Industrial graphene metrology

Abstract

Graphene is an allotrope of carbon whose structure is based on one-atom-thick planar sheets of carbon atoms that are densely packed in a honeycomb crystal lattice. Its unique electrical and optical properties raised worldwide interest towards the design and fabrication of future electronic and optical devices with unmatched performance. At the moment, extensive efforts are underway to evaluate the reliability and performance of a number of such devices. With the recent advances in synthesizing large-area graphene sheets, engineers have begun investigating viable methodologies for conducting graphene metrology and quality control at industrial scales to understand a variety of reliability issues including defects, patternability, electrical, and physical properties. This review summarizes the current state of industrial graphene metrology and provides an overview of graphene metrology techniques. In addition, a recently developed large-area graphene metrology technique based on fluorescence quenching is introduced. For each metrology technique, the industrial metrics it measures are identified--layer thickness, edge structure, defects, Fermi level, and thermal conductivity--and a detailed description is provided as to how the measurements are performed. Additionally, the potential advantages of each technique for industrial use are identified, including throughput, scalability, sensitivity to substrate/environment, and on their demonstrated ability to achieve quantified results. The recently developed fluorescence-quenching metrology technique is shown to meet all the necessary criteria for industrial applications, rendering it the first industry-ready graphene metrology technique.

Chemical vapor deposition of partially oxidized graphene

“…It is likely that the POG lm was folded during the transfer onto the grid. 39 The small particles of high intensity (bright white) dispersed throughout the lm are copper-oxide particles as determined by EDX elemental mapping in Fig. 2b.…”

Graphene Metrology Using Fluorescence Quenching of Different Fluorescent Dyes

“…Moreover, transmission electron microscopy (TEM) has been used to demonstrate the atomic structure of graphene [5]. It has been reported that low-energy electron microscopy (LEEM) can be implemented for spatially-resolved measurements of graphene thickness [5]. Although these techniques can provide sufficient insight about the integrity, quality and defects of graphene sheets, they are time consuming and limited to very small scales.…”

“…Although these techniques can provide sufficient insight about the integrity, quality and defects of graphene sheets, they are time consuming and limited to very small scales. For industrial applications of graphene, a quick, repeatable and decisive metrology method must be developed to allow characterization of entire area or specific regions of interest of graphene sheets on glass or Si/SiO 2 substrates [5,6]. An alternative for high throughput large-scale characterization of graphene is fluorescent quenching microscopy (FQM) [5][6][7][8].…”

“…Typically, scanning electron microscopy (SEM), scanning probe microscopy (SPM) and Raman spectroscopy are used for graphene characterization. Moreover, transmission electron microscopy (TEM) has been used to demonstrate the atomic structure of graphene [5]. It has been reported that low-energy electron microscopy (LEEM) can be implemented for spatially-resolved measurements of graphene thickness [5].…”

“…Furthermore, the imaging time in FQM is relatively shorter. Generally, a thin layer of fluorescent dye is coated on graphene and the energy is transferred from the dye molecules in excited state to graphene [5][6][7][8]. The energy transfer results in fluorescence quenching of the dye by graphene which depends on the thickness of the dye layer which determines the distance between graphene and dye molecules [9][10][11][12].…”