Early stages of growth of Si nanowires by metal assisted chemical etching: A scaling study

Abstract

We have studied the kinetic roughening in the growth of Si nanowires (NWs) by metal assisted chemical etching (MACE) process as a function of the etching time using atomic force microscopy imaging. In the early stage of growth of Si NWs by Ag assisted MACE process, we have determined the scaling exponents α, β, and 1/z. In the formation of Si NWs, nascent Ag+ ions play an important role in diffusing through the Si surface by means of excess holes that control the size of the NWs. In this system, kinetic roughening of the growth front within the detectable range of lengths of Si NWs was observed. We have observed an α = 0.74 ± 0.01 at the early stage of growth of Si NWs. Interface width w increases as a power law of etching time (t), w∼tβ, with growth exponent β = 0.30 ± 0.05 and lateral correlation length ξ grows as ξ∼t1/z with 1/z = 0.32 ± 0.05. These exponents α, β, and 1/z determine the universality class in which the system belongs to. The growth mechanism is explained by conventional shadowing instability model, which is common for columnar type of surface growth.