TiO2和SiO2薄膜应力的产生机理及实验探索

对最常用的TiO₂和SiO₂薄膜应力, 包括应力模型、应力测试方法和不同实验条件下的应力测试结果作了研究.基于曲率法模型，对TiO₂和SiO₂单层膜和多层膜进行了实验测试，得到了一些有价值的结果，特别是离子辅助淀积和基板温度等工艺参数对薄膜应力的影响.提出了薄膜聚集密度是应力的重要因素，低聚集密度产生张应力，而高聚集密度产生压应力.在多层膜中通过调节工艺参数，适当地控制张应力或压应力，可使累积应力趋向于零. 关键词： 薄膜应力 离子辅助淀积 聚集密度     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO2玻璃衬底上用脉冲激光沉积(PLD)技术,分别沉积Ti和Ti/Al膜,经电化学阳极氧化成功制备了多孔TiO2/SiO2和TiO2/Al/SiO2纳米复合结构.其中TiO2薄膜上的微孔阵列高度有序,分布均匀.实验研究了Al过渡层对多孔 TiO2薄膜光吸收特性的影响.结果表明:无Al过渡层的多孔 TiO2薄膜其紫外吸收峰在270 nm处.且峰强不随阳极氧化工艺参数调节;而有Al过渡层的多孔TiO2薄膜其紫外吸收峰红移至293 nm处,峰强和峰形不仅受阳极氧化电压调节而且受Al过渡层厚度的影响也很敏感.进一步分析了两种结构在吸收边附近的光跃迁特性.这些结果对基于多孔 TiO2的光伏电池和紫外光传感器的应用研究非常有益.     

ZrO2/SiO2多层膜中膜厚组合周期数及基底材料对残余应力的影响

ZrO2/SiO2多层膜由相同沉积条件下的电子束蒸发方法制备而成,通过改变多层膜中高(ZrO2)、低(SiO2)折射率材料膜厚组合周期数的方法,研究了沉积在熔石英和BK7玻璃基底上多层膜中残余应力的变化.用ZYGO光学干涉仪测量了基底镀膜前后曲率半径的变化,并确定了薄膜中的残余应力.结果发现,该多层膜中的残余应力为压应力,随着薄膜中膜厚组合周期数的增加,压应力值逐渐减小.而且在相同条件下,石英基底上所沉积多层膜中的压应力值要小于BK7玻璃基底上所沉积多层膜中的压应力值.用x射线衍射技术测量分析了膜厚组合周期数不同的ZrO2/SiO2多层膜微结构,发现随着周期数增加,多层膜的结晶程度增强.同时多层膜的微结构应变表现出了与所测应力不一致的变化趋势,这主要是由多层膜中,膜层界面之间复杂的相互作用引起的.     

退火温度对Ta_2O_5/SiO_2多层反射膜结构和应力特性的影响

介质膜反射镜是星载激光测高仪系统中不可缺少的薄膜元件,其面形质量直接影响探测系统测距的分辨率和精度.本文采用离子束辅助电子束蒸发工艺在石英基底上沉积Ta_2O_5/SiO_2多层反射膜,并在200—600℃的空气中做退火处理.通过X射线衍射、原子力显微镜、分光光度计及激光干涉仪等测试手段,系统研究了退火温度对Ta_2O_5/SiO_2多层反射膜结构、光学性能以及应力特性的影响.结果表明:Ta_2O_5/SiO_2多层反射膜退火后,膜层结构保持稳定,膜层表面粗糙度得到有效改善;反射膜在500—600℃退火后,残余应力由压应力向张应力转变;采用合适的退火温度可以有效释放Ta_2O_5/SiO_2薄膜的残余应力,使薄膜与基底构成的介质膜反射镜具有较好的面形精度.本文的实验结果对退火工艺在介质膜反射镜面形控制技术方面的应用具有重要意义.     

Si/SiO2多层膜的Ⅰ-Ⅴ特性研究

用射频磁控溅射法制备了Si/SiO2多层膜,并对多层膜的Ⅰ-Ⅴ特性实验结果进行了拟合.分析表明,Si/SiO2多层膜的Ⅰ-Ⅴ特性由多种因素决定,单一的电流输运模型不能控制Si/SiO2多层膜的Ⅰ-Ⅴ特性,多层膜结构及氧化硅层的厚度是影响薄膜Ⅰ-Ⅴ特性的主要因素.     

溶胶-凝胶ZrO_2/SiO_2薄膜的激光损伤研究

采用溶胶-凝胶工艺分别制备了SiO2和ZrO2单层薄膜、ZrO2/SiO2双层膜以及ZrO2/SiO2多层高反膜。用输出波长为1064nm、脉宽为6.3ns的YAG激光器对薄膜进行了激光损伤实验。观察了薄膜经强激光辐照后的损伤情况,讨论了薄膜的激光损伤行为,并从理论上分析了产生这些损伤的原因,为进一步镀制高质量的ZrO2/SiO2多层高反膜提供了依据。     

Si／SiO2多层膜的I-V特性研究

用射频磁控溅射法制备了Si／SiO2多层膜,并对多层膜的FV特性实验结果进行了拟合．分析表明,Si／SiO2多层膜的I-V特性由多种因素决定。单一的电流输运模型不能控制Si／SiO2多层膜的I-V特性,多层膜结构及氧化硅层的厚度是影响薄膜I-V特性的主要因素．     

自适应模拟退火遗传算法在薄膜厚度及光学常数反演中的应用

准确的测量薄膜的厚度和光学常数,在薄膜的制备、研究和应用中都是十分重要的。借助Cauchy色散模型,通过薄膜透过率测量曲线,用改进的自适应模拟退火遗传算法对透过率曲线进行全光谱拟合,从而反演得到薄膜的厚度和光学常数。对由电子束蒸发制备的TiO2单层膜和SiO2/TiO2双层膜的厚度和光学常数进行了测量计算。实验结果表明,计算得到的光学参数与实测结果相一致,厚度误差小于2nm,在560nm波长处折射率误差小于0.03。     

双离子束溅射中红外SiO2薄膜热稳定性研究

通过双离子束溅射方法在蓝宝石、硅衬底上制备了单层SiO2薄膜,分析了SiO2薄膜残余应力、表面形貌、微观结构以及光学性能(可见-近红外0.4~1.2 μm和中红外3~5 μm波段)在400 ℃~1 000 ℃温度范围内的演化规律.研究结果表明:在400 ℃附近,SiO2薄膜残余应力存在局部极小值;SiO2薄膜光学性能的演化与膜层表面质量、内部残余应力及微观结构变化密切相关;经1 000 ℃高温处理后,蓝宝石窗口表面SiO2薄膜红外透射性能仍能保持很好的稳定性,且膜层表面没有出现显著的气泡、开裂等损伤形貌.该研究结果可为恶劣环境下光学窗口头罩表面薄膜系统的设计提供指导.     

磁控溅射制备的W,WSi2,Si单层膜和W/Si,WSi2/Si多层膜应力

采用直流磁控溅射技术制备了厚度约100 nm的W,WSi2,Si单层膜和周期约为20 nm,Si膜层厚度与周期的比值为0.5的W/Si,WSi2/Si周期多层膜.利用台阶仪对镀膜前后基底表面的面形进行了测试,计算并比较了不同膜系的应力值.结果表明:W单层膜表现出较大的压应力,而W/Si周期膜则表现为张应力.WSi2单层...     

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.     

Photoemission of LaI2 and CeI2

The electronic structure of the layered compounds LaI₂ and CeI₂ was investigated by photoemission and electron energy loss spectroscopy. From the experimental results we are able to confirm the metallic nature of these compounds, and by using photon energy dependent measurements of the valence band we can identify the orbital character of the conduction band as essentially 5d¹-like. A detailed analysis of the Ce 3d and 4f spectra yields a remarkably small 4f-5d hybridization strength, almost completely decoupling the f-electron from the conduction band, which makes CeI₂ a somewhat unusual system compared to other metallic Ce compounds. Band structure calculations by Jepsen and Andersen [1] confirm these experimental results.     

Photoconversion of 2-amino- and 2-oxyanthraquinone

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 594–600, October, 1991.     

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.     

X-ray photoemission spectra measurements of CeNi2Sb2 and CeCu2Sb2

X-ray photoemission spectra, resistivity and susceptibility of CeNi₂Sb₂ and CeCu₂Sb₂ were measured and are discussed. The results indicate that these alloys are Kondo systems. For comparison of the valence band properties, the spectra of the isostructural alloys of RT₂X₂-type with R = La, Gd, T = Cu, Ni and X = Sn, Sb were investigated, too.     

Vitrification of and optical and photoelectrical properties of AgAsS2, AgSbS2, and AgBiS2

A study is made concerning the photoconductivity, the edge absorption, and the far-infrared spectra of AgAsS₂, AgSbS₂, AgBiS₂ crystals and glasses. The oscillation spectrum of monoclinic smithite (AgAsS₂) and miargyrite (AgSbS₂) is explained here by the presence of As-S, Sb-S, and Ag-S bonds. The rank of symmetry and the degree of bond metallization, which both increase in the order AgAsS₂ AgSbS₂ AgBiS₂, cause the structure of the far-infrared spectra to become simpler and the tendency vitrification to become weaker in the same order.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 39–45, March, 1976.     

Optical properties of 1T and 2H phase of TaS2 and TaSe2

We have calculated the anisotropic frequency dependent dielectric function for the 1T and 2H phases of TaS₂ and TaSe₂ using the linear muffin tin orbital method within the atomic sphere approximation. We find significant anisotropy in the frequency dependent dielectric function for the 1T and 2H phases at low energies (less than 4 eV). Unfortunately there are no experimental data to compare with. The averaged dielectric function agrees with the available experimental data except that the calculated peak heights are underestimated and shifted to higher energies by 1–2eV.     

Synthesis and properties of HgI2 intercalation of Bi2Sr2CaCu2Oy superconductor

Polycrystalline or single crystals of HgI₂ intercalated Bi₂Sr₂CaCu₂O_y (Bi2212) have been synthesized and their properties have been studied together with those of HgBr₂ intercalates. Single crystals of HgI₂ intercalated Bi2212 were synthesized by a stepwise intercalation method using iodine intercalate as a secondary host material. These could not be obtained through direct intercalation methods by which polycrystalline sample were obtained. From ac susceptibility and resistivity measurements, superconducting onset temperature (T_con) for polycrystalline HgI₂ intercalate was found to be 82 K which was higher than that of the host (75 K). On the other hand, T_con for single crystal HgI₂ intercalate was shown to be 79–80 K which is lower than that of host (95–97 K). The effect of HgI₂ or HgBr₂ intercalation on T_c tried discussion from the view point of hole doping and interblock coupling effect.