Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporad...Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporadically in China and have been contained relatively quickly.What is added by this report?Epidemiological investigation with genome sequence traceability analysis showed that the first case of COVID-19 in Nangong City acquired infection from a confirmed case from Shijiazhuang City.展开更多
In this work,a method to acquire freestanding GaN by using low temperature(LT)-GaN layer was put forward.To obtain porous structure and increase the crystallinity,LT-GaN layers were annealed at high temperature.The mo...In this work,a method to acquire freestanding GaN by using low temperature(LT)-GaN layer was put forward.To obtain porous structure and increase the crystallinity,LT-GaN layers were annealed at high temperature.The morphology of LTGaN layers with different thickness and annealing temperature before and after annealing was analyzed.Comparison of GaN films using different LT-GaN layers was made to acquire optimal LT-GaN process.According to HRXRD and Raman results,GaN grown on 800 nm LT-GaN layer which was annealed at 1090℃ has good crystal quality and small stress.The GaN film was successfully separated from the substrate after cooling down.The self-separation mechanism of this method was discussed.Cross-sectional EBSD mapping measurements were carried out to investigate the effect of LT-buffer layer on improvement of crystal quality and stress relief.The optical property of the obtained freestanding GaN film was also determined by PL measurement.展开更多
文摘Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporadically in China and have been contained relatively quickly.What is added by this report?Epidemiological investigation with genome sequence traceability analysis showed that the first case of COVID-19 in Nangong City acquired infection from a confirmed case from Shijiazhuang City.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51702226,51572153 and 51602177)the Natural Science Foundation of Shanxi Province(Grant No.201701D221078).
文摘In this work,a method to acquire freestanding GaN by using low temperature(LT)-GaN layer was put forward.To obtain porous structure and increase the crystallinity,LT-GaN layers were annealed at high temperature.The morphology of LTGaN layers with different thickness and annealing temperature before and after annealing was analyzed.Comparison of GaN films using different LT-GaN layers was made to acquire optimal LT-GaN process.According to HRXRD and Raman results,GaN grown on 800 nm LT-GaN layer which was annealed at 1090℃ has good crystal quality and small stress.The GaN film was successfully separated from the substrate after cooling down.The self-separation mechanism of this method was discussed.Cross-sectional EBSD mapping measurements were carried out to investigate the effect of LT-buffer layer on improvement of crystal quality and stress relief.The optical property of the obtained freestanding GaN film was also determined by PL measurement.
