[Show abstract][Hide abstract] ABSTRACT: Designing new approaches to incorporate dopant impurities in semiconductor materials is essential in keeping pace with electronics miniaturization without device performance degradation. On the basis of a mild solution-phase synthetic approach to functionalize silica nanoparticles, we were able to graft tailor-made boron-molecular precursors and control the thermal release of boron in the silica framework. The molecular-level description of the surface structure lays the foundation for a structure–property relationship approach, which is readily and successfully implemented to dope non-deglazed silicon wafers. As the method does not require an additional oxide capping step and shows minimal risk of carbon contamination, as demonstrated by compositional and electrical characterizations of the wafers, it is perfectly adapted to advanced microelectronics manufacturing processes.
The Journal of Physical Chemistry C 05/2015; DOI:10.1021/acs.jpcc.5b03408 · 4.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The use of reconstructed silicon wafers obtained after high temperature annealing under H2 atmosphere was demonstrated as an efficient way for increasing the bonding energy of silicon hydrophobic bonding (Rauer et al. 2013). Mechanisms occurring in these bondings are the focus of this paper. Si bonding interface closure was analyzed at the nanometer scale using X-Ray Reflectivity and Fourier Transform InfraRed spectroscopy in multiple internal reflexion mode. These two characterization techniques enable one to follow the interface closure taking under consideration mechanical and chemical aspects. We have shown that the terrace morphology and the monohydride surface termination specific to reconstructed Si surfaces both play a role in obtaining an efficient bonding gap closure after annealing at low temperature.
[Show abstract][Hide abstract] ABSTRACT: We report on the efficiency and thermal stability of p-doping by iodine on single and randomly stacked, weakly coupled bilayer polycrystalline graphene, as directly measured by photoelectron emission microscopy. The doping results in work function value increase of 0.4–0.5 eV, with a higher degree of iodine uptake by the bilayer (2%) as compared to the single layer (1%) suggesting iodine intercalation in the bilayer. The chemistry of iodine is identified accordingly as I3− and I5− poly iodide anionic complexes with slightly higher concentration of I5− in bilayer than monolayer graphene, likely attributed to differences in doping mechanisms. Temperature dependent in-situ annealing of the doped films demonstrated that the doping remains efficient up to 200 °C.
[Show abstract][Hide abstract] ABSTRACT: We report the first measurements of photo-carrier lifetimes in silicon nanocrystal-based third generation solar cells by Kelvin force microscopy and x-ray photoelectron spectroscopy under modulated frequency light illumination. A high concentration of active defects at the interface between the nanocrystals and silicon oxide matrix may be passivated by annealing under hydrogen. We found that the carrier lifetime, τ, is τ = 7 × 10(-5) s and τ = 3.5 × 10(-5) s within 10% accuracy for the hydrogen passivated and non-passivated nanocrystals, respectively. We used an exponential model to confirm the experimental potential measurements and to estimate photo-carrier lifetimes.
[Show abstract][Hide abstract] ABSTRACT: La microscopie à sonde de Kelvin (KFM) est capable de fournir une mesure résolue spatialement et en énergie de la structure de bande en surface d'un matériau. Elle dépend néanmoins fortement des propriétés physiques de la pointe utilisée, propriétés pouvant être la largeur de l'apex, la forme géométrique de la surpointe (nanocristal, nanofil) ou encore la raideur du levier. L'idée de ce travail est de comparer les résultats KFM obtenus sur un échantillon de calibration BAM-L200  pour différentes pointes (Pointes conductrices avec ou sans nanocristaux, avec ou sans surpointe, pointes fines) et selon différentes préparations (Abrasion, chauffage).
[Show abstract][Hide abstract] ABSTRACT: Organic photodetectors with inverted structure are fabricated by solution process techniques. A very thin interfacing layer of polyethyleneimine leads to a homogenous interface with low work function. The devices exhibit excellent performances, in particular in terms of low dark current density, wide range linearity, high detectivity, and remarkable stability in ambient air without encapsulation.
[Show abstract][Hide abstract] ABSTRACT: The influence of strain on the thermally induced dewetting mechanism of silicon films is reported. This study shows that the initial strain level in the silicon film significantly affects the final size and shape of the silicon agglomerates resulting from the film dewetting. With the increase of the biaxial strain up to 1.6%, the size of the silicon agglomerates is significantly reduced while their density increases. Moreover, the shape of the agglomerates becomes elongated when the strain favors one of the in-plane crystallographic directions to minimize the total energy of the system. A quantitative analysis of the dewetting mechanism is presented in terms of the agglomerates size and density versus the strain level. Finally, phenomenological laws are extracted, which predict the size and shape of the agglomerates.
[Show abstract][Hide abstract] ABSTRACT: The bonding of hydrophobic, reconstructed (001) Si surfaces obtained with high temperature H2 processes has been studied with atomic force microscopy, low energy electron diffraction spectroscopy, X-ray reflectivity and bonding energy measurements. Surface reconstruction is shown to strongly affect bonding mechanisms. As a consequence, bonding energies of such surfaces are significantly higher, in the room temperature −500 °C range, than those of “HF-last” surfaces.
[Show abstract][Hide abstract] ABSTRACT: Actually, thermally induced thin-films dewetting silicon in the silicon-on-insulator is a way to obtain silicon agglomerates with a size and a density fixed by the silicon film thickness. In this paper we report a new method to monitor both the size and the density of the Si agglomerates thanks to the deposition of a carbon-like layer. We show that using a 5-nm thick layer of silicon and additional ≤1-nm carbonated layer; we obtain agglomerates sizes ranging from 35 nm to 60 nm with respectively an agglomerate density ranging from 38 μm−2 to 18 μm−2. Additionally, for the case of strained silicon films an alternative dewetting mechanism can be induced by monitoring the chemical composition of the sample surface.
[Show abstract][Hide abstract] ABSTRACT: Direct metal bonding represents an advanced joining technology that allows vertical stacking with electrical conduction and even heat dissipation. For most metals used as bonding layers, direct bonding when operating under ambient conditions involves metal oxides. The bonding interface saddles with a trapped oxide layer that might affect electrical conduction and even complete sealing of bonding interface. Titanium especially because of its high affinity with oxygen makes oxide free direct bonding very difficult. In the mean time, the remarkable getter effect of Ti matrix allows the dissolution of oxygen during post bonding annealing. In this paper, the bonding limits with regards to the titanium thickness have been investigated. The key role of layer roughness on the bonding quality and energy has been pointed out. A titanium thickness below 10 nm appears as a limit for an oxide free bonding in our conditions. (C) 2013 The Electrochemical Society.
[Show abstract][Hide abstract] ABSTRACT: Structural, chemical and electronic properties of electroforming in the TiN/HfO(2) system are investigated at the nanometre scale. Reversible resistive switching is achieved by biasing the metal oxide using conductive atomic force microscopy. An original method is implemented to localize and investigate the conductive region by combining focused ion beam, scanning spreading resistance microscopy and scanning transmission electron microscopy. Results clearly show the presence of a conductive filament extending over 20 nm. Its size and shape is mainly tuned by the corresponding HfO(2) crystalline grain. Oxygen vacancies together with localized states in the HfO(2) band gap are highlighted by electron energy loss spectroscopy. Oxygen depletion is seen mainly in the central part of the conductive filament along grain boundaries. This is associated with partial amorphization, in particular at both electrode/oxide interfaces. Our results are a direct confirmation of the filamentary conduction mechanism, showing that oxygen content modulation at the nanometre scale plays a major role in resistive switching.
[Show abstract][Hide abstract] ABSTRACT: Photoelectron emission microscopy (PEEM) is a powerful non-destructive tool for spatially resolved, spectroscopic analysis of surfaces with sub-micron chemical heterogeneities. However, in the case of micron scale patterned semiconductors, band line-ups at pn junctions have a built-in lateral electric field which can significantly alter the PEEM image of the structure with respect to its physical dimensions. Furthermore, real surfaces may also have physical topography which can reinforce or counteract the electrically induced distortion at a pn junction. We have measured the experimental PEEM image distortion at such a junction and carried out numerical simulations of the PEEM images. The simulations include energy filtering and the use of a contrast aperture in the back focal plane in order to describe the changes in the PEEM image of the junction with respect to its real physical dimensions. Threshold imaging does not give a reliable measurement of micron sized p and n type patterns. At higher take-off energies, for example using Si 2p electrons, the pattern width is closer to the real physical size. Physical topography must also be quantitatively accounted for. The results can be generalized to PEEM imaging of any structure with a built-in lateral electric field.
Journal of Electron Spectroscopy and Related Phenomena 02/2013; 186(1):30–38. DOI:10.1016/j.elspec.2013.01.014 · 1.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The influence of strain on the thermally induced dewetting mechanism of silicon films is reported.
This study shows that the initial strain level in the silicon film significantly affects the final size and
shape of the silicon agglomerates resulting from the film dewetting. With the increase of the biaxial
strain up to 1.6%, the size of the silicon agglomerates is significantly reduced while their density
increases. Moreover, the shape of the agglomerates becomes elongated when the strain favors one of
the in-plane crystallographic directions to minimize the total energy of the system. A quantitative
analysis of the dewetting mechanism is presented in terms of the agglomerates size and density
versus the strain level. Finally, phenomenological laws are extracted, which predict the size and
shape of the agglomerates.
Journal of Applied Physics 01/2013; 114:063502. · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this article we demonstrate the growth of silicon carbide pyramidal shaped nanoparticles from the carbonate contamination of (001) silicon surface. The growth process involves thermal annealing under ultra high vacuum conditions at temperatures ranging from 1050 K to 1150 K. The silicon carbide composition of the particles is confirmed by scanning Auger microscopy measurements. These particles have sizes ranging from 5 nm to 20 nm and the same orientation imposed by the underlying crystalline silicon surface. Finally, we show that the density of the nanoparticles can be controlled by monitoring the quantity of carbonated species deposited on top of the silicon surface.
Thin Solid Films 01/2013; 527:133–136. DOI:10.1016/j.tsf.2012.11.055 · 1.76 Impact Factor