Realization of critical distance during the interplay between re-deposition and secondary sputtering from milling of angular side wall with a focused ion beam

In situ observation of critical distance (CD), a distance where secondary sputtering effects diminish and re-deposition starts to dominate is realized during controlled focused ion beam (FIB) sputtering. The experiments were performed on representative high density Ni-alloy and lower density porous Ni–YSZ. For the Ni-alloy case, it was observed that linear extrapolation of re-deposited layer width coincides with CD suggesting uniform sputtering and re-deposition effects. Estimation related to percentage of re-deposition from FIB etched layer at an angle of 50° between the lower membrane and FIB etched side wall clearly demonstrated dominant secondary sputtering, neutralizing sputtering/re-deposition and dominant re-deposition regions. Although the angle between FIB etched angular side wall and re-deposited/etched membrane adds some complication, the suggested overall experimental approach would substantially simplify to develop more realistic models than previously considered complex situations dealing with interplay between the re-deposition and secondary sputtering.