Computer simulation of single-crystal and polycrystal sputtering I

Influence of ion-beam etching by Ar ions with an energy of 200-1000 eV on the roughness and sputtering yield of a single-crystal silicon surface

The behavior of sputtering yield and the surface roughness of monocrystalline silicon of orientations ⟨100⟩, ⟨110⟩, and ⟨111⟩ under the ion-beam bombardment by neutralized Ar ions with energies of 200-1000 eV is studied. The significant dependence (modulation) of sputtering yield on incidence angle due to crystalline structure is observed. It is shown that a sharp increase in the sputtering yield and a decrease in the effective surface roughness at energies above 400 eV occurs. At energies of more than 400 eV for orientations ⟨100⟩, ⟨110⟩, and ⟨111⟩ at normal ion incidence, smoothing of the effective roughness in the range of spatial frequencies ν∈[4.9⋅10^-2-6.3⋅10¹µm^-1] up to a value of 0.17 nm is observed. This makes it possible to use the ion-beam etching technique for finishing polishing, aspherization, and correction of local shape errors of single-crystal silicon substrates, which are of the greatest interest for synchrotrons of the 3rd+ and 4th generation and x-ray free electron lasers.

Fabrication of high-quality single-crystal Cu thin films using radio-frequency sputtering

Copper (Cu) thin films have been widely used as electrodes and interconnection wires in integrated electronic circuits, and more recently as substrates for the synthesis of graphene. However, the ultra-high vacuum processes required for high-quality Cu film fabrication, such as molecular beam epitaxy (MBE), restricts mass production with low cost. In this work, we demonstrated high-quality Cu thin films using a single-crystal Cu target and radio-frequency (RF) sputtering technique; the resulting film quality was comparable to that produced using MBE, even under unfavorable conditions for pure Cu film growth. The Cu thin film was epitaxially grown on an Al₂O₃ (sapphire) (0001) substrate, and had high crystalline orientation along the (111) direction. Despite the 10⁻³ Pa vacuum conditions, the resulting thin film was oxygen free due to the high chemical stability of the sputtered specimen from a single-crystal target; moreover, the deposited film had >5× higher adhesion force than that produced using a polycrystalline target. This fabrication method enabled Cu films to be obtained using a simple, manufacturing-friendly process on a large-area substrate, making our findings relevant for industrial applications.