Defect-selective etching of icosahedral boron arsenide (B ₁₂As ₂) crystals in molten potassium hydroxide

The present work reports on the defect-selective etching (DSE) for estimating dislocation densities in icosahedral boron arsenide (B ₁₂As ₂) crystals using molten potassium hydroxide (KOH). DSE takes advantage of the greater reactivity of high-energy sites surrounding a dislocation, compared to the surrounding dislocation-free regions. The etch pits per area are indicative of the defect densities in the crystals, as confirmed by x-ray topography (XRT). Etch pit densities were determined for icosahedral boron arsenide crystals produced from a molten nickel flux as a function of etch time (1-5 minutes) and temperature (400-700°C). The etch pits were predominately triangle shaped, and ranged in size from 5-25μm. The average etch pit density of the triangle and oval etch-pits was on the order of 5×10 ⁷cm ^-2 and 3×10 ⁶cm ^-2 (respectively), for crystals that were etched for two minutes at 550°C.