Improvements in structural and optical properties of wafer-scale hexagonal boron nitride film by post-growth annealing

Remarkable improvements in both structural and optical properties of wafer-scale hexagonal boron nitride (h-BN) films grown by metal-organic chemical vapor deposition (MOCVD) enabled by high-temperature post-growth annealing is presented. The enhanced crystallinity and homogeneity of the MOCVD-grown h-BN films grown at 1050 degrees C is attributed to the solid-state atomic rearrangement during the thermal annealing at 1600 degrees C. In addition, the appearance of the photoluminescence by excitonic transitions as well as enlarged optical band gap were observed for the post-annealed h-BN films as direct consequences of the microstructural improvement. The post-growth annealing is a very promising strategy to overcome limited crystallinity of h-BN films grown by typical MOCVD systems while maintaining their advantage of multiple wafer scalability for practical applications towards two-dimensional electronics and optoelectronics.11Ysciescopu

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Reaction of ammonia and dioxygen in solid neon excited with far-ultraviolet radiation investigated with electronic and vibrational spectra

Irradiation of dilute mixtures of NH3 and O2 dispersed in solid Ne at 3.6 K with radiation of wave lengths 200, 192.5, 173 and 143 nm from an electron synchrotron initiated photochemical dissociation of those precursors and the production of N, NH, NH2, O, O3, HO2, NO, NO2, N2O, H2O, HONO in both s-cisoid and s-transoid rotational isomers, and HONO2, detected according to their spectra in mid-infrared absorption from 450 to 4000 cm-1, and in absorption and emission from 200 to 1100 nm. HONO2 was not previously detected in related experiments even though our conditions were much more dilute.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Identification of cyc-B3H3 with Three Bridging B–H–B Bonds in a Six-Membered Ring

Documenta Archive_2009 0626 from LAB on Vimeo. Documenta Archive 2_2009 0626 from LAB on Vimeo

Interface Engineering to Enhance the Efficiency of Conventional Polymer Solar Cells by Alcohol-/Water-Soluble C₆₀ Materials Doped with Alkali Carbonates

Two new C₆₀-based n-type materials, <b>EGMC–OH</b> and <b>EGMC–COOH</b>, functionalized with hydrophilic triethylene glycol groups (TEGs), have been synthesized and employed in conventional polymer solar cells. With the assistance of the TEG-based surfactant, <b>EGMC–OH</b> and <b>EGMC–COOH</b> can be dissolved in highly polar solvents to implement the polar/nonpolar orthogonal solvent strategy, forming an electron modification layer (EML) without eroding the underlying active layer. Multilayer conventional solar cells on the basis of ITO/PEDOT:PSS/P3HT:PC₆₁BM/EML/Ca/Al configuration with the insertion of the <b>EGMC–OH</b> and <b>EGMC–COOH</b> EML between the active layer and the electrode have thus been successfully realized by cost-effective solution processing techniques. Moreover, the electron conductivity of the EML can be improved by incorporating alkali carbonates into the <b>EGMC–COOH</b> EML. Compared to the pristine device with a PCE of 3.61%, the devices modified by the Li₂CO₃-doped <b>EGMC–COOH</b> EML achieved a highest PCE of 4.29%. Furthermore, we demonstrated that the formation of the <b>EGMC–COOH</b> EML can be utilized as a general approach in the fabrication of highly efficient multilayer conventional devices. With the incorporation of the <b>EGMC–COOH</b> doped with 40 wt % Li₂CO₃, the <b>PCDCTBT–C8</b>:PC₇₁BM-based device exhibited a superior PCE of 4.51%, which outperformed the corresponding nonmodified device with a PCE of 3.63%

Infrared and Ultraviolet Spectra of Diborane(6): B₂H₆ and B₂D₆

We recorded absorption spectra of diborane(6), B₂H₆ and B₂D₆, dispersed in solid neon near 4 K in both mid-infrared and ultraviolet regions. For gaseous B₂H₆ from 105 to 300 nm, we report quantitative absolute cross sections; for solid B₂H₆ and for B₂H₆ dispersed in solid neon, we measured ultraviolet absorbance with relative intensities over a wide range. To assign the mid-infrared spectra to specific isotopic variants, we applied the abundance of ¹¹B and ¹⁰B in natural proportions; we undertook quantum-chemical calculations of wavenumbers associated with anharmonic vibrational modes and the intensities of the harmonic vibrational modes. To aid an interpretation of the ultraviolet spectra, we calculated the energies of electronically excited singlet and triplet states and oscillator strengths for electronic transitions from the electronic ground state