Growth temperature-dependent phase evolution and photoactivities of sputtering-deposited crystalline Bi2O3 thin films. Issue 25 (10th June 2020)

• Record Type: Journal Article
• Authors: Liang, Yuan-Chang; Chiang, Kai-Jen
• Is Part Of: CrystEngComm. Volume 22:Issue 25(2020)
• Page Start: 4215
• Page End: 4227
• Publication Date: 2020-06-10
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/d0ce00562b
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : Crystalline Bi2 O3 thin films were grown through radio-frequency magnetron sputtering deposition using a bismuth metal target in an Ar/O2 mixed atmosphere and in an Ar atmosphere with further post-annealing procedures in ambient air. Abstract : Crystalline Bi2 O3 thin films were grown through radio-frequency magnetron sputtering deposition using a bismuth metal target in an Ar/O2 mixed atmosphere and in an Ar atmosphere with further post-annealing procedures in ambient air. The crystal structures, surface morphologies, and photoactive performance of various as-synthesized Bi2 O3 thin films were manipulated by controlling the in situ sputtering growth temperature and post-annealing temperature. Structural analysis revealed that the in situ sputtering-grown Bi2 O3 thin films had dual monoclinic α-/tetragonal β-phase structures below the growth temperature of 425 °C with an unexceptional impurity phase of Bi4 O7 in the film; the Bi2 O3 thin film consisted of a pure single β phase when the growth temperature was increased above 425 °C. In contrast, the sputtering deposited metallic bismuth thin films transformed into pure α/β phase-structured Bi2 O3 thin films without any impurity phase when the annealing temperature was below 425 °C; however, Bi4 O7 was formed in the α/β Bi2 O3 film with annealing temperatures above 425 °C in this study. For the Bi2 O3 thin-film crystal grown via in situ sputtering or annealing, the growth temperature effects on impurity phase generation showed the opposite trend. Furthermore, the formation of the impurity Bi4 O7 phase in the Bi2 O3 films may deteriorate the photoactive performance of the Bi2 O3 thin film. The efficient photoexcited charge separation and transfer across the α-β phase heterojunctions in the polymorph α/β Bi2 O3 films accounted for their higher photoactivity among the various Bi2 O3 thin films in this study. The results reported herein show that the α/β dual phase Bi2 O3 film without any impurity phase formed via precise process control is promising for applications in photoactive devices or as a coupling oxide layer in heterogeneous devices.