PP-25 Rearrangement Effect of Surface Atoms on the Alternation of Patterning Regime: Incident Energy Effect of Ar Haeri Kim1,2, Sang-Pil Kim1, and Kwang-Ryeol Lee1 1Computational Science Center, Korea Institute of Science and Technology, Seoul, Korea 2Department of Physics, Ewha Womans University, Seoul, Korea PD(100)기판에 Ar 이온을 Sputtering하는 계산에 대한 내용을 발표 하겠습니다.

Ion Bombardment (Sputtering) Deposition  Film coating Science, 285, 1551 (1999). Ion bombardment  Surface treatment Most works utilized sputtering as deposition tool are focused on the reaction phenomena between recoiled ions from the target and substrate atoms to deposit. Since a possibility to manufacture the nano patterns on the surface was introduced, it has taken an enormous attention to researchers. Such a peculiar process resulted in enhancing the possibility for designing nano sized patterning by cheap and simple method.

Applications Ordered adsorption of large molecules Facsko et al., SCIENCE, 285, 1551 (1999) Chaudhari et al., NATURE 411, 56 (2001) Ordered adsorption of large molecules Optoelectronic devices Molding templates Manipulating magnetism Deposition Catalytically active surface Manipulating film texture Sputtering Azzaroni et al., APL 82, 457 (2003) Moroni et al., PRL 91, 167207 (2003)

Patterning Regimes Ion diffusion : creating surface produced with shape and orientation along crystal orientation(=structure) Ion erosion : creating surface are oriented along the ion beam direction and do not crystal orientation - Figure (a),(b) are taken after normal incidence(diffusive regime) - Figure (c),(d) are taken after grazing incidence sputtering θ=70˚(erosive regime) * *U. Valbusa, Mater. Sci. C 23 (2003) 201-209

Calculation Procedure [110] : φ=45˚ [210] : φ=22.5˚ Ion Ar Target materials Pd(001) Incident energy 0.5/1.0/2.0 keV Polar angle (θ) 30˚/60˚/75˚ Azimuthal angle (φ) 22.5˚ (=[210]) 1,000 trials for each case  Initial Ar positions were randomly selected within surface

Sputtering Information Direction (φ) [110] [210] Penetration Depth [Å] 11 9.43±3.47 Sputtering Yield [atoms/ion] 3.433±1.104 3.073±1.116 Rearrangement Yield [atoms/ion] 10.676±3.044 9.8±2.84 Ratio 3.109 3.19

Results – Ys vs. Yr φ θ Ys Yr Yr / Ys 22.5˚ 45˚ 0.5 keV 3.011 10.32 3.43 30 3.07 9.84 10.68 3.20 3.11 60 2.95 2.52 6.70 6.23 2.28 2.47 75 -* 0.39 0.12 - 1.0 keV　 4.18 13.34 3.19 3.97 4.58 11.91 12.88 3.00 2.81 5.70 4.86 12.78 11.51 2.24 2.36 0.49 1.09 2.26 2.60 4.59 2.37 2.0 keV 4.96 14.65 2.96 5.58 5.87 17.00 16.12 3.05 2.75 8.07 8.98 18.89 19.76 2.34 2.20 3.04 4.24 8.09 8.17 2.41 1.93 The difference of sputtering yield was enhanced in the case of high θ, grazing incidence rather than low θ, nearly normal. It can be deduced that because the lateral force along the beam direction becomes significantly as increasing the θ, Ys computed very sensitive to the beam direction.

Lateral Distributions θ=60°, φ=45° θ=60°, φ=22.5° The intensity of the data points is proportional to the number of the rearranged atoms placed at that position. The distribution was confirmed not a circular shape but a anisotropic diamond shape  strongly affected by the surface structure of Pd (001) Shape of the ripples changes very sensitively for the φ even under the same θ. As increasing the incident energy, the shape of the patterns were affected on the beam direction. 0.5 keV 1.0 keV 2.0 keV

Axis of Symmetric Yr Incidence along [110] dir.  The axes were shown overall 45°, regardless of the incidence energy of Ar. Incidence along [210] dir.  when the incidence energy was 0.5 keV, the axis was shown almost 22.5° at 30° of θ, while 45° of symmetric axis was shown at 60° of θ. Higher incidence energy of Ar could give an enough energy for changing the distributions of the rearranged atoms from the [110] to the [100] directions.

Surface Structure Evolutions φ=45° [110] φ=22.5° [210] (a) (b) Ar bombarding 4,200 3,072 1,024 2,048  In progress... 0.5 keV (c) (d) 1.0 keV Θ=60˚

Conclusions Using the classical MD simulations, quantitative investigations of the rearrangement effects which were occurred consistently during ion beam sputtering were performed. Regardless of the incidence conditions, the rearranged atoms were shown to be 2~3 times larger than the sputtered atoms and confirmed that this behavior was shown very rapidly in a ballistic manner simultaneous with the Ar bombarding. We could elucidate the changing mechanism from the diffusive to the erosive regime for the incidence energy in an atomic point of view, and confirm the rearrangement atoms would play an important role in forming the surface patterns during ion beam sputtering.