CAMP Annual Report:Page 5
Computational and Experimental Study of Airflow and Particulate Pollutant Transport and Concentration around the Center of Excellence Building
Professors Ahmadi and Bohl are studying the airflow conditions and particulate pollutant transport around the Center of Excellence Building in Syracuse. A scaled model of the building has been tested in the wind tunnel. Airflow velocity and turbulence intensity around the building model were measured in the wind tunnel using the PIV technique. A computer model for the airflow condition has been developed and was verified by comparisons with the wind tunnel data. The computer model provides a tool for analyzing the airflow around the actual building. In particular, the particulate pollutant dispersion near the building is being assessed and the results are to be compared with the field data.
Professor Ahmadi, in collaboration with the scientists from the US Department of Energy, is working to assess the safety of carbon dioxide sequestration in geological formation. As part of this project, computer models for gas-liquid flows in porous media as well as in rock fractures are being developed. In particular, the effect of variation of confining pressure on the effective permeability of fracture flows is being analyzed. The eventual goal is to implement research finding into a computational code for modeling large scale geological reservoir simulations.
Professor Devon Shipp and his team have two focus areas of research: new nanomaterials for photovoltaic (PV) devices and novel degradable elastomers. The PV research, which leverages their expertise in polymer synthesis and nanocomposites, aims to create low-cost, large-area PV devices through the use of phase separation in block copolymers leading to well-ordered polymer nanocomposites. Such hybrid nanomaterials have great potential for applications in photo- and electrochemical devices (e.g. solar cells, sensors). The work in Professor Shipp’s laboratory is funded by NYSERDA and the US Army Research Office, and was recently published in ACS Nano. In the second area of research, on degradable elastomeric polymers, Shipp and his students have demonstrated that linear and crosslinked polyanhydrides can be made using photoinitiated thiol-ene chemistry. This is a simple and effective method of making crosslinked structures that have surface degradation characteristics. Papers describing this work recently appeared in Chemical Communications and Macromolecules. This technology may be expected to gain usage in many biomedical applications such as drug delivery, orthopedics, tissue engineering and scaffolds. More information about Professor Shipp’s research activities can be found at www.clarkson.edu/~shippda.
Metal/Barrier and Dielectric Film Polishing and Planarization
Professor S.V. Babu’s research group is continuing its fundamental investigations of various aspects of chemical-mechanical planarization (CMP) of metal and dielectric films. The current focus continues to be on developing more chemically active dispersions for low pressure planarization of InP, Ge, Co, and Ru, while ensuring appropriate selectivity with respect to the underlying low-k dielectric films as well as for planarizing dielectric (oxide, nitride and poly-Si) films with controlled and variable selectivities. The work on Ge and InP is being conducted collaboratively with IMEC, Belgium. One Ph.D. student is currently working there. Several results obtained while polishing Ru and Ge films and structures have been recently published.
The investigation of controlled selectivity in material removal during the polishing of oxide, nitride and poly-Si films has led to several fundamental discoveries. Several ceria and silica based compositions that yield a high nitride and low oxide polish rate and simultaneously a controllable poly-Si removal rate have been identified. It was shown that the presence of protonated functional groups of the additive is critical to suppress nitride removal since they can bind through strong hydrogen bonding to the nitrogen with unpaired electrons on the nitride surface. Both the stress and doping of the nitride film also play a critical role. Oxide polishing and the removal of the surface film on nitride using ceria slurries are controlled by the Ce3+ species and/or the ability of the Ce4+ species to be converted to Ce3+. In both cases of oxide and nitride polishing, pH plays a significant role.
Aqueous and abrasive-free solutions of PDADMAC and PEI as well as several other polymers have been shown to polish poly-Si film at high rates with no oxide or nitride removal. The results were published in several recent papers. Evaluation of the planarization of poly-Si patterned structures, performed jointly with a Lee Cook’s group at Dow Electronic Materials, revealed that these polymer solutions are both self-limiting and self-stopping and are influenced by the polymer molecular weight. Several preliminary results were presented at the recent Lake Placid conference on CMP by Lee Cook and also at the International Conference on Planarization Technology (ICPT) 2011 in Seoul. Also, it was shown earlier that there is a dramatic difference between the removal rates obtained when these films were polished with IC1000 or Politex pads. These results were also discussed in a recent publication.
The Photo-Acoustic Research (PAR) and Nanomechanics/Nanomaterials (NN) Laboratories (PAR) directed and co-directed by Professor Cetin Cetinkaya have been conducting analytical, computational and experimental studies in the areas of laser-based particle removal and contact/non-contact adhesion measurements. There is a critical need in various industries for accurate adhesion measurements and characterization of micro/nanoparticles on flat and rough substrates. The PAR Lab has developed a novel characterization method to quantify the adhesion properties of single microparticles in a non-contact/non-destructive manner under various conditions. Since the non-contact method does not require the dislodgement of the particle from its substrate, the contributions of external effects, such as humidity, electrical field, and temperature, can be studied on a single particle at the same contact point. The current research effort focuses on (nanoparticles) coated toner particles and pharmaceutical particles. The PAR and NN laboratories have received research funds from the National Science Foundation, Intel, SEMATECH, Xerox Corp., Wyeth Pharmaceuticals, Pfizer Inc., the Consortium for the Advancement of Manufacturing in Pharmaceuticals (CAMP), Praxair/Electronics, the US Army, as well as the Center for Advanced Materials Processing (CAMP) at Clarkson.