GaN nanotips array was fabricated by an iodine-assist enhanced focused ions beam etching (IFIBE) via the double masks silver oxide (AgO) and gallium oxide (GaO). The function of AgO is used to protect from the elimination of GaO so as to remain GaO on GaN nanotip. The different size of silver cluster was able to assist the formation of GaN nanotips through the double mask process (AgO and GaO). After IFIBE process, the silver mask disappeared and only gallium oxide with a polycrystalline structure was left on top. Oxide-capping GaN nanotips were able to improve the field emission properties (turn-on field was 2.2 V/μm) due to the lower work function of GaN resulted from the distribution of electron existed the interface between GaN and GaO.
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