Conductivity enhancement and semiconductor–metal transition in Ti-doped ZnO films

Lu, J. J.; Lu, Yang; Tasi, Shih-Jung; Hsiung, Tung Li; Wang, H.P.; Jang, Ling‐Yun

doi:10.1016/j.optmat.2006.08.002

Cited by 99 publications

(53 citation statements)

References 20 publications

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“…In the previous work on ZnO-TiO 2 we found that E g -ZnO > E g -TiO 2 -A [30] and, according to many reports, a large probability exists that E g of ZnO be slightly larger than that of TiO 2 . The value 3.3 eV can be chosen as an acceptable representative value of E g -ZnO [40][41][42][43][44][45]. Electron affinities (χ ) of these three oxides have the same value (4.0 eV) as observed by others researchers [46][47][48].…”

Section: Resultsmentioning

confidence: 83%

Band gap coupling in photocatalytic activity in ZnO–TiO2 thin films

2012

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Zinc oxide and titanium dioxide composite thin films were prepared on Corning 7059 glass substrates by co-sputtering. The reactive gas-surroundings used was ultrahigh purity oxygen. To analyze the structural, optical and photocatalytic properties of the ZnO-TiO 2 samples, X-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption, Raman spectroscopy and methylene blue bleaching were carried out at room temperature. XRD patterns indicate the presence of TiO 2 (anatase and rutile phases), ZnO, ZnTiO 3 , and Zn 2 TiO 4 crystalline structures. AFM images allow the observation of non-homogeneous surface in the ZnO-TiO 2 system, suggesting the separation of different crystalline phases in the composite. Raman studies exhibit different spectra in the films depending on the area analyzed, which can be interpreted as a result of the existence of well separated crystalline regions as seen in AFM images. The photocatalytic activity (PA) of TiO 2 -ZnO-ZnTiO 3 -Zn 2 TiO 4 composite, as expected for adequate coupling semiconductors, is larger than PA of ZnO and TiO 2 oxides, used as references. A simple proposal about the probable alignment of the conduction band, the valence band, and the Fermi level is included. E. García-Ramírez · M. Mondragón-Chaparro ESIME Azcapotzalco, Instituto Politécnico Nacional,

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Section: Resultsmentioning

confidence: 83%

Band gap coupling in photocatalytic activity in ZnO–TiO2 thin films

2012

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“…Generally, two types of mechanisms are dominant in affecting the optical energy gap in ZnO: (i) the Burstein-Moss shift [15], and (ii) band gap shrinkage phenomenon [16]. E g values obtained graphically using this relation are shown for all the films in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Optical properties of Ti-doped ZnO films synthesized via magnetron sputtering

Chen

Ding

Shi

et al. 2012

Journal of Alloys and Compounds

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“…For Ti-doped ZnO, recent experimental reports show evidence that Ti atoms are more likely to substitute the Zn sites than to occupy interstitial sites 41 , and it has been found by Hall-effect measurements 42 that Ti-doped ZnO films prepared by RF magnetron sputtering are n-type semiconductors. We find that a substitutional Ti on the Zn site also acts as a double donor with a doubly occupied singlet defect state in the conduction band, and thus contributes to the n-type conductivity.…”

Section: B Single Dopants/impuritiesmentioning

confidence: 99%

Design of shallow acceptors in ZnO through early transition metals codoped with N acceptors

et al. 2011

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We perform first-principles density-functional theory calculations to study the atomic and electronic properties of early transition metals (Zr, Ti, Y, and Sc) co-doped with N in wurtzite ZnO. By incorporating early transition metals Ti, Zr, Y and Sc with N into ZnO simultaneously, we find that forming complexes (Zr-2N), (Ti-2N), (Y-N) and (Sc-N) induces fully occupied impurity bands with the N 2p character above the valence band maximum of host ZnO. With further doping of N in ZnO, the systems (Zr-2N):N, (Ti-2N):N, (Y-N):N or (Sc-N):N have acceptor ionization energies lower than that of the isolated N acceptor in ZnO. Under different growth conditions (i.e using N2O or NO source for the nitrogen atoms), we calculate the formation energies of the defect complexes and compare the dopability of the selected co-doped systems. Our results show that the valence band maximum characteristic of ZnO can be altered by compensated donor-acceptor pairs, thus improve the p-type dopability.

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Conductivity enhancement and semiconductor–metal transition in Ti-doped ZnO films

Cited by 99 publications

References 20 publications

Band gap coupling in photocatalytic activity in ZnO–TiO2 thin films

Band gap coupling in photocatalytic activity in ZnO–TiO2 thin films

Optical properties of Ti-doped ZnO films synthesized via magnetron sputtering

Design of shallow acceptors in ZnO through early transition metals codoped with N acceptors

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