Physicochemical Characterization of Porous Silicon Surfaces Etched in Salt Solutions of Varying Compositions and pH

2003 ◽  
Vol 762 ◽  
Author(s):  
Mariem Rosario-Canales ◽  
Ana R. Guadalupe ◽  
Luis F. Fonseca ◽  
Oscar Resto
Keyword(s):  
Porous Silicon ◽  
Current Density ◽  
Silicon Oxide ◽  
Physicochemical Characterization ◽  
Silicon Surfaces ◽  
Silicon Oxide Layer ◽  
Electrochemical Processes ◽  
Current Densities ◽  
Secondary Ion

AbstractWe prepared porous silicon (PSi) structures by standard electrochemical processes using aqueous sodium fluoride (NaF) solutions. We report the dependence of the porous structure on the variation of pH and salt concentration of the etching solution, and the applied current density. The PSi structures were characterized by Scanning Electron Microscopy (SEM) and Secondary Ion Mass Spectroscopy (SIMS) to determine the pore size and distribution and the surface chemical composition. Results obtained from SEM show that the PSi grown has two different structures depending on the current density. Low current densities produce a uniform, high-density arrangement of pores while high current densities yield a sponge-like structural network. SIMS results indicate that the porous framework is covered with a silicon oxide layer.

Origin of Mosaic Structure Obtained During the Production of Porous Silicon with Electrochemical Etching

2019 ◽  
Vol 11 (12) ◽  
pp. 1218-1224
Author(s):  
Dao Tran Cao ◽  
Cao Tuan Anh ◽  
Luong Truc Quynh Ngan
Keyword(s):  
Porous Silicon ◽  
Oxide Layer ◽  
Current Density ◽  
Silicon Oxide ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Mosaic Structure ◽  
Anodic Current Density ◽  
Anodic Current ◽  
Silicon Oxide Layer

So far, while producing porous silicon (PSi) with anodic etching of silicon in an aqueous solution of hydrofluoric acid, many researchers (including us) have obtained the crack-into-pieces (or mosaic) structure. Most of the authors believed that the cause of this structure is the collapse and the cracking of the porous, especially highly porous, silicon layer which took place during the drying of PSi after fabrication. However, our study showed that the mosaic structure was formed right during the course of silicon anodization at high anodic current density. Furthermore, our study also showed that at high anodic current density the real silicon etching has been replaced by the growth of a silicon oxide layer. This is a layer of another substance that grows on silicon, so when the layer is too thick (which is obtained when the anodic current density is too high and/or the anodization time is too long) it will crack, creating mosaic pieces. When the silicon oxide layer is cracked, the locations around the cracks will be etched more violently than elsewhere, creating trenches. Thus, the mosaic structure with mosaic pieces emerged between the trenches has formed.

scholarly journals Impedance Characterization of an LCO-NMC/Graphite Cell: Ohmic Conduction, SEI Transport and Charge-Transfer Phenomenon

Batteries ◽  
2018 ◽  
Vol 4 (3) ◽  
pp. 43 ◽  
Author(s):  
Victoria Ovejas ◽  
Angel Cuadras
Keyword(s):  
Charge Transfer ◽  
Solid Electrolyte Interphase ◽  
Impedance Spectrum ◽  
Half Cell ◽  
Electrochemical Processes ◽  
Sei Layer ◽  
Current Densities ◽  
Li Ion ◽  
Impedance Characterization

Currently, Li-ion cells are the preferred candidates as energy sources for existing portable applications and for those being developed. Thus, a proper characterization of Li-ion cells is required to optimize their use and their manufacturing process. In this study, the transport phenomena and electrochemical processes taking place in LiCoO2-Li(NiMnCo)O2/graphite (LCO-NMC/graphite) cells are identified from half-cell measurements by means of impedance spectroscopy. The results are calculated from current densities, instead of absolute values, for the future comparison of this data with other cells. In particular, impedance spectra are fitted to simple electrical models composed of an inductive part, serial resistance, and various RQ networks—the parallel combination of a resistor and a constant phase element—depending on the cell. Thus, the evolution of resistances, capacitances, and the characteristic frequencies of the various effects are tracked with the state-of-charge (SoC) at two aging levels. Concretely, two effects are identified at the impedance spectrum; one is clearly caused by the charge transfer at the positive electrode, whereas the other one is presumably caused by the transport of lithium ions across the solid electrolyte interphase (SEI) layer. Moreover, as the cells age, the characteristic frequency of the charge transfer is drastically reduced by a factor of around 70%.

ChemInform Abstract: Porous Silicon Oxide Layer Formation by the Electrochemical Treatment of a Porous Silicon Layer.

ChemInform ◽  
1990 ◽  
Vol 21 (47) ◽  
Author(s):  
M. YAMANA ◽  
N. KASHIWAZAKI ◽  
A. KINOSHITA ◽  
T. NAKANO ◽  
M. YAMAMOTO ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Oxide Layer ◽  
Silicon Oxide ◽  
Silicon Layer ◽  
Electrochemical Treatment ◽  
Porous Silicon Layer ◽  
Layer Formation ◽  
Silicon Oxide Layer

Optical and Microstructural Investigations of Porous Silicon Coated with a-Si:H Using PECVD Technique

2008 ◽  
Vol 587-588 ◽  
pp. 308-312
Author(s):  
R. Prabakaran ◽  
Hugo Aguas ◽  
Luís Pereira ◽  
E. Elangovan ◽  
Elvira Fortunato ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Current Density ◽  
Spectroscopic Ellipsometry ◽  
Electronic States ◽  
Surface Oxide ◽  
Effective Medium Approximation ◽  
High Current ◽  
Multilayer Model ◽  
Current Densities ◽  
Ftir Investigation

In the present work, the spectroscopic ellipsometry (1.5 - 5.5 eV) was used to investigate the effects of current density induced microstructural variations and their influence on the electronic states of as-prepared and a-Si:H coated porous silicon (PS). The pseudodielectric responses of the low and high current densities (5 and 40 mA/cm2) were analyzed using a multilayer model within the effective medium approximation. The FTIR investigation reveals the enhancement of surface oxide (Si-Ox) layer with current density and the improvement of the Si-Hx band after a-Si:H coating.

Experimental Characterization of the Reliability of Multi-Terminal Dual-Damascene Copper Interconnect Trees

2003 ◽  
Vol 766 ◽  
Author(s):  
C. L. Gan ◽  
C.V. Thompson ◽  
K. L. Pey ◽  
W. K. Choi ◽  
C. W. Chang ◽  
...  
Keyword(s):  
Current Density ◽  
Void Nucleation ◽  
Experimental Results ◽  
Experimental Characterization ◽  
Dual Damascene ◽  
Current Densities ◽  
The Common ◽  
Number Of Segments ◽  
Atomic Source

AbstractThe reliability of Cu dual-damascene interconnect trees with 3-terminal (dotted-I), 4-terminal (‘T’) and 5-terminal (‘+’) configurations has been investigated. The lifetime of multiterminal interconnect trees with the same current density through the common middle via was determined to be independent of the number of segments connected at the common junction. Furthermore, our experimental results on dotted-I test structures showed an increase in the reliability of the interconnect tree when the distribution of a same current was not equal in the two connected segments, especially for the cases where one of the segments was acting as a passive reservoir or active source of Cu atoms for the adjoining segment. Due to the low barrier for void nucleation at the Cu/Si3N4 interface, the presence of any small atomic source in neighboring segments will enhance the reliability of a connected segment in which Cu atoms are being drained away. As a consequence, failure can occur in a tree segment which is stressed at significantly lower current densities than more highly stressed adjoining segments.

Microstructure of Porous Silicon Thin Films

1998 ◽  
Vol 4 (S2) ◽  
pp. 632-633
Author(s):  
Y. Berta ◽  
R. A. Gerhardt
Keyword(s):  
Solar Cells ◽  
Porous Silicon ◽  
Current Density ◽  
Electrochemical Anodization ◽  
Antireflective Coating ◽  
Silicon Thin Films ◽  
Potential Applications ◽  
Current Densities ◽  
Low Efficiency ◽  
The Cost

Porous silicon has potential applications in the microelectronics industry. It has been investigated as an electroluminescent source1, as a sensing device in chemical sensors and as an antireflective coating for solar cells. The low efficiency of the solar cells is enhanced by the antireflective coating that porous silicon provides, while the cost of fabrication of the cells is decreased. Porous silicon is normally processed by electrochemical anodization of silicon wafers. Since parameters such as current density, anodization time, and surface conditions can affect the microstructure of the films obtained, we varied the current density to study the effect of the microstructure on the resultant reflectance for the purpose of improving it. It has been found that higher current densities result in higher reflectance films than the lower current densities.

Nanoparticle-Decorated Surfaces for the Study of Cell-Protein-Substrate Interactions

2004 ◽  
Vol 845 ◽  
Author(s):  
Jake D. Ballard ◽  
Ludovico M. Dell'Acqua-Bellavitis ◽  
Rena Bizios ◽  
Richard W. Siegel
Keyword(s):  
Silica Nanoparticles ◽  
Surface Coverage ◽  
Silicon Oxide ◽  
Substrate Surface ◽  
Silicon Surfaces ◽  
Native Oxide ◽  
Cell Protein ◽  
Fabrication And Characterization ◽  
Nanoscale Features

ABSTRACTThe present study was motivated by the need for accurately-controlled and well-characterized novel biomaterial formulations for the study of cell-protein-material interactions. For this purpose, the current research has focused on the design, fabrication and characterization of model native oxide-coated silicon surfaces decorated with silica nanoparticles of select sizes, and has examined the adhesion of osteoblasts and fibroblasts on these nanoparticle-decorated surfaces. The results demonstrate the capability to deposit nanoparticles of select diameters and substrate surface coverage onto native silicon oxide-coated silicon, the firm attachment of these nanoparticles to the underlying native silicon oxide, and that nanoparticle size and coverage modulate adhesion of osteoblasts and fibroblasts to these substrates. The material formulations tested provide a well-controlled and well-characterized set of model substrates needed to study the effects of nanoscale features on the functions of cells that are critical to the clinical fate of implantable biomaterials.

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