AVS 51st International Symposium
    Manufacturing Science and Technology Tuesday Sessions
       Session MS-TuP

Paper MS-TuP10
Silicon Isotope Enrichment by IRMPD of Si@sub 2@F@sub 6@: A Method for High-Efficiency Enrichment of @super 28@Si by Two-Color CO@sub 2@ Laser Irradiation

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: H. Ohba, Japan Atomic Energy Research Institute, Japan
Authors: H. Ohba, Japan Atomic Energy Research Institute, Japan
A. Yokoyama, Japan Atomic Energy Research Institute, Japan
M. Hashimoto, Japan Atomic Energy Research Institute, Japan
K. Katsumata, Japan Atomic Energy Research Institute, Japan
H. Akagi, Japan Atomic Energy Research Institute, Japan
S. Arai, Hill Research Corporation, Japan
Correspondent: Click to Email
The natural abundance of silicon isotopes is 92.2% @super 28@Si, 4.7% @super 29@Si and 3.1% @super 30@Si. It has been reported that an isotopically pure @super 28@Si single crystal has a thermal conductivity about 60% higher than that of a natural silicon single crystal at room temperature. This pure material is expected to contribute to the creation of higher-density silicon integrated circuits. Laser isotope enrichment processes promise low energy inputs, low capital costs and lower tails assays, hence significant economic advantages. The infrared multiple photon dissociation (IRMPD) of Si@sub 2@F@sub 6@ leads to the formation of SiF@sub 4@ and SiF@sub 2@. The Si@sub 2@F@sub 6@ with enriched @super 28@Si can be obtained by dissociating the Si@sub 2@F@sub 6@ containing @super 29@Si and @super 30@Si selectively. In order to obtain highly enriched @super 28@Si products in the case of a conventional one-color CO@sub 2@ laser irradiation, however, a high fluence and a large number of laser shot are required, and it is unsuitable for large-scale separation. So, we have studied a rapid and highly efficient method for enrichment of silicon isotopes utilizing isotopically selective IRMPD of Si@sub 2@F@sub 6@ by a two-color laser irradiation scheme. We demonstrated that the dissociation rate of Si@sub 2@F@sub 6@ molecule per pulse increased about 10 times compared with the conventional one-color irradiation. And consequently we were able to acquire the highly enriched @super 28@Si at about one tenth of the laser shots required in the case of the conventional method.