Cleaning graphene with a titanium sacrificial layer

Abstract

Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon

Cleaning Transferred Graphene for Optimization of Device Performance

“…Whereas, on the other hand, further AFM data analysis reveals that the PMMA residues coverage on the graphene surface decreased from 75% (as‐baked) to 40% and 34% after NaCl and HCl treatments (Figure e,f), as compared to 70% for DI water‐treated samples. Given that the number of PMMA residues can be reduced by hydrogen fluoride, glacial acetic acid, and HNO 3 based on the chemical reaction between strong acids and polymer molecules, we propose the interaction between HCl/NaCl solutions and PMMA residues as a different reaction by acknowledging that bulk PMMA has high chemical resistance to both HCl and NaCl solutions. Figure g–i shows zoom‐in images with enhanced contrast of the aggregates after immersion in DI water, 1 m HCl, and 1 m NaCl, respectively.…”

Titanium contacts to graphene: process-induced variability in electronic and thermal transport

“…It has been shown that PMMA residues react with Ti overlayers. [41] Other sources of variability in both the interface and contact chemistry could be related to intrinsic defects in the CVD-grown graphene film or due to other extrinsic effects of transfer process including residual Cu, incomplete removal of graphene from the back of the Cu foil, wrinkles and tears in the film, or adsorbates. While measures can be taken to assess the quality and uniformity of the transferred graphene prior to device fabrication, such as characterization with Raman spectroscopy, [37,38,42] these defects are inherent to the transfer process and are fundamentally uncontrollable.…”

“…Therefore it is presumed that all Gr/Ti interfaces will actually be TiOx/Gr with some variation in amount of hydrocarbon incorporated. [41] At this time the impact of the variations in hydrocarbon incorporation at the interface on the thermal boundary conductance is unknown. Therefore, we cannot rule this out as a potential mechanism, and thus leave an intricate study of the chemistry effects on Ti/Gr thermal boundary conductance to future work.…”

Effects of etchants in the transfer of chemical vapor deposited graphene

“…3,14 A large body of research work has been dedicated to minimizing these modifications; examples of such efforts include thermal annealing, electrical current annealing, plasma cleaning, chloroform treatment, and using a sacrificial Ti layer. Yet, these methods can still introduce defects in the graphene sheets or increase toxicity, 7,[15][16][17] and so, techniques to improve graphene quality are still strongly desired. On the other hand, methods to determine the quality of transferred graphene have been developing quickly, such as inductively coupled plasma mass spectrometry, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy (XPS).…”