Subthreshold Picosecond Laser Damage in Silicon Associated with Charge Emission

Abstract

Laser-induced surface damage observed during illumination of semiconductors by intense laser pulses has been much studied. The nature of damage has been established [1,2] by studying the nucleation and growth of damage near threshold intensities. The heterogeneous nucleation of damage in the early stage was also revealed. Furthermore, charge emission from a silicon surface induced by picosecond laser pulses at 532 nm was presented [3,4]. But the energy transfer mechanisms from the radiation field to the semiconductor in the multiple-pulse damage regime are not well understood. To contribute to further understanding of damage mechanisms induced by picosecond Nd:YAG laser pulses at 1.06 μm, damage at laser intensities below the one-shot damage threshold has been investigated. By recording charged particle emission which accompanies damage processes, some interesting information has been revealed. With a small capacitor and/or an electron multiplier tube, one can detect the charge emitted during small pit formation which may be considered as the initial damage morpnology.