A new layer transfer technique which comprised double bonding and a step annealing process was utilized to transfer the GaN epilayer from a sapphire substrate to a Mo substrate. Combined with the application of the th...A new layer transfer technique which comprised double bonding and a step annealing process was utilized to transfer the GaN epilayer from a sapphire substrate to a Mo substrate. Combined with the application of the thermal-stable bonding medium, the resulting two-inch-diameter GaN template showed extremely good stability under high temperature and low stress state. Moreover, no cracks and winkles were observed. The transferred GaN template was suitable for homogeneous epitaxial, thus could be used for the direct fabrication of vertical LED chips as well as power electron devices. It has been confirmed that the double bonding and step annealing technique together with the thermal-stable bonding layer could significantly improve the bonding strength and stress relief, finally enhancing the thermal stability of the transferred GaN template.展开更多
It is increasingly crucial for flexible electronics to efficiently and reliably peel large-area, ultra-thin flexible films off from rigid substrate serving as substrates of flexible electronics device, especially in i...It is increasingly crucial for flexible electronics to efficiently and reliably peel large-area, ultra-thin flexible films off from rigid substrate serving as substrates of flexible electronics device, especially in industrial production. This paper experimentally investigated the mechanism and technologic characteristics of laser lift-off(LLO) process of ultra-thin(～ 2 μm) polyimide(PI)film. It was found increasingly difficult to obtain desirable ultra-thin PI film by LLO with the decrease of the film thickness. The optimal process parameters were achieved considering laser fluence and accumulated irradiation times(AIT), which were found to be strongly correlative to the thickness of PI film. The process mechanism of LLO of PI film was disclosed that laser ablation of interfacial PI will result in the formation of gas products between the PI and glass substrate, enabling the change of interface microstructures to reduce the interface bond strength. The amount of gas products mainly determines the result of LLO process for ultra-thin PI film, from residual adhesion to wrinkles or cracking. The strategy of multi-scanning based on multiple irradiations of low-energy laser pulses was presented to effectively achieve a reliable LLO process of ultra-thin PI film. This study provides an attractive route to optimize the LLO process for large-scale production of ultra-thin flexible electronics.展开更多
激光-EMAT混合激光超声检测系统中,由于EMAT换能效率低,随着到试样表面的距离增大信号成指数衰减,妨碍了激光超声技术的实际应用。前置放大器在保证信号不失真的情况下,通过增大前置放大器的倍数,寻求合理带宽,可以提高EMAT的信号输出...激光-EMAT混合激光超声检测系统中,由于EMAT换能效率低,随着到试样表面的距离增大信号成指数衰减,妨碍了激光超声技术的实际应用。前置放大器在保证信号不失真的情况下,通过增大前置放大器的倍数,寻求合理带宽,可以提高EMAT的信号输出质量。在EMAT内部线圈提离试样表面8 mm的情况下,利用所设计的前置放大器,依旧能够接收到100 m V左右的缺陷信号。该信号的质量已经能够用于后期的信号处理与伤型的判断识别。展开更多
基金supported by the Guangdong Innovative Research Team Program(No.2009010044)the China Postdoctoral Science Foundation(No.2014M562233)+1 种基金the National Natural Science Foundation of Guangdong,China(No.2015A030312011)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics(No.IOSKL2014KF17)
文摘A new layer transfer technique which comprised double bonding and a step annealing process was utilized to transfer the GaN epilayer from a sapphire substrate to a Mo substrate. Combined with the application of the thermal-stable bonding medium, the resulting two-inch-diameter GaN template showed extremely good stability under high temperature and low stress state. Moreover, no cracks and winkles were observed. The transferred GaN template was suitable for homogeneous epitaxial, thus could be used for the direct fabrication of vertical LED chips as well as power electron devices. It has been confirmed that the double bonding and step annealing technique together with the thermal-stable bonding layer could significantly improve the bonding strength and stress relief, finally enhancing the thermal stability of the transferred GaN template.
基金the National Natural Science Foundation of China(Grant Nos.51635007&51705180)Hubei Province Technology Innovation Special Projects(2017AAA002)
文摘It is increasingly crucial for flexible electronics to efficiently and reliably peel large-area, ultra-thin flexible films off from rigid substrate serving as substrates of flexible electronics device, especially in industrial production. This paper experimentally investigated the mechanism and technologic characteristics of laser lift-off(LLO) process of ultra-thin(～ 2 μm) polyimide(PI)film. It was found increasingly difficult to obtain desirable ultra-thin PI film by LLO with the decrease of the film thickness. The optimal process parameters were achieved considering laser fluence and accumulated irradiation times(AIT), which were found to be strongly correlative to the thickness of PI film. The process mechanism of LLO of PI film was disclosed that laser ablation of interfacial PI will result in the formation of gas products between the PI and glass substrate, enabling the change of interface microstructures to reduce the interface bond strength. The amount of gas products mainly determines the result of LLO process for ultra-thin PI film, from residual adhesion to wrinkles or cracking. The strategy of multi-scanning based on multiple irradiations of low-energy laser pulses was presented to effectively achieve a reliable LLO process of ultra-thin PI film. This study provides an attractive route to optimize the LLO process for large-scale production of ultra-thin flexible electronics.
基金supported by the National Key Research and Development Program of China(2017YFE0131500)the National Natural Science Foundation of China(62104204 and U21A20493)。
文摘激光-EMAT混合激光超声检测系统中,由于EMAT换能效率低,随着到试样表面的距离增大信号成指数衰减,妨碍了激光超声技术的实际应用。前置放大器在保证信号不失真的情况下,通过增大前置放大器的倍数,寻求合理带宽,可以提高EMAT的信号输出质量。在EMAT内部线圈提离试样表面8 mm的情况下,利用所设计的前置放大器,依旧能够接收到100 m V左右的缺陷信号。该信号的质量已经能够用于后期的信号处理与伤型的判断识别。
