沉积温度对LaF3薄膜性能的影响

 在189，255，277和321 ℃的沉积温度下用热舟蒸发方法制备了LaF₃薄膜。通过X射线衍射(XRD)测试了薄膜的晶体结构;采用分光光度计测量了薄膜的透射光谱，并计算得到样品的折射率、消光系数和截止波长;利用光学干涉仪测试得到了薄膜的残余应力;采用三倍频Nd:YAG脉冲激光测试了薄膜的激光损伤阈值。结果表明：随沉积温度的提高，LaF₃薄膜的结晶状况明显变好，晶粒尺寸逐渐变大；膜层变得更加致密，折射率变大，然而薄膜吸收变得严重，截止波段向长波漂移，同时薄膜的残余应力也增加，内应力在薄膜的残余应力中起着决定作用；薄膜的激光损伤阈值在高温制备时相对较高。     

532 nm激光辐照下ZnSe薄膜光学特性研究

采用电子束热蒸发技术制备了ZnSe薄膜,研究了532 nm波长的不同能量(2.0 mJ、2.5 mJ、3.0 mJ)、不同脉冲数(3、10、15)激光诱导前后,ZnSe薄膜的透射率、折射率、消光系数、损伤阈值(LIDT)的变迁。研究结果显示,在能量为2.0 mJ激光辐照后,ZnSe薄膜折射率提高,透射率下降。相比较能量为2.5 mJ、3.0 mJ激光辐照,在能量为2.0 mJ激光辐照后折射率提高最明显,由2.489 4提高到2.501 6。薄膜损伤阈值从0.99 J/cm2提高到1.39 J/cm2(10脉冲辐照);薄膜的损伤经过了无损伤到严重损伤突变的损伤演变过程。采用原子力显微镜对预处理后薄膜表面粗糙度进行检测,发现激光预处理后的薄膜表面粗糙度Ra有所下降,从0.563 nm降低到0.490 nm(15脉冲激光辐照)。     

PECVD技术制备单层光学薄膜抗激光损伤特性研究

采用PECVD技术在BK7玻璃基底上沉积了不同厚度的单层SiO2（折射率为1.46）和SiNx（折射率为1.84）光学薄膜,并对这2种膜层进行抗激光损伤阈值（LIDT）测试,分析讨论了PECVD技术制备的单层光学薄膜与抗激光损伤特性之间的关系。实验结果表明:PECVD技术制备的单层SiO2薄膜有较高的LIDT,薄膜光学厚度在o/4~o/2之间时,在光学厚度为350 nm时,LIDT有最小值21.7 J/cm2,光学厚度为433 nm时,LIDT有最大值27.9 J/cm2。SiNx薄膜的LIDT随着光学厚度增加而减小,在光学厚度为o/4时,LIDT有最大值29.3 J/cm2,光学厚度为o/2时,LIDT有最小值4.9 J/cm2。     

不同衬底温度下PLD法制备的氧化锌薄膜的特性

利用GCR-170型脉冲激光器Nd:YAG的三次谐波(355nm),以蓝宝石Al2O3(0001)为衬底,在不同温度下采用脉冲激光沉积法制备了ZnO薄膜.通过原子力显微镜、Raman谱、光致发光谱、红外透射谱、霍尔效应和表面粗糙度分析仪对制备的ZnO薄膜进行了测试.分析了在不同衬底温度下薄膜的表面形貌、光学特性,同时进行了薄膜结构和厚度的测试.研究表明:衬底温度对ZnO薄膜的表面形貌、光学特性、结构特性都是重要的工艺参量,尤其在500℃时沉积的ZnO薄膜致密均匀,并表现出较强的紫外发射峰.     

辐照激光能量对SiO2薄膜特性及结构的影响

 为了认识SiO2薄膜在激光辐照下的变化,本文以K9玻璃为基底,采用电子束热蒸发方法制备了SiO2薄膜,并将此组在相同实验条件下制备的薄膜加以不同能量的激光辐照,研究在激光辐照前后样片的透射率、折射率、消光系数、膜厚、表面形貌及激光损伤阈值（LIDT）的变化。结果表明,样片膜厚随激光能量的增加而减小,辐照激光能改善薄膜表面形貌,并使样片LIDT值提高,最终能使样片的LIDT值从16.96 J/cm2提高至18.8 J/cm2。     

射频磁控反应溅射制备的Ag2O薄膜的椭圆偏振光谱研究

Ag₂O薄膜在新型超高存储密度光盘和磁光盘方面具有潜在的应用前景.利用射频磁控反应溅射技术, 通过调节衬底温度在沉积气压为0.2 Pa、氧氩比为2:3的条件下制备了一系列Ag₂O 薄膜.利用通用振子模型(包括1个Tauc-Lorentz振子和2个Lorentz 振子)拟合了薄膜的椭圆偏振光谱.在1.5-3.5 eV能量区间,薄膜的折射率在2.2-2.7之间, 消光系数在0.3-0.9之间. 在3.5-4.5 eV能量区间,薄膜呈现了明显的反常色散,揭示Ag₂O薄膜的等离子体振荡频率在 3.5-4.5 eV之间. 随着衬底温度的升高,薄膜的光学吸收边总体上发生了红移, 该红移归结于薄膜晶格微观应变随衬底温度的升高而增大. Ag₂O薄膜的光学常数表现出典型的介质材料特性.     

基片温度对PLD制备ZnO薄膜光学常数的影响

光谱椭偏仪被用来研究用脉冲激光沉积方法在Si(100)基片上,温度分别为400,500,600,700 ℃制备的ZnO薄膜的特性。利用三层Cauchy散射模型拟合椭偏参数,计算了每个温度下制备的ZnO薄膜在400~800 nm波长范围内的折射率(n)和消光系数(k)。发现基片温度对光学常数有很大的影响。通过分析XRD表征的晶体结构和 AFM表征的薄膜表面形貌,发现折射率的变化归因于薄膜堆积密度的变化。为了获得具有较好的光学和薄膜质量的ZnO薄膜,相比与其他沉积温度600 ℃或许是最佳的沉积温度。     

溶胶-凝胶法MgF2紫外增透膜的制备和性能研究

 采用溶胶-凝胶法,以醋酸镁和氟化氢为原料,以甲醇为溶剂制备了MgF₂溶胶,利用浸渍提拉法在洁净石英基片上镀膜,考察了反应温度对溶胶微结构、薄膜结构和性能的影响。样品采用激光动态光散射、透射电镜、X射线粉体衍射仪、紫外-可见光谱仪、原子力显微镜进行表征。结果表明：通过该方法制备的表面平整的低折射率MgF₂薄膜,在紫外区具有很好的增透性能,同时在紫外波长355 nm激光的辐照下（脉宽6 ns）,薄膜具有较高的抗激光损伤性能,激光损伤阈值达10.85 J·cm^-2。     

氧分压对ZrO2薄膜激光损伤阈值的影响

 在不同的氧分压下用电子束热蒸发的方法制备了ZrO₂薄膜。分别通过X射线衍射、光学光谱、热透镜技术、抗激光辐照等测试，对所制备样品的微结构、折射率、吸收率及激光损伤阈值进行了测量。实验结果表明，薄膜中晶粒主要是四方相为主的多晶结构，并且随着氧分压的增加，结晶度、折射率以及弱吸收均逐渐降低。薄膜的激光损伤阈值开始随着氧分压增加从18.5J/cm²逐渐增加，氧分压为9×10^-3Pa时达到最大，值为26.7 J/cm²，氧分压再增加时则又降低到17.5 J/cm²。由此可见，氧分压引起的薄膜微结构变化是ZrO₂薄膜激光损伤阈值变化的主要原因。     

溶胶-凝胶法制备高折射率TiO2薄膜

 采用溶胶- 凝胶法制备了TiO₂纳米晶溶胶,并以旋涂法（spin-coating）镀制了高折射率光学薄膜。借助光散射技术和透射电镜研究了溶胶的微结构。采用原子力显微镜、场发射扫描电镜、紫外-可见-近红外光谱仪、椭偏仪、漫反射吸收光谱及强激光辐照实验,对膜层的结构、光学性能及抗激光损伤性能进行了系统的表征。结果显示:纳米晶薄膜的折射率达到了1.9,而传统的溶胶-凝胶薄膜折射率只有1.6;同时纳米晶薄膜的抗激光损伤阈值与传统的溶胶-凝胶薄膜相差不大,在1 064 nm处分别为16.3 J/cm²(3 ns脉冲) 和16.6 J/cm²(3 ns脉冲);纳米晶溶胶薄膜可以在保持较高抗激光损伤阈值情况下,大幅度提高薄膜折射率。     

Sc2O3替代层在532 nm高反膜中的应用

 将Sc₂O₃替代层引入到532 nm高反膜(HfO2/SiO2)n中,利用Sc₂O₃在盐酸中具有较好的溶解性这个特点,把膜层与基片脱离,以方便基片返修,缩短返修周期,降低成本。能量色散谱元素测试表明,脱离后Sc元素残留率为0。用Lamada900分光光度计、WykoNT1100轮廓仪和ZYGO干涉仪分别表征了替代层引入对高反膜的光谱、表面粗糙度和应力的影响,并测试了膜系在532 nm的激光损伤阈值的变化,结果表明Sc₂O₃替代层的引入对高反膜的性能几乎没有负面影响。     

Luminescence of Donor‐Acceptor Pairs in Compounds of Yttrium and Scandium Oxides

The luminescence spectra of Sc₂O₃, Y₂O₃, and Y₂GeO₅ ceramics and thin films exposed to laser and cathode excitation were investigated. The investigation of the properties of longwave luminescence bands in Sc₂O₃ with maxima at 2.65, 2.35, and 2.05 eV, in Y₂O₃ with maxima at 2.60, 2.35, and 2.10 eV, and also in Y₂GeO₅ with maxima at 2.55, 2.25, and 2.00 eV point to the fact that they are caused by radiative recombination of the excited donoracceptor pairs Sc³⁺ (or Y³⁺)O^2–.     

Spectroscopic characterization of Yb:Sc2O3 transparent ceramics

Yb：Sc2O3 transparent ceramics are fabricated by a conventional ceramic process and sintering in H2 atmosphere. The room-temperature spectroscopic properties are investigated, and the Raman spectrum shows an obvious vibration characteristic band centred at 415 cm-1. There are three broad absorption bands around 891, 937, and 971 nm, respectively. The strongest emission peak is centred at 1.04 μm with a broad bandwidth （11 nm） and an emission cross-section of 1.8×10^-20 cm^2. The gain coefficient implies a possible laser ability in a range from 990 nm to 1425 nm. The energy-level structure shows that Yb：Sc2O3 ceramics have large Stark splitting at the ground state level due to their strong crystal field. All the results show that Yb：Sc2O3 transparent ceramics are a promising material for short pulse lasers.     

Optical and scintillation properties of Sc2O3, Y2O3 and Lu2O3 transparent ceramics synthesized by SPS method

Sc₂O₃, Y₂O₃ and Lu₂O₃ transparent ceramics were prepared by the spark plasma sintering (SPS) method. After polishing, the samples were semitransparent. Their optical transmittance was 10–40% at 500 nm which corresponded with their semi-transparency. In the X-ray induced emission spectra, a broad emission peak appeared around 335 nm in each sample. For this wavelength, scintillation decay time for Y₂O₃ and Sc₂O₃ were 22 and 48 ns, respectively. The light yield of Sc₂O₃, Y₂O₃ and Lu₂O₃ was 16,200, 2600, and 200 ph/5.5 MeV-alpha, respectively, which followed from the alpha-ray induced pulse height spectra. The gamma-ray induced light yield of Sc₂O₃ was 11,500 ph/MeV, which is 1.4 times larger than that of conventional single crystal BGO (Bi₄Ge₃O₁₂) scintillator. Light yield non-proportionality and energy resolution of Sc₂O₃ were examined for the first time.     

Enhanced magneto-optical Kerr effects in nanocrystalline Sc-doped CoFe2O4 thin films

Nanocrystalline CoFe_2−xSc_xO₄ (x=0-0.4) thin films were prepared on silicon substrates at reduced temperature by a sol-gel process, and the doping effects of scandium on the microstructure, magnetism and polar magneto-optical Kerr effects of the as-deposited films were examined. It was shown that the intensities of both of the Kerr rotation peaks increase with the doping content x of Sc³⁺. The increase for the peak at 540 nm is due to the decrease of the electrostatic polarization of O²⁻ resulting from the relatively large radius of Sc³⁺, and that for the peak at 620 nm was a result of the migration of Co²⁺ from octahedral to tetrahedral sites in the presence of the dopant of Sc³⁺.     

Theoretical explanation of optical absorption spectra and covalent effect of Ni2+ ions in octahedral sites of Ca3Sc2Ge3O12 crystal

The optical absorption spectra (d-d transition bands) and covalent effect of Ni²⁺ ions in octahedral sites of Ca₃Sc₂Ge₃O₁₂ crystal have been investigated by the full energy matrix based on the two spin–orbit coupling parameters model. The bond length of octahedral site is R_i?=?2.19 Å, which can be determined by the cubic crystal-field parameter and optical spectral data. The lattice distortion of the Ni²⁺ center in Ca₃Sc₂Ge₃O₁₂ crystal is also obtained from the calculations. In addition, the result has shown that the covalent effect of Ni²⁺ ion in the octahedral site of Ga₃Sc₂Ge₃O₁₂ is obvious and cannot be ignored. The calculated d-d transition bands agree well with that of the experimental findings, suggesting that the present methods can explain reasonably the optical spectral data and covalent effect of 3d⁸ ions in octahedral lattices.     

Structural, electrical, and optical properties of ZnInO alloy thin films

Indium zinc oxide (IZO) thin films with different percentages of In content (In/[In+Zn]) are synthesized on glass substrates by magnetron sputtering, and the structural, electrical and optical properties of IZO thin films deposited at different In₂O₃ target powers are investigated. IZO thin films grown at different In₂O₃ target sputtering powers show evident morphological variation and different grain sizes. As the In₂O₃ sputtering power rises, the grain size becomes larger and electrical mobility increases. The film grown with an In₂O₃ target power of 100 W displays the highest electrical mobility of 13.5 cm·V^-1·s^-1 and the lowest resistivity of 2.4 × 10^-3 Ω·cm. The average optical transmittance of the IZO thin film in the visible region reaches 80% and the band gap broadens with the increase of In₂O₃ target power, which is attributed to the increase in carrier concentration and is in accordance with Burstein-Moss shift theory.     

Enhanced luminescence from spontaneously ordered Gd2O3:Eu based nanostructures

Nanostructured Gd₂O₃:Eu³⁺ and Li⁺ doped Gd₂O₃:Eu³⁺ thin films were prepared by pulsed laser ablation technique. The effects of annealing and Li⁺ doping on the structural, morphological, optical and luminescent properties are discussed. X-ray diffraction and Micro-Raman investigations indicate a phase transformation from amorphous to nanocrystalline phase and an early crystallization was observed in Li⁺ doped Gd₂O₃:Eu³⁺ thin films on annealing. AFM images of Li⁺ doped Gd₂O₃:Eu³⁺ films annealed at different temperatures especially at 973 K show a spontaneous ordering of the nanocrystals distributed uniformly all over the surface, with a hillocks (or tips) like self-assembly of nanoparticles driven by thermodynamic and kinetic considerations. Enhanced photoemission from locations corresponding to the tips suggest their use in high resolution display devices. An investigation on the photoluminescence of Gd_2−xEu_xO₃ (x=0.10) and Gd_2−x−yEu_xLi_yO₃ (x=0.10, y=0.08) thin films annealed at 973 K reveals that the enhancement in luminescence intensity of about 3.04 times on Li⁺ doping is solely due to the increase in oxygen vacancies and the flux effect of Li⁺ ions. The observed decrease in the values of asymmetric ratio from the luminescence spectra of Li⁺ doped Gd₂O₃:Eu³⁺ films at high temperature region is discussed in terms of increased EuO bond length as a result of Li⁺ doping.     

Optical and structural properties of thin films deposited from laser fused Zirconia,Hafnia, and Yttria

The optical and structural properties of films deposited from laser sintered Zirconia (ZrO₂), Hafnia (HfO₂), and Yttria (Y₂O₃) and from the commercially available (unprocessed material) Zirconia, Hafnia and Yttria, were studied and compared. All the films had low absorption. Films deposited from the laser sintered material had very low optical inhomogeneity. ZrO₂ films showed negative inhomogeneity for films deposited from the unprocessed material. The refractive index increased for ZrO₂ films deposited from the laser sintered material. HfO₂ and Y₂O₃ films showed positive inhomogeneity when deposited from the unprocessed material. The refractive index of the films of these materials decreased when deposited from the laser sintered material. The thin films of ZrO₂ and Y₂O₃ prepared from laser sintered material had stable monoclinic and cubic structures respectively while HfO₂ films were found to be amorphous.     

Structural and optical properties of Er, Yb co-doped Y2O3 thin films

Thin Er³⁺, Yb³⁺ co-doped Y₂O₃ films were grown on (1 0 0) YAG substrates by pulsed laser deposition. Ceramic targets having different active ion concentration were used for ablation. The influence of the rare-earth content and oxygen pressure applied during the deposition on the structural, morphological and optical properties of the films were investigated. The films deposited at the lower pressure, 1 Pa, and at 1/10 Er to Yb doping ratio are highly textured along the (1 1 1) direction of the Y₂O₃ cubic phase. In addition to the crystalline structure, these films possess smoother surface compared to those prepared at the higher pressure, 10 Pa. All other films are polycrystalline, consisting of cubic and monoclinic phases of Y₂O₃. The rougher surface of the films produced at the higher-pressure leads to higher scattering losses and different behavior of the reflectivity spectra. Optical anisotropy in the films of less than 0.004 was measured regardless of the monoclinic structure obtained. Waveguide losses of about 1 dB/cm at 633 nm were obtained for the films produced at the lower oxygen pressure.