Influence of oxygen, hydrogen, helium, argon and vacuum on the surface behavior of molten InSb, other semiconductors, and metals on silica

Sessile drop experiments were performed on molten indium antimonide on clean quartz (fused silica) surfaces. A cell was constructed through which argon, helium, oxygen, hydrogen or a mixture of these was flowed at 600 °C. Some of the InSb was doped with 0.1% Ga. The surface tension σ of oxide-free molten InSb was smaller in Ar than in He, may have increased with increasing O₂ in the gas, and was not influenced by Ga or H₂. The contact angle θ on silica was higher in the presence of Ar, was lowered by O₂, and was not influenced by H₂ or Ga. The work of adhesion W and the surface energy σ_sv of the silica were higher in He than in Ar. The surface remained free of solid oxide only in flowing gas containing 0.8 ppm O₂. This behavior is attributed to reaction of O₂ at the surface of the melt to form In₂O gas. When solid oxide formed on Ga-doped material, it was strongly enriched in Ga, with the Ga/In ratio increasing with the concentration of O₂ in the gas.

Examination of published sessile-drop results for liquid metals and semiconductors on silica revealed that W and σ_sv were highest for reactive melts, in which SiO₂ dissolves. For non-reactive melts, W and σ_sv were lower and θ higher in a gas than in a vacuum, regardless of whether the experiments had been carried out in sealed ampoules, a flowing gas, or dynamic vacuum. The implication is that the surface of silica was different in a vacuum than in a gas at 1 bar.