Multifunctional III-nitride dilute magnetic semiconductor epilayers and nanostructures as a future platform for spintronic devices

Abstract

This work focuses on the development of materials and growth techniques suitable for future spintronic device applications. Metal-organic chemical vapor deposition (MOCVD) was used to grow high-quality epitaxial films of varying thickness and manganese doping levels by introducing bis-cyclopentadienyl as the manganese source. Highresolution X-ray diffraction indicates that no macroscopic second phases are formed during growth, and Mn containing films are similar in crystalline quality to undoped films Atomic force microscopy revealed a 2-dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. The mean surface roughnesses of optimally grown Ga 1-x Mn x N films were almost identical to that from the as-grown template layers, with no change in growth mechanism or morphology. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the structural, magnetic and opto-electronic properties. SQUID measurements showed an apparent ferromagnetic hysteresis behavior which persisted to room temperature. An optical absorption band around 1.5 eV was observed via transmission studies. This band is assigned to the internal Mn 3+ transition between the 5 E and the partially filled 5 T 2 levels of the 5 D state. The broadening of the absorption band is introduced by the high Mn concentration. Recharging of the Mn 3+ to Mn 2+ was found to effectively suppress these transitions resulting in a reduction of the magnetization. The structural quality, and the presence of Mn 2+ ions were confirmed by EPR spectroscopy, meanwhile no Mn-Mn interactions indicative of clustering were observed. The absence of doping-induced strain in Ga 1-x Mn x N was observed by Raman spectroscopy.

Influence of Cu doping on the local electronic and magnetic properties of ZnO nanostructures

“… 35 Thus, Cu doped ZnO as a DMS is supposed to have a longer coherence time which provides an opportunity for increasing the spin lifetime for practical spintronics applications. 36 Furthermore, the literature states that the doped transition metal ion can change the magnetic properties of ZnO. 37,38 However, the effect of doping is still complicated to understand.…”

Cu-Doped ZnO Hemispherical Shell Structures: Synthesis and Room-Temperature Ferromagnetism Properties

“…Most of the investigations of RTFM ZnO:Cu system have been focused on bulk materials or thin films, whereas only a few reports on nanostructures (e.g., nanoparticles, nanowires, , nanonails, and nanoneedles) have been published to date. These nanostructures have been known to have a longer spin lifetime than that of the film implying that they have great potential in nanoscale spintronic devices . Compared with other one dimension ZnO nanostructures (nanowires, nanorods, nanonails, etc.…”

Magnetic properties of Mg‐doped AlN zigzag nanowires

“…The behavior of carriers in nanostructures may allow the enhancement of the ferromagnetic semiconductor behavior, with potentially higher carrier concentrations and efficient injection of spin‐polarized carrier 2, 5. Nanostructures may have longer spin lifetime in nitride‐based ferromagnetic semiconductor devices for numerous applications 6, such as sensors, magnetic recorder and other devices 7. Due to the wide bandgap (∼6.0 eV) of aluminum nitride (AlN), it has attracted particular research enthusiasm for fabricating AlN based DMSs, which plays an important role in many solid‐state devices 8–10.…”