Photoluminescence from Anodic Aluminum Oxide Formed via Etidronic Acid Anodizing and Enhancing the Intensity

Abstract

Photoluminescence (PL) emission from anodic aluminum oxide (AAO) formed by etidronic acid anodizing was investigated via fluorescence spectroscopy. Highly pure aluminum plates were anodized in an etidronic acid solution under various operating conditions. PL emission from the typical AAO film was identified with an approximately 250–275-nm range in excitation and a 375–450-nm range in emission, and this distribution was greatly different from the AAO film formed by typical carboxylic acid treatment. The PL intensity increased with the decrease of the concentration of etidronic acid solution. The intensity also increased with anodizing time and subsequent thermal treatment, whereas excess anodizing and high temperature treatment caused an intensity decrease. The AAO film consisted of an outer oxide containing incorporated etidronate anions and a thin honeycomb inner oxide without anions, and the oxygen vacancy localized in the AAO film and anion distribution strongly affected the PL intensity. The appropriate operating condition through anodizing in 0.05 M etidronic acid for 40 h and subsequent thermal treatment at 773 K for 2 h caused the maximum enhancement of the PL emission.