Study of the interaction between molten indium and sub-atmospheric pressure hydrogen glow discharge for low-temperature nanostructured metallic particle film deposition

Indium (In) evaporation is enhanced by high-pressure hydrogen glow plasma, and a sponge-like In film containing submicron pores is prepared on the substrate. The glow plasma is generated at a total pressure of 13.3 kPa (100 Torr) as a capacitively coupled plasma. When the process atmosphere is diluted by He and Ar, the In evaporation rate increases by increasing the hydrogen concentration and no evaporation is observed without H-2 gas. The In deposition rate exhibits no dependence on the In temperature in the range from 300 degrees C to 600 degrees C. However, the In deposition rate increases linearly by increasing the input power. The obtained deposition rate reaches 7.5 mg/s with an input power of 800W even at an In temperature of 450 degrees C. The obtained weight deposition rate is equivalent to the thickness deposition rate of 1.6 mu m/s. The prepared In film on the Si substrate is composed of a porous foam-like structure. The particle diameter distributes from 40 nm to a few tens of micrometers. The particles with diameters above a few micrometers reveal a porous structure with a pore size of less than 100 nm. The obtained In film consists of crystalline In. Thermal desorption measurements of the prepared In film reveal that a large amount of H-2 gas is confined in the In film relative to the hydrogen solubility in solid In. The obtained results suggest that the excess hydrogen solubility in the liquid metal induced by H-2 plasma is an important factor for the enhancement of In evaporation. (C) 2017 Elsevier B.V. All rights reserved.