New photopatternable polyimide and programmable nonvolatile memory performances

We report the first photopatternable, nonvolatile memory consisting of high-temperature polyimide (PI), poly (hexafluoroisopropylidenediphthalimide-4-cinnamoyloxytri-phenylamine) (6F-HTPA-CI), and we demonstrate the successful fabrication and programmable operation of 'write-read-erase' memory devices based on nanoscale thin films of 6F-HTPA-CI. The PI thin film enables scalable fine patternability, providing lines and spaces with excellent pattern fidelity. Isolated individual memory devices were successfully fabricated on a bottom electrode via a sequential process of coating, photopatterning, top electrode deposition, developing, rinsing and drying. The 6F-HTPA-CI cells exhibited excellent nonvolatile memory performances in three different modes (unipolar permanent, unipolar flash and bipolar flash memories), regardless of photo-exposure doses. The switching-ON (writing) voltage was in the range of +/- 1.5 to +/- 2.0 V, and the switching-OFF (erasing) voltage was in the range of +/- 0.3 to +/- 0.8 V; these voltages are quite low, indicating that power consumption by the devices during operation is low. The ON/OFF current ratio of the devices was in the range of 10(4)-10(9). Overall, the photopatternable PI 6F-HTPA-CI opens up the possibility of low-cost mass production of high-performance, high-speed, energy-efficient, permanent or rewritable high-density nonvolatile polymer memory devices suitable for future advanced electronics in highly integrated systems.111Ysciescopu

Synchrotron X-ray reflectivity studies of nanoporous organosilicate thin films with low dielectric constants

Quantitative, non-destructive X-ray reflectivity analysis using synchrotron radiation sources was successfully performed on nanoporous dielectric thin films prepared by thermal processing of blend films of a thermally curable polymethylsilsesquioxane dielectric precursor and a thermally labile triethoxy-silyl-terminated six-arm poly(epsilon-caprolactone) porogen in various compositions. In addition, thermogravimetric analysis and transmission electron microscopy analysis were carried out. These measurements provided important structural information about the nanoporous films. The thermal process used in this study was found to cause the porogen molecules to undergo efficiently sacrificial thermal degradation, generating closed, spherical nanopores in the dielectric film. The resultant nanoporous films exhibited a homogeneous, well defined structure with a thin skin layer and low surface roughness. In particular, no skin layer was formed in the porous film imprinted using a porogen loading of 30 wt%. The film porosities ranged from 0 to 33.8% over the porogen loading range of 0-30 wt%open131

Solution structures of RseA and its complex with RseB

Conformational changes of RseA and RseB were observed by circular dichroism and small-angle X-ray scattering upon the formation of their complex

Detection of an intermediate during the unfolding process of the dimeric ketosteroid isomerase

AbstractFailure to detect the intermediate in spite of its existence often leads to the conclusion that two-state transition in the unfolding process of the protein can be justified. In contrast to the previous equilibrium unfolding experiment fitted to a two-state model by circular dichroism and fluorescence spectroscopies, an equilibrium unfolding intermediate of a dimeric ketosteroid isomerase (KSI) could be detected by small angle X-ray scattering (SAXS) and analytical ultracentrifugation. The sizes of KSI were determined to be 18.7Å in 0M urea, 17.3Å in 5.2M urea, and 25.1Å in 7M urea by SAXS. The size of KSI in 5.2M urea was significantly decreased compared with those in 0M and 7M urea, suggesting the existence of a compact intermediate. Sedimentation velocity as obtained by ultracentrifugation confirmed that KSI in 5.2M urea is distinctly different from native and fully-unfolded forms. The sizes measured by pulse field gradient nuclear magnetic resonance (NMR) spectroscopy were consistent with those obtained by SAXS. Discrepancy of equilibrium unfolding studies between size measurement methods and optical spectroscopies might be due to the failure in detecting the intermediate by optical spectroscopic methods. Further characterization of the intermediate using 1H NMR spectroscopy and Kratky plot supported the existence of a partially-folded form of KSI which is distinct from those of native and fully-unfolded KSIs. Taken together, our results suggest that the formation of a compact intermediate should precede the association of monomers prior to the dimerization process during the folding of KSI

Controlled Morphology and Its Impact on Digital Memory Behavior of Well-Defined Functional Polymers in Nanoscale Thin Films

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Structural details of functional nanoscale thin films and nanoparticles probed by synchrotron X-ray scattering

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In situ infrared spectroscopy study on imidization reaction and imidization-induced refractive index and thickness variations in microscale thin films of a poly(amic ester)

Poly(amic ester) (PAE) is a soluble precursor of polyimide that has attracted interest from both the microelectronic and the flat-panel display industries because of its several important advantages, including excellent solubility, high hydrolytic stability, and solvent-free film formation, over the polyimide precursor, poly(amic acid), for which monomer-polymer equilibration always occurs in solution due to its carboxylic acid groups. In this study, poly(3,4'-oxydiphenylene pyromellitamic diethyl ester) (PMDA-3,4'-ODA PAE) was chosen as a PAE precursor, and its thermal imidization behavior in microscale thin films was investigated quantitatively for the first time using time-resolved infrared (IR) spectroscopy. In addition, the variations of the film refractive index and thickness with temperature and time were determined in detail from the time-resolved IR spectra and are fully interpreted in this paper by considering the imidization kinetics of the precursorclose303