Terrace morphology on fused silica surfaces by Ar+ ion bombardment with Mo co-deposition

Abstract

The morphology evolution of self-organized nanopatterns induced during Ar+ ion bombardment (IB) with Mo co-deposition on fused silica (SiO2) surfaces at different incidence angles and fluences was investigated by using atomic force microscopy and transmission electron microscopy. For pure IB at incidence angles from 30° to 70°, SiO2 surfaces evolve from being flat, via ripples, to direction-transversed ripples. In contrast, at the same ion fluence and incidence angles, the simultaneous Mo co-deposition leads to significant terraced structures with significantly enhanced roughness and wavelength. Our observations show that the concurrent Mo co-deposition during IB can reduce the critical incidence angle and the fluence level of terrace formation. Owing to the guidance of the IB-induced morphology, at incidence angles where a well-ordered ripple-mode can be generated, well-ordered terrace morphology is more likely to be formed. Terraced structures are initiated and further grow until the appearance of the nonlinear phase, i.e., where the ripple amplitude is sufficiently high. The enhanced terrace morphology on smooth SiO2 results from the interplay between pure IB and Mo co-deposition. The phase separation is attributed to the formation of crystalline MoOx on the side facing the impurity.