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In this study we used a low-pressure metal organic vapor phase epitaxy method to investigate the growth of GaAs metal gate semiconductor field effect transistor (MESFET) structures on a Si substrate. The buffer layer between the Si substrate and the grown GaAs epitaxial layers was a composite Ge/Si0.05Ge0.95/Si0.1Ge0.9 metamorphic layer. We used transmission electron microscopy to observe the microstructures formed in the grown GaAs/Ge/SixGe1-x/Si material and atomic force microscopy to analyze the surface morphology and the formation of antiphase domains in the GaAs epitaxial layers. The measured Hall electron mobility in the channel layer of a MESFET structure grown on a 6° misoriented Si substrate was 2015 cm2 V-1 s-1 with a carrier concentration of 5.0×1017 cm-3. The MESFET device fabricated on this sample exhibited good current-voltage characteristics. [ABSTRACT FROM AUTHOR]

In this study, we examined the growth of a simultaneous AlN/α-Si3N4 buffer layer for crack-free GaN growth on a Si(111) substrate. The compressive stress in the AlN/α-Si3N4/Si(111) structure retards the cracking in the GaN layer. It is demonstrated that the Al-preseeded layer is a critical factor for accomplishing AlN and the crystalline α-Si3N4 layer simultaneously. The effect of Al layer deposition time on the c-axis lattice constants of the subsequent AlN layer, and the effect of the crystalline α-Si3N4 layer on GaN quality were investigated by X-ray diffraction analysis. The 1:2 lattice coincidently matches at the α-Si3N4(0001)/Si(111) interface, and the 5:2 coincident lattice interface at AlN(0001)/α-Si3N4(0001) reduces the lattice mismatch in the AlN/α-Si3N4/Si(111) structure. The 5:4 coincident lattice in the AlN/α-Si3N4/Si(111) structure is related to the reduction in the tensile stress in the AlN epilayers. The thickness of crack-free GaN is 2.00 µm. The full widths at half-maximum (FWHM) of the X-ray rocking curve and neutral-donor-bound exciton (D0X) are 1012 arcsec and 5.90 meV, respectively. [ABSTRACT FROM AUTHOR]

Background/aim: Cancers of the central nervous system (CNS) pose a significant burden, despite their relatively low incidence compared to other types of cancers. The mortality-to-incidence ratio (MIR) is a crucial indicator of long-term survival and healthcare system performance. Computed tomography (CT) plays a crucial role in the screening, diagnosis, and monitoring of brain tumors, enabling early intervention and treatment. This study aimed to explore the relationship between CT density, CNS cancer incidence, mortality, and MIR to investigate regional variations in CT utilization and their impact on CNS cancer mortality rates., Patients and Methods: Changes in MIR, referred to as δMIR, were calculated based on data from 2012 and 2018. CT density data for the year 2013 were retrieved from the Global Health Observatory data repository. The association between variables was analyzed using Spearman's rank correlation coefficient., Results: Analysis of data from 107 countries revealed a positive association between CT density and both CNS cancer incidence and mortality. However, a trend was observed between CT density and MIR. These findings suggest that in countries with greater accessibility to CT imaging, CNS cancer cases may be detected earlier and lower mortality rates can be achieved., Conclusion: Our research contributes to the understanding of the impact of CT imaging on the management and outcomes of CNS cancers. It informs healthcare strategies and resource allocation to improve patient care., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)