Morphology of macroporous silicon subjected to sintering in argon

Abstract

Sintering of macro‐porous silicon can serve as an additional tool to control its structure and morphology. An inert gas, even of high‐purity, contains a small amount of oxidizing agent, which has a significant impact on the processes of reorganization of the porous structure. It was found that the sintering of macroporous silicon in argon flow containing 2.10−4% O2 is strongly affected by the thermal etching due to the formation of volatile silicon monoxide. This leads to an increase in the porosity, or even to the complete disappearance of the porous layer, and is accompanied by deposition of silicon dioxide in different forms. The thermal etching competes with the characteristic sintering processes of pore closure and prevents the formation of a defect‐free crust on the sample surface. From the isochronous annealing performed at T = 1000–1280 °C for 30 minutes was found the activation energy of Si diffusivity Ea = 2,57 eV. This value together with the results of isothermal experiments are indicative of a mixed mechanism of mass transport by surface and bulk diffusion of silicon atoms. The sintering of macro‐porous structures results in faceting with the crystallographic planes (111), (100), and (110), among which the lowest surface energy corresponds to the (111) planes.The result of competition between sintering and thermal etching: typical worm‐like openings in the surface crust of a macro‐porous silicon annealed in high purity Ar at 1125 °C. Scale bar 1 µm.