Real-time observation of ripple structure formation on a diamond surface under focused ion-beam bombardment

Ripple structures on a diamond surface are created and imaged in real time by focused ion-beam bombardment, and further examined by atomic force microscopy. Beyond a critical incidence angle depending on the ion energy, a ripple structure emerges, and its wavelength remains constant until it breaks down at {~}75^∘{}. The wavelength is independent of the ion flux, but increases linearly with energy. Addition of a conjectured term representing the redistribution of ion-induced surface species to Makeev, Cuerno, and Barab\'asi's equation allows a quantitative description of the wavelength dependence on the incidence angle.