As-grown single-wall carbon nanotubes (SWNTs) and a monochlorobenzene (MCB) solution of polymethylmethacrylate (PMMA) were sonicated using an ultrasonic processor. The SWNTs obtained were short and contained many holes and defects; therefore, they were called 'ragged single-wall carbon nanotubes (r-SWNTs)'. The r-SWNTs were degraded at and above 800 degreesC in a vacuum (10(-7) Torr). All the r-SWNTs disappeared after heat-treatment at 1200 degreesC for 1 h. Since thermal degradation was not observed for as-grown SWNTs or for acid-purified SWNTs, we suggest that the holes and defects in the r-SWNTs were formed by oxidation of chemically damaged sites formed during the polymer-assisted ultrasonication.