退火对电子束热蒸发193nm Al2O3/MgF2反射膜性能的影响

设计并镀制了193nm Al₂O₃/MgF₂反射膜，对它们在空气中分别进行了250—400℃的高温退火，测量了样品的透射率光谱曲线和绝对反射率光谱曲线.发现样品在高反射区的总的光学损耗随退火温度的升高而下降，而后趋于饱和.采用总积分散射的方法对样品在不同退火温度下的散射损耗进行了分析，发现随着退火温度的升高散射损耗有所增加.因此，总的光学损耗的下降是由于吸收损耗而不是散射损耗起主导作用.对Al₂O₃材料的单层膜进行了同等条件的退火处理，由它们光学性能的变化推导出它们的折射率和消光系数的变化，从而解释了相应的多层膜光学性能变化的原因.反射膜的反射率在优化联系、镀膜工艺与退火工艺的基础上达98％以上. 关键词： 193nm 反射膜 退火 光学损耗 吸收     

退火对电子束热蒸发Al2O3薄膜性能影响的实验研究

 用电子束热蒸发方法镀制了Al₂O₃材料的单层膜,对它们在空气中进行了250~400 ℃的高温退火。对样品的透射率光谱曲线进行了测量,计算了样品的消光系数、折射率和截止波长。通过X射线衍射仪（XRD）测量分析了薄膜的微观结构,采用表面轮廓仪测量了样品的表面均方根粗糙度。结果发现随着退火温度的提高光学损耗下降,薄膜结构在退火温度为400 ℃时仍然为无定形态,样品的表面粗糙度随退火温度的升高而增加。引起光学损耗下降起主导作用的是吸收而不是散射,吸收损耗的下降主要是由于退火使材料吸收空气中的氧而进一步氧化,从而使薄膜材料的非化学计量比趋于正常。     

沉积温度对热舟蒸发MgF2薄膜性能的影响

 采用热舟蒸发方法沉积了氟化镁(MgF₂)材料的单层膜,沉积温度从200 ℃上升到350 ℃,间隔为50 ℃。测量了样品的透射率和反射率光谱曲线,进行了表面粗糙度的标定,并在此基础上进行了光学损耗及散射损耗的计算。同时对355 nm波长处的激光诱导损伤阈值进行了测量。结果表明:随着沉积温度的升高,光学损耗增加;在短波长范围散射损耗在光学损耗中所占比例很小,光学损耗的增加主要由吸收损耗引起;在355 nm波长处的损伤阈值变化与吸收损耗的变化趋势相关,损伤机制主要是吸收起主导作用。样品的微缺陷密度也是影响损伤阈值的一个重要因素,损伤阈值随缺陷密度的增加而降低。     

121.6 nm远紫外高反射薄膜研究

远紫外波段高反射薄膜的研究具有重要应用价值。为了实现高反射率,采用高温三步蒸发法沉积MgF_2膜以保护Al膜,制备了远紫外宽带高反射薄膜,并对样品进行退火处理。结果显示,改进制备工艺和退火工艺后,紫外宽带高反射薄膜在121.6 nm处的反射率高达90%,接近理论设计值。同时分析了散射损耗的影响。采用优化的LaF_3/MgF_2膜系结构,制备了窄带反射滤光薄膜,其在中心波长122.5 nm处的峰值反射率为75%且半峰全宽为8 nm,达到了理论设计的预期效果,但退火处理损伤了薄膜表面,散射损耗增加,薄膜反射率下降。     

热舟蒸发LaF3薄膜的紫外性能研究

研究了沉积温度对热舟蒸发氟化镧薄膜结构和光学性能的影响,沉积温度从200℃上升到350℃.间隔为50℃.采用分光光度计测量了样品的透射率和反射率光谱曲线,并在此基础上进行了光学损耗、光学常数以及带隙和截止波长的计算.采用表面轮廓仪进行了表面形貌和表面粗糙度的标定,采用X射线衍射(XRD)方法测量了不同沉积温度下样品的微结构.发现在短波长波段,随着沉积温度的升高,光学损耗增加,晶粒尺寸增大,表面粗糙度略有增加.不过散射损耗在光学损耗中所占比例均很小,光学损耗的增加主要由吸收损耗引起.随着沉积温度的升高,折射率与消光系数增大,带隙变小,相对应的截止波长向长波方向移动.     

热舟蒸发LaF3薄膜的紫外性能研究

研究了沉积温度对热舟蒸发氟化镧薄膜结构和光学性能的影响,沉积温度从200℃上升到350℃,间隔为50℃.采用分光光度计测量了样品的透射率和反射率光谱曲线,并在此基础上进行了光学损耗、光学常数以及带隙和截止波长的计算.采用表面轮廓仪进行了表面形貌和表面粗糙度的标定,采用X射线衍射(XRD)方法测量了不同沉积温度下样品的微结构.发现在短波长波段,随着沉积温度的升高,光学损耗增加,晶粒尺寸增大,表面粗糙度略有增加.不过散射损耗在光学损耗中所占比例均很小,光学损耗的增加主要由吸收损耗引起.随着沉积温度的升高,折射 关键词： 光学薄膜 沉积温度 3')" href="#">LaF₃ 光学损耗     

退火温度对溅射铝膜结构与电性能的影响

 采用直流磁控溅射方法成功地制备了Al膜,研究了退火温度对Al膜表面形貌、晶体结构、应力、择优取向及反射率的影响。研究表明：不同退火温度的薄膜晶粒排布致密而光滑,均方根粗糙度小。XRD测试表明：不同温度退火的铝膜均成多晶状态,晶体结构为面心立方,退火温度升高到400 ℃时,Al膜的应力最小达0.78 GPa,薄膜平均晶粒尺寸由18.3 nm增加到25.9 nm;随着退火温度的升高,(200)晶面择优取向特性变好。薄膜紫外-红外反射率随着退火温度的升高而增大。     

缓冲层对LBO晶体上1 064 nm|532 nm二倍频增透膜的激光损伤阈值的影响

采用电子束蒸发方法在LBO晶体上制备了无缓冲层和具有不同缓冲层的1 064 nm,532 nm二倍频增透膜.利用Lambda900分光光度计和调Q脉冲激光装置对样品的光学性能和抗激光损伤性能进行了测试分析.结果表明,所有样品在1 064 nm和532 nm波长的剩余反射率都分别小于0.1％和0.2％.与无缓冲层样品相比,采用SiO2和MgF2缓冲层薄膜的激光损伤阈值分别提高了23.1％和25.8％,而Al2O3缓冲层的插入却导致薄膜的激光损伤阈值降低.通过观察薄膜的激光损伤形貌,分析破斑的深度信息和电场分布,表明LBO晶体上1 064 nm,532 nm二倍频增透膜的激光损伤破坏主要表现为膜层剥落,激光产生的热冲击应力使薄膜应力发生很大变化,超过膜层之间的结合而引起膜层之间的分离.采用SiO2或MgF2缓冲层可改进Al2O3膜层的质量,从而有利于提高薄膜的激光损伤阈值.     

低温退火的X射线W/Si多层膜应力和结构性能

W/Si多层膜反射镜在硬X射线天文望远镜中有重要应用. 为减小其应力对反射镜面形和望远镜分辨率的影响, 同时保证较高的反射率, 采用150, 175和200 ℃ 的低温退火工艺对采用磁控溅射镀制的W/Si周期多层膜进行后处理. 利用掠入射X射线反射测试和样品表面面形测试对退火前后W/Si多层膜的应力和结构进行表征. 结果表明, 在150 ℃ 退火3 h 后, 多层膜1级峰反射率和膜层结构几乎没有发生变化, 应力减少约27%; 在175 ℃ 退火3 h后, 多层膜膜层结构开始发生变化, 应力减少约50%; 在200 ℃退火3 h 后, 多层膜应力减小超过60%, 但1级布拉格峰反射率相对下降17%, 且膜层结构发生了较大变化. W, Si界面层的增大和相互扩散加剧是应力和反射率下降的主要原因.     

缓冲层对LBO晶体上1 064 nm,532 nm二倍频增透膜的激光损伤阈值的影响

采用电子束蒸发方法在LBO晶体上制备了无缓冲层和具有不同缓冲层的1 064 nm,532 nm二倍频增透膜.利用Lambda900分光光度计和调Q脉冲激光装置对样品的光学性能和抗激光损伤性能进行了测试分析.结果表明,所有样品在1 064 nm和532 nm波长的剩余反射率都分别小于0.1%和0.2%.与无缓冲层样品相比,采用SiO2和MgF2缓冲层薄膜的激光损伤阈值分别提高了23.1%和25.8%,而Al2O3缓冲层的插入却导致薄膜的激光损伤阈值降低.通过观察薄膜的激光损伤形貌,分析破斑的深度信息和电场分布,表明LBO晶体上1 064 nm,532 nm二倍频增透膜的激光损伤破坏主要表现为膜层剥落,激光产生的热冲击应力使薄膜应力发生很大变化,超过膜层之间的结合而引起膜层之间的分离.采用SiO2或MgF2缓冲层可改进Al2O3膜层的质量,从而有利于提高薄膜的激光损伤阈值.     

Magnetic ordering in HoRu2Si2, HoRh2Si2, TbRh2Si2 and TbIr2Si2 by neutron diffraction

Neutron diffraction study of polycrystalline HoRu₂Si₂, HoRh₂Si₂, TbRh₂Si₂, and TbIr₂Si₂ was performed in the temperature range between 4.2 and 300 K. For HoRu₂Si₂ the magnetic spin alignment of a linear transverse wave mode below the Néel temperature 19 K is observed. This static moment wave is propagating along the b-axis with k=(0, 0.2, 0) and is polarized in the c-axis. The root-mean-square and maximum saturation moments per Ho atom are 9.26 and 13.09μ_B, respectively. HoRh₂Si₂, TbRh₂Si₂ an TbIr₂Si₂ are simple collinear antiferromagnets of +-+- type with Néel temperatures of (27±1), (98±2) and (72±3) K, respectively. For TbRh₂Si₂ and TbIr₂Si₂ magnetic moments are localized on RE ions only and are aligned along the tetragonal axis, while for HoRh₂Si₂ they form an angle ø = (28±3)°.     

μ+SR study of LaNi2As2, URh2Si2 and CeRh2Si2

Muon spin relaxation experiments have been carried out in the paramagnetic and magnetically ordered states of URh₂Si₂ and CeRh₂Si₂. As the magnetic structure of these compounds is well known, these measurements can help to characterise their magnetic properties probed by μSR and to understand the μSR results of the heavy fermion compounds of the same crystallographic family. Our measurements show that the muons occupy two different crystallographic sites. The spectra of URh₂Si₂ and CeRh₂Si₂ in the magnetically ordered states are very different, probably reflecting their different magnetic structures. The spectra obtained on CeRh₂Si₂ are similar to the published spectra of the heavy fermion compound CeCu_2.1 Si₂. Muon spin rotation measurements on LaNi₂As₂ indicate that the muon is diffusing at 150 K.     

13C-selective IRMPD of CBr2F2/Cl2 and CCl2F2/Br2 systems

The CO₂ TEA laser irradiation of CBr₂F₂ in the presence of Cl₂ yielded ¹³C-enriched CBrClF₂ and ¹³C-enriched CCl₂F₂ under selected experimental conditions. As the photolysis proceeded, the ¹³C concentration of CBrClF₂ decreased gradually and that of CCl₂F₂ increased up to 90% or higher. These results can be explained by the mechanism involving the secondary ¹³C-selective IRMPD of the primary product CBrClF₂. On the other hand, the carbon-containing product for a CCl₂F₂/Br₂ system was only CBrClF₂; the further IRMPD of which probably regenerated CBrClF₂ in the presence of Br₂. The decomposition probabilities of ¹²C- and ¹³C-containing molecules in both systems were measured as functions of laser line, laser fluence, and reactant pressures.     

Polar optic phonons in Hg2Cl2 and Hg2Br2

Far infrared (30–430 cm^?1) reflectivity measurements of Hg₂Cl₂ and Hg₂Br₂ single crystals have been performed in polarized light. The spectra, which are in agreement with group-theoretical predictions, were analyzed by the oscillator fitting procedure and Kramers-Kronig method. The results are compared with the existing data from other measurements and the large anisotropy of polar modes is briefly discussed. The polarization vectors of all long-wavelength symmetry modes were determined group-theoretically.     

Magnetostriction of SmMn2Ge2 and GdMn2Ge2 intermetallic compounds

Longitudinal and transverse magnetostrictions of polycrystalline samples of intermetallic compounds RMn₂Ge₂ (R=Sm or Gd) are measured in pulsed magnetic fields up to 250 kOe. It is found that linear magnetostrictive strains of about 10^?3 arise in a temperature range in which the magnetic field causes a change in the magnetic state of a manganese magnetic subsystem. The results obtained are described within the model of a two-sublattice ferrimagnet with a negative exchange interaction in the manganese subsystem in terms of a strong dependence of this interaction on interatomic distances.     

Superconductivity in LaPd_2Bi_2 with CaBe_2Ge_2-type structure

正Since the discovery of superconductivity in LaFeAsO_(1-x)F_x,the high-T_c iron-based superconductors have been extensively studied from both experimental and theoretical viewpoints [1-8]. However, the mechanism of the unconventional superconductivity is still to be resolved. To     

Structural,magnetic and neutron diffraction studies on TbFe2-TbAl2, TbCo2-TbAl2 and HoCo2-HoAl2

Both pseudobinary systems exhibit large homogeneous regions of cubic and hexagonal Laves phases. Ordering tendencies on crystallographic sites between Al and the transition metals are observed in the hexagonal type.Electron transfer to the transition metals quenches their moments so that they become nonmagnetic at high Al concentrations. The peculiarities in the mechanism of magnetization which appear in rare earth dialuminides when Al is replaced by a transition metal have been studied in detail at cryogenic temperatures.The first replacement of Al results in a decrease in saturation moment. Neutron diffraction verifies the low ordered rare earth sublattice moments and reveals the ‘lost part’ as a disordered component. Considerable magnetic hardness develops in certain regions of concentration often connected with spontaneous increases in magnetization with field. All available evidence suggests the presence of unusual domain wall effects to be responsible for this effect. High remanences develop in both the hexagonal and in the cubic structures in the intermediate region. The development of disordered magnetic components is connected either with the disorder on crystallographic sites or changes in the free electron concentration.