When MgZnO serves as the shell to passivate a ZnO nanowire, the proportion of Mg is usually small to avoid the unexpected spectrum from the wurtzite to rock salt transformation. Using the effective mass approximation, we investigate the impact of a mixed-phase Mg_xZn_1−xO shell on the optical absorption spectra in ZnO nanowires. The results show that the dual absorption peaks from the coexisting two sets of band offset tend to appear as an intrinsic line broadening. This is because the spacing of dual peaks is small and even less than the full width at half maximum to be distinguished. The dual peaks get closer by increasing x or core size since the energy levels become less insensitive to the difference of the potentials. Enhanced confinement of an electron from higher x and smaller core size induces not only a blueshift and a slower saturation but also a sharper peak. The above two aspects make the dual peaks appear always as a broadening in inter-band V1–C1 transitions, while only appear as a broadening in inter-subband C1–C2 transitions when the core radius gets larger than the critical value for a certain x. The broadening from the mixed-phase MgZnO-coated ZnO nanowire could be restricted by increasing the core size or the proportion of Mg in the shell.

中文翻译：

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混合相MgxZn1-xO壳在ZnO纳米线中吸收光谱的展宽

当MgZnO用作钝化ZnO纳米线的壳时，Mg的比例通常很小，以避免从纤锌矿到岩盐转变的意外光谱。使用有效质量近似，我们研究了混合相Mg _x Zn _{1- x} O壳层对ZnO纳米线中光吸收光谱的影响。结果表明，来自并存的两组带偏移的双吸收峰趋向于作为本征线展宽出现。这是因为双峰的间距很小，甚至小于要区分的最大一半的整个宽度。通过增加x使双峰更近或磁芯尺寸，因为能级对电势差变得不那么敏感。由于较高的x和较小的核尺寸而导致的电子约束增强，不仅会引起蓝移和较慢的饱和度，而且会引起尖锐的峰。以上两个方面使得双峰总是在带间V1-C1跃迁中变宽，而仅在核心半径大于某个x的临界值时才在子带C1-C2跃变中变宽。。混合相MgZnO包覆的ZnO纳米线的增宽可以通过增加核的大小或壳中Mg的比例来限制。