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EPR in
Semiconductors Spin-Hamiltonian parameter database for EPR centers in semiconductors |
| Help top | Policy | How to prepare *.inp file | Command lines | Author's comment lines | S and I | SH parameter matrices | Rotation matrices | Angular parameters | Transition tables | Parameter output(*.out file) | Graph output(*.plt file) | S=1/2 | S=1/2, I=1/2 | S=1 |
EPR is accepted as a powerful and unique tool for studying radicals, impurities, and defects in materials science. Since 1950s, this technique has been widely applied to semiconductors and has revealed a large number of microscopic centers in these materials, which greatly contributed to the development of semiconductor technologies.
Now, about 50 years later, our knowledge about EPR centers in semiconductors has become extremely grown. One can see a major part of this huge knowledge in Landrt-Börnstein New Series Vol. III/22b (1989) and Vol. III/41A2a,b (2002), in which Prof. C.A.J. Ammerlaan (University of Amsterdam, The Netherlands) has made great efforts for summarizing a huge number of previous EPR data. This series is believed to be the most well-established encyclopedia for EPR centers in semiconductors.
However, the number of papers is still continuously increasing, while EPR has become a classical tool and the pioneers or specialists of this field are going to retire in the near future. This situation will make it difficult to keep the huge knowledge being efficiently utilized over the future. Therefore, in order to keep and grow the knowledge and community in this field, our group has started to build up a computer-based Database which corrects Spin-Hamiltonian (SH) parameter matrices of EPR centers in the literature. Using the current Internet technologies, it becomes quite possible to create an Web-based open database by means of relatively small efforts. In fact, there already exists a large-scaled Web database for spin-traps/labels in chemistry and biochemistry (S.T.D.B. in USA and UK).
For semiconductors, however, we encountered a problem to build up such a database. In chemistry or biochemistry, EPR treated isotropic spins in liquids, which greatly simplified their EPR spectra. For instance, such EPR spectra could be easily simulated by a set of isotropic g, hyperfine (A), and fine (D) values. On the contrary, EPR in semiconductors was generally anisotropic; namely, EPR spectra depended on how a semiconductor crystal was mounted with respect to external magnetic field. This is often called ?gangular dependence of EPR spectrum?h. In addition, those EPR spectra generally included multiple lines due to the presence of symmetry-related sites in the crystal. With these reasons, if we tried to compare own experimental data with those of literature, we were required to perform angular-dependence simulation of EPR spectrum using SH parameter tensors (g, A, and D tensors, etc.) in the literature, which was no longer possible for non-EPR specialists and even not easy for EPR specialists. Furthermore, there was another difficulty. The coordinate for defining the SH parameter matrices have not been unified in the literature, resulting in additional complicity. These matters are undesirable for the efficient maintenance and reuse of the valuable knowledge.
An Web-based database combined with EPR-NMR© simulator
Based on the above background, we considered two requirements for our Web-based database for EPR centers in semiconductors. One is a common and easy format for SH parameter matrices. The other is the ability of angular-dependence simulations of EPR spectrum using the formatted SH parameter matrices.
To clear these, we have adopted EPR-NMR© program to the Database, which was developed by the group of Prof. J.A. Weil and Prof. M.J. Mombourquette. Since a member of our group (Prof. J. Isoya) joined the development of this program, we know its great potential and have a large experience of use in real research. We believe that this program is one of the most powerful simulation tools in the EPR field.
Once we describe SH parameter matrices in the form of an input file (.inp text file) for this program, one could execute a wide variety of simulations such as angular-map, EPR, ENDOR (electron-nuclear-double-resonance), ESEEM (electron-spin-echo-envelop-modulation) spectra, etc. Among many functions of EPR-NMR, we here provide only (1) angular-map simulation and (2) EPR-spectrum simulation, because these two types are the standard ways to compare between your experiment data and the literature.
One of the most important functions of this Database is that everyone can upload new SH parameter matrices to here. We expect that this Database is growing by not only us but also every members in this community. Therefore, in accordance with this policy, this Database are free and open for every users in the world. In principle, our group does not interfere your actions in this Web site, unless those actions are destructive to other users.
Some rules for users
Everyone can download any Database files and can use them for the purpose of research. Of course, these are free of charge. Do not download the Database files for a commercial use.
If you show SH parameter matrices of the Database file in your publication, you must explicitly refer the original reference represented inside the file (see author's comment lines).
If your publication use a simulated result obtained from this Web site, explicitly note the use of this site (?gEPR in semiconductors?h, URL: http://www.kc.tsukuba.ac.jp/div-media/epr/index.php) in references or acknowledgements.
Each Database file has a definite Author (represented inside the file) who uploaded the relevant file. Any modifications for a file (edit, rename, and delete) are permitted only to the Author, because of the security against invalid accesses. If you want to upload alternative SH parameter matrices against the already-existing ones, kindly create a new folder and upload your files to there. Then, we would like to leave the judgment to users.
About EPR-NMR
EPR-NMR© program is a valuable software for EPR specialists as well as for conventional users. You can purchase it from J.A. Weil Homepage with a reasonable price. To run this program, you have to separetely install a FORTRAN package to your computer. Our Web site provides you only a few basic functions of EPR-NMR. When you have own EPR-NMR package in your computer, you can perform a variety of simulations using the downloaded files. Or, an original EPR-NMR program enables you to carry out a semi-automatic non-linear-least-squre-fitting determination of SH paramaters using experimental data. Actually, our group has reported many sets of SH parameter matrices by taking advange of this powerful function.