AFM investigation of selective etching mechanism of nanostructured silica

We have developed the atomic force microscope (AFM) for in situ observation of SiO2 etching in the HF aqueous solution. This work is devoted to the AF M investigation of etching of the SiO2 surface layer modified by high-dose Fe+ ion bombardment. Such samples have a two-phase nanostructure (SiO2 cont aining buried Fe nanoparticles). Formation and dissociation of nanorelief d uring etching was observed in situ with AFM. The computer animation of this phenomenon was made with morphing of the experimental AFM images. The addi tional in situ registration of the optical absorption of Fe nanoparticles d uring etching, ex. situ AFM and ferromagnetic resonance measurements enable us to propose that observed morphology transformation takes place because the etching rate of Fe nanoparticles is much higher than the SiO2 etching r ate. This etching mechanism was used for computer simulation of the AFM ima ge transformation during etching of the model samples with buried nanoparti cles. Good correlation of simulated and experimental AFM images and the cor responding surface roughness parameters vs. etching time confirms that this structural model and the mechanism of selective etching are correct. (C) 2 001 Elsevier Science B.V. All rights reserved.