Silicon Nitride and Hydrogenated Silicon Nitride Thin Films: A Review of Fabrication Methods and Applications

Silicon nitride (SiNx) and hydrogenated silicon nitride (SiNx:H) thin films enjoy widespread scientific interest across multiple application fields. Exceptional combination of optical, mechanical, and thermal properties allows for their utilization in several industries, from solar and semiconductor to coated glass production. The wide bandgap (~5.2 eV) of thin films allows for its optoelectronic application, while the SiNx layers could act as passivation antireflective layers or as a host matrix for silicon nano-inclusions (Si-ni) for solar cell devices. In addition, high water-impermeability of SiNx makes it a potential candidate for barrier layers of organic light emission diodes (OLEDs). This work presents a review of the state-of-the-art process techniques and applications of SiNx and SiNx:H thin films. We focus on the trends and latest achievements of various deposition processes of recent years. Historically, different kinds of chemical vapor deposition (CVD), such as plasma enhanced (PE-CVD) or hot wire (HW-CVD), as well as electron cyclotron resonance (ECR), are the most common deposition methods, while physical vapor deposition (PVD), which is primarily sputtering, is also widely used. Besides these fabrication methods, atomic layer deposition (ALD) is an emerging technology due to the fact that it is able to control the deposition at the atomic level and provide extremely thin SiNx layers. The application of these three deposition methods is compared, while special attention is paid to the effect of the fabrication method on the properties of SiNx thin films, particularly the optical, mechanical, and thermal properties

A csillagfejlődés késői állapotai = Late stages of stellar evolution

Tanulmányoztuk a csillagfejlődés, csillagrezgések és -robbanások asztrofizikájának nyitott kérdéseit hazai, külföldi és űrbéli nagyműszerekkel végzett megfigyelésekkel. Vizsgáltuk pulzáló vörös óriás változócsillagoknál a pulzáció kapcsolatát a csillagfejlődéssel és a periódusváltozások okait. Elvégeztük több mint 300 vörös óriáscsillagnak a Kepler-űrtávcsővel készített fénygörbéje analízisét. A csillagoknál Fourier- és wavelet-analízist alkalmaztunk a periodicitás vizsgálatokhoz. Megvizsgáltunk nagy tömegű szuperóriás csillagokat mint lehetséges szupernóva progenitorokat a robbanás előtt. Szupernóvák távolságát, tömegét, luminozitását és fejlődési állapotát határoztuk meg fotometriai és spektroszkópiai megfigyelések alapján. A ROTSE programmal együttműködve megfigyeltünk és elemeztünk mintegy 50 új szupernóvát a 9,2 m-es HET (USA), a 9,3 m-es SALT távcső (Dél-Afrika) és más távcsövek (Piszkéstető, Baja és Szeged) használatával. A projekt új kutatási irányokat nyitott: vörös óriás csillagok rövid periódusú és kis amplitúdójú oszcillációjának vizsgálata a Kepler adatai alapján, és szupernóva-robbanások széles körű tanulmányozása az University of Texas-szal együttműködve. A kutatás végére 96 publikációnk született (ezek közül 1 MTA doktori és 6 PhD értekezés, 1 Science cikk) az OTKA-szám feltüntetésével, összesen 418 impakt faktorral. Ezekre 2013 közepéig 682 hivatkozás történt az ADS szerint (részletes adatok: http://astro.u-szeged.hu/kutatas/.otka/index.html). | In this project we explored open questions of stellar evolution, oscillations and explosions by taking new observations using ground-based and space telescopes. We studied the relationship of pulsation and stellar evolution in red giant stars and physical background of the period changes. We analyzed the light curves of more than 300 red giant stars measured by the Kepler space telescope. We applied Fourier- and wavelet-analysis to perform the periodicity studies. We studied massive supergiants as supernova progenitors before explosion. We determined the distance, mass, luminosity and evolutionary state of supernovae via photometric and spectroscopic measurements. In collaboration with the ROTSE program we observed and studied about 50 new supernovae using observations taken with the 9.2 m HET telescope (USA), the 9.3 m SALT telescope (South Africa) and other telescopes at Piszkéstető, Baja and Szeged. We extended our studies into new directions: the study of short period and small amplitude oscillations of red giant stars based on Kepler data, and comprehensive investigations of supernova explosions in collaboration with University of Texas. We produced 96 publications (among them 1 HAS DSc thesis and 6 PhD theses, 1 Science paper) with the indication of the OTKA-number, the cumulative impact factor is 418. The current number of citations (June 2013) is 682 according to the ADS data base (details: http://astro.u-szeged.hu/kutatas/.otka/index.html)

Investigation of the RF Sputtering Process and the Properties of Deposited Silicon Oxynitride Layers Under Varying Reactive Gas Conditions

In a single process run, an amorphous silicon oxynitride layer was grown, which includes the entire transition from oxide to nitride. The variation of the optical properties and the thickness of the layer was characterized by Spectroscopic Ellipsometry (SE) measurements, while the elemental composition was investigated by Energy Dispersive Spectroscopy (EDS). It was revealed that the refractive index of the layer at 632.8 nm is tunable in the 1.48–1.89 range by varying the oxygen partial pressure in the chamber. From the data of the composition of the layer, the typical physical parameters of the process were determined by applying the Berg model valid for reactive sputtering. In our modelling, a new approach was introduced, where the metallic Si target sputtered with a uniform nitrogen and variable oxygen gas flow was considered as an oxygen gas-sputtered SiN target. The layer growth method used in the present work and the revealed correlations between sputtering parameters, layer composition and refractive index, enable both the achievement of the desired optical properties of silicon oxynitride layers and the production of thin films with gradient refractive index for technology applications

The plasma membrane Ca2+ pump PMCA4b inhibits the migratory and metastatic activity of BRAF mutant melanoma cells

Oncogenic mutations of BRAF lead to constitutive ERK activity that supports melanoma cell growth and survival. While Ca2+ signaling is a well-known regulator of tumor progression, the crosstalk between Ca2+ signaling and the Ras-BRAF-MEK-ERK pathway is much less explored. Here we show that in BRAF mutant melanoma cells the abundance of the plasma membrane Ca2+ ATPase isoform 4b (PMCA4b, ATP2B4) is low at baseline but markedly elevated by treatment with the mutant BRAF specific inhibitor vemurafenib. In line with these findings gene expression microarray data also shows decreased PMCA4b expression in cutaneous melanoma when compared to benign nevi. The MEK inhibitor selumetinib-similarly to that of the BRAF-specific inhibitor-also increases PMCA4b levels in both BRAF and NRAS mutant melanoma cells suggesting that the MAPK pathway is involved in the regulation of PMCA4b expression. The increased abundance of PMCA4b in the plasma membrane enhances [Ca2+ ]i clearance from cells after Ca2+ entry. Moreover we show that both vemurafenib treatment and PMCA4b overexpression induce marked inhibition of migration of BRAF mutant melanoma cells. Importantly, reduced migration of PMCA4b expressing BRAF mutant cells is associated with a marked decrease in their metastatic potential in vivo. Taken together, our data reveal an important crosstalk between Ca2+ signaling and the MAPK pathway through the regulation of PMCA4b expression and suggest that PMCA4b is a previously unrecognized metastasis suppressor

Two tagging single‐nucleotide polymorphisms to capture HLA ‐ DRB1*07:01–DQA1*02:01–DQB1*02:02 haplotype associated with asparaginase hypersensitivity

Aims: Asparaginase (ASP) hypersensitivity is a well-known challenge in the treatment of lymphoblastic malignancies. In terms of cost considerations, the cheap native Escherichia coli ASP, the most immunogenic form of this medication, is used in the first line in middle-income countries. Previously, the role of the HLA-DRB1*07:01-DQA1*02:01-DQB1*02:02 haplotype had been established to associate with E. coli ASP hypersensitivity. We investigated a possible cost-effective genetic testing method to identify patients harbouring the risk HLA haplotype in order to pave the way for safer ASP treatment. Methods: In 241 patients with previously determined HLA-DRB1*07:01-DQA1*02:01-DQB1*02:02 haplotype and known ASP hypersensitivity status, 4 candidate HLA-tagging single-nucleotide polymorphisms (SNP)s were measured, and the performance of the different sets of these tag SNPs was evaluated. Results: We identified a combination of 2 SNPs - rs28383172 and rs7775228 - as a tag for HLA-DRB1*07:01-DQA1*02:01-DQB1*02:02 haplotype with sensitivity and specificity values >95%. In line with previous findings, we found complete concordance between HLA-DRB1*07:01 and rs28383172. With bioinformatics methods, the results were also confirmed in the 1000 Genomes dataset in different ethnic groups. Conclusion: Rs28383172 and rs7775228 are suitable for identifying HLA-DRB1*07:01-DQA1*02:01-DQB1*02:02 carriers. Compared to the rest of the population, patients with hypersensitivity-prone genotype would benefit more from the administration of less immunogenic PEGylated ASP before the hypersensitivity evolves, incurring minimal extra cost

Behavioral, neural and ultrastructural alterations in a graded-dose 6-OHDA mouse model of early-stage Parkinson's disease

Studying animal models furthers our understanding of Parkinson’s disease (PD) pathophysiology by providing tools to investigate detailed molecular, cellular and circuit functions. Different versions of the neurotoxin-based 6-hydroxydopamine (6-OHDA) model of PD have been widely used in rats. However, these models typically assess the result of extensive and definitive dopaminergic lesions that reflect a late stage of PD, leading to a paucity of studies and a consequential gap of knowledge regarding initial stages, in which early interventions would be possible. Additionally, the better availability of genetic tools increasingly shifts the focus of research from rats to mice, but few mouse PD models are available yet. To address these, we characterize here the behavioral, neuronal and ultrastructural features of a graded-dose unilateral, single-injection, striatal 6-OHDA model in mice, focusing on early-stage changes within the first two weeks of lesion induction. We observed early onset, dose-dependent impairments of overall locomotion without substantial deterioration of motor coordination. In accordance, histological evaluation demonstrated a partial, dose-dependent loss of dopaminergic neurons of substantia nigra pars compacta (SNc). Furthermore, electron microscopic analysis revealed degenerative ultrastructural changes in SNc dopaminergic neurons. Our results show that mild ultrastructural and cellular degradation of dopaminergic neurons of the SNc can lead to certain motor deficits shortly after unilateral striatal lesions, suggesting that a unilateral dose-dependent intrastriatal 6-OHDA lesion protocol can serve as a successful model of the early stages of Parkinson’s disease in mice

Brainstem nucleus incertus controls contextual memory formation

Hippocampal pyramidal cells encode memory engrams, which guide adaptive behavior. Selection of engram-forming cells is regulated by somatostatin-positive dendrite-targeting interneurons, which inhibit pyramidal cells that are not required for memory formation. Here, we found that gamma-aminobutyric acid ( GABA)-releasing neurons of the mouse nucleus incertus (NI) selectively inhibit somatostatin-positive interneurons in the hippocampus, both monosynaptically and indirectly through the inhibition of their subcortical excitatory inputs. We demonstrated that NI GABAergic neurons receive monosynaptic inputs from brain areas processing important environmental information, and their hippocampal projections are strongly activated by salient environmental inputs in vivo. Optogenetic manipulations of NI GABAergic neurons can shift hippocampal network state and bidirectionally modify the strength of contextual fear memory formation. Our results indicate that brainstem NI GABAergic cells are essential for controlling contextual memories

Region Specific Differences of Claudin-5 Expression in Pediatric Intracranial Ependymomas: Potential Prognostic Role in Supratentorial Cases

Ependymomas are common pediatric brain tumors that originate from the ependyma and characterized by poor prognosis due to frequent recurrence. However, the current WHO grading system fails to accurately predict outcome. In a retrospective study, we analyzed 54 intracranial pediatric ependymomas and found a significantly higher overall survival in supratentorial cases when compared to infratentorial tumors. Next we performed region-specific immunohistochemical analysis of the ependyma in neonatal and adult ependyma from the central canal of spinal cord to the choroid plexus of lateral ventricles for components of cell-cell junctions including cadherins, claudins and occludin. We found robust claudin-5 expression in the choroid plexus epithelia but not in other compartments of the ependyma. Ultrastructural studies demonstrated distinct regional differences in cell-cell junction organization. Surprisingly, we found that 9 out of 20 supratentorial but not infratentorial ependymomas expressed high levels of the brain endothelial tight junction component claudin-5 in tumor cells. Importantly, we observed an increased overall survival in claudin-5 expressing supratentorial ependymoma. Our data indicates that claudin-5 expressing ependymomas may follow a distinct course of disease. The assessment of claudin-5 expression in ependymoma has the potential to become a useful prognostic marker in this pediatric malignancy