Optical Measurement of the RMS (Root-Mean-Square) Roughness of Ion-Bombarded Surfaces.

Ion implantation and related ion beam processing techniques are used to modify the surface of materials and produce certain desirable properties. However, these methods sometimes roughen the surfaces to which they are applied. If undetected, such roughness can lead to erroneous interpretation of data gathered by most standard surface analysis techniques. Many surface profilometers and scanning electron microscopes lack sufficient spatial resolution to detect fine scale roughness that can complicate the data interpretation. A simple optical instrument has been constructed to measure the root-mean-square rms roughness, below about 100 nm, of ion bombarded surfaces. This instrument measures the total integrated scatter TIS of almost normally incident laser light, which under conditions specified by scalar scattering theory is simply related to the rms surface roughness. This paper describes the construction and calibration of the TIS instrument. In addition, it presents results on the rms roughness of several ion-beam-processed systems, including TiN films on Si, Cr and Cr203 films on AISI 52100 steel, ion beam mixed Mo in Al, SixN1-x refractive layers, and GaAsAlAs superlattices.