The role of etched silicon channels on the pore ordering of mesoporous silica: The importance of film thickness on providing highly orientated and defect-free thin films

If mesoporous thin films (MTFs) are to be utilised in device applications it is important that we produce films which not only possess a single pore direction across large substrate areas (in the range of microns) but are also relatively defect free. In this paper we report the use of confining architectures in the form of topographically patterned rectangular section channels etched into native silicon substrates to promote ordering of the mesopores. We discuss the effects of the channels on films with different thicknesses. The film thickness is shown to be a critical parameter in defining highly orientated and defect-free films and the data demonstrate that it is possible to achieve a single mesoporous silica domain across macroscopic dimensions with thin film thicknesses of approximately 200 nm but that critically pore order can be lost in ultra thin and thicker films produced by these methods.