Influence of heat transfer on nodule height of microstructured silicon fabricated by femtosecond laser pulses

By experiments and theory, we investigate the influence of heat transfer across a gas–solid interface on the nodule height of microstructured silicon fabricated under femtosecond laser pulses. By changing the pressure of the vacuum system, a fast-changing spread in height is found. This is determined by the different heat-transfer flux across the gas–solid interface for different Knudsen-number regimes. Heat transfer affects the energy remaining in the bulk silicon, which determines nodule formation and corresponding height. The rate of change in the heat-transfer flux induces a negative rate of change in the nodule height. These results are important when optimizing the surface microstructure for silicon-based photoelectron devices.