Showing papers by "Deirdre L. Olynick published in 2010"

Formation of bandgap and subbands in graphene nanomeshes with sub-10 nm ribbon width fabricated via nanoimprint lithography.

Abstract: We fabricated hexagonal graphene nanomeshes (GNMs) with sub-10 nm ribbon width. The fabrication combines nanoimprint lithography, block-copolymer self-assembly for high-resolution nanoimprint template patterning, and electrostatic printing of graphene. Graphene field-effect transistors (GFETs) made from GNMs exhibit very different electronic characteristics in comparison with unpatterned GFETs even at room temperature. We observed multiplateaus in the drain current-gate voltage dependence as well as an enhancement of ON/OFF current ratio with reduction of the average ribbon width of GNMs. These effects are attributed to the formation of electronic subbands and a bandgap in GNMs. Such mesoscopic graphene structures and the nanofabrication methods could be employed to construct future electronic devices based on graphene superlattices.

Electron-beam exposure mechanisms in hydrogen silsesquioxane investigated by vibrational spectroscopy and in situ electron-beam-induced desorption

Abstract: Hydrogen silsesquioxane (HSQ) is used as a high-resolution resist with resolution down below 10 nm half-pitch. This material or materials with related functionalities could have widespread impact in nanolithography and nanoscience applications if the exposure mechanism was understood and instabilities controlled. Here we have directly investigated the exposure mechanism using vibrational spectroscopy (both Raman and Fourier-transform infrared) and electron-beam-induced desorption spectroscopy (EBID). In the non-networked HSQ system, silicon atoms sit at the corners of a cubic structure. Each silicon is bonded to a hydrogen atom and bridges three oxygen atoms (formula: HSiO3/2). For the first time, we have shown, via changes in the SiH2 peak at ∼2200 cm−1 in the Raman spectra and the release of SiHx products in EBID, that electron-beam-exposed material cross-links via a redistribution reaction. In addition, we observe the release of significantly more H2 than SiH2 during EBID, which is indicative of addit...

Step and repeat UV nanoimprint lithography on pre-spin coated resist film: a promising route for fabricating nanodevices

Abstract: A step and repeat UV nanoimprint lithography process on pre-spin coated resist film is demonstrated for patterning a large area with features sizes down to sub-15 nm. The high fidelity between the template and imprinted structures is verified with a difference in their line edge roughness of less than 0.5 nm (3σ deviation value). The imprinted pattern's residual layer is well controlled to allow direct pattern transfer from the resist into functional materials with very high resolution. The process is suitable for fabricating numerous nanodevices.

Roller-style electrostatic printing of prepatterned few-layer-graphenes

Abstract: Electrostatic exfoliation of patterned few-layer-graphenes was demonstrated using a method compatible with high throughput roll-to-roll manufacturing. A patterned graphite template was placed on a roller and used to exfoliate patterned graphene on a planar substrate. The exfoliated graphene features were subsequently characterized by Raman spectroscopy. In comparison with previously demonstrated planar electrostatic exfoliation approach, the roller-style method can create a narrower distribution of thickness of few-layer-graphenes, which is attributed to the combinational action of tangential rolling friction and electrostatic forces. This roller-style electrostatic printing technique could be applied for roll-to-roll manufacturing of graphene-based devices in the future.

Nanoimprint-induced molecular stacking and pattern stabilization in a solution-processed subphthalocyanine film.

Abstract: We present a systematic study on the thermal nanoimprinting of a boron subphthalocynamine molecule, 2-allylphenoxy-(subphthalocyaninato)boron(III) (SubPc-A), which represents a class of attractive small-molecular weight organic compounds for organic-based photovoltaics (OPV). The final equilibrium imprinted feature profile strongly depends on the imprinting temperature. The highest feature aspect ratio (or contrast) occurs at a specific window of imprinting temperatures (80−90 °C). X-ray diffraction indicates that the nanoimprint at such a temperature window can induce high-degree molecular stacking, which can help stabilize the imprinted features. Outside this window, we observed a pronounced relaxation of imprinted features after template removal, which is attributed to the surface diffusion. Key factors affecting the final equilibrium profile of the imprinted features were simulated. From the simulation, it was found that the crystallization-induced anisotropy of surface energy stabilized imprinted fea...