Advanced Light Source，
1 Cyclotron Rd, MS15-317LBNL, Berkeley, CA, 94720
题目: Resonant Soft X-ray Scattering for Soft Materials
地点：909号楼一楼B会议室(Conference Room B, 909-1F)
The function and properties of organic and biological soft-condensed matter systems are largely determined by their nano- and mesoscopic chemical morphology. The understanding and rational use of such systems thus require that this structure be known. X-ray scattering technique has been widely used for the characterization of organic material structures. However, the relatively low scattering cross section and contrast of organic constituents in the hard x-ray regime allows transmission measurements of bulk structure from samples approximately millimeters in thickness, but the scattering from tens of nanometer thick organic thin films is difficult to measure, unless the grazing incident geometry is utilized. Using x-ray energies close to the absorption edge of constituent atoms, soft x-ray scattering is a combination of conventional x-ray scattering with x-ray absorption spectroscopy that yields both elemental and chemical sensitivity. The strong resonance enhancement of the scattering contrast offers large scattering signal for thin organic films with only tens of nanometers thick. The enhanced scattering and tunable sensitivity for organic materials can be achieved without any chemical modifications. By taking advantage the unique features including elemental/chemical sensitivity, mesoscale probing size, large coherence length, and molecular orientation sensitivity with the polarization of the beam of photons, soft x-ray scattering provides yet another key to unlock structure-property relationships that will lead to better materials. Recent developments of soft x-rays scattering beamline at ALS BL18.104.22.168 and some recent results on organic PV, block copolymer thin films with future perspectives will be presented.
Cheng Wang obtained his bachelor degree in physics from Jilin University, China. In 2002, he joined Prof. Harald Ade's group at North Caroline State University where he obtained his PhD degree in physics in 2008. He started working at the Advanced Light Source as an ALS doctoral fellow and then continued as a postdoc after his graduation. In 2011, he become a research scientist running the soft x-ray scattering Beamline (BL22.214.171.124) at ALS. His research interests includes developing and establishing new scattering techniques using soft x-rays, resonant soft x-ray scattering (RSoXS), as important complementary tools to x-ray microscopy, spectroscopy and x-ray and neutron scattering for the polymeric and biological materials. As well as applying soft x-ray scattering to forefront scientic problems in material science for faster discoveries of best energy related materials in the areas of organics electronics, articial photosynthesis, batteries, biofuels, carbon capture and storage.