Polaron coupling in graphene field effect transistors on patterned self-assembled monolayer

Abstract

We investigated the device characteristics of a graphene field effect transistor (FET) of which interfaces were controlled by a self-assembled monolayer (SAM). Electrical transport measurements together with Raman spectroscopy characterizations for bilayer graphene (BLG) and single layer graphene (SLG) on micro-patterned SAM (mp-SAM), respectively, elucidate spatial carrier modulations on the graphene sheets driven by mp-SAM. The SLG-mp-SAM-FET device exhibits unconventional graphene p-n junction characteristics depending on the polarity of source-drain voltage. The observed characteristics can be interpreted as a velocity saturation of hole carriers coupled with polaron states, of which phonon energy is around 30 meV, on the SAM molecules at the graphene p-n junction. The SAM-based micro fabrication techniques presented in this report not only provide a spatial control of electronic properties for graphene but also lend a new perspective in the understanding of graphene-substrate interface based molecular self-assembled systems.

Critical Behavior in Doping-Driven Metal–Insulator Transition on Single-Crystalline Organic Mott-FET

“…In this Letter, we report a doping-driven Mott MIT on a solid-gate FET using a single crystal with a highly flat surface as well as a gate dielectric covered with self-assembled monolayers (SAMs). We selected hydrophobic 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFES) and octyltriethoxysilane (OTS) as SAM reagents, which are widely used to improve device performance and are also expected to eliminate the adsorbed solvents on the surface. , By micropatterning these SAMs, , we successfully induced a continuous MIT on a κ-Cl single-crystal channel. Owing to the high resistivity of the bulk channel below T ∼ 50 K, the observed MIT was governed by carriers confined in two dimensions at the interface, exhibiting sheet conductivity equal to ∼ e 2 / h ( e 2 / h = 3.874 × 10 –5 Ω –1 ) on the metal–insulator crossover (MIC) line.…”

Simple Interface Engineering of Graphene Transistors with Hydrophobizing Stamps

“…For example, p–n junction devices using SAM-based interface engineering and the possibility of spatially controlling graphene functionalization by patterning the substrate with a SAM have been reported. Despite the above-mentioned advantages, SAM-based interface engineering may not ensure the long-term stability of a graphene device because SAM molecules may degrade in ambient conditions …”

“…Here we describe an interface engineering strategy based on a polydimethylsiloxane (PDMS) hydrophobizing stamp as an alternative to the use of SAMs. Un-cross-linked low-molecular weight (LMW) PDMSs have recently been shown to diffuse out of bulk PDMS stamps and onto the target contact surface and make it hydrophobic. , It could be a drawback for soft lithography based on contact printing, but it could also be used as a stable surface modifier for various applications. − By using a PDMS stamp instead of a SAM treatment, we can tailor the carbon fractionand hence the hydrophobicityof the surface of the substrate without introducing other chemical elements such as F and N that are usually included in the SAM. And one more attractive characteristic of the PDMS-based hydrophobizer is that it is more stable than any other SAM even in harsh conditions.…”

“…Despite the above-mentioned advantages, SAM-based interface engineering may not ensure the long-term stability of a graphene device because SAM molecules may degrade in ambient conditions. 15 Here we describe an interface engineering strategy based on a polydimethylsiloxane (PDMS) hydrophobizing stamp as an alternative to the use of SAMs. Un-cross-linked low-molecular weight (LMW) PDMSs have recently been shown to diffuse out of bulk PDMS stamps and onto the target contact surface and make it hydrophobic.…”

“…Un-cross-linked low-molecular weight (LMW) PDMSs have recently been shown to diffuse out of bulk PDMS stamps and onto the target contact surface and make it hydrophobic. 15,16 It could be a drawback for soft lithography based on contact printing, but it could also be used as a stable surface modifier for various applications. 17−19 By using a PDMS stamp instead of a SAM treatment, we can tailor the carbon fractionand hence the hydrophobicityof the surface of the substrate without introducing other chemical elements such as F and N that are usually included in the SAM.…”