The etching behavior of n-GaP in aqua regia solutions

Abstract

The etching of GaP, whether in strong HNO 3 or in strong HCl is severely inhibited, whereas mixtures of HNO 3 /HCl are commonly employed as etchants for chemical polishing. The etching mechanism of n-GaP in aqua regia (3HCl/ 1HNO 3 ) has been investigated. Aqua regia etching may occur by accomplishing both the following two processes:(1) oxidation and (2) dissolution. First, the nascent chlorine and nitrate ions obtained from the vigorous interaction between HCl and HNO 3 , may easily oxidize the surface atoms of GaP, then nucleophilic attacked by Cl ) on the electron-poor trivalent gallium ions of the oxide lattice generally takes place over the passive surface. Moreover, the remaining phosphate or phosphorus oxide is very soluble. Ga and P atoms are thus carried away from the surface by the etchant system. In HNO 3 -etch, the nitrate ion formed is a weak nucleophile and the amount of its production is very small. In the HCl-etch, Cl ) causes a direct attack on GaP substrate via an Ga (I) chloro intermediate whose thermodynamics is very unfavorable. Thus, the experimental observations are in good agreement with the mechanistic concepts presented.

Fluid and Highly Curved Model Membranes on Vertical Nanowire Arrays

“…The GaP core was selectively removed by immersing the sample in aqua regia. 12,29 SEM imaging revealed the remaining shell of SiO x on the substrate, indicating that the sputter coating was able to cover the entire nanowire surface on even the densest sample (Figure S1 in the Supporting Information).…”

“…To confirm the uniformity of the oxide layer and verify that the shadowing effect had not prevented SiO x from coating the entire nanowire walls, nanowires from a sample with high nanowire density (9 NW μm –2 ) were transferred to a silicon wafer. The GaP core was selectively removed by immersing the sample in aqua regia. , SEM imaging revealed the remaining shell of SiO x on the substrate, indicating that the sputter coating was able to cover the entire nanowire surface on even the densest sample (Figure S1 in the Supporting Information).…”

Unexpected Dioxin Formation During Digestion of Soil with Oxidizing Acids

“…The slightly different congener profiles might have been caused by different dominant oxidative species between HNO 3 and aqua regia digestion. In terms of oxidizability, aqua regia is much stronger than HNO 3 because reactive chlorine species (Cl 2 , ClO – , ClO 2 – , ClO 2 , ClO 3 – , ClO 5 – , and Cl + ) are produced from the interaction of HCl and HNO 3 . − Therefore, the strong effects of oxidizing acids might be the key factor in PCDD/Fs formation during soil digestion.…”

“…Aqua regia (HCl/HNO 3 = 3:1, v / v ) is commonly used in industrial and commercial processes such as etching and sample digestion for metal analysis. The two acids are mixed to produce nitryl chloride and free chlorine as strong oxidants that can dissolve metals in samples. − The chlorination of some aromatic compounds via aqua regia has been reported due to the presence of strong oxidative conditions with chlorine species. Therefore, PCDD/Fs might form during the digestion of soil with aqua regia through chlorination of organic matter, particularly the lignin matrix and phenolic compounds.…”

Dye Sensitization of n and p Type Gallium Phosphide Photoelectrodes

“…Prior to photoelectrochemical measurements the GaP crystal was polished for 5 min with a soft polishing cloth using 20 nm colloidal silica (Buehler, Inc) to remove the native oxide layer and rinsed with MilliQ 18 M water, followed by an etch in fresh aqua regia (HCl : H 2 SO 4 = 3 : 1 volume ratio) to remove the thin oxide layer. 8,9 Rhodamine 6G (Rh-6G) (ACROS), Rhodamine B (Rh-B) (EAST-MAN), Cresyl Violet Perchlorate (Kodak), Nile Blue A Perchlorate (Kodak) and Crystal Violet (Kodak) were used as received. Cyclic voltammetry, with 2.5 mM dyes and 50 mM supporting electrolyte (tetrabutylammonium hexafluorophosphate (Fluka)) in acetonitrile under inert atmosphere (glove box), was used measure the reduction and the oxidation potentials of the dye molecules.…”