Raman shifts in MBE‐grown SixGe1 − x − ySny alloys with large Si content

We examine the Raman shift in silicon–germanium–tin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, Si–Si, Si–Ge, and Ge–Ge, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1 − x − ySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Peer Reviewe

Serum uric acid and its association with metabolic syndrome and carotid atherosclerosis in obese children

ObjectiveThe association between hyperuricemia, metabolic syndrome (MS), and atherosclerotic vascular disease has been reported in adults, but very little is known about this association in children. The aims of our study were to ascertain the correlates of uric acid (UA) in a sample of obese children, and to investigate whether UA is associated with carotid intima-media thickness (IMT) independently from classical risk factors including MS.MethodsWe analyzed carotid IMT along with serum triglycerides, total and high-density lipoprotein cholesterol, glucose, insulin, insulin resistance index (as homeostasis model assessment of insulin resistance), alanine aminotransferase, γ-glutamyltransferase, creatinine, and UA in 120 obese children and 50 healthy control children.ResultsUA concentrations were significantly higher in obese children compared with controls; moreover, they correlated with the most established cardiovascular risk factors. In the group of obese children, after adjustment for age, sex, pubertal stage, and creatinine, an independent association between UA levels and the presence of MS syndrome was observed (unstandardized coefficient, 0.044 (95% confidence intervals (CI) 0.015–0.072); P<0.01). Carotid IMT significantly increased in the fourth quartile of UA compared with that in the first, second, and third quartile (0.49 (0.46–0.53), 0.53 (0.49–0.56), and 0.55 (0.52–0.59) vs 0.61 (95% CI, 0.58–0.64); P<0.01). When multivariate analysis was performed after adjusting for age, gender, pubertal stage, creatinine, and MS (considered as a single clinical entity), or the individual components of MS simultaneously included, the association between UA and carotid IMT was significant (P<0.01).ConclusionsIn obese children and adolescents, increased UA levels are associated with carotid atherosclerosis

Electrical characterization of n-doped SiGeSn diodes with high Sn content

Diodes incorporating undoped and Sb-doped Si x Ge1−x−y Sn y layers grown by molecular beam epitaxy with different alloy compositions and lattice-matched to Ge were fabricated and characterized experimentally. We discuss material as well as electrical device characterization and investigate different contact metallizations (Ni and Al). In particular, we investigate the formation of Ni(Si x Ge1−x−y Sn y ) on the doped Sb-doped Si x Ge1−x−y Sn y layers via annealing based on material characterization and measurements of specific contact resistivities. Our results can serve as a starting point for the investigation of Si x Ge1−x−y Sn y layers with high Si and Sn content as cladding material in optoelectronic devices such as lasers and light emitting diodes

Raman shifts in MBE‐grown Si x Ge 1 − x − y Sn y alloys with large Si content

We examine the Raman shift in silicon–germanium–tin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, Si–Si, Si–Ge, and Ge–Ge, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1 − x − ySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Peer Reviewe

Composition analysis and transition energies of ultrathin Sn-rich GeSn quantum wells

\u3cp\u3eWhile GeSn alloys with high Sn content constitute direct group-IV semiconductors, their growth on Si remains challenging. The deposition of a few monolayers of pure Sn on Ge and their overgrowth with Ge using molecular beam epitaxy can be a means of obtaining Sn-rich quantum wells with very high Sn content while maintaining high crystal quality. Here, we provide structural and compositional information on such structures with very high accuracy. Based on our characterization results we theoretically predict transition energies and compare them with experimental results from photoluminescence measurements. Our results constitute the groundwork for tuning the molecular beam epitaxy based growth of Sn-rich quantum wells and dots for applications in electronic and optoelectronic devices.\u3c/p\u3

Composition analysis and transition energies of ultrathin Sn-rich GeSn quantum wells

While GeSn alloys with high Sn content constitute direct group-IV semiconductors, their growth on Si remains challenging. The deposition of a few monolayers of pure Sn on Ge and their overgrowth with Ge using molecular beam epitaxy can be a means of obtaining Sn-rich quantum wells with very high Sn content while maintaining high crystal quality. Here, we provide structural and compositional information on such structures with very high accuracy. Based on our characterization results we theoretically predict transition energies and compare them with experimental results from photoluminescence measurements. Our results constitute the groundwork for tuning the molecular beam epitaxy based growth of Sn-rich quantum wells and dots for applications in electronic and optoelectronic devices

Gating of TRP channels: a voltage connection?

TRP channels represent the main pathways for cation influx in non-excitable cells. Although TRP channels were for a long time considered to be voltage independent, several TRP channels now appear to be weakly voltage dependent with an activation curve extending mainly into the non-physiological positive voltage range. In connection with this voltage dependence, there is now abundant evidence that physical stimuli, such as temperature (TRPV1, TRPM8, TRPV3), or the binding of various ligands (TRPV1, TRPV3, TRPM8, TRPM4), shift this voltage dependence towards physiologically relevant potentials, a mechanism that may represent the main functional hallmark of these TRP channels. This review discusses some features of voltage-dependent gating of TRPV1, TRPM4 and TRPM8. A thermodynamic principle is elaborated, which predicts that the small gating charge of TRP channels is a crucial factor for the large voltage shifts induced by various stimuli. Some structural considerations will be given indicating that, although the voltage sensor is not yet known, the C-terminus may substantially change the voltage dependence of these channels