Cornelis De Groot

Orientation and symmetry control of inverse sphere magnetic nanoarrays by guided self-assembly

Inverse sphere shaped Ni arrays were fabricated by electrodeposition on Si through the guided self-assembly of polystyrene latex spheres in Si/SiO2 patterns. It is shown that the size commensurability of the etched tracks is critical for the long range ordering of the spheres. Moreover, noncommensurate guiding results in the reproducible periodic triangular distortion of the close packed self-assembly. Magnetoresistance measurements on the Ni arrays were performed showing room temperature anisotropic magnetoresistance of 0.85%. These results are promising for self-assembled patterned storage media and magnetoresistance devices.

Numerical investigation of domain walls in constrained geometries

In recent years, magnetic domain wall structures in ferromagnetic nanowires have attracted growing attention, opening paths to develop novel devices which exploit magnetoresistive effects. A reduction of the domain wall length in geometrically constrained areas has been predicted and observed. In this article, we consider a rectangular constriction (width s0, length 2d0) in form of a thin film, attached to a rectangular pad (width s1) on either side. The material considered is Ni (Ms=490kA∕m) with a weak in-plane anisotropy (K1=2000J∕m3). We investigate the dependence of the domain wall length as a function of the constriction geometry. Micromagnetic simulations are used to systematically study the head-to-head domain walls between head-to-head domains (case A) and Neel walls between sidewise domain orientations (case B). We present the resulting domain wall length w as a function of 2d0 and s0 and analyze the magnetization patterns. A reduction of the domain wall length to below 11nm is found (where the ...

Dataset for Active Counter Electrode in a-SiC Electrochemical Metallization Memory

Dataset for figures in: Morgan, K. et al (2017). Active Counter Electrode in a-SiC Electrochemical Metallization Memory. Journal of Physics D: Applied Physics.Funded by EPSRC

Dataset for Switching kinetics of SiC resistive memory for harsh environments

Dataset for figures in: Morgan, K. et al (2015). Switching kinetics of SiC resistive memory for harsh environments. AIP Advances.Funded by EPSRC

Coplanar waveguides on gold-doped high resistivity silicon for 67-GHz microwave application

High resistivity handle wafers suitable for radio frequency integrated circuit application have been achieved through deep level doping compensation technique. Ion implantation and subsequent annealing were used to introduce electrically active gold atoms into silicon resulting in an increase in resistivity up to 70 kOhm-cm from a nominal value of 50 Ohm-cm. At 67GHz, attenuation loss for coplanar waveguides shows a strong reduction from 0.88 dB/mm obtained from un-implanted wafers to 0.3 dB/mm in gold-implanted wafers.

Fabrication of Nano-Structured Gold Arrays by Guided Self-assembly for Plasmonics

Gold inverse spherical nanoscale voids have been fabricated in linear arrays for directional plasmon measurements in the visible spectral range. We show that by KOH anisotropic etching in Si, we are able to make V-grooves in which latex spheres of the order of 500 nm self-assemble with largely defect-free cubic symmetry. Both single layer and multilayer assembly in a face-centered close-packed (FCC) lattice can be achieved by varying the width of the trenches. This template is subsequently used for electrodeposition of gold to create the inverse spherical nanovoids.