MASS SPECTROSCOPIC STUDIES ON THE LASER-ABLATION OF BORON-NITRIDE

The laser ablation of pyrolytic boron nitride (pBN) target was investi gated by quadrupole mass spectroscopy, The laser-correlated ion mass s pectra and time-of-flight (TOF) spectra were obtained. B+ and B-2(+) i ons were detected but N+, N-2(+), or BN+ ions were not observabIe. Ins tead, neutral N-2 molecules were detected. The velocity of B+ ions and temperature of the plume were derived by shifted Maxwell-Boltzmann fi tting of the TOF spectra of B+ ions, At the laser fluence of 0.7 J/cm( 2), the velocity of B+ ions was 21.7 km/s and the temperature was 1576 5 K. Also studied were the effects of the retarding field on the energ etics of B+ ions, The space-charge effect was found to influence the d ynamics of plume propagation significantly. The reactive laser ablatio n under N-2 atmosphere has been attempted by using a pulsed valve sync hronized with the laser pulse. (C) 1998 Elsevier Science B.V.