings on the relationships between processing conditions and the microstructure and the chemistries of the films is believed to be an important factor that limits further optimization. In this study, a variety of advanced microscopy techniques such as texture X-ray diffraction, transmission electron microscopy and transmission Kikuchi diffraction were used to study the Si doped ZnO films deposited and processed under different conditions. The results suggest several possible reasons for the large improvement of conductivity after the vacuum annealing and provide a few ideas on avoiding the defects observed in the thin films for future research. In terms of the NIR properties, a more complete coverage of blockage was achieved by the production of Cu2P2O7 thin films, which shows an absorbance of up to 66% of solar irradiance in the 790–1100 nm range while maintaining a good visible transparency (85% of transmittance at 550 nm). Given the little research reported on Cu2P2O7, here for the first time a complete route from the analysis of powder, the production of sputtering targets to the deposition of thin films as well as further analysis on the structure and chemistry of the films is presented. These films are suitable for making low-cost and highly efficient inorganic NIR coating, which can be used in many applications such as energy efficient windows and electromagnetic shielding devices.

We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 A in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window (470–650 nm) by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied.

This study presents a new construction design of a distributed Bragg reflector (DBR) filter and a Fabry–Pérot (FP) filter by using needle technique as a synthesis method. The optimized DBR and FP filters having a proper number of layers with controlling thickness TiO2/SiO2 are utilized to transmit only a certain narrow band of wavelengths while blocking the others. As a proof of concept, the filters are designed to selectively transmit only a very narrow band of wavelength at 780 nm which is the near infrared (NIR) fluorescent emission from Alexa Fluor 750 dye. The obtained results show that the optimized filters represent advanced spectral performance which can be used to improve the sensitivity and the imaging contrast in fluorescence microscopy.

The goal of the study was to identify the environmental hotspots of an experimental research work at lab scale consisting in the physical vapor deposition magnetron sputtering of aluminum titanium nitride based thin coatings onto commercial laminated steel. The findings can provide useful insights for supporting the design of future experimental research campaigns, or instrumentation set-ups, with lower environmental impacts. Results highlighted that the main driver of impacts in the analyzed laboratory activities was the electricity used for instruments operations, in particular for the vacuum keeping. Thus, several optimization strategies were evaluated to reduce the overall electricity consumption, and to improve the environmental profile of experimental activities.

International audience; Molecular dynamics (MD) simulations are used to study AlCoCrCuFeNi high entropy alloy (HEA) thin film growth on a silicon (100) substrate. Effect of the atomic composition is studied on morphology and atomic scale structure. Input data are chosen to fit with experimental operating conditions of magnetron sputtering deposition process. It is observed that the different structures are determined by the chemical composition and atomic size mismatch. The simulated results are in good agreement with the solid-solution formation rules proposed by Zhang et al [1] for multi-principal component HEAs which based on the two parameters \omega and \delta , respectively describing describe the comprehensive effect of the atomic-size difference in the n-element alloy and the effects of enthalpy and entropy of mixing on formation of multi-component solid-solutions. When \omega>= 1.1 and \delta≤ 6.6%, the multi-component solid solution phase could form. In contrast, the multi-component alloys forming intermetallic compounds and bulk metallic glasses (BMG) have larger value of \delta and smaller value of \omega. The value of \omega for BMG is smaller than that of intermetallic compounds.

Cuprous oxide and cupric oxide thin films were deposited on silicon wafer with additional substrate bias voltage using radio-frequency magnetron sputtering of a Cu target with Ar+O2 discharge plasma. Optical emission spectroscopy was employed to monitor the intensity of atomic Cu and O emission lines at various substrate bias voltages and oxygen flow ratios. Thin film transition from cuprous oxide to cupric oxide phase was observed by X-ray diffraction analysis when the oxygen flow ratio increased. This transition was not influenced by the substrate bias voltage. Optical emission spectroscopy showed a real time monitoring results of the transition from cuprous to cupric oxide thin films. The transition was observed at a critical O2 flow ratio of 7%. The results proposed a tightly control of reactive Cu sputtering through a closed loop and real-time monitoring system for precise copper oxide thin films deposition.

Solar radiation and hydrogen generation via splitting water molecules have been recognized as sustainable and clean energy sources having great industrial potentials. In this regard, thin film materials for photovoltaic and photoanodes applications have been widely developed in the last decade. For thin film photovoltaic applications, taking material availability, extraction/processing cost, energy conversion efficiency, and eco-friendliness into account, FeS 2 (pyrite) has been predicted to hold the leading position among the most plausible candidates such as Cu 2 S, Cu 2 O, CuO, etc. On the other hand, feasible water splitting on nanostructured surface and/or hybrid nanostructures has been observed in the last few years. In terms of processing cost, feasibility in scale-up for mass production, material engineering for efficiency, etc., physical vapor depositions (PVDs), e.g., magnetron-sputtering deposition, have great advantages. Here, we present our recent studies on synthesis of iron sulfide and oxide layered and nanostructured films by combining PVD and thermal vapor sulfurization/oxidation techniques.

Measurements of wet-ability of liquid drops have been performed on a 30 nm silicon nitride (Si3N4) film deposited by a PECVD reactor on a silicon wafer and implanted by 40 keV argon ions at different doses. Surface treatments by using Ar ion beams have been employed to modify the wet-ability. The chemical composition of the first Si3N4 monolayer was investigated by means of X-ray Photoelectron Spectroscopy (XPS). The surface morphology was tested by Atomic Force Microscopy (AFM). Results put in evidence the best implantation conditions for silicon nitride to increase or to reduce the wet-ability of the biological liquid. This permits to improve the biocompatibility and functionality of Si3N4. In particular experimental results show that argon ion bombardment increases the contact angle, enhances the oxygen content and increases the surface roughness.

Electron and hole transport properties of the organic small molecule N,N0 -Di(1-naphthyl)-N,N0 - diphenyl-(1,10 -biphenyl)-4,40 -diamine are investigated by space-charge-limited current measurements. The hole transport shows trap-free behavior with a mobility of 2.3 108m2 /Vs at vanishing carrier density and electric field. The electron transport, on the other hand, shows heavily trap-limited behavior, which leads to highly unbalanced transport. A trap concentration of 1.3 1024m3 was found by modeling the electron currents, similar to the universal trap concentration found in conjugated polymers. This indicates that electron trapping is a generic property of organic semiconductors, ranging from vacuum-deposited small-molecules to solution-processed conjugated polymers.

The implementation of organic electronic devices on fibers is a challenging task, not yet investigated in detail. As was shown earlier, a direct transition from a flat device structure to a fiber substrate is in principle possible. However, a more detailed investigation of the process reveals additional complexities than just the transition in geometry. It will be shown, that the layer formation of evaporated materials behaves differently due to the multi-angled incidence on the fibers surface. In order to achieve homogenous layers the evaporation process has to be adapted. Additionally, the fiber geometry itself facilitates damaging of its surface due to mechanical impact and leads to a high surface roughness, thereby often hindering commercial fibers to be used as substrates. In this article, a treatment of commercial polymer-coated glass fibers will be demonstrated that allows for the fabrication of rather flexible organic light-emitting diodes (OLEDs) with cylindrical emission characteristics. Since OLEDs rely the most on a smooth substrate, fibers undergoing the proposed treatment are applicable for other organic electronic devices such as transistors and solar cells. Finally, the technique also supports the future fabrication of organic electronics not only in smart textiles and woven electronics but also in bent surfaces, which opens a wide range of applications.

The growth of vertically aligned carbon nanofibers (VACNFs) in a catalytic dc ammonia/acetylene plasma process on silicon substrates is often accompanied by sidewall deposition of material that contains predominantly Si and N. In fluorescent microscopy experiments, whereby VACNFs are interfaced to cell and tissue cultures for a variety of applications, it was observed that this material is broadly fluorescent. In this paper, we provide insight into nature of these silicon/nitrogen in-situ coatings. We propose a potential mechanism for deposition of SiNx coating on the sidewalls of VACNFs during PECVD synthesis and explore the origin of the coating's fluorescence. It is most likely that the substrate reacts with process gases similar to reactive sputtering and chemical vapor deposition (CVD), forming silane and other silicon bearing compounds prior to isotropic deposition as a SiNx coating onto the VACNFs. The formation of Sinanoclusters (NCs) is also implicated due to a combination of strong fluorescence and elemental analysis of the samples. These broadly luminescent fibers can prove useful as registry markers in fluorescent cellular studies and for tagging and tracing applications.

The influence of energetic species on thin film growth mechanism is a long-term issue in the field of low-pressure plasma-based magnetron sputtering technology. Several species may contribute to the energy flux such a plasma ions, electrons and neutrals, film-forming species, photons, etc. Several research groups have designed probes capable of quantifying energy fluxes in these particular working conditions and experimental strategies to get a better insight on the relationship between the plasma working parameters, the energy flux, the film growth mechanism and the coating properties. In this paper we aim at showing how the thermopile-based probe developed at GREMI laboratory can contribute to this field thanks to its time resolved capability (~ms) and sensitivity (~mW/cm2). We show how such a probe can be used to identify and quantify energetic contributions such as gas conduction, chemical reactions on surfaces such as oxidation, but also radiations emitted from a (hot) sputter target during DC, pulsed-DC and High-power Impulse Magnetron Sputtering (HiPIMS) processes. Both non-reactive and reactive sputtering discharges are studied. Ultimately, we present data on the relationship between the phase composition and the energy deposited during the synthesis of two technologically important thin film materials, namely Titania and Zirconia. Through the reported examples, the advantage and limitations of energy flux measurements and the interest to couple the obtained data to those derived from conventional plasma diagnostics are discussed. The relative importance of various energetic contributions is investigated in a purpose to identify the key parameters driving the film properties.

While organic semiconductors are being widely investigated for chemical and biochemical sensing applications, major drawbacks such as the poor device stability and low charge carrier mobility in aqueous electrolytes have not yet been solved to complete satisfaction. In this work, solution-gated organic field-effect transistors (SGOFETs) based on the molecule α,ω-dihexyl-sexithiophene (DH6T) are presented as promising platforms for in-electrolyte sensing. Thin films of DH6T were investigated with regard to the influence of the substrate temperature during deposition on the grain size and structural order. The performance of SGOFETs can be improved by choosing suitable growth parameters that lead to a two-dimensional film morphology and a high degree of structural order. Furthermore, the capability of the SGOFETs to detect changes in the pH or ionic strength of the gate electrolyte is demonstrated and simulated. Finally, excellent transistor stability is confirmed by continuously operating the device over a period of several days, which is a consequence of the low threshold voltage of DH6T-based SGOFETs. Altogether, our results demonstrate the feasibility of high performance and highly stable organic semiconductor devices for chemical or biochemical applications., This work has been partially supported by the Nanosystems Initiative Munich (NIM) and the Deutsche Forschungsgemeinschaft (DFG) through the SFB 1032.

New ferrocene derivatives, ((4-(1H-pyrrol-1-yl)phenoxy)carbonyl) ferrocene (4) and (6-(4-(1H-pyrrol-1-yl)phenoxy)hexyl) ferrocene (7) were synthesised, characterised and electrochemically evaluated as redox active films formed via anodic oxidation with pyrrole. Thin film studies were conducted and films formed from both compounds resulted in a stable Fe II/III redox couple with Eo = 0.04V and 0.36V vs. Ag/Ag+ for (7) and (4) respectively. Both potential sweeping and chronocoulometry were employed for film formation with the former resulting in controllable, reproducible film deposition. Growth conditions and solution concentrations were varied in the case of both compounds in order to assess influence on electrochemical behavior. Surface coverage’s were of the order 10-8-10-9 mol cm-2, surface confined behavior (ip vs. n) was evident up to 0.2 V s-1 with semi-infinite diffusion (ip vs. n1/2) dominating at higher scan rates. Laviron theory was employed where possible for the determination of electron transfer co-efficient and rate constants.

Low-pressure plasmas offer a unique possibility of confinement, control, and fine tailoring of particle properties. Hence, dusty plasmas have grown into a vast field, and new applications of plasma-processed dust particles are emerging. During the deposition of thin amorphous films onto melamine formaldehyde (MF) microparticles in a C2H2 plasma, the generation of nanosized carbon particles was also studied. The size distribution of those particles is quite uniform. In another experiment, the stability of luminophore grains could be improved by coating with protective Al2O3 films that are deposited by a plasma-enhanced chemical vapor deposition (PECVD) process using a metal-organic precursor gas. Coating of SiO2 microparticles with thin metal layers by magnetron sputtering is also described. Especially the interaction of the microsized grains confined in a radio frequency (rf) plasma with the dc magnetron discharge during deposition was investigated. The observations emphasize that the interaction between magnetron plasma and injected microdisperse powder particles can also be used as a diagnostic tool for the characterization of magnetron sputter sources.

We report the self-buckling (or peeling off) of cubic Cu3N films deposited by DC magnetron sputtering of a Cu target in a nitrogen environment at a gas pressure of 1 Pa. The deposited layer partially peels off as it is exposed to ambient air at atmospheric pressure, but still adheres to the substrate. The chemical composition of the thin film as investigated by means of X-ray photoelectron spectroscopy (XPS) shows a considerable surface oxidation after exposure to ambient air. Grazing incidence X-ray diffraction (GIXRD) confirms the formation of a crystalline Cu3N phase of the quenched film. Notable are the peak shifts in the deposited film to smaller angles in comparison to stress-free reference material. The X-ray pattern of Cu3N exhibits clear differences in the integral width of the line profiles. Changes in the film microstructure are revealed by X-ray diffraction, making use of X-ray line broadening (Williamson–Hall and Stokes–Fourier/Warren–Averbach method); it indicates that the crystallites are anisotropic in shape and show remarkable stress and micro-strain.

We present a self-consistent analysis of a glow discharge sputtering system where the generation of the energetic particles that bombard the cathode, the sputtering process, and the transport through the plasma of the emitted particles from the cathode, are evaluated as coupled processes. Within this scheme we calculate the radial spatial profile of the deposited energy onto the film, carried by the flux of sputtered particles; the influence of the gas pressure and the vacuum chamber geometry are both discussed. We acknowledge financial support from the Spanish DGICYT (projects PB95-0689, PB93-1125 and PB94-0283).

International audience; We prepared V2O3 thin films on C- or R-plane sapphire (Al2O3) substrates by a pulsed laser deposition method. X-ray diffraction analyses confirmed that single-phase V2O3 films were epitaxially grown on both C- and R-planes under an Ar gas ambient of 2 × 10−2 mbar at a substrate temperature of 873 K. Depending on the deposition conditions, c/a ratios at room temperature of (0001)-oriented V2O3 films widely ranged from 2.79 to 2.88. Among them, the films of 2.81 ≤ c/a ≤ 2.84 showed complex metal (M)–insulator (I)–M transition during cooling from 300 to 10 K, while those of larger c/a ratios were accompanied by metallic properties throughout this temperature range. All the films on R-plane substrates underwent simple M-I transition at ∼150 K, which was more abrupt than the films on C-plane, whereas their c/a ratios were narrowly distributed. The distinct difference of M-I transition properties between C- and R-plane films is explained by the intrinsic a- and c-axes evolution through the transition from M to I phases.

Here we report a new sample preparation method for three-dimensional electron tomography. The method uses the standard film deposition and focused ion beam (FIB) methods to significantly reduce the problems arising from the projected sample thickness at high tilt angles. The method can be used to prepare tomography samples that can be imaged up to a ±75° tilt range which is sufficient for many practical applications. The method can minimize the problem of Ga+ contamination, as compared to the case of FIB preparation of rod-shaped samples, and provides extended thin regions for standard 2D projection analyses. Microsc. Res. Tech. 75:1165–1169, 2012. © 2012 Wiley Periodicals, Inc.

International audience; We demonstrate self-sustaining electrical oscillations with frequency of MHz range based on out-of-plane voltage-triggered switching in VO2 thin films grown on conductive layers. VO2 films deposited by a reactive sputtering method at a low temperature of 250 °C on conductive TiN layers showed thermally induced out-of-plane insulator-metal transition with two orders of change in resistance. By applying dc voltage to the layered device in a point contact configuration, self-sustaining electrical oscillations were triggered and the highest frequency of 9 MHz was achieved. Dependence of the frequency on the film thickness, as well as on the source voltage and on the series resistance, was examined in order to clarify the oscillation mechanism and the factors that affect the frequency. The oscillation frequency, which is dominated by recovering time from metallic to insulating state, decreased with increasing film thickness, indicating that the resistance of VO2 film determines the time constant for the recovery path. Self-sustaining oscillation phenomena achieved in point contact devices has great potential for applications in MHz band generators and micro-inverters.

Low original design of Resonant-Cavity-Enhanced photodetectors at 850 nm, realized in microcrystalline silicon by simpe and low-cost thin film deposition processes compatible with standard VLSI technologies is presented. The configuration allows high quantum efficiencies in thin active region. This increases the bandwidth reducign the carrier transit time in teh device. The wavelength selective behavior is a further characterization of high-quality distributed bragg reflectors, necessary to the microcavity definition and optimization, and of the active p-i-n structure are also reported.

Niobium thin films are expected to be free of solid inclusions commonly seen in solid niobium. For particle accelerators, niobium thin film has the potential to replace the solid niobium in the making of the accelerating structures. In order to understand and improve the superconducting performance of niobium thin films at cryogenic temperature, an energetic vacuum deposition system has been developed to study deposition energy effects on the properties of niobium thin films on various substrates. The system directly uses microwave power to create a pure niobium plasma, which can be used to extract niobium ion flux with controllable kinetic energy for direct deposition. The ultra high vacuum avoids the gaseous inclusions in thin films. A retarding field energy analyzer is developed and used to measure the kinetic energy of niobium at the substrate location. A systematic process for thin film characterization is developed and used to analyze the niobium thin films made by this energetic condensation. The properties of niobium thin films at several deposition energies are obtained, and the results show that there exists a preferred deposition energy around 115eV. Ph. D.

We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO2) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111) A GaAs substrates by molecular beam epitaxy. The TiO2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO2/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 +/- 0.02 eV was determined for the amorphous TiO2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO2/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO2/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of Delta E-V(100)> Delta E-V(111)> Delta E-V(110) and a conduction band-offset relation of Delta E-C(110) > Delta E-C(111)> Delta E-C(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO2 for potential high-k dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors. (C) 2014 AIP Publishing LLC. National Science Foundation - Grant No. ECCS-1348653 Intel Corporation U.S. Department of Energy. Office of Basic Energy Science - Grant No. DE-FG02-06ER46290

We studied the pulsed laser deposition of homoepitaxial SrTiO3 thin films in different deposition regimes in order to elucidate the possibility to promote two-dimensional growth by increasing the kinetic energy of the oncoming particles. The kinetic energy of the oncoming species is determined by exploiting plume diagnostics techniques and the resulting nucleation and growth processes are analysed by reflection high-energy electron diffraction and atomic force microscopy. We could show that although the kinetic energy of the oncoming species varies to a great extent, the diffusion process is mostly influenced by the stoichiometry. Under stoichiometric conditions, obtained only in a limited window of process parameters, the adatoms on the surface have the highest diffusivity, thus promoting a step-flow growth mode. Under nonstoichiometric conditions, both Sr- and Ti-rich, the diffusivity is strongly reduced. This results in a transition from a two-dimensional to a three-dimensional growth under Sr-rich conditions. Conversely, in the Ti-rich case, obtained at high laser fluence, the two-dimensional growth sustains until the end of the growth process. We attribute this to the high island density available at high laser fluence which facilitates the diffusion of adatoms to step edges despite of their reduced diffusion length.

Thin-film processing of colloidal semiconductor nanocrystals (NCs) is a prerequisite for their use in (opto-)electronic devices. The commonly used spin-coating is highly materials consuming as the overwhelming amount of deposited matter is ejected from the substrate during the spinning process. Also, the well-known dip-coating and drop-casting procedures present disadvantages in terms of the surface roughness and control of the film thickness. We show that the doctor blade technique is an efficient method for preparing nanocrystal films of controlled thickness and low surface roughness. In particular, by optimizing the deposition conditions, smooth and pinhole-free films of 11 nm CuInSe2 NCs have been obtained exhibiting a surface roughness of 13 nm root mean square (rms) for a 350 nm thick film, and less than 4 nm rms for a 75 nm thick film.

Melanins constitute a very important class of organic pigments, recently emerging as a potential material for a new generation of bioinspired biocompatible electrically active devices. In this paper, we report about the deposition of synthetic melanin films starting from aqueous suspensions by matrix assisted pulsed laser evaporation (MAPLE). In particular, we demonstrate that it is possible to deposit melanin films by MAPLE even if melanin (a) is not soluble in water and (b) absorbs light from UV to IR. AFM images reveal that the film surface features are highly depending on the deposition parameters. UV-VIS and FTIR spectra show both the optical properties and the molecular structure typical of melanins are preserved.

Epitaxial lead iron niobate thin films with thicknesses of 50 nm < t < 500 nm have been deposited by pulsed laser deposition. We have identified the deposition conditions that result in insulating layers. These critical conditions are essential to (i) prevent semiconducting resistivity characteristics, (ii) achieve higher induced polarizations of 70 mu C/cm(2) under E=190 kV/mm, and (iii) obtain remanent polarizations of 17.7 mu C/cm(2), coercive fields of 9.5 kV/mm, and dielectric constants of similar to 1200 at room temperature. (c) 2007 American Institute of Physics. United States. Department of Energy - Contract No. DE-AC02-98CH10886 United States. Air Force. Office of Scientific Research - FA 9550-06-1-0410

Two-dimensional arrays of Fresnel zone microlenses were fabricated and coated with antireflection layers by an ion beam sputter deposition technique. The reflection of these lenses was analyzed on the basis of an angular spectrum approach for different substrate materials. A minimum reflectivity as low as 2 x 10-4 was realized by means of in situ controlled multilayers of TiO2 and SiO2. The lenses have a circular aperture of 2 mm and different focal lengths for the wavelengths of 1.52 and 0.63 μm, respectively. The kinoform profile in each zone of the Fresnel zone lenses was approximated by an eight-level profile. Such stepped profiles were realized with several masks written with an electron beam and transferred by photolithographic technology. Our measurements reveal that the spot sizes of the fabricated microlenses are close to the diffraction-limited values, and the highest measured diffraction efficiencies for the eight-level structures are greater than 80%.

An innovative deposition system has been developed to construct complex material thin films from single-element precursors by chemical beam vapor deposition (CBVD). It relies on well distributed punctual sources that emit individually controlled precursor beams toward the substrate under high vacuum conditions combined with well designed cryo-panel surfaces that avoid secondary precursor sources. In this configuration the impinging flows of all precursors can be calculated at any substrate point considering the controlled angular distribution of the emitted beams and the ballistic trajectory of the molecules. The flow simulation is described in details. The major advantage of the deposition system is its ability to switch between several possible controlled combinatorial configurations, in which the substrate is exposed to a wide range of flow compositions from the different precursors, and a uniform configuration, in which the substrate is exposed to a homogeneous flow, even on large substrates, with high precursor use efficiency. Agreement between calculations and depositions carried out in various system configurations and for single, binary, or ternary oxides in mass transfer limited regime confirms that the distribution of incoming precursors on the substrate follows the theoretical models. Additionally, for some selected precursors and in some selected conditions, almost 100% of the precursor impinging on the substrate is incorporated to the deposit. The results of this work confirm the potentialities of CBVD both as a research tool to investigate efficiently deposition processes and as a fabrication tool to deposit on large surfaces.

Organic-inorganic hybrid tandem heterojunction ITO/AIPc:H2Pc/n-Si/Al photoelectric cell was fabricated by a pressing technology using preliminary vapor deposited bulk heterojunction films of mixed aluminum-phthalocyanine (AIPc) and metal free phthalocyanine (H2Pc) on the n-Si substrate and ITO coated plastic substrate. By keeping face to face the heterojunction films, the substrates (silicon and ITO coated plastic substrates) were pressed and fixed by adhesive at elevated temperature conditions. Total thickness of the AlPc and H2Pc films were equal to 340 nm. On the back side of n-Si substrate the Al film was deposited. Device architecture was the following: ITO/AlPc:H2Pc/n-Si/Al. The morphology of the organic semiconductors film was investigated by AFM. The optical properties of the AIPc-H2Pc film were studied by UV visible spectroscopy. Current Voltage characteristics were measured at dark condition and under illumination as well. Under illumination of 290 W/m(2) the values of V-oc, I-sc, FF and efficiency were equal to 0.32 V, 0.9 mA/cm(2), 0.37 and 0.22 %, respectively.

Thin films find several applications depending on both their morphology and chemistry. We have recently implemented a double step deposition process in which film chemistry can be controlled separately from film growth. The molecules of the substance chosen for the deposit are obtained by dissociating an appropriate precursor into an inductively coupled plasma (ICP) obtained from an argon-oxygen mixture. Molecules formed during this first phase are then extracted through a nozzle into a lower pressure deposition chamber. A supersonic freely expanding jet is thus produced, until recompression occurs through a shock wave. Before and after the latter, the flow properties and the degree of molecule clusterization are different. Consequently, film growth can be controlled by changing the substrate location. We will present the design and properties of this new versatile plasma source for thin film deposition. It is well know that ICP discharges work in the inductive regime (H) only after a transition from the capacitive regime (E), which is obtained if the applied voltage is high enough [1]. This transition has been studied using optical and electrical probes. Optical emission spectroscopy has been chosen as an easy and non-intrusive tool for studying other plasma properties. We have selected and modified a simplified radiative model for argon proposed in reference [2], with the aim of evaluating electron temperature. When plasma is obtain from both argon and oxygen the actinometry technique [3] allows to monitor the abundance of oxygen atoms, which will play a role in precursor dissociation. When the precursor is injected, the shape of light emission spectra is useful for monitoring the deposition process. Flow dynamics and the supersonic expansion influence on film growth will be described. Eventually, a few examples of titanium dioxide deposits will be presented in order to demonstrate this new source potentialities.