Interaction Between Graphene-Coated SiC Single Crystal and Liquid Copper

Abstract

The wettability of graphene-coated SiC single crystal (C Gn /SiC sc ) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100°C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6¢¢ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the C Gn /SiC sc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of h 0 = 121°and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values (h R = 86°and h L = 70°, respectively), while in the next 30 min, h R and h L achieved the same final value of $ 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate (h = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both h R and h L decreased in 17 min to the value of 23°and next, they increased to a final value of 65°. Visual observations revealed a presence of $ 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

Microstructural characterization of reaction products in Cu/Graphene/SiC system

“…The results of structural analyses suggested that the presence of discontinuities in the graphene layer provoked by thermo-mechanical stresses occurred at high temperature, inhibit, but does not completely prevent, the chemical interaction between the liquid droplet of Cu and SiC sc . This effect was more pronounced for the Cu drops which were deposited on the C Gn /SiC sc substrate, structurally and chemically changed by previous contact with liquid Cu [5]. The behavior of the Cu drop in few attempts to detach it from the graphenecoated SiC substrate by rising up a graphite capillary showed a strong adhesion of the liquid Cu to the SiC.…”

“…Specifically, examinations at the Sn/C Gn /Cu interface microstructure clearly put in evidence diffusion phenomena of Sn atoms allowed by discontinuities in the graphene layer, mainly produced by thermos-mechanical stresses at high temperature (stresses). The second attempt to experimentally investigate the "wetting transparency of graphene" was reported by Homa et al [5] for the Cu/C Gn /SiC sc (SiC singlecrystal) system. In particular, the behavior of a liquid Cu drop just dispensed on the surface of a monocrystalline SiC substrate coated by graphene (C Gn /SiC sc ), was similar on C Gn /SiC sc and SiC sc substrates: several attempts to detach the drop of Cu from the C Gn /SiC sc and SiCs substrates by raising the graphite capillary showed strong adhesion of the droplet to the substrate.…”

“…Based on structural and chemical composition examinations, the paper attempts to interpret the phenomena observed during wetting tests in the Cu/C Gn /SiC sc system [5].…”

Understanding Electromagnetic Interactions and Electron Transfer in Ga Nanoparticle–Graphene–Metal Substrate Sandwich Systems

“…[1][2][3], their contact angle with the graphene layer is related to their interfacial free energy. Common plasmonic noble metals such as Au, Ag, and Cu present values of the contact angle with graphene of 113˚ [22], 114˚ [23], and 122˚ [24], respectively. It is also worth mentioning that while for Ag the contact angle remains stable in time [23], for copper the contact angle progressively reduces to a value of 60˚ in 30 min [24].…”

“…Common plasmonic noble metals such as Au, Ag, and Cu present values of the contact angle with graphene of 113˚ [22], 114˚ [23], and 122˚ [24], respectively. It is also worth mentioning that while for Ag the contact angle remains stable in time [23], for copper the contact angle progressively reduces to a value of 60˚ in 30 min [24]. In the case of Ga, the contact angle with smooth graphene layers, like the ones in our experiments, is close to a hemispherical NP shape, ∼80˚.…”