Characterisation of size distribution and positional misalignment of nanoscale islands by small-angle X-ray scattering

Georg Heldt,Philip Thompson,Thomas Thomson,Laura J Heyderman,Stephen Lee,Rajesh V Chopdekar,Joachim Kohlbrecher

doi:10.1063/1.5050882

Abstract

Highly ordered arrays of nanoscale magnetic structures form the basis of artificial spin ices, uniform particles for bio-medical applications, and data storage as Bit Patterned Media. We demonstrate that small-angle X-ray scattering (SAXS) allows the size distribution and the positional alignment of highly ordered arrays to be determined with high spatial and statistical accuracy. The results obtained from the SAXS measurements are compared to an analysis of Scanning Electron Microscopy images and found to be in excellent agreement. This confirms the validity of the technique and demonstrates its potential as a fast, accurate, and statistically reliable method for characterising arrays of ordered nanostructures.

Highlights

Ordered arrays of nanostructures play a key role in many aspects of modern science and technology, such as in artificial spin ices,[1,2] as resonant enhancers in plasmonics,[3,4] in magnetic data storage drives as Bit Patterned Media (BPM),[5–7] for functionalisation of material surfaces,[8] and in biomedical science studying proteins.[9]
We have demonstrated that values for mean diameter, standard deviation, and positional variance are measurable using the small-angle X-ray scattering (SAXS) method for nanostructure arrays
The statistical significance of the SAXS diffraction data is considerably better since orders of magnitude more islands may be sampled in a measurement time of seconds

Summary

INTRODUCTION

Ordered arrays of nanostructures play a key role in many aspects of modern science and technology, such as in artificial spin ices,[1,2] as resonant enhancers in plasmonics,[3,4] in magnetic data storage drives as Bit Patterned Media (BPM),[5–7] for functionalisation of material surfaces,[8] and in biomedical science studying proteins.[9]. To take full advantage of the desired properties of ordered arrays of nanostructures, it is essential to know the structural parameters including mean diameter, standard deviation of the diameter, and position misalignment These parameters can be used to optimise the fabrication process[10] or in theoretical calculations and simulations to predict the performance of the array, for example, in BPM5–7 or artificial spin ices.[11,12]. Small-angle X-ray scattering (SAXS) measurements offer the possibility to investigate a very large number of nanoislands simultaneously in parallel, reducing measurement times to the order of seconds. This provides a method of characterising large arrays of highly ordered nearly uniform nanoislands with high statistical significance. Between 0.16 and 0.3, which covers a significant part of the range of ratios encountered in the literature.[5–7]

EXPERIMENTAL

DATA REDUCTION OF SAXS MEASUREMENT

THEORY AND ANALYSIS OF SAXS DATA

RESULTS

CONCLUSION