Variable-energy Positron Study of Nanopore Structure in Hydrocarbon–Siliconoxide Hybrid PECVD Films

AbstractNanopore formation upon heat treatment of hydrocarbon-siliconoxide hybrid films was investigated by means of the variable-energy positron annihilation γ-ray and lifetime techniques. The films were prepared using plasma enhanced chemicalvapor deposition (PECVD),and nanoscopic poresinthe films weredeveloped throughthe decom positionofasacrificialhydrocarbonous porogenbyannealingthe filmsat temperaturesupto600°C.Asaresultofthe positron annihilation γ-ray measurements, the line-shape S parameter increases with increasing annealing temperature from 150°C to 400°C, while it reduces with further increasing temperature. This suggests that more positronium annihilate with carbonous elements remaining on the wall of pores formed at temperatures up to 400°C. The lifetime measurements revealed the nanopore sizes in the range from 0.2 nm3 to 2.0 nm3. With increasing the pore size the film refractive index reduced from 1.44 to 1.29. The variable-energy positron techniques were demonstrated to be useful to examine the nanoporosity evolution for porous PECVD films

Microvoid formation in hydrogen-implanted ZnO probed by a slow positron beam

ZnO crystals were implanted with 20–80 keV hydrogen ions up to a total dose of 4.4×1015 cm−2. Positron lifetime and Doppler broadening of annihilation radiation measurements show introduction of zinc vacancy-related defects after implantation. These vacancies are found to be filled with hydrogen atoms. After isochronal annealing at 200–500 °C, the vacancies agglomerate into hydrogen bubbles. Further annealing at 600–700 °C causes release of hydrogen out of the bubbles, leaving a large amount of microvoids. These microvoids are annealed out at high temperature of 1000 °C. Raman spectroscopy for the implanted sample shows the enhancement of vibration modes at about 575 cm−1, which indicates introduction of oxygen vacancies. These oxygen vacancies disappear at temperatures of 600–700 °C, which is supposed to contribute to the hydrogen bubble formation. Cathodoluminescence measurements reveal that hydrogen ions also passivate deep level emission centers before their release from the sample, leading to the improvement of the UV emission

Tuning the polarization states of optical spots at the nanoscale on the poincar´e sphere using a plasmonic nanoantenna

It is shown that the polarization states of optical spots at the nanoscale can be manipulated to various points on the Poincar´e sphere using a plasmonic nanoantenna. Linearly, circularly, and elliptically polarized near-field optical spots at the nanoscale are achieved with various polarization states on the Poincar´e sphere using a plasmonic nanoantenna. A novel plasmonic nanoantenna is illuminated with diffraction-limited linearly polarized light. It is demonstrated that the plasmonic resonances of perpendicular and longitudinal components of the nanoantenna and the angle of incident polarization can be tuned to obtain optical spots beyond the diffraction limit with a desired polarization and handedness

MicroRNA expression as risk biomarker of breast cancer metastasis : a pilot retrospective case-cohort study

Background: MicroRNAs (miRNAs) are small, non-coding RNA molecules involved in post-transcriptional gene regulation and have recently been shown to play a role in cancer metastasis. In solid tumors, especially breast cancer, alterations in miRNA expression contribute to cancer pathogenesis, including metastasis. Considering the emerging role of miRNAs in metastasis, the identification of predictive markers is necessary to further the understanding of stage-specific breast cancer development. This is a retrospective analysis that aimed to identify molecular biomarkers related to distant breast cancer metastasis development. Methods: A retrospective case cohort study was performed in 64 breast cancer patients treated during the period from 1998-2001. The case group (n = 29) consisted of patients with a poor prognosis who presented with breast cancer recurrence or metastasis during follow up. The control group (n = 35) consisted of patients with a good prognosis who did not develop breast cancer recurrence or metastasis. These patient groups were stratified according to TNM clinical stage (CS) I, II and III, and the main clinical features of the patients were homogeneous. MicroRNA profiling was performed and biomarkers related to metastatic were identified independent of clinical stage. Finally, a hazard risk analysis of these biomarkers was performed to evaluate their relation to metastatic potential. Results: MiRNA expression profiling identified several miRNAs that were both specific and shared across all clinical stages (p <= 0.05). Among these, we identified miRNAs previously associated with cell motility (let-7 family) and distant metastasis (hsa-miR-21). In addition, hsa-miR-494 and hsa-miR-21 were deregulated in metastatic cases of CSI and CSII. Furthermore, metastatic miRNAs shared across all clinical stages did not present high sensitivity and specificity when compared to specific-CS miRNAs. Between them, hsa-miR-183 was the most significative of CSII, which miRNAs combination for CSII (hsa-miR-494, hsa-miR-183 and hsa-miR-21) was significant and were a more effective risk marker compared to the single miRNAs. Conclusions: Women with metastatic breast cancer, especially CSII, presented up-regulated levels of miR-183, miR-494 and miR-21, which were associated with a poor prognosis. These miRNAs therefore represent new risk biomarkers of breast cancer metastasis and may be useful for future targeted therapies.We thank the Researcher Support Center of Barretos Cancer Hospital, especially the statistician Zanardo C. for assisting in the statistical analysis.This study received financial support from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (Fapesp, Proc: 10/ 16796-0, Sao Paulo, Brazil)

Formation of micrometer-order-thick poly-Si films on textured glass substrates by flash lamp annealing of a-Si films prepared by catalytic chemical vapor deposition

We investigate the microstructures of polycrystalline silicon (poly-Si) films formed by flash lamp annealing (FLA) of 4.5-μm-thick precursor a-Si films prepared by catalytic chemical vapor deposition (Cat-CVD) on Cr-coated textured glass substrates. Crystallization of a-Si is performed, keeping the dome-shaped structure formed during deposition of a-Si. The poly-Si film consists of densely-packed fine grains with sizes on the order of 10 nm. The grain size tends to increase approaching the Si/Cr interface, which can be understood as the result of solid-phase nucleation and following crystallization. Minority carrier lifetimes of the poly-Si films are worse than those formed on flat substrates. This degradation might be due to gaps in the Si layer formed during a-Si deposition or FLA

Preface — 10th international conference on hot-wire CVD (Cat-CVD) processes (HWCVD10)

The 10th International Conference on Hot Wire (Cat) and Initiated Chemical Vapor Deposition (HWCVD10), hosted by Kyushu Institute of Technology, was held in Kitakyushu International Conference Center, Kitakyushu, Japan, on September 3–6, 2018. One of the topics dis- cussed in the conference is the recent progress in catalytic chemical vapor deposition (Cat-CVD), also referred to as hot-wire CVD (HWCVD) or hot-filament CVD (HFCVD), which is a category of CVD using active radicals formed through catalytic cracking of source gases on a heated metal wire. Cat-CVD has been used to form a variety of films, pre- dominantly silicon-based films such as amorphous silicon, nanocrys- talline silicon, and silicon nitride, carbon-based films including dia- mond and graphene, and organic films. In addition to the film formation technology, the conference also covered the utilization of radicals generated by catalytic cracking on a heated wire in a Cat-CVD system for surface treatments and etching. The conference had 80 attendees from 11 countries, and a total of 56 papers, including 11 invited talks, 23 contributed talks, and 22 posters, were presented by the attendees

Durability of polymeric coatings: Effects of artificial and natural weathering.

NatuurwetenskappeInstituut Vir PolimeerwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Temperature Dependence of Defects in Hydrogen-Implanted Silicon Characterized by Positron and Ion-Beam Analyses

AbstractNanometer-sized voids formed in Si after H implantation to a dose of 3¥1016 cm-2 and annealing at 600 or 800 ¡C were characterized by slow-positron and ion-beam analyses. Depth profiles of defects were calculated from the S parameter curves of Doppler broadening and from Rutherford backscattering/channeling spectra. Concentrations of gettering sites were also calculated from the Rutherford backscattering spectra of the samples after Au gettering. Defect profiles by Doppler broadening measurements were found to be shallower than the projected range of implanted H, while profiles of defects and gettering sites detected by the backscattering measurements were close to the projected range. The peak concentrations of defects and gettering-sites were dependent on annealing temperature and analytical techniques. The observed annealing behaviors can be explained by the evolution of vacancy clusters and the interaction of H with defects

Production and recovery of defects in phosphorus-implanted ZnO

Phosphorus ions were implanted in ZnO single crystals with energies of 50–380 keV having total doses of 4.231013–4.231015 cm−2. Positron annihilation measurements reveal the introduction of vacancy clusters after implantation. These vacancy clusters grow to a larger size after annealing at a temperature of 600 °C. Upon further annealing up to a temperature of 1100 °C, the vacancy clusters gradually disappear. Raman-scattering measurements reveal the enhancement of the phonon mode at approximately 575 cm−1 after P+ implantation, which is induced by the production of oxygen vacancies sVOd. These oxygen vacancies are annealed out up to a temperature of 700 °C accompanying the agglomeration of vacancy clusters. The light emissions of ZnO are suppressed after implantation. This is due to the competing nonradiative recombination centers introduced by implantation. The recovery of the light emission occurs at temperatures above 600 °C. The vacancy-type defects detected by positrons might be part of the nonradiative recombination centers. The Hall measurement indicates an n-type conductivity for the P+-implanted ZnO layer, suggesting that phosphorus is an amphoteric dopant