Gd–Reference–Layer Method for the Case of Two Reflectometry Experiments

The article presents an approach to determining the modulus and phase of neutron reflection amplitude using a gadolinium reference layer, which allows reducing the number of necessary experiments from three to two. It is shown that it is possible to reconstruct the reflection amplitude based on the results of only two reflectometric experiments. However, when conducting two experiments, calculating the reflection amplitude is complicated by the fact that there will be two solutions instead of one. Therefore, it is necessary to evaluate the obtained results, since one of these solutions will have no physical meaning. The results are evaluated based on a priori information about the sample or with the help of additional modeling of the interaction potential. The theory of the proposed approach is described in detail, and it is tested on model numerical calculations for the Al₂O₃//Ti film. Experimental results for the test samples Al₂O₃//Nb and Si//Cr/Fe/Cr are presented. A comparison of the moduli and phases of the reflectivity obtained by processing three and two experiments is carried out. It was found that under conditions of poor statistics, conducting two experiments is preferable, since the solution, in this case, contains fewer artifacts of mathematical processing.