Structural and photoelectrochemical properties of SrTaO2N oxynitride thin films deposited by reactive magnetron sputtering

Abstract

Sputtering deposition of SrTaO2N films on different types of substrates  Films approach stoichiometry with a bandgap of 2.33 eV when substrate temperature increases to TS = 800°C  Different degrees of film crystallization, from weakly crystallized to fully c-axis oriented, were obtained  Three limiting factors are identified: 1) low absorption coefficient; 2) short lifetimes of excited charge carriers; and 3) permittivity with moderate values  Dual effects of a higher crystallinity and a greater absorbance for the thickest (600 nm) films.

Fabrication of Semi-Transparent SrTaO2N Photoanodes with a GaN Underlayer Grown via Atomic Layer Deposition

“…Nevertheless, it is commensurate with the values reported for a 150 nm SrTaO2N film photoanode grown on Ta sheet by reactive RF magnetron sputtering. 30 In this report, the enhanced photocurrent was clearly observed upon expanding the film thickness by adjusting the sputtering duration. 30 This photocurrent density is also higher than a 162 nm LaTiO2N and a 177 nm CaNbO2N thin film photoanodes prepared by a modified PLD method on a TiN layer with (001)-oriented supporting MgO, in which photocurrent density less than 1 µA cm −2 was recorded at 1.23 VRHE.…”

“…30 In this report, the enhanced photocurrent was clearly observed upon expanding the film thickness by adjusting the sputtering duration. 30 This photocurrent density is also higher than a 162 nm LaTiO2N and a 177 nm CaNbO2N thin film photoanodes prepared by a modified PLD method on a TiN layer with (001)-oriented supporting MgO, in which photocurrent density less than 1 µA cm −2 was recorded at 1.23 VRHE. 59 In this regard, the present result is promising and the performance is likely to be further improved through extending the oxynitride film thickness and to apply to porous 3D substrates.…”

“…25 We attributed this result mainly to the limited thickness of the oxynitride thin film on the substrate confining the availability of sufficient active sites. 30,59 The photocurrent density derived from photoexcited charge carriers is therefore already saturated at low potential bias during the LSV measurement. The net photocurrent density generated by this SrTaO2N thin film was approximately 6 µA cm −2 at 1.23 VRHE (Figure 5c).…”

Semi-transparent quaternary oxynitride photoanodes on GaN underlayers

“…[22][23][24] This renders semi-transparent quaternary metal oxynitrides generally as very promising photoanode candidates for PEC tandem cells, which could outperform Ta 3 N 5 -based devices. So far, semi-transparent quaternary metal oxynitride films have been mainly fabricated by means of reactive radiofrequency (RF) magnetron sputtering [25][26][27][28] or pulsed laser deposition (PLD) 29,30 on MgO or Nb:SrTiO 3 substrate. In case of the RF approach, the oxynitride sputtering targets have to be made first with multi-step processes, and harsh conditions (usually up to 1073 K for film deposition) are required, too.…”

“…In case of the RF approach, the oxynitride sputtering targets have to be made first with multi-step processes, and harsh conditions (usually up to 1073 K for film deposition) are required, too. 27 The development of photoelectrode materials with more narrow band gaps than Ta 3 N 5 and hematite is mainly motivated by the higher theoretical light absorption capacity. 11 Recently, Domen et al have demonstrated a core-shell heterojunction photoanode of Ta 3 N 5 -nanorods/BaTaO 2 N, generating a stable photocurrent owing to efficient generation and extraction of charge carriers.…”