Mechanisms of arsenic clustering in silicon

A model of arsenic clustering in silicon is proposed and analyzed. The main feature of the proposed model is the assumption that negatively charged arsenic complexes play a dominant role in the clustering process. To confirm this assumption, electron density and concentration of impurity atoms incorporated into the clusters are calculated as functions of the total arsenic concentration. A number of the negatively charged clusters incorporating a point defect and one or more arsenic atoms are investigated. It is shown that for the doubly negatively charged clusters or for clusters incorporating more than one arsenic atom the electron density reaches a maximum value and then monotonically and slowly decreases as total arsenic concentration increases. In the case of doubly negatively charged cluster incorporating two arsenic atoms, the calculated electron density agrees well with the experimental data. Agreement with the experiment confirms the conclusion that two arsenic atoms participate in the cluster formation. Among all present models, the proposed model of clustering by formation of doubly negatively charged cluster incorporating two arsenic atoms gives the best fit to the experimental data and can be used in simulation of high concentration arsenic diffusion.Comment: 13 pages, 4 figures. Revised and shortened version of the paper has been published in Phys. Rev. B, Vol.74 (3), art. no. 035205 (2006

Early-onset atopic dermatitis and food hypersensitivity increase the risk of atopic march

Non peer reviewe

Vacancy-Impurity Complexes in Highly Sb-Doped Si Grown by Molecular Beam Epitaxy

Positron annihilation measurements, supported by first-principles electron-structure calculations, identify vacancies and vacancy clusters decorated by 1–2 dopant impurities in highly Sb-doped Si. The concentration of vacancy defects increases with Sb doping and contributes significantly to the electrical compensation. Annealings at low temperatures of 400–500 K convert the defects to larger complexes where the open volume is neighbored by 2–3 Sb atoms. This behavior is attributed to the migration of vacancy-Sb pairs and demonstrates at atomic level the metastability of the material grown by epitaxy at low temperature.Peer reviewe

Increased Expression of PLS3 Correlates with Better Outcome in Sézary Syndrome.

Dermatology-oncolog

Vacancy-Impurity Complexes in Highly Sb-Doped Si Grown by Molecular Beam Epitaxy

Positron annihilation measurements, supported by first-principles electron-structure calculations, identify vacancies and vacancy clusters decorated by 1-2 dopant impurities in highly Sb-doped Si. The concentration of vacancy defects increases with Sb doping and contributes significantly to the electrical compensation. Annealings at low temperatures of 400 -500 K convert the defects to larger complexes where the open volume is neighbored by 2 -3 Sb atoms. This behavior is attributed to the migration of vacancy-Sb pairs and demonstrates at atomic level the metastability of the material grown by epitaxy at low temperature. DOI: 10.1103/PhysRevLett.94.165501 PACS numbers: 61.72.-y, 61.82.Fk, 78.70.Bj The interest in highly doped Si is fundamentally related to the miniaturization of field-effect transistors, where increased doping is needed to maintain a sufficient conductance of the source and drain regions The molecular beam epitaxy (MBE) growth at low temperature ( < 600 K) can be applied to achieve metastable doping and free electron concentrations, which become compensated only at 10 21 cm ÿ3 In this work we apply positron annihilation spectroscopy to study vacancies formed in the low-temperature MBE growth of highly Sb-doped Si. Positrons get trapped at open-volume defects. The measured annihilation photons carry information on the electron momentum density, which can be utilized to identify the size of the open volume of the defect and the neighboring dopant atoms. Our results show that the MBE growth creates vacancies and vacancy clusters, which are neighbored by 1-2 Sb atoms. The vacancy concentrations are relevant for the compensation of the Sb doping. We also show that the low-temperature MBE Si is atomically metastable, and annealings at low temperatures of 400 -500 K lead to clustering of vacancies and dopant impurities. We studied Si(100) layers grown by MBE on the Si substrate at 550 K We used a low-energy positron beam to measure the Doppler broadened energy spectrum of the annihilation radiation. The shape of the spectrum was described with conventional S and W parameter

Vacancy-impurity complexes in highly Sb-doped Si grown by molecular beam epitaxy

Positron annihilation measurements, supported by first-principles electron-structure calculations, identify vacancies and vacancy clusters decorated by 1 -2 dopant impurities in highly Sb-doped Si. The concentration of vacancy defects increases with Sb doping and contributes significantly to the electrical compensation. Annealings at low temperatures of 400 -500 K convert the defects to larger complexes where the open volume is neighbored by 2 -3 Sb atoms. This behavior is attributed to the migration of vacancy-Sb pairs and demonstrates at atomic level the metastability of the material grown by epitaxy at low temperature. PACS numbers: 61.82.Fk, 78.70.Bj The interest in highly doped Si is fundamentally related to the miniaturization of field-effect transistors, where increased doping is needed to maintain a sufficient conductance of the source and drain regions The molecular beam epitaxy (MBE) growth at low temperature (< 600 K) can be applied to achieve metastable doping and free electron concentrations, which become compensated only at 10 21 cm −3 In this work we apply positron annihilation spectroscopy to study vacancies formed in the lowtemperature MBE growth of highly Sb-doped Si. Positrons get trapped at open volume defects. The measured annihilation photons carry information on the electron momentum density, which can be utilized to identify the size of the open volume of the defect and the neighboring dopant atoms. Our results show that the MBE growth creates vacancies and vacancy clusters, which are neighbored by 1 -2 Sb atoms. The vacancy concentrations are relevant for the compensation of the Sb doping. We also show that the low-temperature MBE Si is atomically metastable, and annealings at low temperatures of 400-500 K lead to clustering of vacancies and dopant impurities. We studied Si(100) layers grown by MBE on Si substrate at 550

A novel desmoplakin mutation causes dilated cardiomyopathy with palmoplantar keratoderma as an early clinical sign

Background PPKs represent a heterogeneous group of disorders with hyperkeratosis of palmar and/or plantar skin. PPK, hair shaft abnormalities, cardiomyopathy and arrhythmias can be caused by mutations in desmosomal genes, e.g. desmoplakin (DSP). PPK should trigger genetic testing to reveal mutations with possible related cardiac disease. Objectives To report a large multigenerational family with a novel DSP mutation associated with early-onset PPK and adult-onset cardiomyopathy and arrhythmias. Methods A custom-designed in-house panel of 35 PPK related genes was used to screen mutations in the index patient with focal PPK. The identified DSP mutation was verified by Sanger sequencing. DNA samples from 20 members of the large multigenerational family were sequenced for the DSP mutation. Medical records were reviewed. Clinical dermatological evaluation was performed, including light microscopy of hair samples. Cardiac evaluation included clinical examination, echocardiography, cardiac magnetic resonance imaging (CMR), electrocardiogram (ECG), Holter monitoring and laboratory tests. Results We identified a novel autosomal dominant truncating DSP c.2493delA p.(Glu831Aspfs*33) mutation associated with dilated cardiomyopathy (DCM) with arrhythmia susceptibility and focal PPK as an early cutaneous sign. The mutation was found in nine affected family members, but not in any unaffected members. Onset of dermatological findings preceded cardiac symptoms which were variable and occurred at adult age. Conclusions We report a novel truncating DSP mutation causing focal PPK with varying severity and left ventricular dilatation and ventricular extrasystoles. This finding emphasizes the importance of genetic diagnosis in patients with PPK for clinical counselling and management of cardiomyopathies and arrhythmias.Peer reviewe

Anti-CD45RC antibody immunotherapy prevents and treats experimental autoimmune polyendocrinopathy-candidiasis- ectodermal dystrophy syndrome

Targeted monoclonal antibody (mAb) therapies show great promise for the treatment of transplant rejection and autoimmune diseases by inducing more specific immunomodulatory effects than broadly immunosuppressive drugs routinely used. We recently described the therapeutic advantage of targeting CD45RC, expressed at high levels by conventional T (Tconv) cells (CD45RC(hi)), their precursors, and terminally differentiated T (TEMRA) cells, but not by regulatory T cells (Tregs; CD45RC(lo/-)). We demonstrated efficacy of anti-CD45RC mAb treatment in transplantation, but its potential has not been examined in autoimmune diseases. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare genetic syndrome caused by loss-of-function mutations of autoimmune regulator (AIRE), a key central tolerance mediator, leading to abnormal autoreactive T cell responses and autoantibody production. Herein, we show that, in a rat model of APECED syndrome, anti-CD45RC mAb was effective for both prevention and treatment of autoimmune manifestations and inhibited autoantibody development. Anti-CD45RC mAb intervention depleted CD45RC(hi) T cells, inhibited CD45RC(hi) B cells, and restored the Treg/Tconv cell ratio and the altered Treg transcriptomic profile. In APECED patients, CD45RC was significantly increased in peripheral blood T cells, and lesioned organs from APECED patients were infiltrated by CD45RC(hi) cells. Our observations highlight the potential role for CD45RC(hi) cells in the pathogenesis of experimental and human APECED syndrome and the potential of anti-CD45RC antibody treatment.Peer reviewe