Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

Abstract

Room-temperature ferromagnetic Co-doped ZnO nanoneedle array prepared by pulsed laser deposition Appl. Phys. Lett. 87, 173119 (2005) We study planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al 2 O 3 ), as well as the Co:ZnO/Al 2 O 3 interface, using aberration-corrected transmission electron microscopy and electron energy-loss spectroscopy. Co:ZnO samples that were deposited using pulsed laser deposition and reactive magnetron sputtering are both found to contain extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers next to the Al 2 O 3 substrate. The stacking fault density is in the range of 10 17 cm À3 . We also measure the local lattice distortions around the stacking faults. It is shown that despite the relatively high density of planar defects, lattice distortions, and small compositional variation, the Co:ZnO films retain paramagnetic properties. V C 2013 AIP Publishing LLC.

Coalescence-driven magnetic order of the uncompensated antiferromagnetic Co doped ZnO

“…The interface between the Al 2 O 3 and the 35% Co:ZnO films is abrupt but moderately enriched with defects, but no indication of secondary phases can be seen. Compared to 10% Co:ZnO, the 20% films have an increased number of point defects [36], which is even further enhanced for higher concentrations and the misorientation of the grains is larger, which is consistent with the moderate increase of the FWHM of the XRD results for increasing Co content. The electron-diffraction pattern in Fig.…”

“…The TEM image taken on the 35% Co:ZnO sample [ Fig. 1(b)] shows the typical columnar growth of the Co:ZnO films [36]. The layer thickness of around 200 nm can be confirmed as well as the smooth surface.…”

“…In addition, a transmission electron microscopy (TEM) specimen has been prepared from the 35% sample according to the procedure described in more detail in Ref. [36].…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…A possible approach to speed up micromagnetic simulations is the use of novel highly parallel computing architectures such as graphics processing units [109], [110], [111]. Alternative strategies include the application of novel algorithms from the rising field of machine learning in order to reduce the complexity of the micromagnetic model [112]. An algorithmic approach that is particularly well suited for magnonics is micromagnetics in the frequency space.…”

A Small Spot, Inert Gas, Ion Milling Process as a Complementary Technique to Focused Ion Beam Specimen Preparation

“…Oxide materials, in interaction with high-energy ions, typically form a lesser amount of an amorphous layer on the surface, but are more sensitive to selective sputtering, which may result in a high surface roughness. Figure 5 shows the images of Co-doped ZnO thin film (Kovács et al, 2013) deposited on Al 2 O 3 (sapphire) as an example of substantial surface modification. The slightly defocused BF-TEM image of the substrate, Figure 5b, shows the nanometer-sized "pits" in sapphire after FIB preparation at 5 keV, which are eliminated by the sequential milling of the specimen at 900 and 500 eV with a concentrated Ar ion beam, as shown in Figures 5c and 5d.…”