Lowering of the laser crystallization threshold of a-Si:H due to the presence of Si clusters at the surface

We present an experimental evidence of the role of a Si cluster suspended above the surface of a hydrogenated amorphous silicon film (a-Si:H) in the crystallization of the film at a laser energy lower than the laser crystallization threshold of the “flat” surface. The local electromagnetic (EM) field enhancement is interpreted by the role of such a sphere–plane system as a laser intensity amplifier. The enhancement factor determined in this work is in the range of 20–30.