Properties of Mn-Doped ZnO

The solubility of Mn into ZnO can exceed the equilibrium limit ( -- 13%) and reaches up to 35% [11] as a result of the nonequilibrium PLD film growth process. 

With increasing Mn content, the lattice constants a and c of wurtzite Zni Mn O increase due to the fact that the ionic radius of Mn (0.66 A) is larger than that of Zn (0.60 A) [23, 119, 121, 132,135], and the bandgap expands with considerable mid-gap absorption. This mid-gap absorption peak centered around 3 eV in Mn-doped ZnO is usually broad and structureless at room temperature owing to the overlap of the intra-d shell transitions of Mn from its ground state Aj (S) to Tj (G), 

Zni fMn,0 films measured at room temperature for variousxvalues. Numbers in the figures denote x. Inset shows the photon energy dependence of squared absorption constant (a ) around the bandgap (Eg), (b) Magnetization 

The blueshift of bandgap energy and the increase of mid-band absorption have also been observed from Zn0.93Mn0.07O deposition by RF magnetron sputtering [124]. 

3C = 0.01 and 0.15. No evidence for a ferromagnetic transition in these systems was observed above 2 K. The authors proposed a model that considers two subsets of spins to explain the observed magnetic properties. One subset of spins, which belongs to the TM ions with no TM nearest neighbors, is completely free (isolated spins). The 

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FIGURE 6.6 XRD pattern (unirradiated and irradiated with 50 MeV LF+ ion beam) of 2 at% Mn-doped ZnO sample. (From Neogi, S.K., Chattopadhyay, S., Baneijee, A., Bandyopadhyay, S., Sarkar, A., and Kumar, R., Effect of 50 MeV Li3 + irradiation on structural and electrical properties of Mn doped ZnO, J. Phys. Condens. Matter, 23, 2011. With permission from lOP Publishing Ltd.)... 

Fukumura T, Zhengwu J, Kawasakib M, Shono T, Hasegawa T, Koshihara S, Koinuma H, Magnetic properties of Mn-doped ZnO, Appl. Phys. Lett, 78, 958-960, 2001. 

Banerjee S, Rajendran K, Gayathri N, Sardar M, Senthikumar S, Sengodan V, Change in the room temperature magnetic property of ZnO upon Mn doping, J. Appl. Phys., 104, 043913-5, 2008. 

Carbothermal route provides a general method for preparing crystaUine nanowires of oxides such as ZnO, Al Oj and Ga Oj, nitrides such as AIN and SijN, and carbides such as SiC [3], The set-up employed for the synthesis of oxide nanomaterials is shown in Figure 3.1. The method has enabled the synthesis of crystalhne nanowires of both silica and sihcon. In the case of GaN, it has been possible to dope it with Mn, Mg and Si to bestow useful optical and magnetic properties. Carbothermal reaction involving Ga Oj powder mixed with activated carbon or carbon nanotubes carried out at 1100 °C in flowing Ar yields nanowires, nanorods as well as novel nanostructures... 

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