Cluster ion beam smoothing of SiC and YBCO surfaces

Optimization of the surface topography, especially in high-temperature superconductor (HTS) and silicon carbide is crucial for device processing. Surface smoothing in these materials was investigated using gas cluster ion beams (GCIB) capable of delivering cluster ions of greater than or equal to 2000 Ar atoms with energies of up to 30 kV. Examination of the surface topography after cluster ion irradiation was done using cross-sectional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results indicate that typical as-deposited YBCO films on MgO substrates have an average roughness of the order of 40 m and interpeak distance between 300 and 600 nm. Application of GCIB to the surface planarization reduces the roughness to only 10 nm. Also, power handling and microwave surface resistance of the YBCO film and its relationship to surface smoothness are reported. Similar observations using bulk SiC are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.