(Invited) Characterization of Semiconductor Materials Using Syncrotron Radiation, XAFS and X-Ray CTR Scattering

Abstract

Synchrotron radiation (SR) is a very powerful tool for the material science. However some of the characterization techniques using the SR are not so popular for the researchers studying on the semiconductors. At the PRiME 2016 meeting, I would like to provide three topics relating to the SR. Two of them are topics on the measurement techniques, which must be interesting for the researchers of semiconductors. The third one is to introduce a compact SR facility recently built in Japan, which is successfully operating for the academic and industrial researchers. X-ray absorption fine structure (XAFS) measurement might be one of the minor techniques for the researchers studying on semiconductors, although it is a very powerful technique to investigate atomic scale structure. For example, by the XAFS measurement, a local structure around a target element in a semiconductor crystal can be revealed. In other words, if impurity atoms in a crystal locate at interstitial site or are substituting matrix can be discussed and the distortion of the lattice around the impurity atoms can also be estimated. Further, if the impurity atoms are ionized or not, is able to be determined by the XAFS measurement. Because the XAFS measurement is a kind of absorption measurement in the energy range of X-ray, the SR is essentially important to scan the energy of the incident X-ray and it is very difficult to conduct the measurement at laboratory using ordinal X-ray sources like X-ray tubes. That might be one of the reasons why the XAFS measurement is not so popular. At the PRiME 2016 meeting, I would like to introduce what the XAFS measurement is, why we can obtain such atomic scale information from the spectra, and for what kind of studies the measurement is useful. X-ray CTR scattering measurement is an important technique to study on layer structures like semiconductor films so precisely in an atomic scale and it is another measurement which essentially needs the SR. In order to measure the so week CTR scattering signal, the intensity of the SR is very important. When the measurement is conducted properly and obtained spectra are analyzed carefully, the results show us the interface structures of semiconductor hetero layers in an atomic scale. I would like to show some of the examples at the meeting. Finally, I am going to introduce a recently built compact SR facility in Aichi, Japan. The facility is named Aichi SR, of which acceleration energy and current are 1.2 GeV and 300mA. By using super conducting bending magnets of 5 T as light source, the facility can provide X-rays in the energy range of hard X-ray, more than 5 keV and up to 20 keV or higher as easy as those in the range of soft X-ray. The specs of the light source are not on cutting edge, however, the general design is so useful and stable for the users who would like to use the SR as a daily tool to characterize their samples. Such a facility must be very important to bottom up the level of the researches.