Graphene on Copper Sample Characterization
The following summarizes the general characteristics of the graphene samples that are grown on 20µm copper foils. The outcome after growth is graphene grown a large scale single preferred copper orientation. A summary of the graphene properties is listed in the table below.
Description of Characterization
|Graphene Coverage (%)
|Multilayer Coverage (%)
|< 1% - Higher coverage on edge of samples is expected
|Average Crystal size
|Sheet resistance (Ω/sq) – large area average
|595 Ω/sq – SD=140 Ω/sq
|I2D/IG Average - after transfer
|ID/IG Average - after transfer
|2D peak width average (cm-1) - after transfer
|Cu grain orientation
After the graphene growth on copper, samples are inspected by optical microscopy, scanning electron microscopy and Raman Spectroscopy then transferred to silicon wafers using the wet etching method for further characterizations. Hereafter details of the characterizations are presented.
Optical Microscopy Images
Samples show high graphene coverage. Few crystal boundaries are seen, indicative of the preferential single orientation of the copper. Few defects/dust residues may be seen as shown on the lower right image.
Scanning Electron Microscopy Images
Graphene on 20µm copper
Notes : The sample shows high graphene coverage (>99%), low number of crystal boundaries are found. Presence of few tears and multilayers are expected on parts of the samples, and specifically at sample edges.
Graphene defect levels are evaluated using Raman Spectroscopy. This technique is sensitive to changes on the atomic scale and is useful for the study of disorder in graphene films. At General Graphene, Raman spectroscopy is performed using InVia Renishaw Raman microscope equipped with 50x and 100x·objectives with 532 nm laser excitation on 1800-line grating.
Raman Spectroscopy shows the presence of G and 2D peaks indicative of graphene presence – A low D-peak (ID/IG < 0.1) may be seen on some parts of the samples.
Raman spectra of graphene on copper:
Four-point probe measurement:
Notes : Electrical measurement is performed using four-point probe at RT and in ambient environment, after graphene transfer to Silicon wafers using wet transfer method.
Rs (average) = 595 Ω/sq SD = 140 Ω/sq