The measured height of polystyrene nanoparticles varies with setpoint voltage during atomic force microscopy (AFM)
tapping-mode imaging. Nanoparticle height was strongly influenced by the magnitude of the deformation caused by the
AFM tapping forces, which was determined by the setpoint voltage. This influence quantity was studied by controlling
the operational AFM setpoint voltage. A test sample consisting of well-dispersed 60-nm polystyrene and gold
nanoparticles co-adsorbed on poly-l-lysine-coated mica was studied in this research. Gold nanoparticles have not only
better mechanical property than polystyrene nanoparticles, but also obvious facets in AFM phase image. By using this
sample of mixed nanoparticles, it allows us to confirm that the deformation resulted from the effect of setpoint voltage,
not noise. In tapping mode, the deformation of polystyrene nanoparticles increased with decreasing setpoint voltage.
Similar behavior was observed with both open loop and closed loop AFM instruments.
Biomass surrounds us from the smallest alga to the largest redwood tree. Even the largest trees owe their strength to a
newly-appreciated class of nanomaterials known as cellulose nanocrystals (CNC). Cellulose, the world's most abundant
natural, renewable, biodegradable polymer, occurs as whisker like microfibrils that are biosynthesized and deposited in
plant material in a continuous fashion. Therefore, the basic raw materials for a future of new nanomaterials
breakthroughs already abound in the environment and are available to be utilized in an array of future materials once the
manufacturing processes and nanometrology are fully developed. This presentation will discuss some of the
instrumentation, metrology and standards issues associated with nanomanufacturing of cellulose nanocrystals. The use of
lignocellulosic fibers derived from sustainable, annually renewable resources as a reinforcing phase in polymeric matrix
composites provides positive environmental benefits with respect to ultimate disposability and raw material use. Today
we lack the essential metrology infrastructure that would enable the manufacture of nanotechnology-based products
based on CNCs (or other new nanomaterial) to significantly impact the U.S. economy. The basic processes common to
manufacturing - qualification of raw materials, continuous synthesis methods, process monitoring and control, in-line
and off-line characterization of product for quality control purposes, validation by standard reference materials - are not
generally in place for nanotechnology based products, and thus are barriers to innovation. One advantage presented by
the study of CNCs is that, unlike other nanomaterials, at least, cellulose nanocrystal manufacturing is already a
sustainable and viable bulk process. Literally tons of cellulose nanocrystals can be generated each day, producing other
viable byproducts such as glucose (for alternative fuel) and gypsum (for buildings).There is an immediate need for the
development of the basic manufacturing metrology infrastructure to implement fundamental best practices for
manufacturing and in the determination of properties for these for nanoscale materials and the resultant products.
Carbon nanotube tips offer a significant improvement over standard scanned probe microscope (SPM) tips for electrical characterization of nanodevice structures. Carbon nanotube tips are compatible with requirements for integrated SPM_probe station instruments in which SPM-based lithography, topography, electric force microscopy, and traditional current-voltage measurements are performed simultaneously or sequentially. As device dimensions shrink, traditional diagnostics will be unable to probe nanometer-scale phenomena that affect device performance and reliability. At the same time, the introduction of novel materials such as silicon-on-insulator into standard processing will require methods that can rapidly identify defects and their local behavior. Electric force microscopy with carbon nanotube tips offers unique capabilities for satisfying these needs.
The rapidly renewable lap is based on the simple concept of generating the figure needed in a lap substrate and then replicating it into a thin film slumped over the substrate. Based on this concept, we describe how efficient laps can be constructed for the lapping and polishing of crystalline, amorphous, and metallic surfaces.
Photoreflectance (PR) spectroscopy has been used to study the Fermi-level pinning position of chemically modified (100) GaAs surfaces. It is shown that there are two pinning positions for the unmodified 9100) GaAs surface. For n-GaAs the Fermi level pins near midgap, while for p-GaAs the Fermi level pins near the valence band. We used an Ar/Cl2 plasma generated by an electro-cyclotron resonance (ECR) source and P2S5 chemical passivation to change the stoichiometry of the surface. We show that ECR etching makes the surface oxide As rich and that the Fermi-level position for this circumstance is near midgap. The P2S5 passivation produces a thin Ga rich oxide which is observed to in the Fermi-level near the valence band. These results allow us to relate the Fermi-level pinning position to the stoichiometry of the GaAs/oxide interface.
A steered beam lithography will represent an essential part of the technology to meet the future need for ultra-high resolution mask making and direct write. Conventional high voltage e-beam lithography is being developed to meet these challenges. However, there are a number of physical limitations (proximity effects, resist sensitivity) which must be overcome. To do so will prove to be extremely expensive if in fact these problems can be overcome. There are significant advantages in going to extremely low energies in e-beam lithography. Proximity effects are eliminated although the electron-optics become more exacting. The need to focus a low energy e-beam can be eliminated by maintaining a sharp tip close to a surface as in a scanning tunneling microscope (STM). We have demonstrated technologically useful lithography with the STM operated with 4 - 50 V between tip and sample. Patterns have been defined in e-beam resists and by selective oxidation of semiconductor substrates under the action of the STM tip. In both cases the pattern can be transferred into the substrate with a dry etch. Sub 50 nm resolution is routine on a variety of substrates. A viable lithographic technology has been demonstrated in the research laboratory. However, several key issues must be addressed to develop a technologically viable lithography system compatible with existing microfabrication practice. These issues include: registration using the imaging properties of the STM for alignment, pattern accuracy and throughput. Advances in STM speed are described and suggestions made for improving lithographic performance with multiple sharp tips (each with an independent servo loop). The potential pay-off is high as a low voltage lithography tool will involve significantly less capital investment (and support cost) than the next generations of high voltage e-beam lithography tools.