Schematic representation of the flexible plasmonic graphene oxide (GO)/heterostructure-based device with dual functionality for electrochemical and SERS detection.
The present study covers the nanoanalysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the downsizing of the geometrical dimensions of the electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale and the simultaneous increase in the functionality density, the previous generation of microanalysis methods is no longer sufficient. Therefore, the metrology of materials' properties with nanoscale resolution is a prerequisite in materials' research and development. The article reviews the standard analysis methods and focuses on the advanced methods with a nanoscale spatial resolution based on atomic force microscopy (AFM): current-sensing AFM (CS-AFM), Kelvin probe force microscopy (KPFM), and hybrid optical techniques coupled with AFM including tip-enhanced Raman spectroscopy (TERS), photothermal-induced resonance (PTIR) characterization methods (nano-Vis, nano-IR), and photo-induced force microscopy (PIFM). The simultaneous acquisition of multiple parameters (topography, charge and conductivity, stress and strain, and chemical composition) at the nanoscale is a key for exploring new research on structure-property relationships of nanostructured materials, such as carbon nanotubes (CNTs) and nano/microelectromechanical systems (N/MEMS). Advanced nanocharacterization techniques foster the design and development of new functional materials for flexible hybrid and smart applications.
Carbon nanomaterials are important for future sensors and electronics. Defects determine the material properties, therefore, it is critical to find new ways to investigate defects at the nanoscale. In this context, Raman spectroscopy (RS) is the tool of choice to study defects in carbon nanomaterials. On the other hand, Kelvin probe force microscopy (KPFM) provides structural and surface potential information at the nanoscale. Here, the authors demonstrate the synergistic application of these methods in the investigation of ion-beaminduced defects in graphite. KPFM and RS imaging are used for visualizing ioninduced defects in a wide range of ion doses from 10 10 to 10 16 ions cm À2 . For the lower range of ion dose, the authors find that RS provides image contrast for the different defect regions in graphite up to a dose of 5 Â 10 13 ions cm À2 . For higher doses, the sp 2 carbon concentration becomes so small that the Raman spectra get dominated by broad amorphous carbon bands. For this dose range, the KPFM contrast allows the defective regions to be differentiated. This contrast in KPFM originates from sp 3 carbons that act as charge traps. The results show that KPFM and Raman microscopy make a powerful and necessary combination for studying the spatial distribution of defects in carbon.
Raman spectroscopy (RS) is the tool of choice for the analysis of carbon nanomaterials. In graphene and carbon nanotubes (CNT), RS provides rich information such as defect concentration, CNT chirality, graphene layer number, doping, strain, and other physical parameters of interest. This work presents the RS investigation of a semiconducting CNT film after high power laser irradiation. Changes were observed in the D band revealing the change in the defect concentration induced by the laser. More importantly, it was found the relative intensity decrease of G À and some radial breathing modes which suggests that the effects of laser irradiation induce diameter-selective effects in CNTs. The spectroscopic changes to the selective electronic structure modification for some semiconducting CNTs were attributed as due to those CNTs getting closer to resonance conditions with the fixed laser excitation.
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