Formation and investigation of porous SiO₂films on Si

Abstract

Porous silica layers on Si substrates were produced by sol-gel spin-on technique. The structural studies and ellipsometric measurements have been carried out in order to investigate the dependence of silica properties on growth technology and thermal annealing. The dense SiO2 layers from acid tetraethoxysilane-based precursors and the layers of increased porosity obtained from precursors containing surfactant cethyltrimethylammonia bromide were investigated. The hybrid type Fe-doped silica layers were also produced and studied. The provided investigations have shown that the method used is perspective for fabrication of porous silica layers and for obtaining hybrid samples.

Scanning probe microscopic and optical detection of DNA integration within multicomponent structures on Si surfaces

“…The samples were prepared by sequential deposition of silica, (3-aminopropyl)-triethoxysilane NH 2 (CH 2 )3Si(OC 2 H 5 ) 3 (APTES), and a solution of polyvinylpropylene (PVP)-covered Ag nanoparticles (∅ ∼ 5 nm) on Si substrates. The SiO 2 layer of 50-150 nm thickness was deposited on cleaned Si substrates by sol-gel spin on technique [16] and annealed at 300 • C for 1 h. On the top of silica-coated Si substrate the APTES layer was formed by immersing the sample into APTES solution (5% v/v) in ethanol for 30 min or (1% v/v) in toluene for 4 min. The APTES-coated substrates modified in ethanol solution were washed in aqueous 1 mM acetic acid AcOH.…”

“…However, the weight factor varied in the range of 0.5-1.0 indicating the (a) (b) porosity of APTES layer, which is known [16] to be dependent on technological regime of formation. The spectral dependence of the ellipsometric parameters Ψ and ∆ for the hybrid sample Ag / APTES / Si was fitted by the optical response of one effective layer ( Fig.…”

Self-formation of Fe/Fe-O nanoparticles in porous SiO2films

“…The sol- gel spin-on processed silica layers on the Si surface, which have been dried at ∼100 • C for 1 h, were dense with porosity of ∼10% at the centre of Si wafer with diameter of 5 cm, and 5% at the edge [10]. However, when Si wafers of a smaller diameter (1-2 cm) were used, the roughness of the surface was ∼250 nm due to formation of clusters composed of rectangular-shaped particles of size ∼50×50 nm 2 and ∼50 nm in height [10]. The cracks were revealed on Au-decorated thick silica films ( Fig.…”

“…In addition, corrections due to depolarization of light should be taken into account in the analysis of spectroscopic ellipsometry data [20]. Therefore, the ellipsometric data can be rather qualitatively interpreted [10,21] by comparing the dielectric function of effective medium, which has been obtained from fitting procedure, with the reference data. Figure 7 illustrates the temperature and magnetic field dependences of magnetization M in hybrid SiO 2 :Fe/SiO 2 /Si samples.…”

“…Nullellipsometry can be efficiently used [10] for estimation of porosity of SiO 2 films on Si. In the case of nonhomogeneous surface films, spectroscopic ellipsometry allows one to determine in-depth variation of optical characteristics [14].…”