REMOVAL OF DIBORANE FROM SILANE BY INFRARED-LASER INDUCED DIELECTRIC-BREAKDOWN AND EXTERNAL HEATING

Experiments involving the use of a CO2 TEA laser and external heating to selectively remove diborane (B2H6) impurity from gaseous silane (SiH4) are reported. The laser method involves dielectric breakdown under the influence of the very high electric fields produced at the focal point of converging, pulsed CO2 laser radiation and relies on the difference in thermodynamic stability of the two components. Diborane is thermally unstable relative to silane and decomposes more rapidly under the severe breakdown conditions forming an unidentified solid and thus effecting a separation. A smaller quantity of silane is also destroyed. Similar results are observed by externally heating mixtures of diborane and silane verifying the thermodynamic selectivity of the laser method. © 1979.