“Effective NIEL” in Silicon: Calculation Using Molecular Dynamics Simulation Results

The non-ionizing energy loss (NIEL), often used to scale the damage coefficients of irradiated electronic components, sometimes fails to make good degradation predictions. The classical non-ionizing energy loss calculation, performed under binary cascade approximation, lacks accuracy at low incident energy for some light particles such as electrons. The amount of displacement damage predicted by molecular dynamics simulations where many-body interactions are naturally included can be significantly different from the classical binary collision calculation. The creation of damage predicted by molecular dynamics technique, within the low energy deposition regime, can be quite different from what can be classically simulated. For instance, earlier studies demonstrated that, under suitable conditions, low energy transfer below the atomic displacement threshold can increase damage production. In the case of silicon material, molecular dynamics simulation results have been incorporated within the definition of a new energy partition function. In comparison with the classical Kinchin Pease approach, our improved model more accurately estimates the number of displacements generated by a primary knock-on atom. This new energy partition function is used to calculate corrected non- ionizing energy loss.