Porous Silicon Formation by Galvanic Etching

Kołasiński, Kurt W.

doi:10.1007/978-3-319-04508-5_3-2

Cited by 2 publications

(2 citation statements)

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“…The galvanic technique relies on using the current generated by the electrochemical potential difference between the exposed Si and the platinum deposited on the backside of the wafer. ,,− The galvanic technique is useful because Si chips of arbitrary dimensions can be etched and the etch rate is quite high, which helps minimize the time the wafer is exposed to HF that can cause damage to the metals of the ignitor wire. The chips are etched for 10 min and produce an nPS film that is ∼65 μm thick as measured by SEM cross section and a porosity measured by the gravimetric method of 79–83%.…”

Section: Methodsmentioning

confidence: 99%

Nanoporous Silicon Combustion: Observation of Shock Wave and Flame Synthesis of Nanoparticle Silica

Becker

Gillen

Staymates

et al. 2015

ACS Appl. Mater. Interfaces

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The persistent hydrogen termination present in nanoporous silicon (nPS) is unique compared to other forms of nanoscale silicon (Si) which typically readily form a silicon dioxide passivation layer. The hydrogen terminated surface combined with the extremely high surface area of nPS yields a material capable of powerful exothermic reactions when combined with strong oxidizers. Here, a galvanic etching mechanism is used to produce nPS both in bulk Si wafers as well as in patterned regions of Si wafers with microfabricated ignition wires. An explosive composite is generated by filling the pores with sodium perchlorate (NaClO4). Using high-speed video including Schlieren photography, a shock wave is observed to propagate through air at 1127 ± 116 m/s. Additionally, a fireball is observed above the region of nPS combustion which persists for nearly 3× as long when reacted in air compared to N2, indicating that highly reactive species are generated that can further combust with excess oxygen. Finally, reaction products from either nPS-NaClO4 composites or nPS alone combusted with only high pressure O2 (400 psig) gas as an oxidizer are captured in a calorimeter bomb. The products in both cases are similar and verified by transmission electron microscopy (TEM) to include nano- to micrometer scale SiOx particles. This work highlights the complex oxidation mechanism of nPS composites and demonstrates the ability to use a solid state reaction to create a secondary gas phase combustion.

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Section: Methodsmentioning

confidence: 99%

Nanoporous Silicon Combustion: Observation of Shock Wave and Flame Synthesis of Nanoparticle Silica

Becker

Gillen

Staymates

et al. 2015

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…Thinning of the space charge region at a high doping level enhances tunneling through the barrier. 34 Therefore, porous and photoluminescent Si NWs can be formed with highly doped Si in analogy to galvanic 35 or electrochemical 36 etching. The dissolution by H 2 O 2 of deposited Ag followed by its redeposition may also play a role in remote etching.…”

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confidence: 99%