A mini-projection technique to be applied to the practical depth profiling in secondary ion mass spectrometry (SIMS) has been developed. This new method is combination of a sample pretreatment and a high acceptance (sensitive) technique for secondary ion optics. The sample pretreatment makes it possible to removes the interfering secondary ions that originate at the periphery of the ion beam etched crater so that high depth resolution can be attained. In this high acceptance technique the least confusion circle (crossover point) of the secondary ion beam is placed at the entrance slit of a double-focussing mass spectrometer so as to obtain high sensitivity in depth profile measurements. To evaluate the detection limit and depth resolution of the mini-projection method, αSi: H thin films deposited on Si wafer and on B-implanted Si wafer were measured in the depth analysis mode. As result, the depth resolution of the O and C atoms included in the αSi thin films increased as indicated by the steepness of the concentration gradient (ΔY was reduced by one-thirds compared to the value obtained by the conventional method). The detection limit for B in this proposed method is also reduced to about 40% of that in the conventional method.
Irradiation of X-ray to solid surfaces causes photoelectron and Auger electron emission from the surfaces. We detected the X-ray excited current from a tip specimen using a scanning tunneling microscope (STM) apparatus for the first time. It was found that the current was amplified by ionization of the gaseous atoms and molecules present in the atmosphere. The dependence of the excited current on the irradiated X-ray intensity, gas pressure, kinds of gases and kinds of solids has been investigated.