沉积速率对热舟蒸发LaF3薄膜性能的影响

用热舟蒸发方法在不同的沉积速率下制备了LaF3单层膜,并对部分单层膜进行了真空退火.分别采用X射线衍射(XRD),Lambda 900光谱仪和355 nm Nd∶YAG脉冲激光测试了薄膜的晶体结构、透射光谱和激光损伤阈值(LIDT),并通过透射光谱计算得到样品的折射率和消光系数.实验结果表明,增大沉积速率有利于LaF3薄膜的结晶和择优生长,可以提高薄膜的致密性和折射率,但薄膜的抗激光损伤能力有所下降;沉积速率太大,又会恶化薄膜的结晶性能,同时薄膜中产生大量孔洞,薄膜的机械强度降低,导致薄膜的折射率减小和抗激光损伤能力降低.真空退火对薄膜的抗激光损伤能力有不同程度的提高.

Deposition Rate''''s Effects on Properties of LaF3 Films Prepared by Thermal Boat Evaporation

LaF3 single-layer coatings were prepared by thermal boat evaporation at different deposition rates. Some of these films were annealed in vacuum. X-ray diffraction (XRD), Lambda 900 spectrophotometer and 355 nm Nd∶YAG laser system were employed to measure crystal structure, transmittance spectra and laser-induced damage threshold (LIDT) of the samples. Moreover, refractive index and extinction coefficient were obtained from the measured transmittance spectra. The results show that the crystallization and the preferential growth are benefited from the increase of the deposition rate, moreover, the refractive index is increased and the film gets more compact. But the defect makes the LIDT of the coating decline. In the other hand, the crystallization status will worsen if the deposition rate is too high. Meanwhile, a lot of pores appear in the film and the mechanical intensity of the film is deteriorated. Consequently, the refractive index and the LIDT are decreased. The LIDTs of the films after annealing are increased with different degree.