Conference Report: MRS Spring 2012, Day 1

The MRS Spring 2012 meeting opened today in Moscone West in San Francisco. Fifty-four technical symposia and 16 tutorials will run concurrently, with over 5,000 paid attendees from 50 countries, 3,100 oral papers, 1,700 posters, 130 exhibitors and 14,400 entries in the authors directory. This author list is comparable to the total MRS membership of over 15,000. Following the meeting, several sessions that will have been videotaped will be posted online at www.mrs.org/s12-video.

The opening day of this week-long meeting consisted of sixteen tutorial sessions related to specific symposia topics, and a light load of five technical symposia that were scheduled to get an early jump on the week. Tutorial topics included phase change materials, NV RAM, compound semiconductors for energy applications, and two sessions related to PV.

Additional presentation details can be found on the MRS Spring 2012 program page, http://www.mrs.org/s12-program/. A downloadable PDF version of the abstracts is promised soon for online access to the symposium contents. The underscored codes at the beginning of papers reviewed below refer to the symposium, session and paper number.

EE1.1 Phaedon Avouris of IBM Watson Research, one of the 2012 MRS Fellow appointees, opened the session on new functional nanocarbon devices to a packed SRO room with a high level look at how graphene and related materials will lend themselves to advanced devices. Among the impressive items waiting to be developed is an rf device capable of operation up to 1THz for airport radar imaging in foggy conditions. Wafer-scale epitaxial graphene is presently made by high temperature evaporation of Si atoms from SiC. Graphene superlattices can be fabricated which are 90% transparent in the visible range but provide 16dB shielding efficiency at microwave frequencies, making for some unique device functionality. One of the speed bumps on the road ahead is the dearth of ultra thin high-κ capacitor materials that are compatible with graphene.

J1.5 Leslie Jimison of Centre Microelectronique de Provence discussed the impact of molecular architecture on transport and device properties in organic electrochemical transistors. The system studied comprised PEDOT:TOS-PEG composites fabricated via vapor phase polymerization. Organic electrochemical transistors are designed for use in aqueous environments, making them well suited for biosensor applications. The addition of PEG does not degrade OECT modulation, nor does it affect the RC properties of the transition. Biocompatibility of PEDOT:TOS-PEG was successfully demonstrated.

J1.6 Robert Mueller of IMEC described a low cost lithographic process for patterning S/D bottom contacts for high mobility p-type pentacene organic TFTs using silver bottom contacts with channel length <10µm. A modified process flow was developed, as the standard flow is incompatible with Ag. The electrical properties were acceptable, demonstrating that Ag can be used as a low cost replacement for Au.

DD2.5 Mark Hersam of Northwestern U talked about several methods for processing monodispersed CNT and other nanomaterials for volume fabrication of functional inks. A chiral surfactant is used to segregate left from right handed tubes with density gradient ultracentrifugation (DGU). Similar methods are used to segregate metallic from semiconducting CNTs. Graphene can likewise be segregated using sonication followed by DGU. Converted to an ink, this material can print a transistor with fT of 8.7GHz after de-embedding, which is 1,000x faster than other organic transistors. DGU was also applied to 100nm Au particles with a 60nm silica shell for high yielding plasmonic nanoantennae. Pluronic and trionic surfactants have been shown to be effective replacements for ionic surfactants to effect separation in SWNT, MWNT and graphene. Pluronic dispersion of graphene oxide significantly reduces the biotoxicity of such materials. A graphene-titania ink was shown to exhibit enhanced photocatalytic reduction of CO2 to CH4. Current global demand for these materials is still in the range of kg/yr, but he foresees no scaling roadblocks to tons.

EE1.4 Ilhan Aksay of Princeton U described the use of functionalized graphene sheets (FGS) in several applications, starting from the perspective of the need for new functionality rather than interest in a fundamental study of graphene and its properties. Target applications include structural elements, sensors and energy sources. Silicone rubber doped with FGS changes its resistance up to 2.5x at 60% strain. The functionalized material is structurally far from pristine graphene, but it performs similarly to its pristine counterpart with respect to many properties. It has too many defects for function in a transistor, but has conductivity that can rival copper for interconnects. FGS added in small amounts (0.5wt%) to rubber increases the strength of rubber, and the strength increases with repeated elongation cycles. This effect is attributed to a distributed deformation phenomenon similar to strategies employed in biological systems such as sea shells. A self-assembled stack of alternating FGS and SnO2 layers has shown charging and discharging rates competitive with Li-ion batteries. In combination with self-assembled mesoporous silica, FGS has demonstrated supercapacitor properties >200F/g, with the mesoporous silica thought to provide a channel for intimate contact of the electrolyte with the FGS layers. In biosensors, FGS shows S/N 3-4 orders of magnitude greater than single layer graphene nanoelectrodes.

Moscone West felt quite crowded and busy all day, even though more than half of the symposium rooms have not yet been called into service. This was just a practice day for the full assault to come tomorrow.

 

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