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- Canestraro, Carla Daniele, et al.
(författare)
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Strong inter-conduction-band absorption in heavily fluorine doped tin oxide
- 2008
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 255:5, s. 1874-1879
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Tidskriftsartikel (refereegranskat)abstract
- The optical, electrical and structural properties of thin. film tin oxide (TO), F-doped tin oxide (FTO; n(F) approximate to 6 x 10(20) cm (3)) and highly F-doped tin oxide (hFTO; n(F) approximate to 10 x 10(20) cm (3)), grown by spray pyrolysis technique, are studied by atomic force microscopy, Hall effect, X-ray. fluorescence and transmission/reflection measurements. The resistivity (rho = 32 x 10 (4) Omega cm for intrinsic tin oxide) shows intriguing characteristics when F concentration n(F) is increased (rho = 6 x 10 (4) Omega cm for FTO but 25 x 10 (4) Omega cm for hFTO) whereas the carrier concentration is almost constant at high F concentration (n(c) approximate to 6 x 10(20) cm (3) for FTO and hFTO). Thus, F seems to act both as a donor and a compensating acceptor in hFTO. The high carrier concentration has a strong effect on the optical band-edge absorption. Whereas intrinsic TO has room-temperature band-gap energy of E-g approximate to 3.2 eV with an onset to absorption at about 3.8 eV, the highly doped FTO and hFTO samples show relatively strong absorption at 2-3 eV. Theoretical analysis based on density functional calculations of FTO reveals that this is not a defect state within the band-gap region, but instead a consequence of a hybridization of the F donor states with the host conduction band in combination with a band. filling of the lowest conduction band by the free carriers. This allows photon-assisted inter-conduction band transitions of the free electrons to energetically higher and empty conduction bands, producing the below-gap absorption peak.
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| 2. |
- Nisar, Jawad, 1980-, et al.
(författare)
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Study of electronic and optical properties of BiTaO4 for photocatalysis
- 2012
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley-VCH Verlagsgesellschaft. - 1610-1634 .- 1610-1642. ; 9:7, s. 1593-1596
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Tidskriftsartikel (refereegranskat)abstract
- We present the optical absorption spectrum of BiTaO4 using the photo acoustic spectroscopy (PAS) technique and first principle approach. Band gap have been estimated 2.65 and 2.45 eV using PAS method and DFT calculations, respectively. Position of reduction and oxidation level with respect to vacuum level are identified, which shows that BiTaO4 can be used as photocatalyst for hydrogen production. Electronic structure is explained by plotting total density of states (TDOS).
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