Systematic THz study of the substrate effect in limiting the mobility of graphene

Abstract

We explore the substrate-dependent charge carrier dynamics of large area graphene films using contact-free non-invasive terahertz spectroscopy. The graphene samples are deposited on seven distinct substrates relevant to semiconductor technologies and flexible/photodetection devices. Using a Drude model for Dirac fermions in graphene and a fitting method based on statistical signal analysis, we extract transport properties such as the charge carrier density and carrier mobility. We find that graphene films supported by substrates with minimal charged impurities exhibit an enhanced carrier mobility, while substrates with a high surface roughness generally lead to a lower transport performance. The smallest amount of doping is observed for graphene placed on the polymer Zeonor, which also has the highest carrier mobility. This work provides valuable guidance in choosing an optimal substrate for graphene to enable applications where high mobility is required.

Graphene Field Effect Transistors: A Sensitive Platform for Detecting Sarin

“…The results in Figure d show that in the presence of a DMMP atmosphere the mobility of the sensors decreases for all concentrations. We find that the mobility is lowered by a larger amount in the presence of higher concentrations of DMMP, corresponding to changes in the overall shape of the resistance versus back-gate voltage curve. − This is consistent with the fact that the presence of a large concentration of DMMP molecules contributes to scattering mechanismslikely long-range Coulomb potentialsthat can decrease the mobility of the carriers in graphene . We note that the mobility at the end of one detection cycle is close in value to the mobility at the beginning of the next cycle, suggesting that graphene is inert to the carrier gas, nitrogen.…”

Chip-Scalable, Room-Temperature, Zero-Bias, Graphene-Based Terahertz Detectors with Nanosecond Response Time

“…The broadband nature of the PTE rectification can be exploited for multifrequency detecting platforms. Optimization of thermoelectric properties could be achieved by transferring SLG on alternative dielectrics , to reduce the residual carrier concentration at the charge neutrality point and bring S b in the 100 μV K –1 range. The dielectric environment can affect the charge inhomogeneity and the residual carrier concentration at the charge neutrality point, which, in turn, has an influence on the Seebeck coefficient (and NEP as demonstrated in Figure a).…”

“…The dielectric environment can affect the charge inhomogeneity and the residual carrier concentration at the charge neutrality point, which, in turn, has an influence on the Seebeck coefficient (and NEP as demonstrated in Figure a). This correlation stems from the resulting graphene quality and from the different densities of free and trapped charges in the different substrates. , The possibility to combine scalable large-area CVD graphene with large-area scalable hBN, in scalable heterostructures, promises significant performance improvements. Large-scale integration could be achieved by implementing a technological flowchart fully compatible with standard CMOS readout integrated circuits.…”

“…This correlation stems from the resulting graphene quality and from the different densities of free and trapped charges in the different substrates. 25,56 The possibility to combine scalable large-area CVD graphene with large-area scalable hBN, in scalable heterostructures, promises significant performance improvements. Large-scale integration could be achieved by implementing a technological flowchart fully compatible with standard CMOS readout integrated circuits.…”

Beam Shift Modulation Based on Larmor Resonance in Graphene–VO2 Photonic Crystal

“…[20] Besides the general features such as high mobility of carriers, flexibility, robustness, and environmental stability, graphene has some properties which can make it a suitable option in designing photonic devices. [21] In addition, graphene has low dissipative in terahertz (THz) magnetic field, and its optical properties can be controlled by changing the chemical potential. [22,23] These characteristics can lead to a tunable GH shift.…”