scholarly journals Низкотемпературная фотолюминесценция монослоя WSe-=SUB=-2-=/SUB=-, полученного механическим слоением с использованием золота

2022 ◽  
Vol 56 (3) ◽  
pp. 335
Author(s):  
С.Н. Николаев ◽  
В.С. Багаев ◽  
М.А. Чернопицский ◽  
И.И. Усманов ◽  
Е.Е. Онищенко ◽  
...  
Keyword(s):  
Optical Properties ◽  
Large Scale ◽  
Spectral Width ◽  
Structural Disorder ◽  
Mechanical Exfoliation ◽  
Radiation Spectra ◽  
Significant Difference ◽  
Scattering Spectra ◽  
Background Doping ◽  
Raman Scattering Spectra

We studied the optical properties of an atomically thin WSe$_2$ film obtained by gold-assisted mechanical exfoliation. Raman scattering spectra, low-temperature photoluminescence, and micro-reflection from large-scale monolayer are investigated. At room temperature, the optical properties of such a film reproduce the properties of WSe$_2$ monolayers obtained by regular mechanical exfoliation. It is shown that at low temperatures, the radiation spectra of the resulting film are determined by standard mechanisms of radiative recombination involving free excitons, bound excitons, and trions. However, in contrast to room temperatures, there is a significant difference in the spectral width and intensity of the lines compared to monolayers WSe$_2$, obtained regular way from the same source material. The differences found, demonstrating a significant increase in background doping and structural disorder when using gold-assisted exfoliation, may be meaningful for a number of optoelectronic applications of atomically thin WSe$_2$ films.

Effect of Gas Pressure on Optical Properties of Nanocrystalline Diamond Films Deposited on SiC Substrates

2011 ◽  
Vol 347-353 ◽  
pp. 537-541
Author(s):  
Nan Chun Wu ◽  
Yi Ben Xia ◽  
Shou Hong Tan ◽  
Lin Jun Wang
Keyword(s):  
Optical Properties ◽  
Raman Scattering ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Gas Pressure ◽  
Nanocrystalline Diamond ◽  
Nanocrystalline Diamond Films ◽  
Scattering Spectra ◽  
Raman Scattering Spectra ◽  
G Ratio

With use of electron-assisted chemical vapor deposition technology, nanocrystalline diamond films were deposited on SiC ceramics substrates at various gas pressure ( 0.5 ~ 2 kPa ). Effect of the gas pressure on optical properties of the nanocrystalline diamond films was studied. Raman scattering spectra were measured. Photoluminescence spectra were investigated in the range of 420 ~ 680 nm. Spectroscopic ellipsometry were analyzed from the near IR to the UV region ( 1.5 ~ 5.0 eV ). Results show that, when the gas pressure increased from 0.5 to 2 kPa, Raman scattering intensity of diamond increase and D/G ratio decrease; when the gas pressure was 0.5kPa and 2kPa, there is not any PL peak, however, there is a stronger PL peak at 485 nm when the gas pressure was 1kPa; extinctive coefficient k for the nanocrystalline diamond films deposited at 1kPa increase obviously with increase of photo energy.

Influence of the Strain of AlN Buffer Layer on the Strain Evolution of GaN Epilayer Grown on 3-in 6H-SiC Substrate

2011 ◽  
Vol 335-336 ◽  
pp. 1242-1245
Author(s):  
Yu Long Fang ◽  
Jia Yun Yin ◽  
Zhi Hong Feng
Keyword(s):  
Large Scale ◽  
Chemical Vapor ◽  
Buffer Layers ◽  
Organic Chemical ◽  
Double Crystal ◽  
Strain Evolution ◽  
Scattering Spectra ◽  
Metal Organic ◽  
Raman Scattering Spectra ◽  
Aln Buffer

The influence of the strain of AlN buffer layers on the strain evolution of GaN epilayers grown on 3-in 6H-SiC substrates by metal-organic chemical vapor deposition was investigated by double-crystal X-ray diffractometry, and Raman scattering spectra. It was found that the tensile strain of the GaN epilayers mainly decreases with the strain of the AlN buffer layers varied from tensile to compressive. A model based on the strain evolution during the epitaxial growth is proposed to provide a valuable reference for the massive production of large scale and high quality GaN epilayers.

scholarly journals Излучение света гетероструктурой CdMnTe/CdMgTe с узкими квантовыми ямами

2019 ◽  
Vol 61 (8) ◽  
pp. 1523
Author(s):  
В.Ф. Агекян ◽  
Е.В. Борисов ◽  
А.Ю. Серов ◽  
Н.Г. Философов ◽  
G. Karczewski
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Barrier Layer ◽  
Integral Intensity ◽  
Manganese Ions ◽  
Excitation Spectra ◽  
Intracenter Luminescence ◽  
Temperature Dependences ◽  
Scattering Spectra ◽  
Raman Scattering Spectra

AbstractThe optical properties of the Cd_0.4Mn_0.4Te/Cd_0.5Mg_0.5Te heterostructure with quantum wells of 7 monolayers in thickness are studied. The temperature dependences of the integral intensity of luminescence of the barrier layer and quantum well and intracenter luminescence of manganese ions are determined, and the luminescence excitation spectra are measured. Numerous components corresponding to LO phonons of the CdTe, MgTe, and MnTe types are observed in the Raman scattering spectra.

scholarly journals Optimizing Manufacturing and Osseointegration of Ti6Al4V Implants through Precision Casting and Calcium and Phosphorus Ion Implantation? In Vivo Results of a Large-Scale Animal Trial

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1670 ◽  
Author(s):  
Wölfle-Roos JV ◽  
Katmer Amet B ◽  
Fiedler J ◽  
Michels H ◽  
Kappelt G ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Large Scale ◽  
In Vivo Studies ◽  
Control Group ◽  
Implant Surface ◽  
Precision Casting ◽  
Pull Out ◽  
Significant Difference ◽  
Calcium And Phosphorus

Background: Uncemented implants are still associated with several major challenges, especially with regard to their manufacturing and their osseointegration. In this study, a novel manufacturing technique—an optimized form of precision casting—and a novel surface modification to promote osseointegration—calcium and phosphorus ion implantation into the implant surface—were tested in vivo. Methods: Cylindrical Ti6Al4V implants were inserted bilaterally into the tibia of 110 rats. We compared two generations of cast Ti6Al4V implants (CAST 1st GEN, n = 22, and CAST 2nd GEN, n = 22) as well as cast 2nd GEN Ti6Al4V implants with calcium (CAST + CA, n = 22) and phosphorus (CAST + P, n = 22) ion implantation to standard machined Ti6Al4V implants (control, n = 22). After 4 and 12 weeks, maximal pull-out force and bone-to-implant contact rate (BIC) were measured and compared between all five groups. Results: There was no significant difference between all five groups after 4 weeks or 12 weeks with regard to pull-out force (p > 0.05, Kruskal Wallis test). Histomorphometric analysis showed no significant difference of BIC after 4 weeks (p > 0.05, Kruskal–Wallis test), whereas there was a trend towards a higher BIC in the CAST + P group (54.8% ± 15.2%), especially compared to the control group (38.6% ± 12.8%) after 12 weeks (p = 0.053, Kruskal–Wallis test). Conclusion: In this study, we found no indication of inferiority of Ti6Al4V implants cast with the optimized centrifugal precision casting technique of the second generation compared to standard Ti6Al4V implants. As the employed manufacturing process holds considerable economic potential, mainly due to a significantly decreased material demand per implant by casting near net-shape instead of milling away most of the starting ingot, its application in manufacturing uncemented implants seems promising. However, no significant advantages of calcium or phosphorus ion implantation could be observed in this study. Due to the promising results of ion implantation in previous in vitro and in vivo studies, further in vivo studies with different ion implantation conditions should be considered.

Cohesive Zone Model for the Interface of Multiwalled Carbon Nanotubes and Copper: Molecular Dynamics Simulation

2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Ibrahim Awad ◽  
Leila Ladani
Keyword(s):  
Carbon Nanotubes ◽  
Normal Stress ◽  
Multiwalled Carbon Nanotubes ◽  
Cohesive Zone ◽  
Large Scale ◽  
Cohesive Zone Model ◽  
Dynamics Simulation ◽  
Zone Model ◽  
Multiwalled Carbon ◽  
Significant Difference

Due to their superior mechanical and electrical properties, multiwalled carbon nanotubes (MWCNTs) have the potential to be used in many nano-/micro-electronic applications, e.g., through silicon vias (TSVs), interconnects, transistors, etc. In particular, use of MWCNT bundles inside annular cylinders of copper (Cu) as TSV is proposed in this study. However, the significant difference in scale makes it difficult to evaluate the interfacial mechanical integrity. Cohesive zone models (CZM) are typically used at large scale to determine the mechanical adherence at the interface. However, at molecular level, no routine technique is available. Molecular dynamic (MD) simulations is used to determine the stresses that are required to separate MWCNTs from a copper slab and generate normal stress–displacement curves for CZM. Only van der Waals (vdW) interaction is considered for MWCNT/Cu interface. A displacement controlled loading was applied in a direction perpendicular to MWCNT's axis in different cases with different number of walls and at different temperatures and CZM is obtained for each case. Furthermore, their effect on the CZM key parameters (normal cohesive strength (σmax) and the corresponding displacement (δn) has been studied. By increasing the number of the walls of the MWCNT, σmax was found to nonlinearly decrease. Displacement at maximum stress, δn, showed a nonlinear decrease as well with increasing the number of walls. Temperature effect on the stress–displacement curves was studied. When temperature was increased beyond 1 K, no relationship was found between the maximum normal stress and temperature. Likewise, the displacement at maximum load did not show any dependency to temperature.

scholarly journals Heterogeneity and effectiveness analysis of COVID-19 prevention and control in major cities in China through time-varying reproduction number estimation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Qing Cheng ◽  
Zeyi Liu ◽  
Guangquan Cheng ◽  
Jincai Huang
Keyword(s):  
Prevention And Control ◽  
Large Scale ◽  
Reproduction Number ◽  
Correlation Method ◽  
Control Measures ◽  
Time Varying ◽  
Short Period ◽  
Significant Difference ◽  
Prevention And Control Measures ◽  
And Control

AbstractBeginning on December 31, 2019, the large-scale novel coronavirus disease 2019 (COVID-19) emerged in China. Tracking and analysing the heterogeneity and effectiveness of cities’ prevention and control of the COVID-19 epidemic is essential to design and adjust epidemic prevention and control measures. The number of newly confirmed cases in 25 of China’s most-affected cities for the COVID-19 epidemic from January 11 to February 10 was collected. The heterogeneity and effectiveness of these 25 cities’ prevention and control measures for COVID-19 were analysed by using an estimated time-varying reproduction number method and a serial correlation method. The results showed that the effective reproduction number (R) in 25 cities showed a downward trend overall, but there was a significant difference in the R change trends among cities, indicating that there was heterogeneity in the spread and control of COVID-19 in cities. Moreover, the COVID-19 control in 21 of 25 cities was effective, and the risk of infection decreased because their R had dropped below 1 by February 10, 2020. In contrast, the cities of Wuhan, Tianmen, Ezhou and Enshi still had difficulty effectively controlling the COVID-19 epidemic in a short period of time because their R was greater than 1.

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