The reported thermal conductivity (kappa) of suspended graphene, 3000 to 5000 watts per meter per kelvin, exceeds that of diamond and graphite. Thus, graphene can be useful in solving heat dissipation problems such as those in nanoelectronics. However, contact with a substrate could affect the thermal transport properties of graphene. Here, we show experimentally that kappa of monolayer graphene exfoliated on a silicon dioxide support is still as high as about 600 watts per meter per kelvin near room temperature, exceeding those of metals such as copper. It is lower than that of suspended graphene because of phonons leaking across the graphene-support interface and strong interface-scattering of flexural modes, which make a large contribution to kappa in suspended graphene according to a theoretical calculation.

We fabricate and characterize dual-gated graphene field-effect transistors (FETs) using Al 2 O 3 as top-gate dielectric. We use a thin Al film as a nucleation layer to enable the atomic layer deposition of Al 2 O 3 . Our devices show mobility values of over 8,000 cm 2

The thermal conductivity of suspended few-layer hexagonal boron nitride (h-BN was measured using a micro-bridge device with built-in resistance thermometers. Based on the measured thermal resistance values of 11-12 atomic layer h-BN samples with suspended length ranging between 3 and 7.5 m, the room-temperature thermal conductivity of a 11-layer sample was found to be about 360 Wm -1 K -1 , approaching the basal plane value reported for bulk h-BN.The presence of a polymer residue layer on the sample surface was found to decrease the thermal conductivity of a 5-layer h-BN sample to be about 250 Wm -1 K -1 at 300 K. Thermal conductivities for both the 5 layer and the 11 layer samples are suppressed at low temperatures, suggesting increasing scattering of low frequency phonons in thin h-BN samples by polymer residue.

Using a novel structure, consisting of two, independently contacted graphene single layers separated by an ultra-thin dielectric, we experimentally measure the Coulomb drag of massless fermions in graphene. At temperatures higher than 50 K, the Coulomb drag follows a temperature and carrier density dependence consistent with the Fermi liquid regime. As the temperature is reduced, the Coulomb drag exhibits giant fluctuations with an increasing amplitude, thanks to the interplay between coherent transport in the graphene layer and interaction between the two layers.PACS numbers: 73.22.Gk Bilayer systems formed by two layers of carriers in close proximity are a fascinating testground for electron physics. In particular, the prospect of electron-hole pair (indirect exciton) formation, and dipolar superfluidity 1 has fueled the research of electron-hole bilayers in GaAs/AlGaAs heterostructures 2,3 . Graphene 4,5 is a particularly interesting material to explore interacting bilayers. The symmetric conduction and valence bands, and the large Fermi energy favor correlated electron states at elevated temperatures 6,7 . The zero energy band-gap allows a seamless transition between electrons and holes in each layer, and obviates the large inter-layer electric field required to simultaneously induce electrons and holes in GaAs bilayers 3 . Coulomb drag, a direct measurement of inter-layer electron-electron scattering 8 can provide insight into the ground state of two-9 and one-10 electron systems, as well as correlated bilayer states 11,12 . Here we demonstrate a novel, independently contacted graphene bilayer, and investigate the Coulomb drag in this system. Two main ingredients render the realization of independently contacted graphene bilayers challenging. First, an ultra-thin yet highly insulating dielectric is required to separate the two layers. Second, a method to position another graphene layer on a pre-existing device with minimum or no degradation is needed to create the second layer of the structure investigated here. The fabrication of our independently contacted graphene bilayers is described in Fig. 1. First, the bottom graphene layer is mechanically exfoliated onto a 280 nm thick SiO 2 dielectric, thermally grown on a highly doped Si substrate. E-beam lithography, metal lift-off, and etching are used to define a Hall bar on the bottom layer [ Fig. 1(a)]. A 7 nm thick Al 2 O 3 is then deposited on the bottom layer using a 2 nm oxidized Al interfacial layer, followed by 5 nm of Al 2 O 3 atomic layer deposition 13 . The second, top graphene layer is also mechanically exfoliated on a similar SiO 2 /Si substrate. A poly methyl metacrylate (PMMA) film is applied on the top layer and cured. Using an NaOH etch 14 , the PMMA film along with the graphene layer, and the alignment marks are detached from the host substrate, forming a free standing membrane. The membrane is placed face down on the substrate containing the bottom graphene layer [ Fig. 1(b)], and aligned with it. A Hall bar is subsequently defined on th...

The thermal conductivity (κ) of two bilayer graphene samples each suspended between two microresistance thermometers was measured to be 620 ± 80 and 560 ± 70 W m(-1) K(-1) at room temperature and exhibits a κ ∝ T(1.5) behavior at temperatures (T) between 50 and 125 K. The lower κ than that calculated for suspended graphene along with the temperature dependence is attributed to scattering of phonons in the bilayer graphene by a residual polymeric layer that was clearly observed by transmission electron microscopy.