分层优化薄膜电致发光器件预热层的研究

在本文的工作中，我们比较了以ＳｉＯ２／Ｙ２Ｏ３和ＳｉＯ２／Ｔａ２Ｏ５为复合预热层及以ＳｉＯ为预热层的电致发光器件的发光亮度和传导电流，我们发现ＳｉＯ作为预热层的器件发光亮度优于其它两种器件。利用数值模拟的方法，推导出热电子能量，结果表明，ＳｉＯ为预热层的电致发光器件的热电子能量也明显高于另外两种器件。     

PZT／Si薄膜的扩散反应研究

运用ＸＰＳ和ＡＥＳ研究了ＰＺＴ膜／Ｓｉ在热处理过程中的薄膜及界面化学反应；在热处理过程中，气氛中的气通过ＰＺＴ的缺陷通道扩散到ＰＺＴ／Ｓｉ同旧，并与界面上的硅发生氧化反应形成ＳｉＯ２界面层。同时基底上的硅通过ＰＺＴ的缺陷扩散么样品表面形成ＳｉＯ２表面层。此外，在ＰＺＴ／Ｓｉ界面上，Ｔｉ的氧化物和Ｓｉ发生还原反应，形成了ＴｉＳｉｘ金属硅化物，并残留在ＰＺＴ膜层和和ＳｉＯ２界面层中。在ＰＺＴ膜层内，有     

PZT／Si界面氧化反应机理及动力学研究

运用俄歇电子能谱深度剖析和线形分析研究了ＰＺＴ／Ｓｉ界面氧化反应的机理和动力学过程，研究结果表明，在ＰＴ／Ｓｉ样品的热处理过程中，环境气氛中的氧可以透过ＰＺＴ薄膜层扩散到ＰＴ／Ｓｉ界面，并与硅基底反庆形成ＳｉＯ２界面层，界面氧化反应由氧在ＰＴ层和ＳｉＯ２层中的扩散过程所控制。     

纳米硅基薄膜光致发光机制的初步研究

用等离子体化学气相沉积方法制备氢化非晶硅合金薄膜，经高温退火及高温氧化可制备纳米尺寸的晶粒，室温下能发出可见光。实验表明，高温氧化后的纳米颗粒被镶嵌在ＳｉＯ２的无序网络中，其晶粒尺寸减少，而发光强度增强，发光峰位置向短波方向移动。这些结果说明，发光来源于纳米晶粒的量子尺寸效应和覆盖晶粒表面的ＳｉＯ２层的发光中心。     

用溶胶—凝胶法制备的Y2SiO5：Gd,Eu荧光粉的发光性能

用溶胶－凝胶法合成了Ｙ２ＳｉＯ５：Ｇｄ,Ｅｕ红色荧光粉。探讨了烧结工艺对粉体的结构及发光性能的影响。首次报道了搀杂Ｇｄ的Ｙ２ＳｉＯ５：Ｅｕ红色荧光粉的发光性能。研究结果表明,搀杂适当浓度的Ｇｄ,可以显著提高ＹｓＳｉＯ５：Ｅｕ红色荧光粉的发光强度,在Ｙ２ＳｉＯ５基质中,Ｇｄ＾３＋是Ｅｕ＾３＋的优良敏化剂。     

高温高压合成的硅酸锶铕铋的发光特性

用高温高压方法合成了Ｓｒ２ＳｉＯ４：Ｅ３＋ｕ，Ｂｉ３＋和ＳｒＳｉＯ３：Ｅｕ３＋，Ｂｉ３＋研究了合成压力对其发光性能的影响，与用溶胶－凝胶共沉淀法和常压高温法合成的产品作比较．常压制备的ＳｒＳｉＯ３：Ｅｕ３＋，Ｂｉ３＋为六角结构，而在２．３４—４．１０ＧＰＳ的合成压力范围内，它转变为反正交结构；常压下Ｓｒ２ＳｉＯ４：Ｅｕ３＋，Ｂｉ３＋为单斜结构，在４．２ＧＰａ的合成压力下，未发现其结构相变．高压合成产物的发光强度和相对量子发光效率降低，半宽度明显增加，且伴有红移发生．发光强度的改变是压致晶场的变化引起的     

Si3N4陶瓷材料高温氧化层的分析

利用ＸＲＤ，ＥＰＭＡ，ＸＰＳ和ＳＥＭ的分析方法，研究了在１３００℃下氧化后Ｓｉ３Ｎ４陶瓷材料表面氧化层的组成的形貌，结果表明，Ｓｉ３Ｎ４陶瓷材料的表面氧化层是由方石英相和含有Ａｌ２Ｏ３，ＣａＯ等杂质的ＳｉＯ２质玻璃相所组成，其中ＳｉＯ２玻璃相听Ａｌ２Ｏ３，ＣａＯ等杂质的含量随氧化时间的增加而逐渐增加，同时在氧化层的内部都还存在部分Ｓｉ２Ｎ２Ｏ相。     

叠加能量Si^＋,N^＋共注入SiO2薄膜的光致发光

报道了用叠加能量Ｓｉ＾＋，Ｎ＾＋共注入ＳｉＯ２薄膜研究硅基发光材料，Ｓｉ＾＋，Ｎ＾＋先后注入ＳｉＯ２薄膜，并在衬底中重叠，样品退火后紫外光激发下，可以观察到很强的紫外（～３４０ｎｍ）和紫色（～４２７ｎｍ）光致发光（ＰＬ），还研究了光致发光激发（ＰＬＥ）谱并对发光机制进行了探讨。     

溶胶—凝胶制备TiO2／SiO2复合薄膜的FT—IR表征

ＦＴ－ＩＲ吸收谱用来研究具有多孔结构的ＴｉＯ２／ＳｉＯ２复合薄膜；薄膜在１２００ｃｍ＾－１有一较强的肩峰，其强度与峰位随热处理温度度而生变化。在９５５ｃｍ＾－１的吸收峰是由于Ｓｉ－Ｏ－Ｔｉ和Ｓｉ－ＯＨ的结果，并随着热处理 度的提高其吸收峰完全是Ｓｉ－Ｏ－Ｔｉ振动所引起的，其峰位随着ＴｉＯ２的增加，向低频区域移动。     

锗纳米镶嵌薄膜的电致发光及其机制

采和射频磁控溅射技术,在Ge纳米镍嵌薄膜的基础上制备出电致发光器件。器件的结构为半透明Au膜／Ge纳米镍嵌薄膜／p-Si基片。当正向邻居坟大于6V时,用肉眼可以观察到可见的电致发光,但在反向偏压下探测不到光发射。所测电致发光谱中只有一个发光峰,峰位在510nm（2．4eV,绿光）,并且随着正向偏坟的升高,峰位不发生移动;对于不同温度退火的样品,峰位也保持不变。根据分析结果讨论了可能的电致发光机制。     

Effects of gamma irradiation on electroluminescence spectra from Au/amorphous Si/SiO2 superlattices/p-Si structures

Amorphous-Si/SiO₂ superlattices have been grown using the two-target alternation magnetron sputtering technique. The thickness of the SiO₂ layers in all the superlattices was 2.0 nm and that of the Si layers in nine types of the superlattice ranged from 0.6 to 3.8 nm in steps of 0.4 nm. Visible electroluminescence (EL) spectra of Au/amorphous-Si/SiO₂ superlattices/p-Si structures with Si layers of nine different thicknesses showed a peak located at 650 nm. After gamma irradiation, the EL peak increased 2.5 times in intensity. Moreover, a strong new 470 nm blue peak emerged from the EL spectra in all the Au/amorphous-Si/SiO₂ superlattices/p-Si structures. The experimental results indicate that the EL recombination process mainly originates from luminescence centers in the SiO₂ layers rather than from the Si layers in the superlattices.     

Structures and light emission properties of nanocrystalline FeSi2/Si formed by ion beam synthesis with a metal vapor vacuum arc ion source

Thin layers of nanocrystalline FeSi₂ embedded in Si structures have been formed by Fe implantation using a metal vapor vacuum arc (MEVVA) ion source under various implantation and thermal annealing conditions. The microstructures were studied in details and correlated with the photoluminescence (PL) properties. It is found that higher lattice coherence between the FeSi₂ nanocrystals and the Si matrix is associated with better light emission efficiency. Multiple-cycle implantation schemes were introduced and it is shown that with appropriate process design the dose quenching effect can be suppressed to achieve light emission enhancement in higher dose samples. De-convolution of the PL spectra into two or three peaks was performed and their temperature and excitation power dependence were analyzed. The analysis results indicate that the 1.55-μm emission really originated from FeSi₂ and that the emission peaks are likely donor- or accepted-level-related. MOS structures with the incorporation of implanted nanocrystalline FeSi₂ were fabricated. Electroluminescence (EL) spectra from these devices showed two peak features of which one peak corresponds to FeSi₂ emission and the other corresponds to enhanced Si band-edge emission. Clear room-temperature EL signals from these device structures were observed. A model is proposed to qualitatively understand the temperature dependence of the EL spectra.     

Influence of oxidized layer on operating voltage and luminance of nanocrystalline silicon electroluminescent device

A direct current (DC) operating voltage and luminescence property of red electroluminescent (EL) devices with and/or without a silicon dioxide (SiO2) layer at interface between nanocrystalline Si (nc-Si) region and Si substrate has investigated. The removal of SiO2 layer in the EL device led to the lowering of DC operating voltage from 4.0 up to 2.0 V and the increase of luminescence intensity more than one order of magnitude. The external quantum efficiency of red luminescence from the EL device without the SiO2 layer at the DC operating voltage of 3.0 V was 0.5%. These were realized by the efficient and easy injection of carriers to the radiative recombination centers in the nc-Si region due to the removal of SiO2 layer. These results indicate that the removal of SiO2 layer is drastically improved the DC operating voltage and luminescence intensity for the nc-Si based EL device.     

半绝缘Si/SiO_2超晶格结构在交流电场下的电致发光特性

本文研究了SiO2和Si层的厚度分别为2-8nm和1.5-3nm的Si/SiO2超晶格在交流电场下的电致发光特性。以超晶格中SiO2层内加速的过热电子碰撞激发纳米Si层中密集的硅量子点,获得了Si/SiO2超晶格蓝绿色交流电致发光。Si/SiO2超晶格的电致发光亮度随电压升高呈现指数增强,最高发光亮度可达到1.4cd/m2。随着Si层厚度的增加,Si/SiO2超晶格电致发光谱的低能侧发光峰相对增强,可以归结为纳米Si层厚度对其中硅量子点尺寸分布的限制作用。当超晶格中SiO2层厚度小于过热电子的平均自由程时,过热电子的平均能量减小导致短波侧的发光强度迅速下降,电致发光强度随之迅速降低。     

Crystalline core/shell Si/SiO2 nanotubes formed via interfacial stress imbalance

Crystalline core/shell Si/SiO2 nanotubes (NTs) with outer diameters of 130-220 nm and lengths of approximately 1 microm have been synthesized using thermal evaporation. High resolution scanning electron microscopy reveals that the NT formation stems from the intrinsic interfacial stress imbalance in the strained Si/SiO2 bilayered film, consequently leading to NTs with different orifice levels. The NT diameters depend strongly on the bilayer film thicknesses and crystal orientations of the Si and SiO2 layers. A modified Timoshenko formula is derived to calculate the dependence of the tube diameter on the bilayer film thickness. The obtained results are consistent well with experimental data.     

Investigation of bonding characteristics between Si quantum dots and a SiO2 matrix

In order to understand and control the properties of Si quantum dot (QD) superlattice structures (SLS), it is necessary to investigate the bonding between the dots and their matrix and also the structures' crystallinities. In this study, a SiOx matrix system was investigated and analyzed for potential use as an all-silicon multi-junction solar cell. Si QD SLS were prepared by alternating deposition of Si rich SiOx (x = 0.8) and SiO2 layers using RF magnetron co-sputtering and subsequent annealing at temperatures between 800 and 1,100 degrees C under nitrogen ambient. Annealing temperatures and times affected the formation of Si QDs in the SRO film. Raman and FTIR spectra revealed that nanocrystalline Si QDs started to precipitate after annealing at 1,100 degrees C for 1 hour. TEM images clearly showed SRO/SiO2 SLS and Si QDs formation in SRO layers after annealing at 1,100 degrees C for 2 hours. XPS analysis showed that Si-Si and Si-O bonding changes occurred above 1,100 degrees C. XPS analysis also revealed that Si QD SLSs started stabilizing after 2 hours' annealing and approached completion after 3 hours'. The systematic investigation of Si QDs in SiO2 matrices and their properties for solar cell application are presented.     

Si nanocrystals in SiO2 films analyzed by small angle X-ray scattering

Amorphous SiO/SiO₂ multilayers were studied using grazing-incidence small-angle X-ray scattering (GISAXS). Such SiO/SiO₂ superlattices were prepared by alternately magnetron sputtering of 3 nm thin films of SiO and 3 nm of SiO₂ (10 layers each) on Si (100) substrate. Rotation of the Si substrate during evaporation ensures the homogeneity of the films over the whole substrate. After evaporation the samples were annealed at 1050 °C for 2 h in vacuum or in air. The analysis of the 2D GISAXS pattern has shown that Si nanocrystals are formed in the annealed samples. Using a Guinier approximation, the inter-nanocrystal distance (10.5 nm) and radius of gyration (2.3 nm) have been obtained for the samples annealed in vacuum. Samples annealed in air have shown similar peak values which were however, much wider distributed.     

Low-plasma and high-temperature PECVD grown silicon-rich SiO(x) film with enhanced carrier tunneling and light emission

Low-plasma and high-temperature chemical vapor deposition of Si-rich SiO(x) for concurrently enhancing the carrier tunneling and light emission efficiency is investigated. The O/Si composition ratio of the SiO(x) film significantly decreases from 2 to 1.2 as the substrate temperature increases from 200 to 400?°C, corresponding to the enhanced precipitation of Si nanocrystals in the Si-rich SiO(x). In comparison with stoichiometric SiO(2), the Si-L(2,3) transition induced kinetic energy loss of the primary electron transmitted through the Si-rich SiO(x) sample grown at 400?°C is red-shifted by 5?eV. The strongest Si nanocrystal related photoluminescence (PL) can be obtained from the Si-rich SiO(x) film prepared at a threshold plasma power of 30?W and substrate temperature of 400?°C. In low-plasma and high-temperature deposited samples, the threshold Fowler-Nordheim (F-N) tunneling field and the indium tin oxide (ITO)-SiO(x) junction potential barrier height of ITO/SiO(x) /p-Si/Al metal-oxide-semiconductor light emitting diodes (MOSLEDs) are concurrently reduced due to the increasing density of Si nanocrystals precipitated within the SiO(x) matrix. A thermal activation energy of 0.8?eV was observed for initiating the F-N tunneling process in the MOSLEDs. The electroluminescence (EL) intensity and efficiency of the MOSLEDs are improved by at least 10?dB due to the oxygen deficient plasma enhanced chemical vapor deposition (PECVD) of Si-rich SiO(x) at low plasma power and high temperatures.     

Active doping of B in silicon nanostructures and development of a Si quantum dot solar cell

Active doping of B was observed in nanometer silicon layers confined in SiO(2) layers by secondary ion mass spectrometry (SIMS) depth profiling analysis and confirmed by Hall effect measurements. The uniformly distributed boron atoms in the B-doped silicon layers of [SiO(2) (8 nm)/B-doped Si(10 nm)](5) films turned out to be segregated into the Si/SiO(2) interfaces and the Si bulk, forming a distinct bimodal distribution by annealing at high temperature. B atoms in the Si layers were found to preferentially substitute inactive three-fold Si atoms in the grain boundaries and then substitute the four-fold Si atoms to achieve electrically active doping. As a result, active doping of B is initiated at high doping concentrations above 1.1 × 10(20) atoms cm( - 3) and high active doping of 3 × 10(20) atoms cm( - 3) could be achieved. The active doping in ultra-thin Si layers was implemented for silicon quantum dots (QDs) to realize a Si QD solar cell. A high energy-conversion efficiency of 13.4% was realized from a p-type Si QD solar cell with B concentration of 4 × 10(20) atoms cm( - 3).     

Au/锗/氧化硅纳米多层膜/p-Si结构的电致发光机制研究

用射频磁控溅射法制备了锗/氧化硅纳米多层膜,在室温下测量了Au/锗/氧化硅纳米多层膜/pSi结构的电致发光.利用位形坐标模型分析了锗/氧化硅纳米多层膜的发光中心,并用量子限制-发光中心模型对该纳米结构的电致发光过程作了研究,研究表明锗/氧化硅纳米多层膜的电致发光主要来自SiO2层的发光中心.