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The Horizon 2020 project PECSYS aims to build a large area demonstrator for hydrogen production from solar energy via integrated photovoltaic (PV) and electrolysis systems of different types. In this study, Si- and CIGS-based photovoltaics are developed together with three different electrolyzer systems for use in the corresponding integrated devices. The systems are experimentally evaluated and a general model is developed to investigate the hydrogen yield under real climatic conditions for various thin film and silicon PV technologies and electrolyser combinations. PV characteristics using a Si heterojunction (SHJ), thin film CuInxGa1-xSe2, crystalline Si with passivated emitter rear totally diffused and thin film Si are used together with temperature dependent catalyst load curves from both acidic and alkaline approaches. Electrolysis data were collected from (i) a Pt-IrO2-based acidic electrolysis system, and (ii) NiMoW-NiO-based and (iii) Pt-Ni foam-based alkaline electrolysis systems. The calculations were performed for mid-European climate data from Julich, Germany, which will be the installation site. The best systems show an electricity-to-hydrogen conversion efficiency of 74% and over 12% solar-to-hydrogen (STH) efficiencies using both acidic and alkaline approaches and are validated with a smaller lab scale prototype. The results show that the lower power delivered by all the PV technologies under low irradiation is balanced by the lower demand for overpotentials for all the electrolysis approaches at these currents, with more or less retained STH efficiency over the full year if the catalyst area is the same as the PV area for the alkaline approach. The total yield of hydrogen, however, follows the irradiance, where a yearly hydrogen production of over 35 kg can be achieved for a 10 m(2) integrated PV-electrolysis system for several of the PV and electrolyser combinations that also allow a significant (100-fold) reduction in necessary electrolyser area for the acidic approach. Measuring the catalyst systems under intermittent and ramping conditions with different temperatures, a 5% lowering of the yearly hydrogen yield is extracted for some of the catalyst systems while the Pt-Ni foam-based alkaline system showed unaffected or even slightly increased yearly yield under the same conditions.

3C-SiC layers (7 and 15 μm thick), epitaxially grown on silicon, were covered with gold nanoparticles by immersion in a solution containing HF and KAuCl4. The surface of the layers played a crucial role in the morphology of the deposited metal network and large gold agglomerates developed on the pronounced antiphase domain boundaries of the thinner layer. Preferential growth was not observed on the smooth surface of the 15 μm thick layer. Rutherford backscattering spectrometry and electron microscopy outlined a progressive nucleation that takes place for less than 60 s immersion times under a kinetic control process. For longer deposition time each cluster grows under a diffusion control process, resulting in flower-like gold particles. However, the nucleation and growth processes can be strongly modified by multiple immersions in solution after rinsing in water. The adopted procedure allows the tailoring of the particles size and avoids the aggregation, therefore improving by about 1 order of magnitude t...

Platinum thin films are deposited on open-cell nickel foam with porosity of 95% via spontaneous galvanic displacement. Ni foams with different morphologies and pore size are compared and characterized by electrochemical and structural analysis techniques. The effect of Pt coating on the electrochemical activity is studied by using the Pt coated foam as electrode material for hydrogen evolution reaction in an aqueous alkaline electrolyte. The electrocatalytic activity of the electrodes is evaluated using linear sweep voltammetry curves and Tafel plots as a function of deposition time. The comparison with scanning electron microscopy analyses demonstrates that the catalytic activity has a maximum when the platinum film completely covers the Ni surface. The further increase of the Pt thickness leads to mechanical instability with crack formation and delamination. The effect of the foam morphology on the Pt deposition rate has been evaluated and discussed, determining the minimum Pt amount required to achieve the maximum electrochemical activity, as well as the maximum thickness in order to assure stable characteristics before delamination occurs.

We have realized tandem amorphous Si / microcrystalline Si PV cells and modules with an n+ SiOx emitter heterojunction with microcrystalline Si. The SiOx films show filamentary nanostructures and high electrical conductivity. Excellent photovoltaic characteristics are demonstrated.

This work presents a preliminary study on the electrical characterization of high efficiency bifacial solar cells. An opening discussion on the state-of-the-art of such advanced technology is initially proposed and the experimental characterization of some prototypes is described. From this analysis, it can be stated that the bifacial silicon solar cells can be a very promising technology with high electrical performances and efficiency.

We experimentally analyze the signal-to-noise ratio of continuous wave (CW) near infrared spectroscopy (NIRS) reflectance systems based on light emitting diodes and silicon photomultipliers for high performance low cost NIRS biomedical systems. We show that under suitable experimental conditions such systems exhibit a high SNR, which allows an SDS of 7 cm, to our knowledge the largest ever demonstrated in a CW-NIRs system. (C) 2016 Optical Society of America

We study the spontaneous recovery phenomenon displayed by solar cells sensitized with a ruthenium complex-based dye N719, which manifests with the increase over the time (from several minutes up to some days) of the short circuit current density J sc and the open circuit voltage V oc , during cell illumination. Under dark conditions the current decreases over time after the application of forward bias voltages. We investigate the effects of temperature and electrolyte composition by means of current–voltage measurements and electrochemical impedance spectroscopy, both under dark and illumination conditions. The main result is that the recovery of the performances depends on the charge transport mechanism at the TiO 2 /electrolyte interface and is caused by the increasing of the electron lifetime in the titania. This effect could be explained by intercalation of ions H + present in the electrolyte that limits the recombination of electrons from TiO 2 to the triiodide.

The photoelectrochemical (PEC) water splitting cell, a device that uses sunlight to produce hydrogen, has garnered very much interest due to its simple structure, low fabrication cost and good performance. In these cells, a semiconductor photoelectrode is immersed in a liquid and, when illuminated, hydrogen and/or oxygen can be generated on its surface by electrolysis. Metal catalysts are often used to enhance the activity of the semiconductor, but the lifetime of the semiconductor photoelectrode is still the main bottleneck of this technology. In this manuscript we report the ageing mechanisms of silicon photoanodes coated with nickel films of different thicknesses (under the light-driven oxygen evolution reaction, OER). The n-Si photoanodes coated with 2 nm-thick, 5 nm-thick and 10 nm-thick nickel layers showed lifetimes of similar to 18 h, similar to 150 h and >260 h, respectively. While the 2 nm-thick sample degraded due to the formation of a thin SiOX layer at the metal-silicon interface, the performance of the thicker samples decreased due to the formation of holes. The 5 nm-thick and 10 nm-thick nickel films turned into homogeneous potassium-free NiOX films suitable for water splitting, and this conversion markedly enhanced the performance of the cells. The density/size of holes in the surface decreased/increased with the metal thickness. The potassium contamination in the 2 nm-thick Ni sample took place in the form of nanofilaments, and we demonstrated that the widely used X-ray photoelectron spectroscopy tests are blind to these features, which may have been ignored in all previous reports. These results could be useful for understanding the degradation and enhancing the yield of water-splitting solar cells.

The dark current behavior of the pixels forming the Si photomultiplier as a function of the applied overvoltage and operation temperature is studied. The data are modeled by assuming that dark current is caused by current pulses triggered by events of diffusion of single minority carriers injected from the peripheral boundaries of the active area depletion layer and by thermal emission of carriers from Shockley-Read-Hall defects in the active area depletion layer.

In this paper, an extensive investigation of hybrid molecular/Si field-effect memories is presented, where redox ferrocene (Fc) molecules play the role of the memory charge storage nodes. Engineering of the organic linkers between Fc and Si is achieved by grafting Fc with different linker lengths. The study shows a clear correlation between results from atomistic computational density functional theory, electrochemical measurements (cyclic voltammetry) and electrical data obtained by a detailed study on capacitors and pseudo-MOS devices. Physical-chemical analyses (atomic force microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy), corroborate the quality of molecular layers on devices.

Dielectric breakdown (BD) of nFETs with TiN metal gates and HfO 2 /interfacial layer with 1.09 nm EOT is studied. Occurrence of progressive BD at low current levels is demonstrated. A new measurement methodology for extraction of the PBD time and its dependence on gate voltage are reported.

In this paper, we evaluate the potentialities of hafnium-aluminates (HfAlO) materials as possible candidates for the interpoly dielectrics of future Flash memory devices. HfAlO layers of different thicknesses and compositions are integrated in single-layers and in Oxide/HfAlO/Oxide (OHO) triple-layer stacks, and analyzed in terms of coupling and insulating capabilities. We demonstrate that increasing the Hf content allows reducing the leakage current at high voltages but it results in a stronger leakage current at low voltages. We also show that once normalized in electric fields, the leakage current characteristics are independent of the high-k thickness. The electron conduction modes in these materials, at different temperatures, are also investigated. The activation energy increases with the Hf concentration in the HfAlO alloy, resulting in a higher leakage current at elevated temperatures. Finally, it is demonstrated that the conduction in triple-layer stacks is limited by a Poole–Frenkel conduction in the high-k layers, while the trap contribution in the case of single-layers becomes dominant when the HfAlO layer is thicker than 8 nm.

In this paper, we present the results regarding the electrical and optical characterization of bidimensional arrays of silicon single photon avalanche photodiodes (SPAD). Low average dark count rates and crosstalk probability, good timing jitter and high quantum detection efficiency in the visible range have been measured over 5 × 5 SPAD arrays with 40 μm single pixel active area diameter. Moreover, a very good uniformity of these parameters has been found over the single pixels. These good electro-optical performances make our photodiodes attractive for the fabrication of arrays with a larger number of SPAD. In view of the design of a dense array to be used as a silicon photomultiplier (SiPM) for medical diagnostic tools, 5 × 5 SPAD arrays have been also tested in the photon-resolving mode. Charge spectra show that the arrays, in this configuration, allow to resolve several photoelectron peaks with a good single photoelectron resolution.

In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes (GMAP) fabricated by silicon standard planar technology. Low dark count rates, negligible afterpulsing effects, good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields, as telecommunications and nuclear medical imaging.

We study the filament structure in 50 nm × 50 nm Resistive Random Access Memory (ReRAM) cells in the forming/set state with a Hf/HfO2/TiN metal-insulator-metal stack by scanning transmission electron microscopy in cross section view. We reveal the filament morphology and, by the measurement of filament size and electrical resistance, evaluate the average resistivity of the filament material. The combination of the various data indicates the nanostructure of the conductive filament.

In this paper, we present a nanometer-sized floating-gate memory device, fabricated on silicon-on-insulator substrate and using silicon nanocrystals as storage nodes. Single electron charging and discharging phenomena occurring at room temperature will be demonstrated and discussed by means of simple analytical models. A deeper investigation of the impact of critical dimensions of the memory cell (i.e., active area and channel width and length) on the device operation (in particular, memory programming window), performed on a large number of samples, will be reported. Qualitative explanations for the observed experimental behaviors will be given.

Nanoscale structures have been recently proposed as charge storage nodes due to their potential applications for future nanoscale memory devices. Our approach is based on the idea of using Si nanodots as discrete floating gates. To experimentally investigate such potential, we have fabricated MOS structures with Si nanocrystals. The dots have been deposited onto an ultra-thin tunnel oxide by chemical vapor deposition (CVD) of SiH 4 , and then annealed at 1000 °C for 40 s, to crystallize all the dots. After deposition, the dots have been covered by a CVD SiO 2 layer, thus resulting completely embedded into stoichiometric silicon oxide. The nanocrystal density and size have been studied by energy filtered TEM (EFTEM) analysis. An electrostatic force microscope has been used to locally inject and image charge. By applying a relatively large tip voltage and reducing the tip to sample separation down to the contact with the surface sample, a few dots have been charged, by appearing as protrusions on the surface. The charged dots have been monitored for up to 30 min, by showing no discharge effects either vertically, through the double barrier of oxide layers, or laterally, via cross talk effect between other close dots.

Design and fabrication of single photon avalanche detector (SPAD) in planar technology is reported. Device design and critical issues in the technology are discussed. Experimental test procedures are described for dark-counting rate, afterpulsing probability, photon timing resolution, and quantum detection efficiency. Low-noise detectors are obtained, with dark counting rates down to 10 c/s for devices with 10 /spl mu/m diameter, down to 1 kc/s for 50 /spl mu/m diameter. The technology is suitable for monolithic integration of SPAD detectors and associated circuits.

Silicon quantum dots have been deposited on top of a 3-nm tunnel oxide by Low Pressure Chemical Vapour Deposition (LPCVD) and coated with a 7-nm Chemical Vapour Deposited (CVD) oxide. This stack was then incorporated in Metal-Oxide-Semiconductor structure and used as floating gate of a memory cell. The presence of 3 nm of tunnel oxides allows the injection of the charge by direct tunnel (DT) using low voltages for both program and erase operations. The charge stored in the quantum dots is able to produce a well-detectable flat band shift in the capacitors or, equivalently, a threshold voltage shift in the transistors. Furthermore, due to the presence of SiO 2 between the grains, the lateral charge loss is reduced and, thus, long retention time are possible. In this work we present good memory action characterised by low write voltages, write times of the order of milliseconds and long retention time in spite of the low tunnel oxide thickness. © 2002 Elsevier Science B.V. All rights reserved.

The improvement of tandem hydrogenated amorphous/microcrystalline Si solar cells under prolonged exposure to reverse bias direct current electric fields and illumination has been investigated. In this work, the authors show that the application of reverse bias stress in the presence of illumination slows down the solar cell ageing kinetics (caused mainly by the Staebler–Wronski effect and by the increase in the series resistance) and, in suitable conditions, it produces an improvement of the solar cell characteristic parameters as a function of stress time. The authors discuss the effect of temperature, electric field intensity, and illumination level.

Radiation damage in silicon photomultipliers (SiPM) caused by exposure to 60Co γ-rays is experimentally evaluated and discussed. SiPM devices were irradiated to doses up to 9.4 kGy. Dark current, dark count rate, gain, single photon counting capability, and cross-talk probability among SiPM pixels are evaluated as a function of irradiation dose. Fil: Pagano, R.. Istituto per la Microelettronica e Microsistemi. Catania; Italia Fil: Lombardo, S.. Istituto per la Microelettronica e Microsistemi. Catania; Italia Fil: Palumbo, Félix Roberto Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Technion - Israel Institute of Technology; Israel Fil: Sanfilippo, D.. STMicroelectronics. Catania; Italia Fil: Valvo, G.. STMicroelectronics. Catania; Italia Fil: Fallica, G.. STMicroelectronics. Catania; Italia Fil: Libertino, S.. Istituto per la Microelettronica e Microsistemi. Catania; Italia

We have investigated the electrical transport and luminescence of Si dots embedded in SiO 2 . The dots have been obtained by high temperature annealing of silicon rich oxides prepared by chemical vapor deposition. Transmission electron microscopy analysis demonstrates the presence of crystalline Si dots with grain radii down to 1 nm. The data of luminescence and electrical transport appear correlated with the dot size distribution. Moreover, the analysis of the electrical characteristics of metal-oxide–semiconductor capacitors with silicon rich oxide films indicates that such systems may reversibly store charge, thus exhibiting the function of a memory.

We have studied the effects of nitridation with nitric oxide on the leakage current of thin (

We compare polysilicon emitter bipolar transistors fabricated by using diAerent treatments of the interface between single crystal and polycrystalline Si (polysilicon) in the emitter region. One of the treatments consisted in an in situ cleaning of the silicon surface performed in the deposition chamber prior to the polysilicon deposition, resulting in an oxide free interface. A detailed structural and electrical characterization of transistors with and without an oxide free interface is presented. It is shown that, even if common emitter current gain decrease is observed, a strong improvement of base resistance and breakdown voltage can be achieved, while maintaining noticeable high frequency characteristics. # 1999 Elsevier Science Ltd. All rights reserved.

The solid phase crystallization of chemical vapor deposited amorphous silicon films onto oxidized silicon wafers, induced either by thermal annealing or by ion beam irradiation at high substrate temperatures, has been extensively developed and it is reviewed here. We report and discuss a large variety of processing conditions. The structural and thermodynamical properties of the starting phase are emphasized. The morphological evolution of the amorphous towards the polycrystalline phase is investigated by transmission electron microscopy and it is interpreted in terms of a physical model containing few free parameters related to the thermodynamical properties of amorphous silicon and to the kinetical mechanisms of crystal grain growth. A direct extension of this model explains also the data concerning the ion-assisted crystal grain nucleation.

A detailed model for the reset process kinetics in HfO2-based RRAM is presented describing the transition between low and high resistance states at the atomic level. Based on the filament characteristics as observed by TEM, the kinetics of the reset operation is simulated using the Time Dependent Monte Carlo (TDMC) method incorporating ab-initio calculated microscopic characteristics of the oxygen ions in hafnia. Temperature and field driven oxygen diffusion in the oxide surrounding the filament is shown to provide the needed supply of oxygen to re-oxidize the tip of the filament and switch the device to the High Resistance State (HRS).

We have investigated the relationship between microstructure and electrical conductivity in semi-insulating polycrystalline silicon (SIPOS) with oxygen concentrations in the 2–35 at.% range and the effect of doping with boron, phosphorus, arsenic and erbium by ion implantation. SIPOS thin films are mixtures of silicon and silicon oxide phases. The chemical and morphological evolution of these phases upon annealing is emphasized. Electrical conductivity measurements are interpreted in terms of a physical model containing few free parameters related to the material microstructure. A direct extension of this model explains also the conductivity increase in SIPOS doped with elements of the third or the fifth group. In the last part of the paper, data of electroluminescence at 1.54 μm in Er-implanted SIPOS due to intra-4f transitions of the Er3+ ion are shown and discussed.

We have investigated the electrical characteristics of p+–n Si junction diodes implanted with 300 keV C ions at fluences of 0.5 and 1×1015 cm−2 and annealed at 900 or 1100 °C. In all cases cross‐sectional transmission electron microscopy shows an excellent crystalline quality, with no extended defects, and the C‐rich region is characterized by an n‐type doping. In the material annealed at 900 °C the C‐rich region shows a low electron mobility and the presence of deep donor levels, and, as a consequence, the diode characteristics are nonideal. These effects can be attributed to the formation of C–Si self‐interstitial‐type complexes after the 900 °C anneal. At 1100 °C part of the C–Si complexes dissolve and the electrical characteristics of the materials noticeably improve.

We have investigated electrical and structural characteristics of C coimplanted GexSi1−x layers formed by high dose Ge implantation in (100) Si followed by rapid thermal annealing at 1100 °C for 10 s. In the absence of C the layers, with Ge peak concentrations of about 15 at. %, are epitaxial and fully strained but show extrinsic dislocation loops in the Ge end of range region. In C coimplanted GexSi1−x the crystalline quality of the materials is improved since the formation of defects at the end of range is suppressed and the strain is reduced. From an electrical point of view the situation is reversed. The electrical characterization of p+/n diodes shows that, without C coimplantation, in GexSi1−x the hole mobility is larger than in Si, and the bandgap narrowing results in an increase of the minority carrier concentration. Moreover, the diffusion of minority carriers does not appear to be influenced by the presence of the secondary defects at the end of range. Vice versa, in C coimplanted GexSi1−x, even...

The photoluminescence of erbium‐doped semi‐insulating polycrystalline and amorphous silicon containing 30 at. % oxygen is studied. The films were deposited on single‐crystal Si substrates by chemical vapor deposition, implanted with 500 keV Er to fluences ranging from 0.05 to 6×1015 ions/cm2, and annealed at 300–1000 °C. Upon optical pumping near 500 nm, the samples show room‐temperature luminescence around 1.54 μm due to intra‐4f transitions in Er3+, excited by photogenerated carriers. The strongest luminescence is obtained after 400 °C annealing. Two classes of Er3+ can be distinguished, characterized by luminescence lifetimes of 170 and 800 μs. The classes are attributed to Er3+ in Si‐rich and in O‐rich environments. Photoluminescence excitation spectroscopy on a sample with 1×1015 Er/cm2 shows that ∼2% of the implanted Er is optically active. No quenching of the Er luminescence efficiency is observed between 77 K and room temperature in this Si‐based semiconductor. The internal quantum efficiency for the excitation of Er3+ via photogenerated carriers is 10−3 at room temperature. A model is presented which explains the luminescence data in terms of trapping of electrical carriers at localized Er‐related defects, and subsequent energy transfer to Er3+ ions, which can then decay by emission of 1.5 μm photons.

Room‐temperature electroluminescence at 1.54 μm is demonstrated in erbium‐implanted oxygen‐doped silicon (27 at. % O), due to intra‐4f transitions of the Er3+. The luminescence is electrically stimulated by biasing metal‐(Si:O, Er)‐p+ silicon diodes. The 30‐nm‐thick Si:O, Er films are amorphous layers deposited onto silicon substrates by chemical‐vapor deposition of SiH4 and N2O, doped by ion implantation with Er to a concentration up to ≊1.5 at. %, and annealed in a rapid thermal annealing furnace. The most intense electroluminescence is obtained in samples annealed at 400 °C in reverse bias under breakdown conditions and it is attributed to impact excitation of erbium by hot carriers injected from the Si into the Si:O, Er layer. The electrical characteristics of the diode are studied in detail and related to the electroluminescence characteristics. A lower limit for the impact excitation cross section of ≊6×10−16 cm2 is obtained.

We demonstrate sharp room-temperature electroluminescence at 1.54 μm due to intra-4f transitions of Er3+ in semi-insulating polycrystalline silicon (SIPOS) implanted with Er and annealed for implant damage recovery. Our measurements refer to SIPOS containing ≈ 30 at.% O, doped with Er to concentrations of about 1 at.% and annealed at a temperature in the 400–1100°C range. The luminescence has been excited either by optically pumping with an Ar laser or by biasing suitable metal-SIPOS-p+ silicon devices.

The electrical characterization of a-Si:H(n)/c-Si(p) structures prepared by three different deposition techniques is provided by the analysis of the dark and light I-V and C-V-F measurements. Obtained is the insight on the interface quality and contacts in the structure. The analysis of C-V-F measurements was supported by AFORS-HET simulation. Results have revealed the presence of the Schottky barrier in the structure deteriorating performance of the solar cells.

The formation of p‐ and n‐type layers of semi‐insulating polycrystalline silicon has been investigated by implantation and diffusion of B, P, and As. At room temperature the material resistivity can be changed by more than six orders of magnitude for both p‐ and n‐type doping. A dramatic decrease of resistivity is observed for dopant concentrations above a threshold level which corresponds to the complete filling of midgap grain‐boundary traps. The determination of this critical concentration allows the evaluation of the donor and acceptor grain‐boundary trap densities which are found to lie in the range from 7 to 14×1012/cm2. The charged traps produce depletion layers and potential barriers at the grain boundaries; these barriers drive the free‐carrier motion under external fields. Above the threshold concentration, the barrier height decreases with the increasing concentration of active dopant, going from ≊0.5 eV to nearly 0 and correspondingly the resistivity drops down. Thermionic emission and tunneli...

The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO 2 layers [used as gate dielectric in a metal-oxide-semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh time compared to conventional dynamic random access memory cells. © 2002 American Institute of Physics.

This paper reports on the electrical characteristics of silicon photomultipliers (SiPM) with optimized optical trench technology. The SiPM arrays were characterized from single pixels up to the full 64×64 pixel device. The data clearly show a perfect scaling of the dark current with the pixel number, thus indicating an almost ideal insulation among the pixels in the whole voltage operating range.

In this paper we show that single-photon avalanche detectors (SPADs) may have a strong potential as very sensitive on-wafer tools for lifetime monitoring, given their simple fabrication process and their straightforward use in the measurements. We have fabricated Si SPADs with n + -p structures and we show that dark counting has a simple exponential dependence on time, thus making it possible to extract a single lifetime parameter.

Silicon photomultipliers are nowadays considered a promising alternative to conventional vacuum tube photomultipliers. The physical mechanisms operating in the device need to be fully explored and modeled to understand the device operational limits and possibilities. In this work we study the dark current behavior of the pixels forming the Si photomultiplier as a function of the applied overvoltage and operation temperature. The data are well modeled by assuming that dark current is caused by current pulses triggered by events of diffusion of single minority carriers (mostly electrons) injected from the boundaries of the active area depletion layer (dominating at temperatures above 0°C) and by thermal emission of carriers from Shockley-Read-Hall defects in the depletion layer (dominating at temperatures below 0°C).

In this paper an extensive investigation of hybrid molecular/silicon field-effect memories is presented, where Redox Ferrocene (Fc) molecules play the role of the memory charge storage nodes. Engineering of the organic linkers between Fc and Si is achieved by grafting Fc with different linker lengths. The study shows a clear correlation between results from atomistic computational Density Functional Theory (DFT), electrochemical measurements (Cyclic Voltammetry) and electrical data obtained by a detailed study on Pseudo-MOS devices. Physical- chemical analyses (Atomic Force Microscopy, high-resolution Transmission Electron Microscopy, X-Ray Photoelectron Spectroscopy), were used to monitor the molecular layers.

We report experimental investigations on the amorphous-to-crystal transition in silicon during ion bombardment. The transition was induced by 600 keV Kr irradiation of an amorphous layer in contact with a crystalline substrate. The growth rate depends on the substrate temperature, orientation and the logarithm of the dopant concentration. The crystallization was also stimulated in absence of a planar seed by irradiating an amorphous silicon layer deposited on a thick layer of SiO2. The presence of crystal seeds with radius of the order of a few nanometers in the as-deposited material has been observed. The growth of these seeds is controlled by the motion of [111] boundaries. The grain density is constant with the irradiation dose but it decreases with the substrate temperature. All of the data are discussed in terms of a phenomenological model based on the assumption that the same defects are responsible for the amorphous-to-crystal transition both in pure thermal and in ion-assisted processes.

The diffusion into a p‐type Si substrate of arsenic ions implanted into TiSi2 layers has been investigated for several thermal diffusion treatments in the 900–1100 °C temperature range. The drive‐in was performed using either a rapid thermal annealing system or a traditional furnace. Shallow (20–80‐nm depth) junctions were obtained with a high (1019–1020/cm3) dopant concentration at the silicide‐silicon interface. The amount of diffused arsenic atoms measured by Rutherford backscattering spectrometry increases linearly with the square root of the annealing time. A similar relation was found for the amount of electrically active arsenic, as measured by Van der Pauw structure in combination with anodic oxidation. The two quantities differ and the inactive dopants precipitate in the diffused layer as seen by transmission electron microscopy. This behavior might be associated to the high tensile stress induced by the silicide layer on the surface silicon region and to its influence on the solid solubility and...

We present the realization of hybrid silicon core/silicon nitride shell nanodots by Low Pressure Chemical Vapor Deposition (LPCVD) and their application as floating gate in Non Volatile Memory (NVM) devices. The LPCVD process includes three steps: nucleation using SiH4, selective growth of the silicon nuclei using SiH2Cl2 and finally selective growth of silicon nitride using a mixture of SiH2Cl2 and NH3 around the silicon dot. The two first steps have already been described in literature. We will therefore focus on the selective growth of a nitride layer on silicon dots. Morphological characterization using Scanning Electron Microscopy (SEM) allows control over dots size – 5 to 10nm – and density – up to 1E12/cm2. High Resolution Transmission Electron Microscopy (HRTEM) shows a crystalline silicon core and an outer shell of amorphous silicon nitride. Energy Filtered TEM pictures confirm that the nitride layer is deposited only around the silicon dots and not on the oxide. Oxidation resistance of the silicon nitride shell is also investigated. A 2nm thick silicon nitride layer is an efficient barrier to an oxidation at 800°C in dry oxygen for 5 minutes. We thus have a very thin high quality stoechiometric nitride layer. Such a high quality nitride film can only be achieved using in-situ deposition i.e. on an oxide-free silicon surface. Finally, hybrid Si/SiN nanodots are integrated in a single memory cell with high-K interpoly dielectric. Electrical results show large threshold voltage shift of 6V. The use of silicon nitride shells on the silicon dots has therefore two main advantages: it provides both oxidation resistance and charge storage enhancement.

The integration of silicon nanocrystal (Si-nc) nonvolatile memory (NVM) arrays with HfAlOx based interpoly dielectric (IPD) is presented for the first time. The data obtained on array vehicles programmed in Fowler-Nordheim operation regime are in excellent agreement with previously presented results on single cells, as well as theoretical data and allow the evaluation of the scalability of the Si-nc concept.

In this paper, we evaluate the potentiality of hafnium aluminium oxide (HfAlO) high-k materials for control dielectric application in non-volatile memories. We analyze the electrical properties (conduction and parasitic trapping) of HfAlO single layers and SiO"2/HfAlO/SiO"2 triple layer stacks as a function of the HfAlO thickness and Hf:Al ratio. A particular attention is given to the electrical behaviour of the samples at high temperature, up to 250^oC. Experimental results obtained on silicon nanocrystal memories demonstrate the high advantage of HfAlO based control dielectrics on the memory performances for Fowler-Nordheim operation. Then an analytical model is presented, to simulate the program erase characteristics in the transient regime and at saturation, depending on the high-k control dielectric properties. A very good agreement is obtained between the experimental data and the simulation results.

We studied the enzyme glucose oxidase (GOx) immobilization on silicon oxide surfaces. In particular, we optimized the immobilization protocol and verified that it fulfills both requirements of enzyme preservation (measured by enzymatic activity) and VLSI compatibility. The immobilization consists of four steps: oxide activation, silanization, linker molecule deposition and GOx immobilization. It is crucial to form an uniform linker layer on the sample surface in order to maximize the sites available for enzyme bonding and achieving the best enzyme deposition. In this study, utilizing glutaraldehyde as bifunctional reagent, we monitored its uniformity on the surface through X-ray Photoelectron Spectroscopy (XPS). Once optimized, the same protocol was used to anchor the enzyme in a porous silicon dioxide matrix. Gold labeled GOx molecules were monitored by electron diffraction X-ray (EDX) measurements coupled with scanning electron microscopy (SEM). The enzymatic activity was also monitored to confirm the goodness of the proposed immobilization method. Finally, the electrical characterization of MOS capacitors, showing a shift of about 1 V in the flat band voltage, demonstrated the possibility to use this approach for electrical detection.

International audience; In this paper we show for the 1 st time that Silicon nanocrystal (Si-ncs) memories with high-k (HfO2, Al2O3 and HfAlO) interpoly dielectrics (IPD) can offer excellent behaviour in the Fowler-Nordheim regime, with great relevance for future sub-45nm NAND memory generations. We significantly advance the state-of-the-art by showing a strict correlation between the different IPD properties (high-k dielectric constants, leakage currents) and the performance obtained on memory transistors down to 90nm gate lengths. In particular the results demonstrate that HfAlO IPDs combine the fast p/e and good 10 5 cycles endurance behaviour of HfO2 and the long retention of Al2O3 with no activation up to 125°C. Then, in order to boost the memory window, we also integrated a hybrid Si-nc/SiN layer floating gate, with a HfAlO based IPD. It is shown that a 6V Vth can be achieved, with good retention and cycling behaviours. Finally, a physical model of Si-nc memories is introduced which explains the impacts of IPD characteristics on memory performance. Introduction The large success of mobile equipment is leading to a dramatic increase of the market for NAND Flash, key devices for mass data storage [1]. Discrete trap memories, such as TANOS [2] and Si-nc memories [3,4] are one of the most suitable candidates to push integration density further beyond the 45nm node, because of their good scalability, robustness against SILC and low floating gate (FG) to floating gate coupling. In particular, Si-nc memories offer the potential of better data-retention at high temperature (the stored electrons being trapped in the Si-nc energy conduction band, rather than in temperature-activated deep traps of nitride), as well as mitigated lateral charge migration (the Si-ncs being isolated from one to the other by silicon dioxide rather than nitride). However, up to now, Si-nc memories have always shown poor FN program/erase characteristics, due to the small Si-nc/control gate coupling. In order to overcome this issue, engineering of the tunnel dielectric and/or IPD [5, 6] is necessary. In particular, in this paper, we present for the 1 st time to our knowledge an exhaustive experimental and theoretical study of Si-nc memories where the conventional HTO or oxide/nitride/oxide (ONO) interpoly dielectric is replaced by HfO2, Al2O3 or HfAlO based IPD. Excellent performance and clear correlations between the device electrical results and the IPD material properties are shown. We also suggest how to solve another issue of Si-nc devices, which makes them poorly interesting for multi-level NAND applications, i.e. the relatively small programming window. As a possible solution we propose the addition of a thin SiN layer over the Si-ncs, which allows for a significant increase of the memory window. Our approach is widely validated through in-depth analysis of Si-nc memories with HfO2, Al2O3 or HfAlO IPD, based on several material results, electrical data on memory transistors, physical modelling and TCAD three-dimensional simulations.

FinFETs have been proposed for transistor scaling because of their improved robustness to short channel effects and excellent current drive. Recently, the finFET concept together with discrete trap storage has been studied for Flash memory scaling because of the advantage of reduced floating gate interferences and reduced cell-to-cel cross talk in high-density devices. We have realized Si nano-floating gate (NFM) finFET Flash devices with highly scaled active width and channel length. Improved performances and endurance compared with planar NFM devices are observed in 3D structures (fin width down to 20 nm). Localization of the inversion charge favors low aspect ratio finFET Flash devices with the additional advantage of improved manufacturability.

Praseodymium based dielectric thin films have been deposited by Metal-Organic Chemical Vapour Deposition (MOCVD). Special emphasis has been placed upon deposition parameters crucial to obtain Pr2O3 phase and upon interfacial characterization. In addition, dielectric properties have been correlated to structural and compositional characteristics of praseodymium containing films. The breakdown (BD) characteristics of Pr2O3 films have been investigated by an innovative and handling approach based on C-AFM. Moreover, the BD kinetics have been elucidated considering the role of defects in the conduction mechanisms.

In this work, we present an experimental study on the single-electron effects observed at room temperature in silicon nanocrystal memories. The electrical characterization has been performed by means of a purposely designed low noise high bandwidth measurement system. Relevant statistical properties of the threshold voltage shifts induced by single-electron trapping and detrapping in the silicon dots are reported. The kinetics of electron capture and emission is also discussed.

The formation of Si dots by chemical vapor deposition is studied from the very early stages of the dot formation up to about 25% of substrate coverage. Structural characterization is mainly performed by means of energy filtered transmission electron microscopy, which couples chemical information to very high spatial resolution. The dots are shown to be surrounded by Si-free regions and this is attributed to the Si adatom capture mechanism from each nucleus. The data are discussed in the framework of a self-similar model, which takes into account the dot local environment, the adatom diffusion and the continuous nucleation of new islands. From the fit to the data the correlation between the dot size and the capture area is obtained and the number of deactivated nucleation sites is quantified.