Setsuo Nomura

Secondary Ion Yield Changes in Si due to Topography Changes during Cs^+ Ion Bombardment

Depth profiles of 30Si negative secondary ions were measured at Cs+ ion impact energies of 10.5 keV, 14.5 keV and 17.5 keV and a 45° impact angle by means of secondary ion mass spectrometry (SIMS). Yield changes due to surface topography changes occurred at 14.5 keV and 17.5 keV impact energy, although no surface topography change has ever been reported during Cs+ ion bombardment. No yield change was detected at 10.5 keV impact energy. The topography changes and ion yield changes are obviously affected by the Cs+ ion impact energy.

Cesium liquid metal ion source for secondary ion mass spectrometry

A Cs liquid metal ion source (LMIS) and focused ion beam system for microarea secondary ion mass spectrometry (SIMS) have been developed. Because of the chemical activity, low surface tension, and high vapor pressure of Cs, few successful Cs LMISs have heretofore been reported, as opposed to the many successful applications of Ga in LMIS. A new Cs‐LMIS design had to be developed to supply Cs to the emitter/reservoir under UHV to prevent oxidation, to prevent liquid Cs from dripping off the emitter substrate, and to minimize the surface area exposed so as to minimize thermal evaporation. The last consideration is very important since the evaporation rate of Cs is many orders of magnitude higher than, e.g., Ga at the melting point. A focused Cs beam was obtained with a newly designed SIMS system, which is about 0.1 μm beam size and a beam current density on the specimen of 0.8 A/cm2. An operating time of more than 600 h has been achieved at a total emission current of 1 μA without resupplying the source mat...

High Contrast of Scanning Ion Microscopy Images Shows Element Segregation

Scanning ion microscopy (SIM) provides image contrast clearly higher than that of scanning electron microscopy (SEM). SEM and SIM images of the same sample have been taken in the same instrument under the same field of view conditions, and then compared. SIM reveals element segregation, but SEM does not. It is shown that the elemental contrast of SIM, when using positive secondary ions as the imaging signal, is made by variation of the secondary ion yield of the implanted primary beam element. The variation is caused by differences of sample elements. The high contrast provided by SIM gives valuable information about elements and microcrystallites in material science.