Investigations on Electrode-Less Wet Etching of GaN Using Continuous Ultraviolet Illumination

Green, R. T.; Tan, W. S.; Houston, P.A.; Wang, T.; Parbrook, P. J.

doi:10.1007/s11664-006-0070-8

Cited by 15 publications

(16 citation statements)

References 17 publications

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“…In plasma-assisted electrochemistry configurations, which are systems wherein the working electrode is replaced by a DC microplasma, the half-reactions take place at the counter electrode and the PLI . Electrolytic systems capable of initiating redox reactions using reactive species without requiring electrical contact with a counter electrode have been described as a form of electrodeless electrochemical systems. − One such example of an electrodeless system is a free atmospheric pressure plasma jet (APPJ) impinging upon a liquid solution (Figure ). The absence of solid electrodes obscures the locations of the half-reactions (i.e.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Structure of the Plasma–Liquid Interface

Oldham

Thimsen

2022

J. Phys. Chem. C

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Nonthermal atmospheric pressure plasma in contact with a liquid yields a variety of energetic photons, ions, and electrons, which can be transported into the plasma–liquid interface (PLI). Similar to the electrochemical interface formed between a solid electrode and electrolyte in conventional electrochemical systems, the charge-transfer process across the PLI is able to promote reduction–oxidation (redox) reactions. However, in the case of free plasma jets in contact with liquids, the absence of solid electrodes obscures the spatial locations of the electrochemical half-reactions. Herein, we present a spatial electrochemical measurement technique used to characterize an aqueous solution in contact with an atmospheric pressure plasma jet. The technique is based on measuring the potential difference between two identical Ag/AgCl electrochemical electrodes positioned at different locations within the solution. More specifically, electrochemical maps were made by measuring the potential of one electrochemical electrode positioned at different locations near the PLI with respect to the other electrochemical electrode positioned far away from the PLI in the bulk solution. Regions in the map with negative and positive potential differences between these electrochemical electrodes were used to identify the electrodeless cathode and anode, respectively. Visualization of the spatial distribution of molecular colorimetric redox indicators by multispectral imaging revealed that reduction was occurring near the plasma jet centerline while oxidation was occurring further away in solution, which constitutes an independent confirmation of the electrochemical maps.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Structure of the Plasma–Liquid Interface

Oldham

Thimsen

2022

J. Phys. Chem. C

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“…Many reports on GaN PEC etching are available. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Here, we mention conventional PEC etching, which includes electrodes. Photo-assisted anodic oxidation is the basis of the PEC etching of GaN.…”

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confidence: 99%

Simple wet-etching technology for GaN using an electrodeless photo-assisted electrochemical reaction with a luminous array film as the UV source

Horikiri

Fukuhara

Ohta

et al. 2019

Appl. Phys. Express

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A simple setup for electrodeless photo-assisted electrochemical (PEC) etching was discussed from the viewpoint of the experimental geometry, in which the sample was dipped into the electrolyte under ultraviolet (UV) irradiation. Sulfate radicals ( ) were produced from K2S2O8 with UV light as the oxidizing agent; this consumed the extra UV photogenerated electrons, making it electrodeless. The transmittances were measured for various concentrations of K2S2O8 (aq.) to adjust the electrolyte depth. The effect of tetramethylammonium hydroxide post-treatment was also examined. The results indicate that damage-free PEC etching is feasible for everyone, even those who are not familiar with electrochemistry.

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“…The inhomogeneity arises and is enhanced by the difference in etching rate between n + -GaN and i-GaN at the initial etching stage. To reduce the roughness originating from PEC etching, etching under diffusion-limited conditions is assumed to be useful, 44) so a smooth etched surface is expected to be obtained by using a higher UVC light intensity and a more diluted KOH solution. In fact, the surface roughness is larger for higher concentrations of KOH in the electrolyte, as shown in Figs.…”

Section: •-mentioning

confidence: 99%

Fabrication of GaN nanowires containing n⁺-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

Shimauchi

Miwa

Toguchi

et al. 2021

Appl. Phys. Express

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We attempted to fabricate GaN nanowires by electrodeless photo-assisted electrochemical (PEC) etching and successive alkaline solution treatment. The sample consisting of n + -doped and unintentionally doped GaN grown on a GaN substrate was selectively etched using a Ti mask in a mixed solution of K 2 S 2 O 8 and KOH under UV light radiation. This specific layer structure required a relatively concentrated KOH solution for etching. The PEC etching resulted in the formation of a tapered cone structure of GaN with its top diameter determined by the mask size. Successive KOH treatment after PEC etching yielded GaN nanowires with diameters of about 220 nm.

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Investigations on Electrode-Less Wet Etching of GaN Using Continuous Ultraviolet Illumination

Cited by 15 publications

References 17 publications

Electrochemical Structure of the Plasma–Liquid Interface

Electrochemical Structure of the Plasma–Liquid Interface

Simple wet-etching technology for GaN using an electrodeless photo-assisted electrochemical reaction with a luminous array film as the UV source

Fabrication of GaN nanowires containing n⁺-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

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Investigations on Electrode-Less Wet Etching of GaN Using Continuous Ultraviolet Illumination

Cited by 15 publications

References 17 publications

Electrochemical Structure of the Plasma–Liquid Interface

Electrochemical Structure of the Plasma–Liquid Interface

Simple wet-etching technology for GaN using an electrodeless photo-assisted electrochemical reaction with a luminous array film as the UV source

Fabrication of GaN nanowires containing n+-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

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Fabrication of GaN nanowires containing n⁺-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment