Stability of diatomic hydrogen in oxygen‐deficient ZnO

Karazhanov, Smagul

doi:10.1002/pssb.200844441

Cited by 6 publications

(1 citation statement)

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“…The complex comprises two weakly coupled hydrogen atoms each of which is bound to the neighboring oxygen and zinc atoms [20]. In the case of strained and oxygen-deficient ZnO the configuration of separated hydrogen substituting for oxygen (H O ) and interstitial hydrogen (H BC ) was found to be more stable than H * 2 [21]. Contrary to these authors, Du and Biswas claim that molecular hydrogen in ZnO is stable but located within the oxygen vacancy rather than at an interstitial lattice site [22].…”

Section: Introductionmentioning

confidence: 99%

Towards understanding the hydrogen molecule in ZnO

2014

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The hydrogen molecule H 2 (or "hidden" hydrogen) in ZnO is studied by Raman scattering spectroscopy. It is shown that H 2 is practically a free rotator stable up to 700 • C, which is formed by two mobile interstitial hydrogen atoms. The concentration profile of the hydrogen molecule anticorrelates with hydrogen substituting for oxygen (H O ) created at the sample surface during the high temperature hydrogenation. The H 2 dissociation at elevated temperatures in the bulk regenerates interstitial (H BC ) hydrogen, whereas the formation of H O and hydrogen out-diffusion are dominant decay channels of the molecule near the surface. The latter mechanisms are responsible for the lower stability of H 2 in the subsurface region. An ortho-para conversion between the nuclear spin states 1 and 0 of the molecule at 79 K was found to occur within 7.5 h, whereas the back conversion at room temperature occurs faster than 0.5 h. A shift in frequency of the H 2 local vibrational mode with annealing time and temperature is associated with the thermal anneal of lattice imperfections. The coupling of transitions between rotational states of the molecule and lattice phonons influences the ro-vibrational properties. Interstitial lattice sites and/or larger vacancy clusters are preferred trapping centers for H 2 in ZnO.

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Section: Introductionmentioning

confidence: 99%