Cecilia Århammar
Royal Institute of Technology
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Publication
Featured researches published by Cecilia Århammar.
Applied Physics Letters | 2010
C. Moysés Araújo; Mukes Kapilashrami; Xu Jun; O. D. Jayakumar; Sandeep Nagar; Yan Wu; Cecilia Århammar; Börje Johansson; Lyubov Belova; Rajeev Ahuja; G. A. Gehring; K. V. Rao
Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wid ...
Proceedings of the National Academy of Sciences of the United States of America | 2011
Cecilia Århammar; Annette Pietzsch; Nicolas Bock; Erik Holmstroem; C. Moysés Araújo; Johan Gråsjö; Shuxi Zhao; Sara Green; Travis B. Peery; Franz Hennies; Shahrad Amerioun; Alexander Foehlisch; Justine Schlappa; Thorsten Schmitt; V. N. Strocov; Gunnar A. Niklasson; Duane C. Wallace; Jan-Erik Rubensson; Börje Johansson; Rajeev Ahuja
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.
Scientific Reports | 2013
Xue Jiang; Cecilia Århammar; Peng Liu; Jijun Zhao; Rajeev Ahuja
Pressure-induced bond type switching and phase transformation in glassy carbon (GC) has been simulated by means of Density Functional Theory (DFT) calculations and the Stochastic Quenching method (SQ) in a wide range of pressures (0–79 GPa). Under pressure, the GC experiences a hardening transition from sp- and sp2-type to sp3-type bonding, in agreement with previous experimental results. Moreover, a new crystalline carbon allotrope possessing R3 symmetry (R3-carbon) is predicted using the stochastic SQ method. The results indicate that R3-carbon can be regarded as an allotrope similar to that of amorphous GC. A very small difference in the heat of formation and the coherence of the radial and angular distribution functions of GC and the R3-carbon structure imply that small perturbations to this crystalline carbon allotrope may provide another possible amorphization pathway of carbon besides that of quenching the liquid melt or gas by ultra-fast cooling.
EPL | 2010
Lunmei Huang; Cecilia Århammar; C. Moysés Araújo; Fredrik Silvearv; Rajeev Ahuja
The electronic structure and magnetic properties of In2O3 with four kinds of intrinsic point defects (O vacancy, In interstitial, O interstitial, and In vacancy) have been theoretically studied usi ...
Physical Review B | 2009
Cecilia Århammar; C. Moysés Araújo; Rajeev Ahuja
Acta Materialia | 2011
Jose L. Endrino; Cecilia Århammar; A. Gutiérrez; R. Gago; David Horwat; L. Soriano; G.S. Fox-Rabinovich; D. Martín y Marero; J.-H. Guo; Jan-Erik Rubensson; Joakim Andersson
Physical Review B | 2011
Jawad Nisar; Cecilia Århammar; Erik Jämstorp; Rajeev Ahuja
Physical Review B | 2010
Cecilia Århammar; C. Moysés Araújo; K. V. Rao; Susanne Norgren; Börje Johansson; Rajeev Ahuja
18th Plansee Seminar, 3 – 7 June, 2013 in Reutte, Austria | 2013
Bartek Kaplan; Andreas Blomqvist; Cecilia Århammar; Malin Selleby; Susanne Norgren
Surface & Coatings Technology | 2011
Andreas Blomqvist; Cecilia Århammar; Henrik Pedersen; Fredrik Silvearv; Susanne Norgren; Rajeev Ahuja