Crystallization of Amorphous SiO₂ Microtubes Catalyzed by Lithium

Abstract

Amorphous silica formed by thermally oxidizing silicon is commonly eligible for lithographic patterning or can be grown on patterned substrates. However, it is still a challenge to combine controlled microstructuring with controlled crystallization of SiO2. Here, it is shown that traces of volatile lithium species transported through the gas phase catalyze the crystallization of silica integrated into common silicon microstructures. The selected crystallization temperature determines which polymorph forms. As an example, the formation of quartz, tridymite, and cristobalite microtubes by thermally oxidizing macroporous silicon is investigated. Lithium‐induced crystallization may extend state‐of‐the‐art silicon technology and yield nano‐ and microstructures consisting of different silica polymorphs, which are, in contrast to many functional oxides, nontoxic.

Real-time multi-length scale chemical tomography of fixed bed reactors during the oxidative coupling of methane reaction

“…The solid-state evolution of SiO2 at relatively low temperatures (800 °C) when alkali metals are present has been reported and investigated on several occasions [83][84][85][86] . Venezia et al…”

Reactive Templates: Doing Chemistry with Pore Walls

“…They consist of large single-crystalline segments. [17] The formation of the different polymorphs can be controlled by the process temperature. In the range from 600 8C [18] to 1050 8C predominantly quartz forms (Fig.…”

Observation of Crystalline Oxidized Silicon Phase

“…Furthermore, crystalline clusters (or precipitates) of SiO x have been observed . Moreover, incorporation of lithium atoms into silica has been found to enhance its crystallization . It has been also described that a growth of crystalline SiO x films (by electron‐beam deposition) having oxygen atomic concentration between 10% and 40% (sum of O atoms divided by sum of O and Si atoms) is possible .…”