title: Fabrication of volcano-shaped nano-patterned sapphire substrates using colloidal self-assembly and wet chemical etching.
abstract: Patterned sapphire substrates (PSS) have been widely used to enhance the light output power in GaN-based light emitting diodes. The shape and feature size of the pattern in a PSS affect its enhancement efficiency to a great degree. In this work we demonstrate the nanoscale fabrication of volcano-shaped PSS using a wet chemical etching approach in combination with a colloidal monolayer templating strategy. Detailed analysis by scanning electron microscopy reveals that the unique pattern shape is a result of the different corrosion-resistant abilities of silica masks of different effective heights during wet chemical etching. The formation of silica etching masks of different effective heights has been ascribed to the silica precursor solution in the interstice of the colloidal monolayer template being distributed unevenly after infiltration. In the subsequent wet chemical etching process, the active reaction sites altered as etching duration was prolonged, resulting in the formation of volcano-shaped nano-patterned sapphire substrates.
authors.affiliation: Department of Chemistry, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Chong
authors.initials: C
authors.lastname: Geng
authors.forename: Lu
authors.initials: L
authors.lastname: Zheng
authors.forename: Huajing
authors.initials: H
authors.lastname: Fang
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Yan
authors.forename: Tongbo
authors.initials: T
authors.lastname: Wei
authors.forename: Zhibiao
authors.initials: Z
authors.lastname: Hao
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Wang
authors.forename: Dezhong
authors.initials: D
authors.lastname: Shen