['After', 'polishing', 'with', 'the', '1μm', 'diamond', 'suspension', ',', 'the', 'coupons', 'were', 'ultrasonically', 'cleaned', 'in', '2', '-', 'propanol', 'for', '3×5min', ',', 'with', 'fresh', 'propanol', 'for', 'each', 'cleaning', 'cycle', '.']