MS39-P04 Enhancement of Accuracy of Neutron Atomic Resolution Holography Needless to say, the properties of the materials strongly depend on arrangements of atoms. In particular, for functional materials, the properties are controlled by doping a small amount of foreign elements, in which slight difference between the local atomic structures around the dopants and average structures of the crystals is important for the properties. However, the diffraction cannot observe such local structures because of lack of translational symmetry. Atomic resolution holography (ARH) is the unique technique that can directly observe the local structures in a three dimensional space within 20 Å from the selected atoms (dopants). On the other hand, ARH reproduces artifacts in principle, so called twin images. Note that such artifacts can be avoided by using data obtained with many different wavelengths . Thus, we are developing ARH using pulsed neutrons at Japan Proton Accelerator Research Complex at Tokai, Japan, which can obtain holograms of 130 different wavelengths at once by the time of flight method .
We measured a single crystal of 0.13 at% B doped Si, and succeeded in visualizing the local structure around B; we confirmed that most of doped B are located at the substitutional site. As a next step, to estimate positional accuracy of obtained atomic images of B doped Si quantitively, we measured a single crystal of NaCl as a standard sample. For neutron ARH, prompt γ-rays from the dopants are observed. Thus, as a required condition of good standard samples, the elements in the samples have to generate high intensity prompt γ-rays. Though intensity of γ-rays from Na and Cl is about 500 times smaller than that of B, total No. of Na and Cl atom is 300 times larger than that of the doped B in Si; therefore, ARH of NaCl single crystal is feasible. Besides, NaCl is a good example to confirm whether materials with elements which generate weak prompt γ-rays can be targets of neutron ARH. In our presentation, the results of B doped Si and the estimation of accuracy based on the analysis of NaCl will be reported.
From the recent results, we believe that neutron ARH is a powerful probe for determination of local structures around dopants in various and exotic materials. In particular, investigations of hydrides will be feasible in near future.References:
 K. Hayashi et al., J. Phys.: Condens. Matter,24 (2012) 9320.
 K. Hayashi et al., Sci. Adv., 3(2017) e1700294.Keywords: neutron, local structure,B doped Si