|
Posted: May 25th, 2012 Researchers realize the world's first oxidation reaction withwell-defined molecular alignment and spin directions ( Nanowerk News ) A research group consisting of Dr. Mitsunori Kurahashi , Principal Researcher, and Dr. Yasushi Yamauchi , Group Leader of the Spin Characterization Group, both of the NanoCharacterization Unit of the National Institute for MaterialsScience, developed the world's first O 2 molecular beam which enables us to designate the alignment of themolecular axis and spin direction. The NIMS researchers appliedthis beam to the surface oxidation of silicon, and discovered thatonly oxygen molecules with the molecular axis nearly parallel tothe surface contribute to the silicon oxidation. Molecular oxygen (O 2 ) is one of the most important chemical species in virtually allfields of fundamental science and materials development. O 2 has an anisotropic shape, i.e., is a linear molecule, andpossesses spin originating from two unpaired electrons. However,until now, there have been no experimental methods which enable usto investigate how the shape and spin of an O 2 molecule influence oxidation reactions. Even though the initialoxidation of silicon has been studied in detail to understand thethermal oxidation of silicon used for fabricating gate insulatorfilms, the origin of the particularly low initial reactionprobability has not been understood well. Fig:(top) Control of the alignment of the O 2 molecular axis by the magnetic field direction and (bottom) timeevolution of the O 2 adsorption probability on the Si(100) surface, showing that thereaction probability changes greatly when the O 2 alignment is changed in accordance with a control signal. Using the magnetic hexapolar field technique, the team headed byDr. Kurahashi developed the world's first single quantumstate-selected O 2 beam which enables us to designate both the alignment of themolecular axis and the spin direction. By applying this beam to thesurface oxidation of silicon, Dr. Kurahashi's team discovered thatonly O 2 molecules with the molecular axis nearly parallel to the surfacecontribute to the silicon oxidation. This research clarified thatthe silicon oxidation is inefficient due to the stringentgeometrical requirement for the O 2 axis direction, and only those molecules that satisfy a certainangular condition can participate in the reaction. This research established a new experimental technique foranalyzing the effects of the O 2 alignment and the spin direction on oxidation reactions, andelucidated the origin of the inefficiency in the silicon oxidation.This technique not only enables us to scrutinize the mechanism ofoxidation, but also opens up a possibility to control reactions orcreate new high quality materials by controlling the O 2 alignment and/or spin direction. These research results were achieved as part of the NIMS 3rdMid-Term Program Project "Development and Application of AdvancedMaterial Characterization Technologies" (Leader: Daisuke Fujita)and the Japan Society for the Promotion of Science (JSPS)Grants-in-Aid for Scientific Research/Basic Research (B)"Elucidation of Spin/Steric Effect in Surface Oxidation usingSingle Quantum State-Selected Triplet Oxygen Molecular Beam"(Research Representative: Mitsunori Kurahashi). These results werepublished on April 19 in the online edition of Physical Review B (Rapid Communication) of the American Physical Society ( "Huge steric effects in surface oxidation of Si(100)" ). We are high quality suppliers, our products such as China Commercial Bouncy Castles , Inflatable Amusement Park for oversee buyer. To know more, please visits Outdoor Inflatable Water Slides.
Related Articles -
China Commercial Bouncy Castles, Inflatable Amusement Park,
|
