Simultaneous control of growth mode and ferromagnetic ordering in Co-doped ZnO layers with Zn polarity
Simultaneous control of growth mode and ferromagnetic ordering in Co-doped ZnO layers with Zn polarity
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DOI：
10.1103/physrevb.75.014438
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发表时间：
2007-01
影响因子：
3.7
通讯作者：
H. Matsui;H. Tabata
中科院分区：
文献类型：
--
作者：
H. Matsui;H. Tabata
在本文中，我们描述了一种新的生长技术，实现了Co掺杂层中生长模式和铁磁有序性的同时控制。由于钴离子的掺杂，生长发生了显着的变化。考虑到二维（2D）模式下带负电的生长表面的稳定性，暴露等离子体以产生富氧气氛对于制造未掺杂层是必不可少的。相反，在没有等离子体源的情况下，层的二维模式被充分保留，这归因于Co离子的特性与Zn离子的特性相比所提供的共价性。层的自发磁化强度与自由电子的数量密切相关，自由电子的数量受施主能级的活化能控制。 O-极性层也证实了这一点。在接近莫特跃迁的值处观察到铁磁（FM）排序，并导致浅施主带之间的跳跃传导。然而，低于该水平会产生 FM 有序化，从而产生凹坑表面并导致晶体劣化。鉴于我们对凹坑形成机制的理解，我们应用了周期性氧压调制外延，从而实现了二维模式的钴掺杂层的相干生长。这种特定的生长可以有效地在大面积上产生无凹坑的表面均匀性，从而保持 FM 有序性。
In this paper, we describe a new growth technique realizing the simultaneous control of growth mode and ferromagnetic ordering in Co-dopedlayers. Remarkable changes in growth occurred as a result of doping with Co ions. Exposure toplasma to generate an oxygen-rich atmosphere was indispensable for the fabrication of undopedlayers given stabilization of the negatively charged growing surface in a two-dimensional (2D) mode. In contrast, the 2D mode oflayers was adequately retained in the absence of a plasma source, and was attributable to the covalence provided by thecharacter of Co ions compared with thecharacter of Zn ions. Spontaneous magnetization oflayers was closely correlated with the number of free electrons, which was controlled by the activation energy of donor levels. This was also confirmed for O-polarlayers. Ferromagnetic (FM) ordering was observed atvalues close to the Mott transition and led to hopping conduction between shallow donor bands. However, levels ofbelowthat yielded FM ordering generated a pitted surface and led to crystalline deterioration. Given our understanding of the formation mechanism of pits, we applied a periodic oxygen pressure-modulated epitaxy that resulted in the coherent growth of Co-dopedlayers with a 2D mode. This specific growth was effective in producing pit-free surface uniformities over large areas that maintained FM ordering.