Morphologies of porous silicon etched by the electrochemical etching method with alcohols additives

Several porous silicon (PS) films with macropores are fabricated by electrochemical etching method using five different monohydric normal alcohol additives without any illumination. The experiment results show that as the number of carbon atoms increases, the branch length elongates, the pore density decreases because the ability of anisotropic etching of the solution is enhanced gradually and the space charge region (SCR) width of PS becomes larger. Furthermore, except for methanol (MeOH) and n-pentanol (n-PeOH), with the increasing number of carbon atoms in alcohol, the main pore size deceases and the depth increase because the isotropy becomes weaker. PS in MeOH has small main pore size and large depth because most of charges accumulated at the bottom of pores and promote the growth of the depth. PS in n-PeOH has a small depth because of its strong hydrophobicity property, which hinders the etching at the length direction. These experimental results demonstrate the important role of alcohols on the dissolution kinetics with silicon, which has a direct impact on the pore growth process.