Subtractive Low-Temperature Preparation Route for Porous SiO2 Used for the Catalyst-Assisted Growth of ZnO Field Emitters

The possibility to gradually increase the porosity of thin films facilitates a variety of applications, such as anti-reflective coatings, diffusion membranes, and the herein investigated tailored nanostructuring of a substrate for subsequent self-assembly processes. A low-temperature (<160 degrees C) preparation route for porous silicon oxide (porSiO(2)) thin films with porosities of about 60% and effective refractive indices down to 1.20 is tailored for bulk as well as free-standing membranes. Subsequently, both substrate types are successfully employed for the catalyst-assisted growth of nanowire-like zinc oxide (ZnO) field emitters by metal organic chemical vapor deposition. ZnO nanowires can be grown with a large aspect ratio and exhibit a good thermal and chemical stability, which makes them excellent candidates for field emitter arrays. We present a method that allows for the direct synthesis of nanowire-like ZnO field emitters on free-standing membranes using a porSiO(2) template. Besides the application of porSiO(2) for the catalyst-assisted growth of nanostructures and their use as field emission devices, the herein presented general synthesis route for the preparation of low refractive index films on other than bulk substrates-such as on free-standing, ultra-thin membranes-may pave the way for the employment of porSiO(2) in micro-electro-mechanical systems.

Automated summary

The study focuses on a low-temperature preparation method that can increase the porosity of silicon oxide thin films to 60% and reduce the refractive index to 1.20, suitable for various applications. It is found that this method allows for the direct synthesis of nanowire-like zinc oxide field emitters on free-standing membranes, with a large aspect ratio and good stability.