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

Local temperature rise theta in focused-ion-beam (FIB) sample preparation has been calculated using a formalism for laser beam heating by Nissim et al, Typical calculations have been carried out for Si, GaAs, and 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 the FIB, and the hemisphere closely follows the scanning FIB, theta(max) values of less than 100 K are predicted for Si and GaAs samples having their shapes of bulk, semi-bulk, and sheet (sustained with the substrate) 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 thermal conductivity and diffusivity of heat, As to a pillar-shaped sample, the theta(max) value is rather enhanced due to its poor heat conduction.