9 research outputs found
Oxygen plasma and warm nitric acid surface activation for low-temperature wafer bonding
In this paper, the void formation and the surface energy for low-temperature Si-Si wafer bonding technique as a function of the annealing time and temperature as well as warm nitric acid and O-2-plasma-assisted surface pretreatments are considered and compared. The analysis of the surface energy vs annealing time exhibits two main bonding mechanisms: (i) rapid reaction between silanol groups which leads to a quick enhancement of the bonding strength, and (ii) slow further increase of bonding strength and improvement of the bonding uniformity thanks to the out-diffusion of interface voids. (c) 2006 The Electrochemical Society
Silicon Nanowires/Reduced Graphene Oxide Composites for Enhanced Photoelectrochemical Properties
The top of silicon nanowires (SiNWs)
arrays was coated with reduced graphene oxide (rGO) by the facile
spin-coating method. The resulting SiNWs/rGO composite exhibits enhanced
photoelectrochemical properties, with short-circuit photocurrent density
more than 4 times higher than that of the pristine SiNWs and more
than 600 times higher than that of planar Si/rGO composite. The trapping
and recombination of photogenerated carriers at the surface state
of SiNWs were reduced after the application of rGO. The results of
electrochemical impedance spectroscopy measurements suggest that the
reduction of trapping and recombination of photogenerated carriers
as well as remarkably enhancement of photoelectrochemical properties
can be attributed to the low charge transfer resistance at the SiNWsârGO
interface and rGOâelectrolyte interface. The method and results
shown here indicate a convenient and applicable approach to further
exploitation of high activity materials for photoelectrochemical applications
Effect of Fluoride Ions on the Surface Dissolution of Vanadium-Bearing Biotite
In shale vanadium ore, vanadium is mainly formed as a low-V(III) homogeneous phase to partially replace Si and exists in the lattice structure of aluminosilicate minerals such as biotite. During the acid leaching of shale vanadium ore, an activator is needed to effectively extract vanadium. Using biotite as a tetrahedral structure doped with Aluminum-Silicon tetrahedron structure, the interaction between leaching-agent ions (H+), activator ions (F−), and vanadium-containing biotite surface was discussed by DFT quantum chemical calculations. The dissolution behavior of activator fluoride ions on the surface of vanadium-bearing biotite during sulfuric acid leaching was revealed. According to the simulated leaching results, the oxygen on the biotite surface first absorbed hydrogen ions to undergo complete hydroxylation, and then combined with hydrogen ions to form water molecules. However, in the presence of activator (NaF), fluoride ions were adsorbed on the surface cations, which catalyzed the formation of water molecules and promoted the dissolution of surface cations. SEM–EDS analysis showed that the surface of vanadium-bearing minerals became very irregular, and the number of voids and cracks greatly increased. At the same time, XPS showed that the addition of activator fluoride ions destroyed the Al-O tetrahedron structure. Many Al and V atoms dissolved in the solution, which improved the leaching rate of vanadium
Effect of Fluoride Ions on the Surface Dissolution of Vanadium-Bearing Biotite
In shale vanadium ore, vanadium is mainly formed as a low-V(III) homogeneous phase to partially replace Si and exists in the lattice structure of aluminosilicate minerals such as biotite. During the acid leaching of shale vanadium ore, an activator is needed to effectively extract vanadium. Using biotite as a tetrahedral structure doped with Aluminum-Silicon tetrahedron structure, the interaction between leaching-agent ions (H+), activator ions (Fâ), and vanadium-containing biotite surface was discussed by DFT quantum chemical calculations. The dissolution behavior of activator fluoride ions on the surface of vanadium-bearing biotite during sulfuric acid leaching was revealed. According to the simulated leaching results, the oxygen on the biotite surface first absorbed hydrogen ions to undergo complete hydroxylation, and then combined with hydrogen ions to form water molecules. However, in the presence of activator (NaF), fluoride ions were adsorbed on the surface cations, which catalyzed the formation of water molecules and promoted the dissolution of surface cations. SEMâEDS analysis showed that the surface of vanadium-bearing minerals became very irregular, and the number of voids and cracks greatly increased. At the same time, XPS showed that the addition of activator fluoride ions destroyed the Al-O tetrahedron structure. Many Al and V atoms dissolved in the solution, which improved the leaching rate of vanadium