Details

Autor(en) / Beteiligte

• Wan, Meinan
• Xiong, Mo
• Li, Neng
• Liu, Baoshun
• Wang, Shuo
• Ching, Wai-Yim
• Zhao, Xiujian

Titel

Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO2

Ist Teil von

• Applied surface science, 2017-07, Vol.410, p.363-372

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2017

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• [Display omitted] •N-doped VO2(M1) thin films have been synthesized by annealing in NH3 atmosphere.•The phase purity, microstructure and optical property of VO2 thin film can be regulated by NH3 concentration.•First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO2(M1).•The energy band gaps of VO2(M1) are tuned by substitution N-doping or interstitial N-doping. Research on monoclinic (M1) phase of VO2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO2(M1) thin films with high purity by heat treatment in NH3 atmosphere. The N dopant in the film can be regulated by varying NH3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO2 thin films increase with NH3 concentration. The metal to insulator transition (MIT) temperature (τc,h) of the VO2 thin film is effectively reduced from 80.0 to 62.9°C, while the solar modulation efficiency (ΔTsol) and the modulation efficiency at 2000nm (ΔT2000nm) are 7.36% and 55.6% respectively. The band gap of N-doped VO2 thin films related to MIT (Eg1) is estimated to be as low as 0.18–0.25eV whereas the band gap associated with the visible transparency (Eg2) is about 1.50–1.58eV. Based on the highly accurate first-principles calculations, the Eg1 of VO2 (M1) is reduced after substituted or interstitial N-doping, while the Eg2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.