Limits...
Bistability of hydrogen in ZnO: origin of doping limit and persistent photoconductivity.

Nahm HH, Park CH, Kim YS - Sci Rep (2014)

Bottom Line: Up to now, there is no satisfactory theory about two puzzles.We report the bistability of HO in ZnO through first-principles electronic structure calculations.We suggest that the bistability can give explanations to two puzzling aspects.

View Article: PubMed Central - PubMed

Affiliation: 1] Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Pusan 609-735, Korea [2] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [3] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea [4] Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Korea.

ABSTRACT
Substitutional hydrogen at oxygen site (HO) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 10(18) cm(-3), even if solubility limit is much higher. Another puzzling aspect of ZnO is persistent photoconductivity, which prevents the wide applications of the ZnO-based thin film transistor. Up to now, there is no satisfactory theory about two puzzles. We report the bistability of HO in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the HO can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects.

No MeSH data available.


Related in: MedlinePlus

Total energy profiles of the structural transitions between HO and H-DX configurations as a function of H displacement (Q) in the (1−), (0), and (1+) charge states.The energy barrier (Eb) for the structural transition from the HO+ + 2e to the H-DX− is indicated, and the optical excitation energy (Eopt) for the transition from H-DX− to H-DX0 is also shown.
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f4: Total energy profiles of the structural transitions between HO and H-DX configurations as a function of H displacement (Q) in the (1−), (0), and (1+) charge states.The energy barrier (Eb) for the structural transition from the HO+ + 2e to the H-DX− is indicated, and the optical excitation energy (Eopt) for the transition from H-DX− to H-DX0 is also shown.

Mentions: We estimated total energy profile for the structural transformation between HO and H-DX. The H-DX structure in the neutral or (+)-charge state is unstable. When the high concentration of electron carriers is present at conduction band, two electrons can be captured by the HO through the deformation toward H-DX structure, and the H-DX− state can be more stable than the HO+ + 2e (at CB). We calculated the variation of the total energy according to the structural deformation, as shown in Fig. 4, and we find that there is the energy barrier for the structural recovery: HO+ + 2e → H-DX−. It is estimated to be 0.36 eV.


Bistability of hydrogen in ZnO: origin of doping limit and persistent photoconductivity.

Nahm HH, Park CH, Kim YS - Sci Rep (2014)

Total energy profiles of the structural transitions between HO and H-DX configurations as a function of H displacement (Q) in the (1−), (0), and (1+) charge states.The energy barrier (Eb) for the structural transition from the HO+ + 2e to the H-DX− is indicated, and the optical excitation energy (Eopt) for the transition from H-DX− to H-DX0 is also shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927214&req=5

f4: Total energy profiles of the structural transitions between HO and H-DX configurations as a function of H displacement (Q) in the (1−), (0), and (1+) charge states.The energy barrier (Eb) for the structural transition from the HO+ + 2e to the H-DX− is indicated, and the optical excitation energy (Eopt) for the transition from H-DX− to H-DX0 is also shown.
Mentions: We estimated total energy profile for the structural transformation between HO and H-DX. The H-DX structure in the neutral or (+)-charge state is unstable. When the high concentration of electron carriers is present at conduction band, two electrons can be captured by the HO through the deformation toward H-DX structure, and the H-DX− state can be more stable than the HO+ + 2e (at CB). We calculated the variation of the total energy according to the structural deformation, as shown in Fig. 4, and we find that there is the energy barrier for the structural recovery: HO+ + 2e → H-DX−. It is estimated to be 0.36 eV.

Bottom Line: Up to now, there is no satisfactory theory about two puzzles.We report the bistability of HO in ZnO through first-principles electronic structure calculations.We suggest that the bistability can give explanations to two puzzling aspects.

View Article: PubMed Central - PubMed

Affiliation: 1] Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Pusan 609-735, Korea [2] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [3] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea [4] Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Korea.

ABSTRACT
Substitutional hydrogen at oxygen site (HO) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 10(18) cm(-3), even if solubility limit is much higher. Another puzzling aspect of ZnO is persistent photoconductivity, which prevents the wide applications of the ZnO-based thin film transistor. Up to now, there is no satisfactory theory about two puzzles. We report the bistability of HO in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the HO can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects.

No MeSH data available.


Related in: MedlinePlus