Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

Razi, F.; zad, Azam Iraji; Rahimi, Firoozeh

doi:10.1016/j.snb.2010.01.047

Cited by 30 publications

(22 citation statements)

References 33 publications

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“…This thesis builds on the large number of studies by other scientists who have used porous silicon as an electrochemical gas sensor [6,7,8], which works on very simple principles.…”

Section: Electrochemical Sensorsmentioning

confidence: 99%

“…-If the porous layer is to be treated as its own thin film, then it has an interface which contains a depletion region between itself and the crystalline material underneath, even if they are both made of silicon [3,8]. The existence of this layer has actually been heavily studied and soundly proved [3], although the nature of this depletion region is always difficult to predict in any way.…”

Section: The Fourth Corner: Materials Properties Reduxmentioning

confidence: 99%

“…While all reported studies have used their own values for each of the parameters, one parameter remains remarkably constant in every sensor fabrication experiment in literature: the decision to always etch pores out of p-type silicon [6,7,8].…”

Section: Previous Workmentioning

confidence: 99%

“…Since in p-doped silicon the front-side is in forward bias, the back-side is in reverse and to overcome it an ohmic contact must be made onto this interface. This back-side ohmic contact is critical and is usually achieved through a metal evaporation or physical sputtering process; adding an extra, potentially expensive, processing step before etching can even begin [6,7,8].…”

Section: Previous Workmentioning

confidence: 99%

“…Less material leads to less light absorption and fewer nucleation sites, a perpetual problem in many reported studies. The other frequently reported problem: p-type layers often collapse when the catalyst deposits, due to the thin porous walls not able to bear the new metal [8,24].…”

Section: Previous Workmentioning

confidence: 99%

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Fabrication and Characterization of a Palladium/Porous Silicon Layer

Lui¹

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Fabrication and Characterization of a Palladium/ Porous Silicon Layer Nicholas LuiA scientific paper can be considered a journey into the logic and mind of the scientist who performed the experiment. This paper, a little unconventional, is written as a reflection of how the author organizes and thinks through his topic. In the telling of it this way, he hopes the journey is as compelling for the reader as it was for him.When porous silicon is plated with a catalytic metal, the two materials can act together as a single entity whose electrical properties are sensitive to its environment -the sensing component of an electrochemical gas sensor. Etching pores into silicon is an electrochemical process; and which type of doped silicon used is one of its key parameters. For nearly all reported porous silicon gas sensors, the silicon has been of the p-doped variety -because pdoped porous etching is better understood and the layers that result from it are more predictable -despite n-doped silicon having potentially significant benefits in ease of fabrication and being more conducive to plating by a catalyst. This experiment is an attempt at creating a palladium plated n-doped porous silicon layer, and an examination into what differentiates this fabrication process and the layers that result from the traditional p-doped type.The porous layers to be plated are to be the same and would ideally have properties that are a close approximation to what a functional gas sensor would require. This experiment defined a process that fabricated this "ideal" layer out of N-type, <100>, double polished silicon wafers with a resistance of 20 Ω cm. The wafers were subjected to the anodic etching method with an HF/ethanol mixture as the electrolyte; and only two (of among many) fabrication parameters were varied: HF concentration of the electrolyte and total etching time. We find that a concentration of 12% HF (by volume) and an etching time of 6 hours result in layers most appropriate to carry into plating. The anodization current density is 15 mA cm -2. Deposition of the catalyst, palladium, is done using the electroless method by immersing the porous layer in a .001M PdCl 2 aqueous bath.Characterization of this Pd/Porous Silicon layer was done by measuring resistivity by four point probe and imaging through Scanning Electron Microscopy. It was found that layers of a v maximum average of 63 ± 6% porosity were created using our fabrication method. There is evidence of palladium deposition, but it is spotty and irregular and is of no improvement despite the n-doping wafer makeup. Resistivity in well-plated regions was measured to be 7-10 Ωcm, while resistivity in regions not well-plated was measured to be 70-140 Ω cm. This is comparable to previous literature values, indicating n-silicon porous silicon can be fabricated and still have potential as a catalytic layer, should metal deposition methods improve.Keywords: Porous Silicon, Electroless Plating, Anodic Etching. vi Chapter 1: IntroductionAt its most general, a porous mate...

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“…This thesis builds on the large number of studies by other scientists who have used porous silicon as an electrochemical gas sensor [6,7,8], which works on very simple principles.…”

Section: Electrochemical Sensorsmentioning

confidence: 99%

Section: The Fourth Corner: Materials Properties Reduxmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

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Fabrication and Characterization of a Palladium/Porous Silicon Layer

Lui¹

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A novel approach for osteocalcin detection by competitive ELISA using porous silicon as a substrate

Rahimi

Arough

Yaghoobi

et al. 2017

Biotech and App Biochem

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In this study, porous silicon (PSi) was utilized instead of prevalent polystyrene platforms, and its capability in biomolecule screening was examined. Here, two types of porous structure, macroporous silicon (Macro-PSi) and mesoporous silicon (Meso-PSi), were produced on silicon wafers by electrochemical etching using different electrolytes. Moreover, both kinds of fresh and oxidized PSi samples were investigated. Next, osteocalcin as a biomarker of the bone formation process was used as a model biomarker, and the colorimetric detection was performed by competitive enzyme-linked immunosorbent assay (ELISA). Both Macro-PSi and Meso-PSi substrates in the oxidized state, specifically the Meso-porous structure, were reported to have higher surface area to volume ratio, more capacitance of surface-antigen interaction, and more ability to capture antigen in comparison with the prevalent platforms. Moreover, the optical density signal of osteocalcin detected by the ELISA technique was notably higher than the common platforms. Based on the findings of this study, PSi can potentially be used in the ELISA to achieve better results and consequently more sensitivity. A further asset of incorporating such a nanometer structure in the ELISA technique is that the system response to analyte concentration could be maintained by consuming lower monoclonal antibody (or antigen) and consequently reduces the cost of the experiment.

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Pd‐Ni/Cd loaded PPy/Ti composite electrode: Synthesis, characterization, and application for hydrogen storage

et al. 2019

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Summary A wide compositional range of Pd‐Ni/Cd on polypyrrole (PPy)‐modified Ti plates (Pd‐Ni/Cd/PPy/Ti) was fabricated via electrochemical deposition. The hydrogen absorption properties of the prepared Pd‐Ni/Cd/PPy/Ti electrodes were evaluated using cyclic voltammetry and chronoamperometry in acidic media. The optimal Pd36‐Ni7/Cd57/PPy/Ti electrode achieved a hydrogen storage capacity of 331.3 mC cm−2 mg−1 and an H/Pd ratio of 0.77. The enhancement of the hydrogen storage was attributed to a synergistic effect between the Pd‐Ni/Cd catalysts. The surface morphology, crystallinity, and chemical composition of the Pd‐Ni/Cd/PPy/Ti electrode were characterized using scanning electron microscope (SEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS), respectively. Hydrogen spillover occurred on the trimetallic catalysts, and secondary hydrogen spillover occurred on the PPy/Ti support. The enhanced hydrogen sorption capacity was due to both the synergistic effect of the trimetallic catalysts and the assistance of PPy, making Pd‐Ni/Cd/PPy/Ti a promising hydrogen storage material.

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Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

Cited by 30 publications

References 33 publications

Fabrication and Characterization of a Palladium/Porous Silicon Layer

Fabrication and Characterization of a Palladium/Porous Silicon Layer

A novel approach for osteocalcin detection by competitive ELISA using porous silicon as a substrate

Pd‐Ni/Cd loaded PPy/Ti composite electrode: Synthesis, characterization, and application for hydrogen storage

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