Properties of graphene deposited on GaN nanowires: influence of nanowire roughness, self-induced nanogating and defects.

Jakub Kierdaszuk,Aleksandra Krajewska,Wawrzyniec Kaszub,Aleksandra Przewłoka,Justyna Grzonka,Aneta Drabińska,Piotr Kaźmierczak,Zbigniew R Zytkiewicz,Andrzej Wysmołek,Marta Sobanska,Maria Kamińska

doi:10.3762/bjnano.12.47

Jakub Kierdaszuk, Aleksandra Krajewska + Show 9 more

Open Access

https://doi.org/10.3762/bjnano.12.47

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Abstract

We present detailed Raman studies of graphene deposited on gallium nitride nanowires with different variations in height. Our results indicate that different density and height of nanowires impact graphene properties such as roughness, strain, and carrier concentration as well as density and type of induced defects. Tracing the manifestation of those interactions is important for the application of novel heterostructures. A detailed analysis of Raman spectra of graphene deposited on different nanowire substrates shows that bigger differences in nanowires height increase graphene strain, while a higher number of nanowires in contact with graphene locally reduces the strain. Moreover, the value of graphene carrier concentration is found to be correlated with the density of nanowires in contact with graphene. The lowest concentration of defects is observed for graphene deposited on nanowires with the lowest density. The contact between graphene and densely arranged nanowires leads to a large density of vacancies. On the other hand, grain boundaries are the main type of defects in graphene on rarely distributed nanowires. Our results also show modification of graphene carrier concentration and strain by different types of defects present in graphene. Therefore, the nanowire substrate is promising not only for strain and carrier concentration engineering but also for defect engineering.

Highlights

The combination of excellent electrical and mechanical properties with interesting physical phenomena occurring in twodimensional structures makes graphene an interesting experimental material to study [1,2,3]
We present detailed statistical studies of Raman spectra of graphene deposited on gallium nitride nanowires (GaN NWs) with different variations in height
We transferred graphene onto GaN NWs with 0, 100, and 500 nm variations in height and studied their properties by scanning electron microscopy (SEM) and Raman spectroscopy

Summary

Introduction

The combination of excellent electrical and mechanical properties with interesting physical phenomena occurring in twodimensional structures makes graphene an interesting experimental material to study [1,2,3]. In order to recognize how NWs locally modify graphene strain, carrier concentration, and defects, a statistical analysis of band parameters over the whole Raman micro-mapping area was per- According to the analysis of 2D energy, different values of 2D band FWHM for N0 and N100 samples cannot be explained only by the effect of graphene strain.

Results

Conclusion