Heteroepitaxial growth behavior of Mn-doped ZnO thin films on Al2O3 (0001) by pulsed laser deposition

Abstract

Heteroepitaxial growth behavior of Mn-doped ZnO thin films (Zn1−xMnxO) on Al2O3 (0001) substrates by pulsed laser deposition was investigated particularly as a function of Mn content (0.00⩽x⩽0.35) using synchrotron x-ray scattering and atomic force microscopy. The undoped ZnO film was grown epitaxially with a 30° rotation of ZnO basal planes with respect to the Al2O3 substrate while having a small amount of grains with another epitaxial relationship, i.e., the hexagon-on-hexagon growth. A small amount of Mn doping (x=0.05) not only greatly improved the atomic alignment both in the in-plane and in the out-of-plane directions, but also led to a singly oriented film by totally suppressing the hexagon-on-hexagon growth. With further incorporation of Mn into ZnO beyond that content, the epitaxial nature again deteriorated. The superior epitaxial growth of the film with an optimum Mn content is attributed to the formation of much larger grains in it. In addition, our Mn-doped ZnO thin films showed a paramagnetic behavior.

Magnetic, Structural, and Optical Properties of Low Temperature ZnMnO Grown by Atomic Layer Epitaxy

“…From X-ray diffraction (XRD) they evidenced the presence of several manganese oxides in their ZnMnO samples, including Zn • C [12]. The inclusions of Mn oxides have strong impact on magnetic properties of ZnMnO films [3], as it is also demonstrated in the present work.…”

“…Values of c (increases) and a (decreases) axis parameters change upon Mn doping. This formally should allow us to estimate Mn fractions in our films [8,9,12]. We found however that the dependences given in Refs.…”

“…The following experimental observations for ZnMnO (also for ZnCoO) confirmed or rejected the presence of FM ordering, leading to a quite confusing situation. RT FM phase was reported by Sharma et al [3], Lee et al [4], Lim et al [5], Theodoropoulou et al [6], low temperature FM phase was reported by Jung et al [7], spin glass phase was reported by Fukumura et al [8], whereas Tiwari et al [9] and Kolesnik et al [10,11] and Kim et al [12] did not find any FM ordering. Kolesnik and co-workers related FM phase reported by other groups to inclusions of foreign phases of Mn oxides.…”

“…For example, for one of ZnMnO films grown with Mn(thd) 3 precursor we got 5% Mn fraction using the dependence of c vs. Mn concentration given in [8], about 20% using the analogous dependence given in [9], and well below 1% based on the similar dependence given in Ref. [12]. Such large spread of estimations of Mn fractions may likely be the consequence of large differences in amounts of inclusions of Mn foreign phases in the samples studied in Refs.…”

Magnetic and Electrical Properties of Undoped and Holmium Doped ZnO Thin Films Grown by Sol-Gel Method

“…Lately, ZnO-based diluted magnetic semiconductors (DMSs) have been of great interest because of some theoretical predictions of room temperature ferromagnetism [3]. So far, doping ZnO with transition metals like Co, Fe, Mn, Ni was usually employed in order to obtain ferromagnetic properties in ZnO [4][5][6][7][8][9][10][11][12]. However, the origin of the ferromagnetism is already controversial.…”