MODIFICATION OF THE SURFACE-PROPERTIES OF MATERIALS BY PULSED PLASMA BEAMS

The paper describes various types of modifications of the surface prop erties of solids under the influence of short-duration (10(-6) s), hig h-power (several megawatts) pulses of dense (10(13)-10(17) ions cm(-2) ) plasma with various elemental compositions, generated by rod-plasma injector-type machines developed at SINS. Depending on the operational conditions, a wide range of elemental compositions in the plasma puls es can be obtained from an almost pure metallic plasma of the discharg e electrode material through mixed gaseous-metallic plasmas to a pure plasma of the working gas. Such pulses, apart from depositing plasma m aterial on the substrate surface carry sufficient energy to melt the s urface layer. This leads to a number of interesting effects like diffu sion in the molten phase, fast epitaxial re-crystallization, rapid re- solidification accompanied by the formation of new phases, mixing (all oying) of the surface layer with the bulk material and others. The pec uliar features of pulsed plasma beam interactions with the substrate a re discussed for a number of cases, in particular: formation of photov oltaic p(+)-n and n(+)-p junctions and ohmic contacts in Si under the influence of BF3 and PF5 plasma pulses; nitriding of steels and marten site-austenite transitions under the influence of N plasma pulses; coa ting of steel with intermixed (alloyed) layers of Cu using N plasma pu lses with controlled content of the appropriate metal; and transition from deposition to ablation for Cu-N plasma pulses for varying proport ions of constituents. The results presented in the paper indicate that intense pulse plasma beams may be an extremely valuable tool in the m odification of the surface properties of materials of technological im portance. (C) 1998 Elsevier Science S.A.