二维层状Cr_(x)Te_(y)超薄膜高效电磁屏蔽材料及其航天应用研究

High Efficiency Electromagnetic Shielding and the Aerospace Applications of Two Dimensional Layered Cr_(x)Te_(y) Ultrathin Film

电磁屏蔽是有效抑制电磁危害的手段之一,电磁屏蔽材料的性质与其抗电磁辐射能力密切相关。Cr_(x)Te_(y)合金材料的晶体结构呈现二维多层结构,具有优异的屏蔽电磁波的潜能,可以作为未来航天领域的优选材料。通过脉冲激光沉积手段,CrTe_(2)和Cr_(4)Te_(5)两种组分薄膜被外延沉积在蓝宝石Al2O3衬底上。X射线衍射和原子力显微镜测量结果显示薄膜为外延单晶生长,同时薄膜表面的粗糙度起伏不超过2 nm。其中光电子能谱对Cr_(4)Te_(5)薄膜的扫描结果证明其化学计量比符合4∶5,且在空气中放置一个月后未发现明显氧化。变温的磁化强度测量显示CrTe_(2)和Cr_(4)Te_(5)薄膜分别在198 K和257 K发生标准的顺磁--铁磁相变行为。温度范围从5 K到320 K,薄膜始终显示为金属性。电输运物理机理的模拟分析得出,电子--电子散射和电子--磁子散射分别对居里点以上和以下导电性起主导作用。这些优异的性能集一体,使得Cr_(x)Te_(y)材料在未来航天领域可以发挥电磁屏蔽的重要作用。

Electromagnetic shielding is one of the effective means to restrain electromagnetic hazards,and the properties of electromagnetic shielding materials are strongly correlated with their ability to resist electromagnetic radiation.The Cr_(x)Te_(y) material shows a two-dimensional crystal structure,which will be possibly utilized in the future electromagnetic shielding area of aerospace due to their excellent potentials for shielding electromagnetic waves.By using pulsed laser deposition technology,we realized a single crystal growth of CrTe_(2) and Cr_(4)Te_(5) thin films on Al 2O 3 substrate.Their epitaxial growth characteristics and the surface roughness have been examined by the measurement of X-ray diffraction and the atomic force microscopy.The results of X-ray diffraction show that all of thin films epitaxially grow.Meanwhile,their surface roughness is also no more than 2 nm.For the Cr_(4)Te_(5) thin film,the detection of X-ray photoelectron spectra proves that its chemical components ratio is consistent with 4∶5.Its chemical property can remain very stable as it is placed at atmospheric environment for one month.Based on the measurement of magnetiza-tion dependence on temperature,we find thatan obvious paramagnetic-ferromagnetic phase transition occurs at 198 K and 257 K,respectively for CrTe_(2) and Cr_(4)Te_(5) films.We also proved that the film conductivity exhibited a metallic electronic transport at the temperature range of 5~320 K by the measurement of resistance dependence on temperature.The study of electrical conductivity mechanism shows that electron-electron scattering and electron-magnet on scattering respectively play an important role in conductivity above and below the Curie point.Based on these unique properties,we believe that Cr_(x)Te_(y) will play a key role in the ongoing development of aerospace field for the electromagnetic shielding.