Post deposition annealing of epitaxial Ce1-xPrxO2-δ films grown on Si(111)

In this work the structural and morphological changes of Ce1−xPrxO2−δ (x = 0.20, 0.35 and 0.75) films grown on Si(111) due to post deposition annealing are investigated by low energy electron diffraction combined with a spot profile analysis. The surface of the oxide films exhibit mosaics with large terraces separated by monoatomic steps. It is shown that the Ce/Pr ratio and post deposition annealing temperature can be used to tune the mosaic spread, terrace size and step height of the grains. The morphological changes are accompanied by a phase transition from a fluorite type lattice to a bixbyite structure. Furthermore, at high PDA temperatures a silicate formation via a polycrystalline intermediate state is observed

Control of electron-state coupling in asymmetric Ge/Si−Ge quantum wells

Theoretical predictions indicate that the n-type Ge / Si − Ge multi-quantum-well system is the most promising material for the realization of a Si -compatible THz quantum cascade laser operating at room temperature. To advance in this direction, we study, both experimentally and theoretically, asymmetric coupled multi-quantum-well samples based on this material system, that can be considered as the basic building block of a cascade architecture. Extensive structural characterization shows the high material quality of strain-symmetrized structures grown by chemical vapor deposition, down to the ultrathin barrier limit. Moreover, THz absorption spectroscopy measurements supported by theoretical modeling unambiguously demonstrate inter-well coupling and wavefunction tunneling. The agreement between experimental data and simulations allows us to characterize the tunneling barrier parameters and, in turn, achieve highly controlled engineering of the electronic structure in forthcoming unipolar cascade systems based on n-type Ge / Si − Ge multi-quantum-wells

On the local electronic and atomic structure of Ce1-xPrxO2-\u3b4 epitaxial films on Si

The local electronic and atomic structure of (111)-oriented, single crystalline mixed Ce1xPrxO2d (x\ubc0, 0.1 and 0.6) epitaxial thin films on silicon substrates have been investigated in view of engineering redox properties of complex oxide films. Non-destructive X-ray absorption near edge structure reveals that Pr shows only \ufe3 valence and Ce shows only nominal \ufe4 valence in mixed oxides. Extended x-ray absorption fine structure (EXAFS) studies were performed at K edges of Ce and Pr using a specially designed monochromator system for high energy measurements. They demonstrate that the fluorite lattice of ceria (CeO2) is almost not perturbed for x\ubc0.1 sample, while higher Pr concentration (x\ubc0.6) not only generates a higher disorder level (thus more disordered oxygen) but also causes a significant reduction of Ce\u2013O interatomic distances. The valence states of the cations were also examined by techniques operating in highly reducing environments: scanning transmission electron microscopy-electron energy loss spectroscopy and X-ray photoemission spectroscopy; in these reducing environments, evidence for the presence of Ce3\ufe was clearly found for the higher Pr concentration. Thus, the introduction of Pr3\ufe into CeO2 strongly enhances the oxygen exchange properties of CeO2. This improved oxygen mobility properties of CeO2 are attributed to the lattice disorder induced by Pr mixing in the CeO2 fluorite lattice, as demonstrated by EXAFS measurements. Thus, a comprehensive picture of the modifications of the atomic and electronic structure of Ce1xPrxO2d epitaxial films and their relation is obtained

Oxygen vacancy induced room temperature ferromagnetism in Pr-doped CeO2 thin films on silicon

Integration of functional oxides on Si substrates could open a pathway to integrate diverse devices on Si-based technology. Oxygen vacancies (Vo(\ub7\ub7)) can strongly affect solid state properties of oxides, including the room temperature ferromagnetism (RTFM) in diluted magnetic oxides. Here, we report a systematical study on the RTFM of oxygen vacancy engineered (by Pr(3+) doping) CeO2 epitaxial thin films on Si substrates. High quality, mixed single crystalline Ce1-xPrxO2-\u3b4 (x = 0-1) solid solution films were obtained. The Ce ions in CeO2 with a fluorite structure show a Ce(4+)-dominant valence state in all films. The local crystal structures of the films were analyzed in detail. Pr doping creates both Vo(\ub7\ub7) and PrO8-complex defects in CeO2 and their relative concentrations vary with the Pr-doping level. The RTFM properties of the films reveal a strong dependence on the relative Vo(\ub7\ub7) concentration. The RTFM in the films initially increases with higher Pr-doping levels due to the increase of the F(+) center (Vo(\ub7\ub7) with one occupied electron) concentration and completely disappears when x > 0.2, where the magnetic polaron concentration is considered to decline below the percolation threshold, thus long-range FM order can no longer be established. We thus demonstrate the possibility to directly grow RTFM Pr-doped CeO2 films on Si substrates, which can be an interesting candidate for potential magneto-optic or spintronic device applications

Rare copy number variation in posttraumatic stress disorder.

Posttraumatic stress disorder (PTSD) is a heritable (h <sup>2</sup> = 24-71%) psychiatric illness. Copy number variation (CNV) is a form of rare genetic variation that has been implicated in the etiology of psychiatric disorders, but no large-scale investigation of CNV in PTSD has been performed. We present an association study of CNV burden and PTSD symptoms in a sample of 114,383 participants (13,036 cases and 101,347 controls) of European ancestry. CNVs were called using two calling algorithms and intersected to a consensus set. Quality control was performed to remove strong outlier samples. CNVs were examined for association with PTSD within each cohort using linear or logistic regression analysis adjusted for population structure and CNV quality metrics, then inverse variance weighted meta-analyzed across cohorts. We examined the genome-wide total span of CNVs, enrichment of CNVs within specified gene-sets, and CNVs overlapping individual genes and implicated neurodevelopmental regions. The total distance covered by deletions crossing over known neurodevelopmental CNV regions was significant (beta = 0.029, SE = 0.005, P = 6.3 × 10 <sup>-8</sup> ). The genome-wide neurodevelopmental CNV burden identified explains 0.034% of the variation in PTSD symptoms. The 15q11.2 BP1-BP2 microdeletion region was significantly associated with PTSD (beta = 0.0206, SE = 0.0056, P = 0.0002). No individual significant genes interrupted by CNV were identified. 22 gene pathways related to the function of the nervous system and brain were significant in pathway analysis (FDR q < 0.05), but these associations were not significant once NDD regions were removed. A larger sample size, better detection methods, and annotated resources of CNV are needed to explore this relationship further

Enhancing discovery of genetic variants for posttraumatic stress disorder through integration of quantitative phenotypes and trauma exposure information

BACKGROUND: Posttraumatic stress disorder (PTSD) is heritable and a potential consequence of exposure to traumatic stress. Evidence suggests that a quantitative approach to PTSD phenotype measurement and incorporation of lifetime trauma exposure (LTE) information could enhance the discovery power of PTSD genome-wide association studies (GWASs). METHODS: A GWAS on PTSD symptoms was performed in 51 cohorts followed by a fixed-effects meta-analysis (N = 182,199 European ancestry participants). A GWAS of LTE burden was performed in the UK Biobank cohort (N = 132,988). Genetic correlations were evaluated with linkage disequilibrium score regression. Multivariate analysis was performed using Multi-Trait Analysis of GWAS. Functional mapping and annotation of leading loci was performed with FUMA. Replication was evaluated using the Million Veteran Program GWAS of PTSD total symptoms. RESULTS: GWASs of PTSD symptoms and LTE burden identified 5 and 6 independent genome-wide significant loci, respectively. There was a 72% genetic correlation between PTSD and LTE. PTSD and LTE showed largely similar patterns of genetic correlation with other traits, albeit with some distinctions. Adjusting PTSD for LTE reduced PTSD heritability by 31%. Multivariate analysis of PTSD and LTE increased the effective sample size of the PTSD GWAS by 20% and identified 4 additional loci. Four of these 9 PTSD loci were independently replicated in the Million Veteran Program. CONCLUSIONS: Through using a quantitative trait measure of PTSD, we identified novel risk loci not previously identified using prior case-control analyses. PTSD and LTE have a high genetic overlap that can be leveraged to increase discovery power through multivariate methods.</p