Jose Perez - US grants

This planning grant will allow the Principal Investigator to develop a research proposal for a program in ultrahigh vacuum scanning tunneling microscopy. The research areas of interest are surface modification on a nanometer scale, magnetic force microscopy of thin magnetic films, and the structural and electronic properties of semiconductor surfaces.

9311724 Perez Fundamental studies of epitaxial growth of diamond films by chemical vapor deposition (CVD) will be conducted using scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV), and Raman spectroscopy to determine the quality of the grown films. It is planned to study, at atomic resolution detail, the growth of epitaxial diamond films on natural diamond substrates, and the role that hydrogen plays in growth. Polycrystalline films on other substrates will also be studied. The overall objectives include the study of both the nucleation and growth of diamond films, and the role that hydrogen plays in these processes. %%% Diamond films have a large number of potential applications due to the unique chemical and physical properties of diamond. Potential applications for diamond films include protective coatings, heat sinks, optical windows, and transistors capable of operation at high temperature, for example, at the internal operating temperatures of automobile or airplane engines. This research is expected to contribute significantly to our fundamental understanding of the formation of diamond films at low temperature and pressure, and thereby to aid in the development of practical applications of this unique material. ***

9705187 Golden This project aims to improve understanding of fundamental properties of CVD-grown diamond films on refractory metal microtips, including the mechanism for negative electron affinity and the effects of surface passivation. The approach is to study the photoelectric threshold of CVD diamond films with and without adsorbates such as Cs and Ti, Mo and other refractory metal microtips, and refractory metal microtips that have been carburized and had thin diamond coatings applied. Techniques to be used in the study include atomic resolution scanning tunneling microscopy,. ultraviolet photoelectron spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. %%% The project addresses basic research issues in a topical area of materials science having technological relevance to electronics and photonics. The research will contribute basic materials science knowledge at a fundamental level to provide a basis for incorporating diamond films into devices such as large area displays. An important feature of the program is the integration of research and education through the training of students in a research area with strong technological relevance. ***

This project aims to grow and characterize nanostructured carbon films consisting of carbon nanotube and amorphous carbon films. Films will be grown by CVD (chemical vapor deposition). Structural and electronic properties will be studied as a function of growth conditions using atomic resolution ultra-high vacuum (UHV) scanning tunneling microscopy (STM), Raman spectroscopy, Auger spectroscopy, ultraviolet photoemission spectroscopy and x-ray photoemission spectroscopy. The turn-on field for field emission (FE), emission site density, electron energy distribution, and stability and lifetime of the FE current will also be measured. Effects of residual gases on FE properties will be studied in detail. For carbon nanotube and amorphous carbon films, growth conditions resulting in optimum tube and asperity density, respectively, will be assessed for FPD applications. Such films have potential techno-logical applications as cold cathode electron emitters in flat panel displays (FPDs), miniature micro-wave sources, highly collimated electron sources and vacuum microelectronics. Using UHV STM, the effects of adsorbates on the structural and electronic properties of the caps of individual carbon nano-tubes will be studied. UHV STM will also be used to study structural and electronic properties of ad-sorbates that induce negative electron affinity in diamond such as hydrogen, Ti and Cs. The FE proper-ties of carbon nanotube and amorphous carbon films will be compared with those of diamond films and diamond-coated Mo microtips to determine the best material for FE applications.
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The project addresses basic research issues in a topical area of materials science with high technologi-cal relevance. Advanced characterization techniques allow greater understanding and control of ele-mentary processes which will allow advances in fundamental materials science and technology. The basic knowledge and understanding gained from the research is expected to contribute to flat panel dis-play, and related applications of electronic and photonic materials. An important feature of the pro-gram is the integration of research and education through the training of students in a fundamentally and technologically significant area.
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1135101
This project supports a cooperative research project by Dr. Witold Brostow of the Department of Materials Science & Engineering and Dr. Jose Perez, Department of Physics at the University of North Texas (UNT), Denton and Dr. Ayman Mohamady Atta at the Egyptian Petroleum Research Institute (EPRI) in Cairo, Egypt. They plan to study the Synthesis and evaluation of porous polymers for absorbing petroleum spills based on recycled poly (ethylene terephthalate) (PET)

Intellectual Merit: The practical importance of absorption of petroleum spills is obvious well recognized. However, understanding of interactions between petroleum and absorbents is poor. One of the consequences is a small number of absorption - desorption cycles that extant petroleum sorbers can survive. The PIs will synthesize a variety of sorbents involving alkyl acrylates (octyl, dodecyl and octadecyl) copolymerized in turn with styrene, acrylic acid, methacrylic acid and olefines. Poly (ethylene terephthalate) (PET) will be recycled and fibers made from the recyclate. Subsequently, the copolymers will be grafted on nonwoven fibers of PET by two procedures: thermal and photochemical grafting. Properties of the prepared sorbents will be evaluated, including crosslink density, sorption time, sorption capacity, effects of repetitive sorption-desorption cycles and flexibility. Absorbed compositions will be studied by Raman spectroscopy and Fourier-transform infrared spectroscopy to characterize interactions of petroleum components with each polymer sorber. Connections of the sorption capacity to sorber material porosity, surface roughness and surface area will be determined by atomic force microscopy at the UNT. The UNT team has several capabilities indispensable for the project for characterization of the sorbers in particular. The EPRI partners have previous experience in dealing with oil spills and thus have a clear set of requirements for oil sorbers, and also have a track record in polymer synthesis including development of porous polymers. They will be able to provide unique resources for the project in addition to those from the UNT.

Broader impacts: Two potential outcomes from this project can be pertinent for protection of the environment: one is development of polymers with oil absorption capability and the second is using PET which is now being thrown out into the environment as waste. There are large amounts of PET waste; here in the US all 2 liter soft drink bottles are made from PET, and of course not only in this size and not only bottles. Using recycled PET as one of the starting materials will result in less petroleum used in making virgin polymers, lower cost of making polymeric sorbers than from virgin polymers only and less PET thrown into environment as waste. Advantages of the development of sorbers that can be used in more absorption- desorption cycles are clear. Five US graduate and undergraduate students will participate in the research project at UNT and at EPRI in Egypt, and will gain an international outlook on science and technology. Instructional articles in the Journal of Materials Education are expected to result from the project, providing the educators and students with pertinent knowledge on petroleum composition and properties, on oil spills, on development of porous polymers and on characterization of polymer-based materials.