Layered structure of anodic SiO2 films doped with phosphorus or boron

Abstract

It is shown that anodic silicon oxide films deposited by reanodization (repeated anodic oxidation) of p- and n-type silicon in phosphate (1.5 M H3PO4), borate (1.5 M H3BO3), and nitrate (0.04 M NH4NO3) electrolytes based on tetrahydrofurfuryl alcohol have a three- or four-layer structure both before and after high-temperature annealing. It is assumed that this circumstance accounts for the nonuniform distribution of phosphorus and boron across the thickness of anodic SiO2.