CALCULATION OF LOCAL TEMPERATURE RISE IN FOCUSED-ION-BEAM SAMPLE PREPARATION

Local temperature rise theta in focused-ion-beam (FIB) sample preparat ion has been calculated using a formalism for laser beam heating by Ni ssim et al, Typical calculations have been carried out for Si, GaAs, a nd SiO2 samples bombarded by the usual 30 keV FIBs. It is figured that an FIB-heated region is like a hemisphere with double the radius of t he FIB, and the hemisphere closely follows the scanning FIB, theta(max ) values of less than 100 K are predicted for Si and GaAs samples havi ng their shapes of bulk, semi-bulk, and sheet (sustained with the subs trate) under the usual FIB conditions of I-p/d = 20 nA/mu m at maximum , For SiO2 sample, on the other hand, the theta(max) values are larger by about 100 times than those for Si sample because of its low therma l conductivity and diffusivity of heat, As to a pillar-shaped sample, the theta(max) value is rather enhanced due to its poor heat conductio n.