A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully de...A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully deposited by double bias voltage nucleation and grid bias voltage growth. The Micro-Raman XRD SEM and AFM are used to investigate the diamond grain size, microstructure, surface morphology, and nucleation density. Results show that the obtained NCD has grain size of about 20 nm. The effect of grid bias voltage on the nucleation and the diamond growth is studied. Experimental results and theoretical analysis show that the positive grid bias increases the plasma density near the hot filaments, enhances the diamond nucleation, keeps the nanometer size of the diamond grains, and improves the quality of diamond film.展开更多
To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the fa...To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. Both numerical and test results confirmed that the cracking load, yield and ultimate load were strongly influenced by axial force, and it was also proved that the yield and ultimate load would increase with the increase of reinforcement ratio, but the cracking load was almost not affected. The cracking load, yield and ultimate load are about 28.7%, 500% and 460% larger due to the effect of axial force respectively. The comparison between numerical calculation and test results showed that the finite element analysis resuits were in good agreement with the test results.展开更多
Growth of semi-polar （1-101）GaN has been attempted on a patterned （001） silicon substrate adopting selective area MOVPE. The growth was initiated on （111） facets of the Si, which had been prepared by anisotropy ...Growth of semi-polar （1-101）GaN has been attempted on a patterned （001） silicon substrate adopting selective area MOVPE. The growth was initiated on （111） facets of the Si, which had been prepared by anisotropy etching in a KOH solution. A uni- form semi-polar layer was achieved by coalescence of stripes. Since the growth was performed on facets, the surface was atomically fiat in AFM surface analyses. By using a high temperature grown A1N nucleation layer, we achieved low threading dislocation density at the top most surface. Moreover, by tilting the c-axis of the GaN on the Si substrate, the effect of the thermal expansion coefficient mismatch was much reduced. As the result, we achieved a crack free （1-101）GaN template on （001）Si. On the thus prepared （1-101）GaN, a GalnN/GaN LED was fabricated, which showed excellent performance with weak quantum confined Stark effect.展开更多
Nano-hole patterned sapphire substrates （NHPSSs） were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography （LIL） combined with reactive ion etching （RIE...Nano-hole patterned sapphire substrates （NHPSSs） were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography （LIL） combined with reactive ion etching （RIE） and inductively coupled plasma （ICP） techniques. Gallium nitride （GaN）-based light emitting diode （LED） structure was grown on NHPSS by metal organic chemical vapor deposition （MOCVD）. Photoluminescence （PL） measurement was conducted to compare the luminescence efficiency of the GaN-based LED structure grown on NHPSS （＇NHPSS-LED） and that on unpatterned sapphire substrates （UPSS-LED）. Electroluminescence （EL） measurement shows that the output power of NHPSS-LED is 2.3 times as high as that of UPSS-LED with an injection current of 150 mA. Both PL and EL results imply that NHPSS has an advantage in improving the crystalline quality of Gab/epilayer and light extraction efficiency of LEDs at the same time.展开更多
文摘A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully deposited by double bias voltage nucleation and grid bias voltage growth. The Micro-Raman XRD SEM and AFM are used to investigate the diamond grain size, microstructure, surface morphology, and nucleation density. Results show that the obtained NCD has grain size of about 20 nm. The effect of grid bias voltage on the nucleation and the diamond growth is studied. Experimental results and theoretical analysis show that the positive grid bias increases the plasma density near the hot filaments, enhances the diamond nucleation, keeps the nanometer size of the diamond grains, and improves the quality of diamond film.
基金Supported by National Natural Science Foundation of China (No. 10902073)
文摘To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. Both numerical and test results confirmed that the cracking load, yield and ultimate load were strongly influenced by axial force, and it was also proved that the yield and ultimate load would increase with the increase of reinforcement ratio, but the cracking load was almost not affected. The cracking load, yield and ultimate load are about 28.7%, 500% and 460% larger due to the effect of axial force respectively. The comparison between numerical calculation and test results showed that the finite element analysis resuits were in good agreement with the test results.
基金supported by the Grant in Aid for Scientific Research by JSPS and Nagoya University Akasaki Research Center
文摘Growth of semi-polar （1-101）GaN has been attempted on a patterned （001） silicon substrate adopting selective area MOVPE. The growth was initiated on （111） facets of the Si, which had been prepared by anisotropy etching in a KOH solution. A uni- form semi-polar layer was achieved by coalescence of stripes. Since the growth was performed on facets, the surface was atomically fiat in AFM surface analyses. By using a high temperature grown A1N nucleation layer, we achieved low threading dislocation density at the top most surface. Moreover, by tilting the c-axis of the GaN on the Si substrate, the effect of the thermal expansion coefficient mismatch was much reduced. As the result, we achieved a crack free （1-101）GaN template on （001）Si. On the thus prepared （1-101）GaN, a GalnN/GaN LED was fabricated, which showed excellent performance with weak quantum confined Stark effect.
基金supported by the National Key Scientific Instrument and Equipment Development Projects of China(No.2012YQ17000406)the Foshan-CAS Cooperated Projects(No.2012A01)
文摘Nano-hole patterned sapphire substrates （NHPSSs） were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography （LIL） combined with reactive ion etching （RIE） and inductively coupled plasma （ICP） techniques. Gallium nitride （GaN）-based light emitting diode （LED） structure was grown on NHPSS by metal organic chemical vapor deposition （MOCVD）. Photoluminescence （PL） measurement was conducted to compare the luminescence efficiency of the GaN-based LED structure grown on NHPSS （＇NHPSS-LED） and that on unpatterned sapphire substrates （UPSS-LED）. Electroluminescence （EL） measurement shows that the output power of NHPSS-LED is 2.3 times as high as that of UPSS-LED with an injection current of 150 mA. Both PL and EL results imply that NHPSS has an advantage in improving the crystalline quality of Gab/epilayer and light extraction efficiency of LEDs at the same time.
