热蒸发沉积TiO_2薄膜的光学及激光损伤特性

采用电子束热蒸发技术,用不同沉积速率制备了TiO_2薄膜。根据透射率谱计算了薄膜的光学带隙,采用椭偏法测量了薄膜的折射率、消光系数及厚度,分析了薄膜内部的电场强度分布,对其激光损伤特性进行了研究。结果表明,在所研究的工艺参数范围内,TiO_2薄膜的光学带隙比较稳定,随沉积速率的变化并不显著,其值大小在3.95eV-3.97eV。当沉积速率从0.088nm/s,0.128nm/s增加到0.18nm/s时,薄膜折射率从1.9782,1.9928,升高到2.0021(波长1064nm),但当沉积速率继续增加到0.327nm/s时,折射率反而降低到1.9663,薄膜的消光系数随着沉积速率的增加单调增加。采用同一高能激光损伤薄膜后,当沉积速率较低时制备薄膜的损伤斑大小基本一致,但以0.327nm/s较高速率制备的薄膜,其损伤斑明显增大。高沉积速率下制备的TiO_2薄膜的吸收较大,激光损伤阈值较低。     

电子束蒸发法制备TiO2薄膜的折射率研究

用电子束蒸发法制备TiO2薄膜,并对其进行300℃、400℃、850℃热处理和掺杂.详细研究了工艺参数、热处理和掺杂对TiO2薄膜折射率的影响.实验结果表明:镀制高折射率的氧化钛薄膜最佳工艺参数为基片温度200℃、真空度2×10-2 Pa、沉积速率0.2 nm/s;随着热处理温度的升高,薄膜折射率也逐渐增大;适量掺杂CeO2(CeO2:Ti0质量比1.7:12)会提高薄膜的折射率,过量掺杂CeO2反而会降低折射率.     

单层二氧化铪（HfO2）薄膜的特性研究

利用电子束蒸发、离子束辅助沉积和离子束反应溅射三种制备方法制备了单层HfO2薄膜,对薄膜样品的晶体结构、光学特性、表面形貌以及吸收特性进行了研究。实验结果表明,薄膜特性与制备工艺有着密切的关系。电子束蒸发和离子束反应溅射制备的薄膜为非晶结构,而离子束辅助制备的薄膜为多晶结构。电子束蒸发制备的薄膜折射率较低,薄膜比较疏松,表面粗糙度较小,吸收相对较小,而离子束辅助以及离子束反应溅射制备的薄膜折射率较高,薄膜的结构比较致密,但表面粗糙度较大,吸收相对较大。不同制备工艺条件下薄膜的光学能隙范围为5.30～5.43eV,对应的吸收边的范围为228.4～234.0nm。     

ZnS薄膜沉积过程的基材效应

采用热蒸发及离子束辅助沉积技术制备了单层ZnS薄膜,研究了Si、Ge、K9及石英玻璃基材对薄膜沉积速率及光学特性的影响。采用椭偏法拟合了薄膜的厚度和折射率,分析了不同基材上沉积薄膜的色散特性。研究结果表明,薄膜的生长存在明显的基材效应,无论室温沉积、基温200℃,还是采用离子束辅助沉积,石英基材上均具有最高的沉积速率。室温沉积时,4种基材上薄膜的沉积速率差为3.3 nm/min,加热进一步扩大了这种差异(5.2 nm/min),而离子束辅助则在一定程度上缩小了这种差异(1.86 nm/min)。在室温下,石英基材上沉积的ZnS薄膜具有最低的折射率,其他几种基材上折射率差异不大。加热会使Si、Ge及K9玻璃上的折射率差异变大,与石英玻璃上薄膜折射率差异减小,离子源的使用则进一步缩小了这种差异。透射率光谱测试证实了这一结果。     

温度对化学水浴法制备ZnS薄膜的影响

采用化学水浴法在玻璃上制备了太阳能电池中的ZnS缓冲层。采用SEM、EDS、XRD和nkd-分光光度计等手段研究了水浴温度对ZnS薄膜的表面形貌、结构和光学性能的影响。结果表明,升高温度不能明显改变薄膜的结晶性、形貌和沉积生长方式,能否成膜与温度的关系也不大,但成膜速率对温度的依赖性较大。随温度的升高,薄膜的透过率先减小后增大,反射率则先增大后减小。对同一试样而言,透过率和反射率对应较好。当温度为70℃时,可制得禁带宽度为3.83eV、符合化学计量比、平整的非晶ZnS薄膜。     

LaTiO_3薄膜的光学及激光损伤特性

研究了工艺条件(沉积温度、真空度、蒸发束流)对LaTiO3薄膜光学和激光损伤特性的影响。采用椭偏法测量了薄膜的光学常数,分析了不同工艺条件下制备薄膜的折射率和消光系数,得出工艺参数与薄膜光学性能的相互关系。研究结果表明,当沉积温度从室温(未加热)升高到220℃,所制备薄膜的折射率从1.9334增大到1.9644(d光)。当真空度从6.5×10-3(未充O2)降低到2.0×10-2Pa时,薄膜的折射率从1.9726下降到1.9268。随着束流从75增加到140 m A,薄膜的折射率从1.9337到1.9548略微有所增加。在所研究的工艺参数范围内,薄膜的折射率基本稳定,消光系数均小于1.74×10-3,尤其当沉积速率低于0.44 nm/s时,所制备薄膜的消光系数优于10-6。LaTiO3薄膜的激光损伤形貌随制备工艺而不同,其激光损伤阈值约为16.2~18.8 J/cm2(1064 nm,10 ns)。     

垂直结构LEDNi/Sn合金背金层的制备及其性能研究

采用真空蒸镀法制备了垂直结构LED Ni/Sn合金背金层,通过扫描电子显微镜、X射线衍射对薄膜的物相和微观结构进行了表征,同时还研究了该合金作为LED背金层的光电性能。实验结果表明,在相同的蒸发速率条件下,随着基底温度的升高,沉积的合金颗粒逐渐增大,相应的薄膜的电阻率呈下降趋势。以蒸发速率为2/s、基底温度为100℃作为工艺条件制得背金层薄膜垂直结构LED,其电学性能与贵金属Au作为LED背金层的垂直结构芯片电学性能相当。     

衬底温度对柔性硫化锌薄膜结构与光学性能的影响北大核心CSCD

本文利用射频磁控溅射薄膜沉积技术在柔性聚酰亚胺(PI)、氧化铟锡(ITO)玻璃及石英玻璃衬底上制备了透明硫化锌(ZnS)薄膜。通过改变生长过程中的衬底温度,全面系统地研究了衬底温度对柔性和刚性ZnS薄膜的晶体结构、光透过率、光学常数以及表面性能影响的规律。研究表明升高衬底温度有利于形成ZnS薄膜(111)晶面的择优取向生长。不同衬底温度条件下制备的柔性和刚性ZnS薄膜在可见光波长范围内的平均光透过率均大于80%;在红外波长范围的平均光透过率达到85%。柔性ZnS薄膜在400 nm-890 nm波长范围内的光学折射率为2.21-2.56。刚性ZnS薄膜的光学折射率随着衬底温度的升高有所增加,当衬底温度为300℃时,刚性ZnS薄膜在890 nm波长处的折射率达到2.26。柔性ZnS薄膜厚度及表面粗糙度均随着衬底温度的升高而降低,当衬底温度为300℃时,柔性ZnS薄膜表面均方根粗糙度达到最小值2.99 nm。为实现高性能柔性ZnS光电器件,应控制生长柔性ZnS薄膜的衬底温度在200℃-300℃,以获得最优化的器件性能。     

In_2O_3：W薄膜的制备及光电性能研究

采用直流磁控溅射法制备了掺钨氧化铟（In2O3：W,IWO）薄膜,研究了制备工艺对薄膜表面形貌和光电性能的影响。结果表明薄膜的表面形貌与其光电性能有着紧密联系。氧分压显著影响薄膜的表面形貌进而对薄膜的光电性能产生影响,同时溅射时间的变化也显著影响薄膜的光电性能：随着氧分压以及溅射时间的升高,薄膜的电阻率均呈现先减小后增大的变化规律,在氧分压为2.4×10-1Pa条件下,制备样品的表面晶粒排布最细密,其电阻率达到6.3×10-4Ω.cm,载流子浓度为2.9×1020cm-3,载流子迁移率为34cm2/（V.s）,可见光平均透射率约为85%,近红外光平均透射率〉80%。     

自供能ZnO/ZnS异质结紫外探测器的性能研究

用化学浴法在ZnO纳米棒表面沉积ZnS制备出ZnO/ZnS核壳纳米棒阵列,使用SEM、XRD和XPS等手段表征了样品的形貌、结构和成分。结果表明,ZnO/ZnS核壳纳米棒阵列表面粗糙,生长致密、分布均匀,其平均直径约为150 nm。以Pt为对电极组装的自供能ZnO/ZnS异质结紫外探测器,对紫外光具有很好的探测性能,能循环工作且性能稳定。这种探测器对微弱的紫外光也有较强的响应和较高的光敏性,且随着光强度的提高光电流密度线性增大。与自供能ZnO纳米棒紫外探测器相比,ZnO/ZnS异质结紫外探测器具有更高的响应速度,上升时间和下降时间分别提高到0.02 s和0.03 s。     

Microstructure of magnesium fluoride films deposited by boat evaporation at 193 nm

Single layer magnesium fluoride (MgF2) was deposited on fused-silica substrates by a molybdenum boat evaporation process at 193 nm. The formation of various microstructures in relation to the different substrate temperatures and deposition rates were investigated. The relation between these microstructures (including cross-sectional morphology, surface roughness, and crystalline structures), the optical properties (including refractive index and optical loss) and stress, were all investigated. It was found that the laser-induced damage threshold (LIDT) would be affected by the microstructure, optical loss, and stress of the thin film. To obtain a larger LIDT value and better optical characteristics, MgF2 films should be deposited at a high substrate temperature (300 degrees C) and at a low deposition rate (0.05 nm s(-1)).     

Indium doped ZnO films prepared by RF magnetron sputtering: effect of substrate temperature on the strain-induced band gap

Indium doped zinc oxide (InZnO) thin films were deposited onto corning glass substrates by RF magnetron sputtering. The dependence of crystal structure, surface morphology, optical properties and electrical conductivity on substrate temperature was investigated using XRD, AFM, UV-vis Spectrophotometer, Fluorescence Spectrophotometer and four-point probe. The films were prepared at different substrate temperatures viz, room temperature (RT), 473 K and 673 K at RF power 200 W. All the films showed preferred orientation along (002) direction. Crystallite size increased from 14 to 19 nm as the substrate temperature was increased to 473 K. With increase in substrate temperature the crystallites did not show any further growth. AFM analysis showed that the rms roughness value decreased from 60 nm to 23 nm when the substrate temperature was increased to 673 K. Optical measurements revealed maximum band gap and minimum refractive index for the film prepared at 473 K. A strong correlation between the band gap variation and the strain developed at different substrate temperatures is established.     

Optical and mechanical characteristics of zinc sulphide-thorium fluoride mixed composition thin films for use in the near infrared region (1–10µm)

Mixed composition thin films of zinc sulphide-thorium fluoride have been deposited on glass and silicon substrates by thermal evaporation of mixtures of these materials in different proportions, from a single resistively heated source. The films are characterized for their optical properties (refractive index and extinction coefficient), mechanical properties (intrinsic stress), surface morphology and chemical composition. It is found that these films have tailorable refractive indices and low losses, and that films with certain compositions have low intrinsic stress and smooth surface morphology, making them suitable for incorporation in thin film multilayers for use in the near infrared region up to at least 10μm.     

Structure and electrical properties of ITO thin films deposited at high rate by facing target sputtering

High rate deposition of ITO thin films at a low substrate temperature was attempted by using a facing target sputtering (FTS) system. Deposition rate as high as 53 nm/min was realized on polycarbonate film substrate of 80-μm thickness. When the film was deposited at a deposition rate above 80 nm/min, polycarbonate film substrate was thermally damaged. The film deposited by FTS has much smaller compressive film stress than the film deposited by conventional magnetron sputtering. The film stress was reduced significantly by increasing the sputtering gas pressure and stress-free films can be obtained by adjusting the sputtering gas pressure. This may be mainly caused by the fact that bombardment by high energy negative oxygen ions to substrate surface during deposition can be completely suppressed in the FTS. Film structure and electrical properties changed little with substrate position, and uniform films were obtained by the FTS.     

Characterization of AlF3 thin films at 193 nm by thermal evaporation

Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 degrees C. The LIDT of the films prepared at a deposition rate of 2 A/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.     

Low refraction properties of F-doped SiOC:H thin films prepared by PECVD

Low refractive index materials which F-doped SiOC:H films were deposited on Si wafer and glass substrate by low temperature plasma enhanced chemical vapor deposition (PECVD) method as a function of rf powers, substrate temperatures, gas flow ratios (SiH₄, CF₄ and N₂O). The refractive index of the F-doped SiOC:H film continuously decreased with increasing deposition temperature and rf power. As the N₂O gas flow rate decreases, the refractive index of the deposited films decreased down to 1.378, reaching a minimum value at an rf power of 180 W and 100 °C without flowing N₂O gas. The fluorine content of F-doped SiOC:H film increased from 1.9 at.% to 2.4 at.% as the rf power was increased from 60 W to 180 W, which is consistent with the decreasing trend of refractive index. The rms (root-mean-square) surface roughness significantly decreased to 0.6 nm with the optimized process condition without flowing N₂O gas.     

Deposition at low substrate temperatures of high-quality TiO2 films by radical beam-assisted evaporation

We deposited high-quality TiO(2) films by an oxygen-radical beam-assisted evaporation (RBE) method at a lower substrate temperature (Ts) than that for a TiO(2) film deposited by conventional thermal evaporation (TE) with neutral-oxygen gas. The films were then evaluated in terms of refractive index, shift of wavelength of a peak in the reflection curve, and absorption coefficient. The TiO(2) films deposited by RBE at Ts < 473 K showed higher refractive indices, were more compact, and had lower absorption coefficients than the film deposited by TE at Ts = 473 K.     

Effect of substrate temperature and precursor ratio on properties of thin ZnS films sprayed by improved method

Zinc sulphide (ZnS) thin films were prepared by improved spray pyrolysis (ISP) method. The ISP parameters, such as carrier gas flow rate, solution flow rate and substrate temperature, were controlled with an accuracy of ±0.25 lpm, ±1 ml/h and ±1 °C, respectively. The solution was sprayed in a pulsed mode. The substrate temperature was optimized by analyzing substrate temperature dependent properties of thin films. The thin film deposited at a temperature of 450 °C was dense and fairly smooth with satisfactory crystallinity and very small impurity content. The effect of precursor ratio in the solution on structural, compositional and optical properties of thin ZnS films, deposited at a temperature of 450 °C, was studied. A gradual increase in band gap energy from 3.524 eV to 3.634 eV, refractive index from 2.5 to 2.9 and dielectric constant from 6.6 to 8.7 were observed with the variation of solution precursor (Zn:S) ratio from (1:2) to (1:6). The structural and compositional studies support this kind of enhancement in optical properties. The results show that the thin ZnS film prepared by ISP at the substrate temperature of 450 °C from a solution with specific precursor ratio can be used for optoelectronic and photovoltaic applications.     

Multilayer antireflective and protective coatings comprising amorphous diamond and amorphous hydrogenated germanium carbide for ZnS optical elements

To effectively protect and improve the transmittance of ZnS optical elements in the far infrared band, combined amorphous diamond (a-D) and amorphous hydrogenated germanium carbide (a-Ge_1−xC_x:H) films have been developed. The optical interference coatings were designed according to the layer optics theory. The a-D films, of which refractive index and film thickness were controlled by changing substrate bias and deposition time respectively, were deposited by filtered cathodic vacuum arc technology. The a-Ge_1−xC_x:H films were prepared by radio frequency sputtering technology. During this process their refractive index was modulated by changing the gas flow rate ratio and their film thickness was controlled by the flow rate ratio and deposition time. It has been shown that the combined films are superexcellent antireflective and protective coatings for ZnS optical elements.