【作者】 彭爱华；

【导师】 谢二庆；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2006， 博士

【摘要】 多孔硅的研究与开发对于实现硅基光电集成电路具有重要意义。稀土掺杂多孔硅可以获得从紫外、可见到红外波段的有效发光,可应用于各类光电器件中。本论文主要在多孔硅的制备工艺改进和稀土掺杂对多孔硅发光性能改善方面开展了工作。同时对多孔硅的整流特性、场发射性质以及多孔硅衬底对薄膜发光材料发光性能的影响进行了研究。得到了以下主要结论: （1） 多孔硅的制备工艺改进:研究了腐蚀电流、退火对多孔硅发光性能的影响;金属（铁）掺杂对多孔硅发光的影响;多孔硅的纳米颗粒在溶液中的发光;湿法腐蚀,可以得到不同波长的多孔硅的发光;发现了制备方法更为简便的镍酸镧电极取代铝电极工艺。 （2） 稀土掺杂对多孔硅发光性能改善:用电化学方法对多孔硅薄膜进行了稀土（Tb、Gd、Pr、Dy、Sc）离子的化学掺杂。利用荧光分光光度计测试了样品的光致发光（PL）特性。用扫描电镜（SEM）研究了薄膜的表面形貌。用卢瑟福背散射谱（RBS）分析了稀土离子在多孔硅薄膜中的分布情况。结果表明,Tb的掺入显著增强了多孔硅的发光强度,并且发光峰位出现蓝移。这是由于Tb³⁺的4f能级⁵D₄-⁷F₃,⁵D₄-⁷F₂,和⁵D₄-⁷F₀,的跃迁发光引起的。而在掺入Gd的情况下,则观察到蓝光发射。Dy的掺杂可产生较强的蓝光发射,其强度可与多孔硅的红光强度相比较,适当的Pr和Sc的掺杂也可一定程度地增强多孔硅的蓝光发射。 发现稀土掺杂增强了多孔硅的蓝光发射,尤其是稀土掺杂多孔硅后产生蓝光发射的可能机理为:稀土掺杂引入新的表面态,形成硅、氧、稀土间新的键合方式O-Si-O-Re-O,从而在多孔硅表面形成新的发光中心;稀土离子丰富的能态在多孔硅发光过程中起到了能量传递作用,从而增强了多孔硅的蓝光发射。 （3）多孔硅衬底对薄膜发光材料发光性能的影响:将TiO₂:Eu³⁺薄膜沉积到4种不同的基底:Si,Al,AAO（氧化铝模板anodic alumina oxide）和多孔硅。我们发现稀土在AAO做基底时的发光强度与Si或Al做基底时相比增强了4倍,稀土的发光强度在多孔硅做基底时与Si或Al做基底时相比有明显降低。稀土的发光强度在多孔硅做基底时与Si或Al做基底时相比有明显降低的主要原因是多孔硅的表面颜色呈黑褐色,深颜色的表面吸收光多,反射的少。而抛光过的Si更多还原

【Abstract】 The research and development of porous silicon have promising applications in photoelectric integrated circuit. Through doping rare earth into porous silicon, the luminescence ranging from ultraviolet, visible to infrared can be obtained, and it can be used in many kinds of photo electricity devices. This thesis mainly described the improvement of porous silicon’s preparation technology and enhancement of luminescence intensity for porous silicon by doping rare earth. Rectification character, field emission character of porous silicon and effect of porous silicon on luminescence character of film luminescence material are studied, too. The mainconclusions of the thesis are as follows:（1） Improvement of preparation technology for porous silicon. We studied the effect of changing current and anneal on photoluminescence properties of porous silicon;How does the doping of Fe affect photoluminescence of porous silicon;The photoluminescence of nano-particles of porous silicon in liquid;Through wet etching, we get photoluminescence of porous silicon in different wave range;We find that LaNiO₃ electrode whose preparation method is more simple can replace Al electrode.（2） Doping rare earth improves luminescence of porous silicon. Rare earth （Tb, Gd, Pr, Dy, Sc） ions were embedded into porous silicon films by electrochemical method. Fluorescence photo spectrometer and scanning electron microscope were employed to characterize the photoluminescence and surface morphology of samples. The distribution of rare earth ions embedded into porous silicon films was examined by Rutherford backscattering spectrometry. The luminescence intensity of porous silicon after doping Tb is greatly increased. Blue shift of luminescence peak was also observed. The luminescence peaks are attributed to intra-4f transitions of Tb³+, including ⁵D₄ —⁷F₃, ⁵D₄ —⁷F₂ and ⁵D₄ —⁷F₀. Blue luminescence was observed after doping with Gd. When Dy was doped, intense blue light was obtained. The intensity is approximately equal to the red luminescence intensity of the porous silicon without doping. The blue luminescence can be enhanced in a certain extent when proper amounts of Pr and Sc were doped.We find that the blue emission of porous silicon was increased after rare earth was doped. The mechanisms of blue emission may be as follows: new surface states were introduced in porous silicon after rare earth doping and the new bonding O—Si—O—Re—O was formed, so the new emission centers are formed on the surface of porous silicon. The rich energy states of rare ions may play an important role in energy transfer so as to enhance the blue emission intensity.（3） Effect of porous silicon on luminescence properties of films deposited on porous silicon. TiO2: Eu3+ films are deposited on four different substrates: Si, Al, AAO （anodic alumina oxide） and porous silicon. We find that the luminescence intensity on AAO substrate increased 4 times comparing with that on Si or Al, and luminescence intensity decreases obviously on porous silicon substrate. The main reason of decrease is that the surface color of porous silicon is brownish black and the deep color surface absorbs light more and reflects little. The polished Si and Al can reflect light well. We know T1O2: Eu3+ film is transparent, good reflection property of substrate is beneficial to the effective luminescence of the film. Also it is possible that nano silicon in porous silicon absorbs ultraviolet light more than bulk silicon, which weakens the reflection of substrate too. Energy transfer mechanism from TiO2 host to Eu + is deduced through analysis of photoluminescence and photoluminescence excitation spectrum. Concentration quenching of Eu3+ does not appear even at high atomic concentration of 7.69%.（4） Field emission and rectification character of porous silicon. Special porous silicon is prepared which can emit ballistic electrons to examine its field emission character. After electrochemical oxidizing, the character of field emission improved. Cut-in voltage is reduced and emission current is enhanced. Current’s diminution in well-proportioned speed in etching one piece of porous silicon, is compared with current keep invariable, we find that the former is an effective method to enhance field emission character. Cut-in voltage is reduced. Emission current increased greatly. As current change, the field emission of samples doesn’t show obvious law of change. About rectification character of porous silicon, we get that after electrochemical oxidizing in concentrated sulfuric acid, the rectification character of porous silicondisappear;after annealing in N2, the rectification character of porous silicon increased.更多还原