A combination of electromagnetic alignment and topological pattern assisted alignment to position magnetic nanowires, which is referred to as the Patterned Electromagnetic Alignment (PEA), is developed and examined. Electrodeposited, FeNiCo nanowires with different lengths were used as the test nanomaterial, and the microscale grooved surface was formed by UV nanoimprint lithography. The accuracy of the PEA with FeNiCo nanowires was evaluated by measuring the deviation angle from the direction of the magnetic field line for different magnetic field strengths and nanowire lengths, and a statistical alignment distribution was reported for different nanowire length groups. The results were compared with those of the electromagnetic alignment on flat surfaces and in grooved-patterned substrates without electromagnetic alignment. Overall, the deviation angle for the PEA was lower than that for the electromagnetic alignment when all other experimental conditions were identical, indicating that the alignment accuracy along the direction of the magnetic field lines was enhanced in the presence of surface micro grooves. This can be attributed to the fact that, upon attachment of nanowires to the substrate surface, the surface micro grooves in the PEA add additional deterministic characteristics to the otherwise stochastic nature of the nanowire deposition and solvent evaporation processes compared to the sole electromagnetic alignment.
The aluminum content is widely used in III-N semiconductors as a determiner of material etch characters. Applications consisting of thin GaN/AlGaN heterostructures can afford a maximum of 6 nm of a thin AlGaN layer over etch demand complex processes with precise low etch rates and low etched GaN surface roughness. In this paper, the effects of bias power and SF6 flow ratios on the chlorine chemistry etch rate, selectivity, and GaN surface roughness are investigated in a high-frequency bias generator and low power inductively coupled plasma configuration. Bias power and SF6 flow control the etch responses and are used to find the optimal spots for low etch rate, low GaN roughness, and high GaN:AlGaN selectivity for the fabrication of devices consisting of thin GaN/AlGaN heterostructures. The results are compared with the other selective gas chemistries and the more common 13.56 MHz frequency bias generator.
Alloy nanowires containing Fe, Ni and Co are of interest as electrode materials in miniaturized devices due to their ability to align them under a magnetic field. In order to improve their resistivity while retaining their magnetic behavior, Fe-Ni-Co nanowires were electrodeposited and decorated with Au; single nanowires were then further characterized (Fig. 1). The nanowires were deposition under a constant applied potential within a nanoscale alumina template, followed by dissolution of the membrane, release of the nanowires, and subsequent treatment in a gold acid electrolyte. Au clusters formed on the Fe-Ni-Co surface through simultaneous displacement and corrosion reactions. The morphology, composition and structure was examined before and after modification, revealing a change in crystallinity and composition that impacted the nanowire’s electrical and magnetic properties. Transferring a single nanowire to a lithographically prepared two-point probe enabled the electrical and magnetic characterization of the Au decorated nanowire. Averaging results of quadruplicate replicates, a low coverage of discontinuous Au clusters on Fe-Ni-Co nanowires significantly decreased the resistivity, not attributed entirely to the lower resistivity of Au, but as a consequence of changes of the Fe-Ni-Co crystallinity. A high coverage of the Fe-Ni-Co by Au had no further benefit, and even increased the resistivity. Since bulk gold is diamagnetic and decoration of Au onto the Fe-Ni-Co nanowires may compromise the overall magnetic property, the magnetoresistance and electron mobility were determined. Both decreased, as expected, with coverage of Au clusters on the nanowires, suggesting that there may be an optimal cluster density for modifying the Fe-Ni-Co nanowires. Figure 1. Electrodeposited nanowires initially amorphous then decorated with Au showing a change in crystallinity and subsequent characterization with a two-point probe. Figure 1
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