The effect of low-energy Ar+ irradiation on the surface of monocrystalline α-Al2O3 (0001)Faramarz Sahra Gard and Elena ForlererEur. Phys. J. Appl. Phys., 85 2 (2019) 21302DOI: https://doi.org/10.1051/epjap/2019180241