ABSTRACT
Recently, integrated flexible devices based on silicon nanowires (Si-NWs) have received significant attention as high performance flexible devices. However, most previous assembly methods can generate only specifically-shaped devices and require unconventional facilities, which has been a major hurdle for industrial applications. Herein, we report a simple but very efficient method for assembling Si-NWs into virtually generally-shape patterns on flexible substrates using only conventional microfabrication facilities, allowing us to mass-produce highly flexible low-noise devices. As proof of this method, we demonstrated the fabrication of highly bendable top-gate transistors based on Si-NWs. These devices showed typical n-type semiconductor behaviors, and exhibited a much lower noise level compared to previous flexible devices based on organic conductors or other nanowires. In addition, the gating behaviors and low-noise characteristics of our devices were maintained, even under highly bent conditions.
ABSTRACT
We have developed a method to selectively assemble and align carbon nanotubes (CNTs) on soft substrates for use as flexible biosensors. In this strategy, a thin oxide layer was deposited on soft substrates via low temperature plasma enhanced chemical vapor deposition, and a linker-free assembly process was applied on the oxide surface where the assembly of carbon nanotubes was guided by methyl-terminated molecular patterns on the oxide surface. The electrical characterization of the fabricated CNT devices exhibited a typical p-type gating effect and 1/f noise behavior. The bare oxide regions near CNTs were functionalized with glutamate oxidase to fabricate selective biosensors to detect two forms of glutamate substances existing in different situations: L-glutamic acid, a neurotransmitting material, and monosodium glutamate, a food additive.
ABSTRACT
Self-assembled monolayer (SAM) patterns on electrodes are often utilized to guide the assembly of single-walled carbon nanotubes (SWCNTs) onto the electrodes to form desired device structures. In this case, the SWCNTs are in contact with the electrodes through the SAM which comprises molecular wires. Presumably, it is desirable to use conjugated molecular wires for a low contact resistance because they have been reported as a better electric conductor than non-conjugated ones. However, until now, the directed-assembly of SWCNTs has been driven mostly via molecular wires with alkane backbones which are known to be relatively poor conductors. Herein, we report large-scale directed-assembly of SWCNTs utilizing SAM patterns comprising conjugated molecular wires. We achieved highly selective adsorption and precision alignment of SWCNTs utilizing polar SAM patterns comprising conjugated molecular wires, while SAM patterns with non-polar terminal groups efficiently prevented adsorption of SWCNTs. Furthermore, we developed a process for assembling a SWCNT across two electrodes coated with conjugated molecular wires, and the electrical conduction through the SWCNT was measured via a conducting atomic force microscope. This result could be an important guideline for large-scale directed-assembly of SWCNT-based devices in the future.
