Effect of temperature and incident ion energy on nanostructure formation on silicon exposed to helium plasma

Helium plasma can be used to deliver low-energy (<100 eV) helium ions to stimulate the growth of nanostructures on silicon surfaces. This can produce a wide range of surface features including nanoscale roughening, nanowires and porous structures. In this study, nanostructure sizes varied from similar to 10 to over 100 nm in diameter. The effect of these structures on surface reflectivity for photovoltaic and photocatalytic applications is also investigated. Broadband suppression of photoreflectivity is achieved across the 300-1,200 nm wavelength range studied for silicon exposed to helium plasma at 600 degrees C, with an average reflectivity of 3.2% and 2.9% for incident helium ion energies of 42 and 62 eV, respectively.