Gold-coated Silicon Wafer Research Articles

Electric field induced structural change for poly(vinylidene fluoride-co-trifluoroethylene) ultrathin films studied by scanning Maxwell stress microscope

Poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF/TrFE), VDF 75 mol %] ultrathin films of 10 nm thickness were prepared on gold coated silicon wafer substrates by a spin-coating method and their aggregation states were investigated by Fourier transform infrared reflection absorption spectroscopic measurement. It was found that P(VDF/TrFE) formed a ferroelectric phase even in a confined state such as an ultrathin film. The electric field was locally imposed on the ultrathin film through a gold coated cantilever tip. The change of dipole moment orientation of P(VDF/TrFE) was evaluated by measuring surface potential change, performed by scanning Maxwell stress microscopy (SMM). The SMM images revealed that the local dipole moment orientation of P(VDF/TrFE) in ultrathin films could be changed by an application of electric field through an atomic force microscope tip.

Multilayer Dendrimer–Polyanhydride Composite Films on Glass, Silicon, and Gold Wafers

A Velcro-like thin-film composite in which dendrimers acts as burrs and a reactive anhydride copolymer acts like wool (see schematic representation on the right) can be readily prepared from commercially available reagents. Films that are 10–50 nm thick and contain alternating layers of both components were synthesized on glass, silicon, and gold-coated silicon wafers.

Self-assembled monolayers exposed by metastable argon and metastable helium for neutral atom lithography and atomic beam imaging

We used a beam of noble gas atoms in a metastable excited state to expose a thin (1.5 nm) self-assembled monolayer resist applied over a gold-coated silicon wafer. We determined exposure damage as a function of dose of metastable atoms by processing the samples in a wet-chemical etch to remove the gold from unprotected regions and then measuring the reflectivity with a laser and observing the microstructure with an atomic force microscope. We found that the minimum dose required to damage the resist substantially was 1.7(3)×1015 atoms/cm2 for metastable helium, and 25(7)×1015 atoms/cm2 for metastable argon.

Optimization of a charge coupled device imaging enzyme linked immuno sorbent assay and supports for the simultaneous determination of multiple 2,4-D samples

A chemiluminescent microformat enzyme linked immuno sorbent assay (ELISA) has been optimized for the simultaneous determination of multiple 2,4-dichlorophenoxyacetic acid (2,4-D) samples. The competitive immunoassay employed a 2,4-DBSA conjugate, anti-2,4-D monoclonal antibodies and alkaline phosphatase (AP) labelled anti-mouse IgG. The bound AP conjugate was determined by quantitating the chemiluminescence emission from the enzymatic decomposition of the luminogenic substrate, CSPD, by AP using a cooled charge coupled device (CCD) camera. The detection limit for the simultaneous determination of multiple samples was 4.3 × 10 −10 M corresponding to 96 pg ml −1 or 192 fg well with a coefficient of variation (CV, %) of 12.5%. The linear range of the assay was 4.5 × 10 −7–4.5 × 10 −10M. The ability of gold coated silicon wafers and glass capillaries to serve as solid phase supports in the imaging ELISA was investigated. The highly reflective gold surfaces improved both the linear range and the sensitivity of the assay, as compared to thick-film patterned surfaces. The capillary supports, on the other hand, lead to a reduction in the linear range and the sensitivity of the assay, as compared to the thick-film patterned surfaces. Initial studies indicate that the capillaries guide the light and may provide a built-in mechanism for collecting the emitted light. Strategies for further development of support materials for imaging-based detectors will be discussed.

HREELS detection of resonance electron scattering in oriented polytetrafluoroethylene films

Resonance electron scattering from surfaces of oriented polytetrafluoroethylene (PTFE) has been investigated using high-resolution electron energy loss spectroscopy (HREELS). Oriented samples were made by friction-deposition onto gold-coated silicon wafers. A resonance enhancement of the 730 cm −1, Raman-active ν (CC) stretch vibrational mode was detected near 5 eV beam energy with width of about 2 eV. The maximum intensity occurs for parallel alignment of the scattering plane with respect to the polymer chain, while no resonance is detected for perpendicular alignment. Studies were made for both specular and off-specular geometries. The origin of the resonance can be attributed to negative ion trapping into the (CC) σ ∗ orbital. We have also obtained high resolutions of about 40 cm −1 for the first time in polymer systems.

Tunneling probes for metrological applications using a long-range profilometer

The construction of a long-range tunneling profilometer based on a ‘‘Nanostep’’ slideway is reported. This profilometer has potential capability of measuring surface profiles over a complete traverse of 50 mm horizontally and 15 μm vertically. Its characteristics have been investigated over both long and short scanning ranges. Results are presented of a series of repeat measurements over 1.4-mm traces on a gold-coated silicon wafer. A repeatability of better than 0.2 nm is obtained and surface features of a few nanometers have been resolved laterally. Anomalies in the characteristic of tunneling current with the bias voltage are discussed in terms of surface contaminants and physical contact between tip and sample. Some problems in the application of STM in nanometric metrology are also discussed.

On the characterization of surface VOx-species by XPS: layered oxidic systems as model catalysts

The influence of the support on vanadia, immobilized on Au, SiO2, Al2O3 and TiO2, suitable for the selective catalytic reduction (SCR) of nitric oxide by ammonia has been investigated. The layered oxidic substrates, which are deposited onto gold coated silicon wafers, represent model systems for the surfaces of technical SCR catalysts, that are suitable for surface science investigations. The oxidation states of the surface vanadia species immobilized on these samples have been studied by XPS after well-defined sample treatment in both oxygen and hydrogen atmospheres at 573 K and 723 K. From the observed shifts of the V 2p3/2 binding energies, and from peak deconvolution, vanadia layers on gold, silica and alumina are found to exhibit characteristics similar to those of bulk vanadia. This behavior is characterized by the relative stability against a reductive atmosphere at 573 K. Changes in the oxidation states of the surface vanadia species are prominent only after treatment at 723 K. Titania exhibits a unique support interaction with vanadia which allows the reduction of vanadia at temperatures as low as 573 K. This fact may contribute to the outstanding performance of VOx/TiO2 in the selective reduction of nitric oxide by ammonia in waste gases.