u parameters for the wurtzite structure of ZnS and ZnO using powder neutron diffraction
15 Dec 1989-Acta Crystallographica Section C-crystal Structure Communications (International Union of Crystallography (IUCr))-Vol. 45, Iss: 12, pp 1867-1870
TL;DR: In this article, the atomes Zn occupent la position speciale 2(b) avec les coordonnees 1/3, 2/3, Os et O occupent egalement la positionspeciale 2 (b) with les coordainees 1 3, 2 3, u. Dans les deux cas, u et c/a se conforment a la correlation comme entre ces parametres.
Abstract: ZnS cristallise dans P6 3 mc avec a=8227 et c=6,2607 A, Z=2; affinement jusqu'a R=0,017. ZnO cristallise dans P6 3 mc avec a=3,2501 et c=5,2071 A, Z=2 affinement jusau'a R=0,012. Les atomes Zn occupent la position speciale 2(b) avec les coordonnees 1/3, 2/3, Os et O occupent egalement la position speciale 2(b) avec les coordonnees 1/3, 2/3, u. Pour ZnS, u=0,3748 et pour ZnO, u=0,3817. Dans les deux cas, u et c/a se conforment a la correlation comme entre ces parametres
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TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...
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TL;DR: A review of defects in ZnO is presented in this paper, with an emphasis on the physical properties of point defects in bulk crystals, and the problem of acceptor dopants remains a key challenge.
Abstract: Zinc oxide (ZnO) is a wide band gap semiconductor with potential applications in optoelectronics, transparent electronics, and spintronics. The high efficiency of UV emission in this material could be harnessed in solid-state white lighting devices. The problem of defects, in particular, acceptor dopants, remains a key challenge. In this review, defects in ZnO are discussed, with an emphasis on the physical properties of point defects in bulk crystals. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. However, experiments and theory have shown that O vacancies are deep donors, while Zn interstitials are too mobile to be stable at room temperature. Group-III (B, Al, Ga, and In) and H impurities account for most of the n-type conductivity in ZnO samples. Interstitial H donors have been observed with IR spectroscopy, while substitutional H donors have been predicted from first-principles calculations but not observed directly. Despite numerous reports, reliable p-t...
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TL;DR: In this article, Tauc plots are fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called “Tauc” plots).
Abstract: One of the most frequently used methods for characterizing thin films is UV–Vis absorption. The near-edge region can be fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called “Tauc” plots). While the technique is powerful and simple, the accuracy of the fitted band-gap result is seldom stated or known. We tackle this question by refitting a large number of Tauc plots from the literature and look for trends. Nominally pure zinc oxide (ZnO) was chosen as a material with limited intrinsic deviation from stoichiometry and which has been widely studied. Our examination of the band gap values and their distribution leads to a discussion of some experimental factors that can bias the data and lead to either smaller or larger apparent values than would be expected. Finally, an easily evaluated figure-of-merit is defined that may help guide more accurate Tauc fitting. For samples with relatively sharper Tauc plot shapes, the population yields Eg(ZnO) as 3.276 ± 0.033 eV, in good agreement with data for single crystalline material.
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203 citations
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