[show abstract][hide abstract] ABSTRACT: Directional transport properties at the nanoscale remain a challenge
primarily due to issues associated with control over the underlying anisotropy
and scalability to macroscopic scales. In this letter, we develop a facile
approach based on template-guided fluidic assembly of high mobility building
blocks - single walled carbon nanotubes (SWNTs) - to fabricate ultra-thin and
anisotropic SWNT films. A major advancement is the complete control over the
anisotropy in the assembled nanostructure, realized by three-dimensional
engineering of dip-coated SWNT thin films into alternating hydrophilic and
hydrophobic micro-line patterns with prescribed intra/inter-line widths and
line thicknesses. Variations in the contact line profile results in an
evaporation-controlled assembly mechanism that leads to the formation of an
alternating, and more importantly, contiguous SWNT network. Evidently, the
nanoscopic thickness modulations are direct reflections of the substrate
geometry and chemistry. The nanostructured film exhibits significant anisotropy
in their electrical and thermal transport properties as well as optical
transparency, as revealed by characterization studies. The direct interplay
between the anisotropy and the 3D micro-line patterns of the substrate combined
with the wafer-level scalability of the fluidic assembly allows us to tune the
transport properties for a host of nanoelectronic applications.
[show abstract][hide abstract] ABSTRACT: Efforts aimed at large-scale integration of nanoelectronic devices that exploit the superior electronic and mechanical properties of single-walled carbon nanotubes (SWCNTs) remain limited by the difficulties associated with manipulation and packaging of individual SWNTs. Alternative approaches based on ultrathin carbon nanotube networks (CNNs) have enjoyed success of late with the realization of several scalable device applications. However, precise control over the network electronic transport is challenging due to (i) an often uncontrollable interplay between network coverage and its detailed topology and (ii) the inherent electrical heterogeneity of the constituent SWNTs. In this article, we use template-assisted fluidic assembly of SWCNT networks to explore the effect of geometric confinement on the network topology. Heterogeneous SWCNT networks dip-coated onto submicrometer wide ultrathin polymer channels become increasingly aligned with decreasing channel width and thickness. Experimental-scale coarse-grained computations of interacting SWCNTs show that the effect is a reflection of a topology that is no longer dependent on the network density, which in turn emerges as a robust knob that can induce semiconductor-to-metallic transitions in the network response. Our study demonstrates the effectiveness of directed assembly on channels with varying degrees of confinement as a simple tool to tailor the conductance of the otherwise heterogeneous network, opening up the possibility of robust large-scale CNN-based devices.
[show abstract][hide abstract] ABSTRACT: We present integration of single-stranded DNA (ss-DNA)-decorated single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry as nanoscale chemical sensors. SWNTs were assembled onto CMOS circuitry via a low voltage dielectrophoretic (DEP) process. Besides, bare SWNTs are reported to be sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances the sensing specificity and sensitivity. After decorating ss-DNA on SWNTs, we have found that the sensing response of the gas sensor was enhanced (up to approximately 300% and approximately 250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. The SWNTs coupled with ss-DNA and their integration on CMOS circuitry demonstrates a step towards realizing ultra-sensitive electronic nose applications.
[show abstract][hide abstract] ABSTRACT: The removal of nanoparticles form patterned wafers is one of the main challenges facing the semiconductor industry. In this paper, the removal of 100 and 200nm polystyrene latex (PSL) particles from silicon trenches was investigated. Red fluorescent PSL particles were utilized in the cleaning experiments and were counted using fluorescent microscopy. All the experiments were conducted in a single wafer megasonic tank using deionized water (DI). Trenches were fabricated with widths varying from 200nm to 2μm and with an aspect ratio of one. Results show that removal of particles from larger trenches is faster compared to smaller trenches and that megasonics power is more important in the removal process than cleaning time.