John P. Katsoudas

The New MRCAT (Sector 10) Bending Magnet Beamline at the Advanced Photon Source

The Materials Research Collaborative Access Team (MRCAT) has completed construction of its bending magnet beamline at the Advanced Photon Source, with commissioning ongoing since October 2008. Full operations including General User access will begin in January 2010. The beamline is designed to operate in two distinct modes: pink beam for lithography, photochemistry and tomography; and monochromatic beam for x‐ray absorption spectroscopy and tomography. Pink beam is obtained by means of a 880 mm water cooled Pt mirror combined with filters, while monochromatic beam is selected using a water‐cooled double‐crystal Si(111) monochromator, providing an energy range from below 4 keV to greater than 33 keV. Switching between modes is accomplished in under one hour.

Quantum dots by ultraviolet and x-ray lithography

Highly luminescent semiconductor quantum dots have been synthesized in porous materials with ultraviolet and x-ray lithography. For this, the pore-filling solvent of silica hydrogels is exchanged with an aqueous solution of a group II metal ion together with a chalcogenide precursor such as 2-mercaptoethanol, thioacetamide or selenourea. The chalcogenide precursor is photodissociated in the exposed regions, yielding metal chalcogenide nanoparticles. Patterns are obtained by using masks appropriate to the type of radiation employed. The mean size of the quantum dots is controlled by adding capping agents such as citrate or thioglycerol to the precursor solution, and the quantum yield of the composites can be increased to up to about 30% by photoactivation. Our technique is water-based, uses readily available reagents, and highly luminescent patterned composites are obtained in a few simple processing steps. Polydispersity, however, is high (around 50%), preventing large-scale usage of the technique for the time being. Future developments that aim at a reduction of the polydispersity are presented.

Note: Sample chamber for in situ x-ray absorption spectroscopy studies of battery materials

In situ x-ray absorption spectroscopy (XAS) provides element-specific characterization of both crystalline and amorphous phases and enables direct correlations between electrochemical performance and structural characteristics of cathode and anode materials. In situ XAS measurements are very demanding to the design of the experimental setup. We have developed a sample chamber that provides electrical connectivity and inert atmosphere for operating electrochemical cells and also accounts for x-ray interactions with the chamber and cell materials. The design of the sample chamber for in situ measurements is presented along with example XAS spectra from anode materials in operating pouch cells at the Zn and Sn K-edges measured in fluorescence and transmission modes, respectively.

Electrodeposition Assisted X-ray Lithography: Single Step Approach

This paper reports on the development of a novel single-step approach for the formation of patterned metal deposits from metal salt solution using X-ray lithography approach. The technique is based on simultaneously exposing the substrate to masked X-rays within an electric field, in order to utilize the effects of radiolysis and potentiostatic electrodeposition. The experimental results demonstrate the possibility of patterned silver deposition from the salt solution without the use of resist-substrate material. It is confirmed that the simultaneous exposure to X-rays with the application of an electric filed was required in obtaining our pattern.