X-ray Diffraction of Photonic Colloidal Single Crystals

We have resolved a great number of Bragg peaks of photonic
colloidal single crystals by synchrotron
small angle X-ray scattering (SAXS). We find that
charge-stabilized colloids form face-centered cubic
crystals at all densities up to ∼60 vol %. The colloidal
particles are highly ordered on their lattice sites,
which confirms that these self-organizing materials are suitable
building blocks for optical photonic matter.
The experiments demonstrate that synchrotron SAXS with
two-dimensional detection is a powerful tool
to study systems with length scales comparable to optical
wavelengths.

本研究借助同步辐射小角度X射线散射（SAXS），解析了光子胶体单晶的大量布拉格峰（Bragg peaks）。研究发现，电荷稳定胶体（charge-stabilized colloids）在最高约60%体积分数的所有密度下，均会形成面心立方（face-centered cubic）晶体。胶体粒子在晶格位点（lattice sites）上呈现高度有序排布，这证实了这类自组织材料（self-organizing materials）可作为光学光子材料（optical photonic matter）的理想构筑基元。实验结果表明，配备二维探测（two-dimensional detection）的同步辐射SAXS是研究长度尺度（length scales）与光波长（optical wavelengths）相当的体系的有力工具。