Germanium-catalyzed hierarchical Al2O3 and SiO2nanowire bunch arrays

Abstract

Germanium (Ge), a Group IV semiconductor, was recently used as an effective catalyst to grow individual, single-crystalline ZnOnanowires through a vapor-liquid-solid (VLS) process [Pan et al., Angew. Chem., Int. Ed., 2005, 44, 274–278]. Here, we show that Ge can also act as an efficient catalyst for the large-scale growth of highly aligned, closely-packed polycrystalline Al₂O₃ and amorphous SiO₂nanowire bunch arrays. The Ge-catalyzed Al₂O₃ and SiO₂nanowire growth exhibits many interesting growth behaviors including (i) multiple nanowire growth catalyzed by one micrometer-size Ge particle, (ii) branching growth and (iii) batch-by-batch growth. These growth phenomena are distinct from the conventional Au-catalyzed nanowire growth but are analogous to the recently reported Ga-catalyzed SiO₂nanowire growth. It is anticipated that many other oxidenanowires and nanowire assemblies can be synthesized through the Ge-catalyzed VLS process. The Ge-catalyzed Al₂O₃ and SiO₂nanowires emit strong visible light under ultraviolet light excitation.