5 research outputs found
Ultrasmooth gold surfaces prepared by chemical mechanical polishing for applications in nanoscience
For over 20 years, template stripping has been the best method for preparing ultrasmooth metal surfaces for studies of nanostructures. However, the organic adhesives used in the template stripping method are incompatible with many solvents, limiting the conditions that may subsequently be used to prepare samples; in addition, the film areas that can be reliably prepared are typically limited to ∼1 cm2. In this article, we present chemical-mechanical polishing (CMP) as an adhesive-free, scalable method of preparing ultrasmooth gold surfaces. In this process, a gold film is first deposited by e-beam evaporation onto a 76-mm-diameter silicon wafer. The CMP process removes ∼4 nm of gold from the tops of the grains comprising the gold film to produce an ultrasmooth gold surface supported on the silicon wafer. We measured root-mean-square (RMS) roughness values using atomic force microscopy of 12 randomly sampled 1 μm × 1 μm areas on the surface of the wafer and repeated the process on 5 different CMP wafers. The average RMS roughness was 3.8 ± 0.5 Å, which is comparable to measured values for template-stripped gold (3.7 ± 0.5 Å). We also compared the use of CMP and template-stripped gold as bottom electrical contacts in molecular electronic junctions formed from n-alkanethiolate self-assembled monolayers as a sensitive test bed to detect differences in the topography of the gold surfaces. We demonstrate that these substrates produce statistically indistinguishable values for the tunneling decay coefficient β, which is highly sensitive to the gold surface topography
Silver nanowire/optical adhesive coatings as transparent electrodes for flexible electronics
We present new flexible, transparent, and conductive coatings composed of an annealed silver nanowire network embedded in a polyurethane optical adhesive. These coatings can be applied to rigid glass substrates as well as to flexible polyethylene terephthalate (PET) plastic and elastomeric polydimethylsiloxane (PDMS) substrates to produce highly flexible transparent conductive electrodes. The coatings are as conductive and transparent as indium tin oxide (ITO) films on glass, but they remain conductive at high bending strains and are more durable to marring and scratching than ITO. Coatings on PDMS withstand up to 76% tensile strain and 250 bending cycles of 15% strain with a negligible increase in electrical resistance. Since the silver nanowire network is embedded at the surface of the optical adhesive, these coatings also provide a smooth surface (root mean squared surface roughness \u3c10 nm), making them suitable as transparent conducting electrodes in flexible light-emitting electrochemical cells. These devices continue to emit light even while being bent to radii as low as 1.5 mm and perform as well as unstrained devices after 20 bending cycles of 25% tensile strain. © 2013 American Chemical Society
Ultrasmooth Gold Surfaces Prepared by Chemical Mechanical Polishing for Applications in Nanoscience
For
over 20 years, template stripping has been the best method
for preparing ultrasmooth metal surfaces for studies of nanostructures.
However, the organic adhesives used in the template stripping method
are incompatible with many solvents, limiting the conditions that
may subsequently be used to prepare samples; in addition, the film
areas that can be reliably prepared are typically limited to ∼1
cm<sup>2</sup>. In this article, we present chemical–mechanical
polishing (CMP) as an adhesive-free, scalable method of preparing
ultrasmooth gold surfaces. In this process, a gold film is first deposited
by e-beam evaporation onto a 76-mm-diameter silicon wafer. The CMP
process removes ∼4 nm of gold from the tops of the grains comprising
the gold film to produce an ultrasmooth gold surface supported on
the silicon wafer. We measured root-mean-square (RMS) roughness values
using atomic force microscopy of 12 randomly sampled 1 μm ×
1 μm areas on the surface of the wafer and repeated the process
on 5 different CMP wafers. The average RMS roughness was 3.8 ±
0.5 Ã…, which is comparable to measured values for template-stripped
gold (3.7 ± 0.5 Å). We also compared the use of CMP and
template-stripped gold as bottom electrical contacts in molecular
electronic junctions formed from <i>n</i>-alkanethiolate
self-assembled monolayers as a sensitive test bed to detect differences
in the topography of the gold surfaces. We demonstrate that these
substrates produce statistically indistinguishable values for the
tunneling decay coefficient β, which is highly sensitive to
the gold surface topography
Silver Nanowire/Optical Adhesive Coatings as Transparent Electrodes for Flexible Electronics
We present new flexible, transparent, and conductive coatings composed of an annealed silver nanowire network embedded in a polyurethane optical adhesive. These coatings can be applied to rigid glass substrates as well as to flexible polyethylene terephthalate (PET) plastic and elastomeric polydimethylsiloxane (PDMS) substrates to produce highly flexible transparent conductive electrodes. The coatings are as conductive and transparent as indium tin oxide (ITO) films on glass, but they remain conductive at high bending strains and are more durable to marring and scratching than ITO. Coatings on PDMS withstand up to 76% tensile strain and 250 bending cycles of 15% strain with a negligible increase in electrical resistance. Since the silver nanowire network is embedded at the surface of the optical adhesive, these coatings also provide a smooth surface (root mean squared surface roughness \u3c10 nm), making them suitable as transparent conducting electrodes in flexible light-emitting electrochemical cells. These devices continue to emit light even while being bent to radii as low as 1.5 mm and perform as well as unstrained devices after 20 bending cycles of 25% tensile strain. © 2013 American Chemical Society