Magnesiothermic Reduction of Thin Films: Towards Semiconducting Chiral Nematic Mesoporous Silicon Carbide and Silicon Structures. (25th February 2015)

• Record Type: Journal Article
• Authors: Nguyen, Thanh‐Dinh; Kelly, Joel A.; Hamad, Wadood Y.; MacLachlan, Mark J.
• Is Part Of: Advanced functional materials. Volume 25:Number 14(2015)
• Page Start: 2175
• Page End: 2181
• Publication Date: 2015-02-25
• Subjects: cellulose nanocrystals -- chiral nematic structure -- magnesiothermic reduction -- porosity -- silicon‐based semiconductors; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201404304
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : There is a growing demand for new methods to prepare porous Si‐based materials for applications in optoelectronic and microelectronic devices. In this work, the preparation of SiC and Si from magnesiothermic reduction of chiral nematic SiO2 /C composites and mesoporous SiO2, respectively, is reported. The SiO2 /C composites are prepared by cocondensing SiO2 with cellulose nanocrystals (CNCs) followed by pyrolysis. The magnesiothermic reduction of the composites produces SiC after prolonged solid‐state reaction, with mixed MgC2 /SiC intermediates. Iridescent mesoporous tetragonal MgC2 /SiC structures that retain the long‐range twisted organization of the starting composites transform to mesoporous cubic SiC with a chiral nematic hierarchical structure, but with some loss of order. On the other hand, the magnesiothermic reduction of the chiral nematic mesoporous SiO2 templated from CNCs affords mesoporous Si materials with a layered hierarchical structure. The structural properties and the conductivity of the products, as well as the reaction pathways by analysis of the materials at intermediate stages, are investigated. These experimental results show that the magnesiothermic reduction is a promising way to obtain new porous semiconducting materials with chiral nematic structures. Abstract : Magnesiothermic reduction of chiral nematic silica/carbon and mesoporous silica films templated by cellulose nanocrystals is investigated. The reduction process of silica/carbon forms MgC2 /SiC intermediates and then transforms to chiral nematic mesoporous SiC, while silica produces mesoporous Si with a layered hierarchical structure. These novel semiconducting materials are available as film replicas and may be useful for developing thin film sensors.