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

Atomic structures of the various structures of hydrogen at an O-site in ZnO: (a) HO, (b) H-DX, and (c) H-DX*.The (red)-dashed arrow lines in (b) and (c) indicate the direction of H-displacement for the formations of H-DX− structures. (c) H-DX* is a meta-stable structure. The open circles describe VO0 site in the H-DX− which is a complex defect of Hi− and VO0.
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f1: Atomic structures of the various structures of hydrogen at an O-site in ZnO: (a) HO, (b) H-DX, and (c) H-DX*.The (red)-dashed arrow lines in (b) and (c) indicate the direction of H-displacement for the formations of H-DX− structures. (c) H-DX* is a meta-stable structure. The open circles describe VO0 site in the H-DX− which is a complex defect of Hi− and VO0.

Mentions: In ZnO, a H atom is suggested to be strongly captured by an O-vacancy, which is a substitutional impurity at O-site (HO), as shown in Fig. 1(a). The HO state is known to be a robust state, and normally positively charged, as suggested by Janotti et al.8, since the highest occupied state from the hydrogen state is located above the CBM. However, here we find that HO can be negatively charged and capture electrons through a large lattice relaxation (LLR). We find that in the negative charge state, the H atom can be significantly displaced into an interstitial hollow (H)-site2223. The LLR structure is described by Fig. 1(b).


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

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

Atomic structures of the various structures of hydrogen at an O-site in ZnO: (a) HO, (b) H-DX, and (c) H-DX*.The (red)-dashed arrow lines in (b) and (c) indicate the direction of H-displacement for the formations of H-DX− structures. (c) H-DX* is a meta-stable structure. The open circles describe VO0 site in the H-DX− which is a complex defect of Hi− and VO0.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Atomic structures of the various structures of hydrogen at an O-site in ZnO: (a) HO, (b) H-DX, and (c) H-DX*.The (red)-dashed arrow lines in (b) and (c) indicate the direction of H-displacement for the formations of H-DX− structures. (c) H-DX* is a meta-stable structure. The open circles describe VO0 site in the H-DX− which is a complex defect of Hi− and VO0.
Mentions: In ZnO, a H atom is suggested to be strongly captured by an O-vacancy, which is a substitutional impurity at O-site (HO), as shown in Fig. 1(a). The HO state is known to be a robust state, and normally positively charged, as suggested by Janotti et al.8, since the highest occupied state from the hydrogen state is located above the CBM. However, here we find that HO can be negatively charged and capture electrons through a large lattice relaxation (LLR). We find that in the negative charge state, the H atom can be significantly displaced into an interstitial hollow (H)-site2223. The LLR structure is described by Fig. 1(b).

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