Polymer-assisted deposition technique has been used to deposit Al2O3 and N-doped Al2O3（AlON） thin films on Si（100） substrates.The chemical compositions,crystallinity,and thermal conductivity of the as-grown films ...Polymer-assisted deposition technique has been used to deposit Al2O3 and N-doped Al2O3（AlON） thin films on Si（100） substrates.The chemical compositions,crystallinity,and thermal conductivity of the as-grown films have been characterized by X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,and 3-omega method,respectively. Amorphous and polycrystalline Al2O3 and AlON thin films have been formed at 700℃and 1000℃.The thermal conductivity results indicated that the effect of nitrogen doping on the thermal conductivity is determined by the competition of the increase of Al-N bonding and the suppression of crystallinity.A 67%enhancement in thermal conductivity has been achieved for the samples grown at 700℃,demonstrating that the nitrogen doping is an effective way to improve the thermal performance of polymer-assisted-deposited Al2O3 thin films at a relatively low growth temperature.展开更多
Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT ...Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT of VO_(2)thin film is important for the applications of this material in various devices.Here,the changes in thermal conductivity of epitaxial and polycrystalline VO_(2)thin film across MIT are probed by the time-domain thermoreflectance(TDTR)method.The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO_(2)film to attenuate the impact from extra thermal interfaces.It is demonstrated that the method is feasible for the VO_(2)films with thickness values larger than 100 nm and beyond the phase transition region.The observed reasonable thermal conductivity change rates across MIT of VO_(2)thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate,which is different from the reported behavior of single crystal VO_(2)nanowires.The recovery of the relationship between thermal conductivity and electrical conductivity in VO_(2)film may be attributed to the increasing elastic electron scattering weight,caused by the defects in the film.This work demonstrates the possibility and limitation of investigating the thermal properties of VO_(2)thin films by the TDTR method without depositing any metal thermoreflectance layer.展开更多
FeS因具有较高的比容量和优异的环境友好性,被认为是一种极具竞争力的锂/钠离子电池负极材料.然而,循环过程中缓慢的电荷转移动力学和较大的体积变化阻碍了它的实际应用.本文通过在超薄FeS/C复合材料中构建应变缓冲(气泡膜状)结构,从根...FeS因具有较高的比容量和优异的环境友好性,被认为是一种极具竞争力的锂/钠离子电池负极材料.然而,循环过程中缓慢的电荷转移动力学和较大的体积变化阻碍了它的实际应用.本文通过在超薄FeS/C复合材料中构建应变缓冲(气泡膜状)结构,从根本上解决了FeS动力学缓慢和体积变化大的问题.有限元模拟和非原位透射电镜结果验证了气泡膜状碳基质可作为保护壳层缓解FeS的巨大体积变化,还能提高其电子导电性.得益于这种独特的结构设计,该电极材料表现出显著增强的性能.其在5 A g^(-1)下的储锂容量为469 mA h g^(-1),在1 A g^(-1)下循环1500次后的储钠容量为354 mA h g^(-1).此外,由该电极与LiFePO_(4)正极组装的全电池即使在100次循环后也能提供558 mA h g^(-1)的比容量,展现出优异的循环稳定性.这一策略也可应用于其它导电性差、体积变化大的负极材料,以促进高倍率和长寿命电池的发展.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60976061 and 11028409)
文摘Polymer-assisted deposition technique has been used to deposit Al2O3 and N-doped Al2O3（AlON） thin films on Si（100） substrates.The chemical compositions,crystallinity,and thermal conductivity of the as-grown films have been characterized by X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,and 3-omega method,respectively. Amorphous and polycrystalline Al2O3 and AlON thin films have been formed at 700℃and 1000℃.The thermal conductivity results indicated that the effect of nitrogen doping on the thermal conductivity is determined by the competition of the increase of Al-N bonding and the suppression of crystallinity.A 67%enhancement in thermal conductivity has been achieved for the samples grown at 700℃,demonstrating that the nitrogen doping is an effective way to improve the thermal performance of polymer-assisted-deposited Al2O3 thin films at a relatively low growth temperature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61825102,51872038,and 52021001)the“111”Project,China(Grant No.B18011).
文摘Vanadium dioxide(VO_(2))is a strongly correlated material,and it has become known due to its sharp metal-insulator transition(MIT)near room temperature.Understanding the thermal properties and their change across MIT of VO_(2)thin film is important for the applications of this material in various devices.Here,the changes in thermal conductivity of epitaxial and polycrystalline VO_(2)thin film across MIT are probed by the time-domain thermoreflectance(TDTR)method.The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO_(2)film to attenuate the impact from extra thermal interfaces.It is demonstrated that the method is feasible for the VO_(2)films with thickness values larger than 100 nm and beyond the phase transition region.The observed reasonable thermal conductivity change rates across MIT of VO_(2)thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate,which is different from the reported behavior of single crystal VO_(2)nanowires.The recovery of the relationship between thermal conductivity and electrical conductivity in VO_(2)film may be attributed to the increasing elastic electron scattering weight,caused by the defects in the film.This work demonstrates the possibility and limitation of investigating the thermal properties of VO_(2)thin films by the TDTR method without depositing any metal thermoreflectance layer.
基金supported by the National Natural Science Foundation of China(51874362)。
文摘FeS因具有较高的比容量和优异的环境友好性,被认为是一种极具竞争力的锂/钠离子电池负极材料.然而,循环过程中缓慢的电荷转移动力学和较大的体积变化阻碍了它的实际应用.本文通过在超薄FeS/C复合材料中构建应变缓冲(气泡膜状)结构,从根本上解决了FeS动力学缓慢和体积变化大的问题.有限元模拟和非原位透射电镜结果验证了气泡膜状碳基质可作为保护壳层缓解FeS的巨大体积变化,还能提高其电子导电性.得益于这种独特的结构设计,该电极材料表现出显著增强的性能.其在5 A g^(-1)下的储锂容量为469 mA h g^(-1),在1 A g^(-1)下循环1500次后的储钠容量为354 mA h g^(-1).此外,由该电极与LiFePO_(4)正极组装的全电池即使在100次循环后也能提供558 mA h g^(-1)的比容量,展现出优异的循环稳定性.这一策略也可应用于其它导电性差、体积变化大的负极材料,以促进高倍率和长寿命电池的发展.
