Preferred Alignment of Mesochannels in a Mesoporous Silica Film Grown on a Silicon (110) Surface

Abstract

It has been proved that surfactant−silicate supramolecular architecture formed on a silicon substrate is strongly affected by the crystal orientation of a silicon wafer, indicating the variation of the interactions between the surfactants and the silicon surfaces. The hexagonal mesoporous silica film with aligned mesochannels was grown on a (110) wafer, whereas the mesochannels were not aligned in the films grown on (100) and (111) wafers. The alignment direction of the mesochannels on the (110) wafer is parallel to the [001] direction. The Gaussian distribution of the alignment direction with a full width at half-maximum (fwhm) of 29° was shown by in-plane X-ray diffraction. The hexagonal packing of the mesochannels in the film is distorted. The strong anisotropy of the atomic arrangement of silicon on the (110) surface causes the preferential alignment of mesochannels.

Optical properties of photo-electrochemical etching of anisotropic silicon (110)

“…Since groove formation usually follows the <100> axes of Si wafer [6,9] and based on Fig. 1 (f), (110) plane [7] the morphology of photo-electrochemical etched Si (110) shows grooves in (100) direction. Note that although high magnification measurements were performed, no significant pores can be observed and this may most probably due to the pores size is too fine (roughly < 10 nm).…”

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

“…One of the most successful techniques to date for aligning mesochannels on a global scale (centimetre) has originated from a technique known as 'rubbing', pioneered by researchers at Cannon and Waseda University, and initially demonstrated for mesoporous particles in 1999 and for films in 2000 [5,[75][76][77][78][79][80]. The technique entails using a 10 nm thin polyimide coating to induce preferred unidirectional alignment and orientation of the mesochannels in the overlaying film.…”

Review. Fluorescence Microscopy Studies of Porous Silica Materials

“…Since there are many applications that could greatly benefit from mesopore alignment on a macroscopic scale, such as nanofluidics and nanoreactors [31], oriented growth of nanowires [32], and optoelectronic devices [33], a lot of effort was put into developing methods that can help achieving this goal. These methods include the use of microtrenches [34,35], external electric [36,37] and magnetic [38] fields, substrate surface modification [18,39,40], and shear flow control [41,42]. However, these approaches often require specialized equipment or impose constraints on the applicable substrates or surfactants.…”

“…While this approach also allows for a perpendicular alignment of the mesochannels with respect to the substrate plane, it requires very specialized equipment. Another approach was pursued by Yang et al and Miyata et al, who deposited thin silica films on mica [18] or singlecrystal silicon wafers [39] and found that the crystallographic orientation of the substrate surface can influence the mesopore alignment to a certain degree. Miyata et al also suggested another way to introduce mesopore alignment by substrate surface modification, namely by creating a thin polyimide layer on the substrate and subjecting it to a rubbing treatment that can help to align the polymeric chains [40].…”