Tunneling Atomic Layer-Deposited Aluminum Oxide: a Correlated Structural/Electrical Performance Study for the Surface Passivation of Silicon Junctions.

Passivation is a key process for the optimization of silicon p-n junctions. Among the different technologies used to passivate the surface and contact interfaces, alumina is widely used. One key parameter is the thickness of the passivation layer that is commonly deposited using atomic layer deposition (ALD) technique.

Triangular nanoperforation and band engineering of InGaAs quantum wells: a lithographic route toward Dirac cones in III-V semiconductors.

The design of two-dimensional periodic structures at the nanoscale has renewed attention for band structure engineering. Here, we investigate the nanoperforation of InGaAs quantum wells epitaxially grown on InP substrates using high-resolution e-beam lithography and highly plasma based dry etching. We report on the fabrication of a honeycomb structure with an effective lattice constant down to 23 nm by realising triangular antidot lattice with an ultimate periodicity of 40 nm in a 10 nm thick InGaAs quantum well on a p-type InP.

Electrical detection of plasmon-induced isomerization in molecule-nanoparticle network devices.

We use a network of molecularly linked gold nanoparticles (NPSAN: nanoparticle self-assembled network) to demonstrate the electrical detection (conductance variation) of plasmon-induced isomerization (PII) of azobenzene derivatives (azobenzene bithiophene: AzBT). We show that PII is more efficient in a 3D-like NPSAN (cluster-NPSAN) than in a purely two-dimensional NPSAN (i.e.

Enhanced photovoltaic performance of inverted polymer solar cells through atomic layer deposited AlO passivation of ZnO-nanoparticle buffer layer.

In this work, an atomic layer deposited (ALD) AlO ultrathin layer was introduced to passivate the ZnO-nanoparticle (NP) buffer layer of inverted polymer solar cells (PSCs) based on P3HT:PCBM. The surface morphology of the ZnO-NP/AlO interface was systematically analyzed by using a variety of tools, in particular transmission electron microscopy (TEM), evidencing a conformal ALD-AlO deposition. The thickness of the AlO layers was optimized at the nanoscale to boost electron transport of the ZnO-NP layer, which can be attributed to the suppression of oxygen vacancy defects in ZnO-NPs confirmed by photoluminescence measurement.

Local Schottky contacts of embedded Ag nanoparticles in AlO/SiN :H stacks on Si: a design to enhance field effect passivation of Si junctions.

This paper describes an original design leading to the field effect passivation of Si n-p junctions. Ordered Ag nanoparticle (Ag-NP) arrays with optimal size and coverage fabricated by means of nanosphere lithography and thermal evaporation, were embedded in ultrathin-AlO/SiN :H stacks on the top of implanted Si n-p junctions, to achieve effective surface passivation. One way to characterize surface passivation is to use photocurrent, sensitive to recombination centers.

Shallow Heavily Doped n++ Germanium by Organo-Antimony Monolayer Doping.

Functionalization of Ge surfaces with the aim of incorporating specific dopant atoms to form high-quality junctions is of particular importance for the development of solid-state devices. In this study, we report the shallow doping of Ge wafers with a monolayer doping strategy that is based on the controlled grafting of Sb precursors and the subsequent diffusion of Sb into the wafer upon annealing. We also highlight the key role of citric acid in passivating the surface before its reaction with the Sb precursors and the benefit of a protective SiO overlayer that enables an efficient incorporation of Sb dopants with a concentration higher than 10 cm.

Enhancement of Electrical Properties of Nanostructured Polysilicon Layers Through Hydrogen Passivation.

The light absorption of polysilicon planar junctions can be improved using nanostructured top surfaces due to their enhanced light harvesting properties. Nevertheless, associated with the higher surface, the roughness caused by plasma etching and defects located at the grain boundary in polysilicon, the concentration of the recombination centers increases, leading to electrical performance deterioration. In this work, we demonstrate that wet oxidation combined with hydrogen passivation using SiN(x):H are the key technological processes to significantly decrease the surface recombination and improve the electrical properties of nanostructured n(+)-i-p junctions.

Confinement-modulated junctionless nanowire transistors for logic circuits.

We report the controlled formation of nanoscale constrictions in junctionless nanowire field-effect transistors that efficiently modulate the flow of the current in the nanowire. The constrictions act as potential barriers and the height of the barriers can be selectively tuned by gates, making the device concept compatible with the crossbar geometry in order to create logic circuits. The functionality of the architecture and the reliability of the fabrication process are demonstrated by designing decoder devices.

Nanoscale carrier multiplication mapping in a Si diode.

Carrier multiplication (CM), the creation of electron-hole pairs from an excited electron, has been investigated in a silicon p-n junction by multiple probe scanning tunneling microscopy. The technique enables an unambiguous determination of the quantum yield based on the direct measurement of both electron and hole currents that are generated by hot tunneling electrons. The combined effect of impact ionization, carrier diffusion, and recombination is directly visualized from the spatial mapping of the CM efficiency.

Direct characterization of native chemical ligation of peptides on silicon nanowires.

We describe the site-specific and chemoselective immobilization of peptides on hydrogen-terminated silicon nanowires (SiNWs) using native chemical ligation (NCL) (i.e., the reaction of a thioester group with a cysteine moiety to give a stable amide bond).

Narrowing the length distribution of Ge nanowires.

Synthesis of nanostructures of uniform size is fundamental because the size distribution directly affects their physical properties. We present experimental data demonstrating a narrowing effect on the length distribution of Ge nanowires synthesized by the Au-catalyzed molecular beam epitaxy on Si substrates. A theoretical model is developed that is capable of describing this puzzling behavior.

Efficient photogeneration of charge carriers in silicon nanowires with a radial doping gradient.

by performing electrodeless time-resolved microwave conductivity measurements, the efficiency of charge carrier generation, their mobility, and the decay kinetics on photoexcitation were studied in arrays of Si nanowires grown by the vapor-liquid-solid mechanism. Large enhancements in the magnitude of the photoconductance and charge carrier lifetime are found depending on the incorporation of impurities during the growth. They are explained by the internal electric field that builds up, due to higher doped sidewalls, as revealed by detailed analysis of the nanowire morphology and chemical composition.

Atomic scale investigation of silicon nanowires and nanoclusters.

In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed.

Synthesis of long group IV semiconductor nanowires by molecular beam epitaxy.

We report the growth of Si and Ge nanowires (NWs) on a Si(111) surface by molecular beam epitaxy. While Si NWs grow perpendicular to the surface, two types of growth axes are found for the Ge NWs. Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls.

Coulomb energy determination of a single Si dangling bond.

Determination of the Coulomb energy of single point defects is essential because changing their charge state critically affects the properties of materials. Based on a novel approach that allows us to simultaneously identify a point defect and to monitor the occupation probability of its electronic state, we unambiguously measure the charging energy of a single Si dangling bond with tunneling spectroscopy. Comparing the experimental result with tight-binding calculations highlights the importance of the particular surrounding of the localized state on the effective charging energy.

The collagen assisted self-assembly of silicon nanowires.

The paper reports on self-assembly of silicon nanowire junctions assisted by protocollagen, a low cost soluble long fiber protein and precursor of collagen fibrils. First, the collagen was combed on an octadecyl-terminated silicon surface with gold electrodes. Then the combed surface was exposed to an aqueous suspension of silicon nanowires.

Characterization of nanogap chemical reactivity using peptide-capped gold nanoparticles and electrical detection.

Nanogaps are usually combined with synthetic or biological molecules to produce nanodevices having novel properties. This combination is better realized by controlling the chemical properties of the nanogap. We show here that the presence of a specific chemical group inside nanogaps (30-90 nm) can be probed electrically using 10 nm gold nanoparticles derivatized by complementary functional groups.

Probing the carrier capture rate of a single quantum level.

The performance of many semiconductor quantum-based structures is governed by the dynamics of charge carriers between a localized state and a band of electronic states. Using scanning tunneling spectroscopy, we studied the transport of inelastic tunneling electrons through a prototypical localized state: an isolated dangling-bond state on a Si(111) surface. From the saturation of the current at an energy resonant with this state, the hole capture rate by the dangling bond was determined.

Current based antibodies detection from human serum enhanced by secondary antibodies labelled with gold nanoparticles immobilized in a nanogap.

We present the electrical detection of immunoglobulin G (IgGs) from human serum using a nanogap-based biosensor. The detection method is based on the capture of IgGs by a probe immobilized between gold nanoelectrodes of 30-90nm spacing. The captured IgGs are further reacted with secondary antibodies labelled with gold nanoparticles (GNPs).

Electrical detection of human immunoglobulins G from human serum using a microbiosensor.

A biosensor for the electrical detection of human antibodies from serum has been fabricated and experimentally demonstrated. The device is based on the immobilization of proteins used as probes between a set of microelectrodes. Incubation with diluted human serum was followed by incubation with anti-human secondary antibodies labeled with gold nanoparticles (GNPs) and then precipitation of silver on the nanoparticles.

Electron transport via local polarons at interface atoms.

Electronic transport is profoundly modified in the presence of strong electron-vibration coupling. We show that in certain situations, the electron flow takes place only when vibrations are excited. By controlling the segregation of boron in semiconducting Si(111)-square root 3 x square root 3 R 30 degrees surfaces, we create a type of adatom with a dangling-bond state that is electronically decoupled from any other electronic state.

Fluidics of a nanogap.

We have determined the filling properties of nanogaps with chemically heterogeneous walls. The quantitative criteria we present allow the prediction of the liquid loading of the nanostructure. They can easily be applied in combination with contact-angle measurements on planar substrates of the nanogap materials.

Detecting the chemoselective ligation of peptides to silicon with the use of cobalt-carbonyl labels.

While fluorescent-based methods are generally used to detect the immobilization and the interactions of biomolecules to solid supports, recent studies have shown their limitations in the case of silicon surfaces. As an alternative, we investigated the synthesis of peptides labeled with a metal transition complex and their subsequent immobilization to the silicon surfaces. The feasibility of using such probes has been explored by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS).

Trichlorosilane isocyanate as coupling agent for mild conditions functionalization of silica-coated surfaces.

Despite the importance of the isocyanate group in chemistry, very few examples of isocyanate-modified silicas have been reported, and all of the strategies described so far led to partial or total hydrolysis or condensation of the isocyanate group. By synthesizing trichlorosilane isocyanate as the coupling reagent, we show that oxidized silicon wafers are successfully modified with the isocyanate group. Our method is achieved in mild conditions, at low temperature, without side-reactions and allows the formation of a self-assembled monolayer (SAM) of isocyanates.