Healing Ion-Implanted Semiconductors by Hybrid Microwave Annealing: Activation of Nitrogen-Implanted TiO2

Abstract

In order to recover the damaged structure of a nitrogen-implanted TiO2 photoanode, hybrid microwave annealing (HMA) is proposed as an alternative postannealing process instead of conventional thermal annealing (CTA). Compared to CTA, HMA provides distinctive advantages: (i) facile transformation of the interstitial N-N states into substitutional N-Ti states, (ii) better preservation of the ion-implanted nitrogen in TiO2, and (iii) effective alleviation of lattice strain and reconstruction of the broken bonds. As a result, the HMA-activated photoanode improves the photocurrent density by a factor of similar to 3.2 from 0.29 to 0.93 mA cm(-2 )at 1.23 V-RHE and the incident photon-to-current conversion efficiency (IPCE) from similar to 2.9% to similar to 10.5% at 430 nm relative to those of the as-prepared N-I-TiO2 photoanode in photoelectrochemical water oxidation, which are much better than those of the CTA-activated photoanode (0.58 mA cm(-2) at 1.23 V-RHE and IPCE of 5.7% at 430 nm), especially in the visible light region >= 420 nm).