Enhancement of lattice defect signatures in graphene and ultrathin graphite using tip‐enhanced Raman spectroscopy

Abstract

Understanding the role of defects in graphene is the key to tailoring the properties of graphene and promoting the development of graphene-based devices. Defects can affect the electronic properties of a device while also offering a means by which to functionalize the local properties. Using tip-enhanced Raman spectroscopy (TERS), heightened defect sensitivity was demonstrated on graphene edges, folds, and overlapping regions. Measurements confirm that TERS can provide simultaneous structural and spectral information on a localized scale, hence offering defect characterization on a scale that is not obtainable using conventional Raman spectroscopy. This study observed preferential enhancement of the D band signal on multilayered graphene and ultrathin graphite; in addition, other key defect signatures were also enhanced and detected. We present our findings in relation to theoretical predictions of graphene defect signatures and an analysis of the sensitivity of TERS in measuring two-dimensional structures.

Tip-enhanced Raman spectroscopy: principles and applications

“…5b, a metal tip is mounted on to the prong of a quartz tuning fork. TERS measurements are conducted by positioning the tip at the centre of the laser focus, and accurately controlling the tip-sample distance using shear-force as the feedback [44,45]. In case of STM-TERS, the tip-sample distance is controlled via a feedback loop using the tunnelling current between the tip and sample, as shown schematically in Fig.…”

Local hole doping concentration modulation on graphene probed by tip-enhanced Raman spectroscopy

“…Since the first TERS measurement for graphene in 2008 [29], TERS has been intensively used for investigating local material properties of various types of graphene, such as mechanically-exfoliated graphene on glass [30][31][32][33][34][35][36][37][38], on Au [39], chemical vapor deposition (CVD)-grown graphene on glass [38] or on Cu [39], epitaxially-grown graphene on SiC [40][41][42], and polymerized graphene [43]. On the other hand, there has been little TERS works for graphene nanodevice analysis.…”

Characterization of SiC-grown epitaxial graphene microislands using tip-enhanced Raman spectroscopy

“…By using a metallic nanotip, plasmon enhancement is confined to the small area at the tip apex and the Raman signal solely from this area can be detected. [27][28][29][30][31] Due to its excellent spatial resolution, TERS has been used in graphene studies, especially in the investigation of small features such as edge boundaries, [18][19][20]32,33 nanodefects, [34][35][36] gap modes, 37,38 and local strain. 9,39,40 Using this technique, our previous study presented Raman spectra of ridge, crack, and step nanostructures on epitaxial graphene, which revealed direct evidence for the proposed mechanism that the nanoridges are formed through a relaxation against compressive strain.…”