Mass measurement of graphene using quartz crystal microbalances

Abstract

Current wafer-scale fabrication methods for graphene-based electronics and sensors involve the transfer of single-layer graphene by a support polymer. This often leaves some polymer residue on the graphene, which can strongly impact its electronic, thermal, and mechanical resonance properties. To assess the cleanliness of graphene fabrication methods, it is thus of considerable interest to quantify the amount of contamination on top of the graphene. Here, we present a methodology for direct measurement of the mass of the graphene sheet using quartz crystal microbalances (QCM). By monitoring the QCM resonance frequency during removal of graphene in an oxygen plasma, the total mass of the graphene and contamination is determined with sub-graphene-monolayer accuracy. Since the etch-rate of the contamination is higher than that of graphene, quantitative measurements of the mass of contaminants below, on top, and between graphene layers are obtained. We find that polymer-based dry transfer methods can increase the mass of a graphene sheet by a factor of 10. The presented mass measurement method is conceptually straightforward to interpret and can be used for standardized testing of graphene transfer procedures in order to improve the quality of graphene devices in future applications. arXiv:1902.11098v1 [cond-mat.mes-hall]

Quartz crystal microbalance monitoring of large-area graphene anodization reveals layer fracturing

“…By dividing an estimated surface area by a sensor area, and it was determined that a mass corresponding to ~ 13 and 20 layers of ideal monolayer graphene was deposited on sensors. These findings match up to a previous report [12] where deposited CVD graphene layers were removed from QCM sensors with oxygen plasma with continuous monitoring in the process.…”

Nanoelectromechanical Sensors Based on Suspended 2D Materials

“…The application of pressure on the stamp can affect the value and uniformity of the pretension in the suspended membrane and thus influence its mechanical resonance frequency and stiffness. Moreover, nonuniformity of the strain in the transfer layer can lead to wrinkled graphene membranes, and polymeric residues of a few nanometers from the stamp can be present [ 128 ]. In general, few-layer membranes are more stable, show a higher yield of intact membranes after fabrication [ 127 ], and can be suspended across larger areas.…”

“…The responsivity of resonant mass sensors is given by Δ ω res = −½ ω res Δ m / m eff [ 261 , 262 ], which shows that for a small mass m of the graphene membrane or ribbon, a relatively large frequency shift will occur. The high sensitivity of this principle was shown by adding and removing layers of pentacene with an equivalent mass of 6 layers of monolayer graphene and monitoring its effect on the resonance frequency of a graphene membrane ( Figure 7(p) ) [ 128 ]. Such suspended graphene resonant mass sensors are expected to find applications in fields where it is required to determine mass changes much less than a monolayer of a 2D material.…”

“…Such suspended graphene resonant mass sensors are expected to find applications in fields where it is required to determine mass changes much less than a monolayer of a 2D material. In comparison, conventional quartz crystal monitors have been shown to be able to measure the mass of a single monolayer of graphene [ 128 ]. The sensitivity of graphene-based mass sensors can reach a value of 10 −27 g/Hz [ 263 ], which greatly outperforms silicon membrane-based sensors, with typical sensitivity values of only 10 −18 g/Hz [ 264 ].…”

Development and Characterization of Drug‐Loaded PVP/PAN/Gr Electrospun Fibers for Drug Delivery Systems

“…The QCM results for both mediums show that P3 fiber has a comparatively lower frequency shift than those of P1 and P2 fiber samples. The frequency change of crystal depending on mass was measured until a constant baseline was acquired [41,50] . The mass reduction was assigned to the rapid drug release from the P2 fiber‐coated QCM electrode, and specifically the P3 fiber coated‐QCM electrode, as shown in Figure 1a and 1c.…”