Shaped silicon wafers obtained by hot plastic deformation: Performance evaluation for future astronomical x-ray telescopes

In order to develop lightweight and high angular resolution x-ray mirrors, we have investigated hot plastic deformation of 4 in. silicon (111) wafers. A sample wafer was deformed using hemispherical dies with a curvature radius of 1000mm. The measured radius of the deformed wafer was 1030mm, suggesting that further conditioning is indispensable for better shaping. For the first time to our knowledge, x-ray reflection on a deformed wafer was detected at Al K _α 1:49keV. An estimated surface roughness of <1nm from the x-ray reflection profile was comparable to that of a bare silicon wafer without deformation. Hence, no significant degradation of the microroughness was seen.