Hydrogen in metals causes hydrogen embrittlement, which is the process of various metals to become brittle and fracture. Surface stress measurement is an effective technique for gas detection. In this study we focused on the stress of hydrogen contained in metals. We have detected a surface stress of stainless steel coated micro-cantilever under hydrogen irradiation. Meanwhile, it is not known the existing position of hydrogen in an alloy attributed to the complex structure of the alloy.

Metal thin films with the thickness of 20-50nm were deposited by RF magnetron sputtering on silicon micro cantilever (MCS: thickness of 1 micron and length of 500 micron). We found both of austenite and martensite structure in the film. The stress under hydrogen plasma irradiation was measured in-situ using a bending of cantilever beam [1]. MCS bended toward compressive surface stress and saturated under the irradiation. Probably it was a stress change due to hydrogen absorption although the bending might include temperature effect. After the irradiation stop, the bending curve decreased gradually. In 2nd experiment running, the saturated value of the bending was smaller than the 1st. After 10 times of the irradiation experiments (10 h irradiation) the bending did not decrease more.

In this study we tried to investigate hydrogen behavior in metal alloys from observation of two-dimensional hydrogen distribution on metal surface using a method of DIET (Desorption Induced by Electronic Transition). For the experiment we divided a vacuum container into two rooms. A part of a vacuum wall, between the two rooms, was a sample. Surface of the sample membrane thickness of 200 mm, had ring shape lines of 40micron pitch. The lines, which is a trace of the blade, were formed when the surface was flattened by a lathe. Cutting blade made un-uniformity of dislocations, too. H₂ gas was supplied from the backside room, H atom (ion) permeated through a sample and was desorbed into the vacuum room by electron irradiation. DIET mapping shows the hydrogen concentration reflects a density of dislocations, which has 40micron pitch [2]. It should be considered more by the comparing of DIET experiments with the structure measurement, grains, grain boundaries and dislocations [3]. Schematic diagram of the new experiment is shown in fig1. In the presentation we will show higher resolution images of DIET mapping, which can be compared with grains in SEM picture.