Abstract
Ordered Fe-doped In2O3 nanodot arrays with diameters between 35 nm and 80 nm are fabricated using pulsed laser deposition with the aid of ultrathin porous anodized aluminumoxide templates. The 5 at.% Fe doped In2O3 nanodot arrays are shown to consist of the cubic bixbyite structure of In2O3. The nanodot arrays are demonstrated to be doped by Fe ions with mixed valences of +2 and +3, ruling out the presence of cluster and secondary phase related to Fe. The nanodot arrays exhibit the ferromagnetism at room temperature, where the magnetic moment increases as the dot size is reduced, rising to a maximum of about 230 emu/cm3 (equivalent to an average moment on the Fe ions of 15.30 µB/Fe). This indicates an effect due to the surface of the nanodot arrays. The optical band width is also increased to 4.55 eV for the smallest dot array, thus indicating that the surface states are responsible for the magnetism and also enhance the band gap due to Burstein-Moss effect. Our results will be benefit for understanding the physical properties of oxide semiconductor nanostructures in the application of nano-spintronics devices.
Highlights
Dilute magnetic semiconductors (DMSs), combining both semiconductor and ferromagnetic properties, have gained great attention due to their potential applications in spintronic devices[1]
We presented the growth of DMS nanodot arrays by pulsed laser deposition (PLD) using the porous anodized aluminum (PAA) templates, and provided the insights into the origin of the room temperature (RT) ferromagnetism in Fe-doped In2O3 nanodot arrays by a comprehensive analysis of structure and magnetic properties of the arrays
A slight shift in the position of the (222) peaks to higher angles is observed, indicating a reduction in the lattice constant (see Fig. 2(b)), which might be due to the increased oxygen vacancies in the surface of the smaller nanodot arrays derived from their larger surface-to-volume[28]
Summary
The saturation magnetic moment (Ms) of nanodot arrays sharply increases from 1.85 to 15.30 μB/Fe as the nanodot size decreases (Noted that the calculated dot volume is based on its surface and cross-section morphology in order to reduce calculate error, which is shown in Supplementary), which is much larger than that of the 5 at.% Fe doped In2O3 films[8,11]. Such huge Ms in zero dimensional nanodot arrays may be attributed to the abundant.
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