TY  - JOUR
A1  - Pietzsch, Annette
A1  - Hennies, Franz
A1  - Miedema, Piter S.
A1  - Kennedy, Brian
A1  - Schlappa, Justine
A1  - Schmitt, Thorsten
A1  - Strocov, Vladimir N.
A1  - Föhlisch, Alexander
T1  - Snapshots of the Fluctuating Hydrogen Bond Network in Liquid Water on the Sub-Femtosecond Timescale with Vibrational Resonant Inelastic x-ray Scattering
JF  - Physical review letters
N2  - Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevLett.114.088302
SN  - 0031-9007
SN  - 1079-7114
VL  - 114
IS  - 8
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Arhammar, C.
A1  - Pietzsch, Annette
A1  - Bock, Nicolas
A1  - Holmstroem, Erik
A1  - Araujo, C. Moyses
A1  - Grasjo, Johan
A1  - Zhao, Shuxi
A1  - Green, Sara
A1  - Peery, T.
A1  - Hennies, Franz
A1  - Amerioun, Shahrad
A1  - Föhlisch, Alexander
A1  - Schlappa, Justine
A1  - Schmitt, Thorsten
A1  - Strocov, Vladimir N.
A1  - Niklasson, Gunnar A.
A1  - Wallace, Duane C.
A1  - Rubensson, Jan-Erik
A1  - Johansson, Borje
A1  - Ahuja, Rajeev C.
T1  - Unveiling the complex electronic structure of amorphous metal oxides
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.
KW  - stochastic quench
KW  - X-ray absorption spectroscopy
KW  - ab initio
KW  - coating
Y1  - 2011
U6  - https://doi.org/10.1073/pnas.1019698108
SN  - 0027-8424
VL  - 108
IS  - 16
SP  - 6355
EP  - 6360
PB  - National Acad. of Sciences
CY  - Washington
ER  -