硅表面硅镱键合与量子级联结构的发光

用纳秒强激光脉冲制备了纳米硅和硅表面的硅镱键合结构,检测了纳米硅表面硅镱键合的发光特性,并对这种结构相应的光致发光(PL)和电致发光(EL)的动力学机理进行了研究。观察到纳米硅表面硅镱键合在700nm附近尖锐的强发光峰,结合第一性原理计算认为是硅镱键合在弯曲纳米硅表面的局域态发光;利用纳秒脉冲激光沉积技术(PLD)制备多晶硅薄膜,发现由硅镱界面的失配形成表面的突触,其上的硅镱键合产生带隙中的电子局域态,该局域态发光分布在1250~1650nm波长范围,有增强的EL发光;用PLD方法制备硅镱多层膜量子级联结构,测量到光通信窗口的多个发光峰,并观察到随膜层数增加且发光峰增多。     

CdS纳米颗粒填充的自支撑多孔硅光致发光特性

为了研究CdS纳米颗粒填充的自支撑多孔硅的光致发光特性,选用电阻率为0.01~0.02Ω·cm的P型硅片,先采用二步阳极氧化法制备自支撑多孔硅,再利用电泳法将CdS纳米颗粒填充入该自支撑多孔硅中.采用扫描电子显微镜、X射线能谱分析、X射线衍射分析、光致发光谱分析对所制备样品的形貌、相结构、组份及发光性能进行研究.实验结果表明:自支撑多孔硅内部成功填充了CdS纳米颗粒,该CdS纳米颗粒衍射峰为(210);CdS纳米颗粒填充的自支撑多孔硅光致发光峰峰位发生红移,且从570nm转移到740nm;电泳时间直接影响CdS纳米颗粒的填充量,导致相关的发光峰强度及发光峰位明显不同.     

纳米Si/SiO2多层膜的结构表征及发光特性

采用等离子体化学气相沉积系统生长非晶硅薄膜并用原位等离子体氧化的方法制备出具有不同子层厚度的非晶Si/SiO₂多层膜,然后利用限制性晶化原理使非晶硅层晶化生成纳米硅。利用Raman、TEM等手段对薄膜结构进行了系统表征,在室温下观测到了光致发光信号,其发光峰峰位在750nm附近。进而在样品上下表面蒸镀电极,构建了电致发光原型器件并观测到了室温下的电致发光谱,开启电压约为6V,有两个明显的发光带,分别位于在650nm和520nm处。初步探讨了纳米硅及纳米硅/二氧化硅界面态对发光特性的影响。     

用PAA模板法实现硅基纳米孔阵列结构

用二次阳极氧化方法制备出分立、双向贯通并且超薄（500—1000 nm）的多孔阳极氧化铝膜,贴合到硅片上进行干法刻蚀,实现图形转移,得到了硅基纳米孔阵列结构,并对工艺中影响图形转移质量的因素进行了探索.扫描电镜（SEM）测试结果表明该途径得到的纳米结构孔形态均匀且大面积有序,孔深度可达到125 nm.对该样品进行热氧化处理后进行光致发光（PL）测试,结果表明其光致发光机理是基于通常较微弱的TO声子辅助的硅带边发光,并实现了显著发光增强,对这种增强效果的物理机理进行了理论分析.该结构具有的独特光学特性为利用 关键词： 多孔阳极氧化铝模板 硅基纳米孔阵列结构 图形转移     

循环氧化/退火制备GeOI薄膜材料及其性质研究

采用超高真空化学气相淀积系统在SOI(绝缘体上硅)衬底上生长了Si_0.82Ge_0.18外延层,通过循环氧化/退火工艺,制备出Ge组分从0.24到1的绝缘体上锗硅(SGOI)材料.采用高分辨透射电镜、拉曼散射光谱和光致发光谱表征了其结构及光学性质,对氧化过程中SiGe层中的Ge组分和应变的演变进行了分析.最后制备出11 nm厚的绝缘体上Ge材料(GeOI),具有完整的晶格结构和平整的界面.室温下观测到绝缘体上Ge直接带跃迁光致发光,发光峰值位于1540 nm,发光 关键词： GeOI 氧化 退火 光致发光谱     

脉冲激光退火纳米碳化硅的光致发光

采用XeCl准分子脉冲激光退火技术制备了纳米晶态碳化硅薄膜(nc-SiC),并对薄膜的光致发光(PL)特性进行了分析。结果表明,纳米SiC薄膜的光致发光表现为300～600 nm范围内的较宽发光谱带,随退火激光能量密度的增加,nc-SiC薄膜398 nm附近的发光峰相对强度增加,而470 nm附近发光峰相对减小。根据nc-SiC薄膜的结构特性变化, 认为这两个发光峰分别来源于6H-SiC导带到价带间的复合发光和缺陷态发光,并且这两种发光过程存在竞争。     

锗/多孔硅和锗/氧化硅薄膜光致发光的比较研究

采用磁控溅射技术,以锗为溅射靶,在多孔硅上沉积锗薄膜,沉积时间分别为4,8和12 min,及以锗-二氧化硅复合靶为溅射靶,在n型硅衬底上沉积了含纳米锗颗粒的氧化硅薄膜,锗与总靶的面积比分别为5%,15%,30%.各样品在氮气氛中分别经过300,600及900℃退火30 min.对锗/多孔硅和锗/氧化硅薄膜进行了光致发光谱的对比研究,用红外吸收谱分析了锗/多孔硅的薄膜结构.实验结果显示,锗/多孔硅薄膜的发光峰位于517 nm附近,沉积时间对发光峰的强度有显著影响,锗层越厚峰强越弱.锗/氧化硅薄膜的发光峰位于580 nm附近,锗与总靶的面积比对发光峰的强度影响较大,锗/氧化硅薄膜中的锗含量越高峰强越弱.不同的退火温度对样品的发光峰强及峰位均没有明显影响.可以认为锗/多孔硅的发光峰是由多孔硅与孔间隙中的锗纳米晶粒两者界面的锗相关缺陷引起的,而锗/氧化硅的发光峰来自于二氧化硅的发光中心.     

内电场对纳米硅光致发光谱的影响

从量子限制发光中心模型出发，计算了纳米硅的光致发光（PL）特征与发光中心间的关系. 研究发现，纳米硅与发光中心间的内电场对载流子复合率及峰位振荡有着十分重要的影响. 在2—5 nm的尺寸范围内，纳米硅发光中心上的载流子复合概率远大于内部复合概率，仅需考虑发光中心上的载流子复合发光. 还发现发光中心与纳米硅粒子间的内电场对于纳米硅的发光峰位振荡有着显著的影响.发光中心与纳米硅粒子间的内电场的存在会显著减小纳米硅粒子的内部发光效率以及外部相应发光中心上的发光强度，使得纳米硅PL谱的峰位随纳米晶粒尺寸变化而发生 关键词： 内电场 纳米硅 光致发光 量子限制发光中心     

铕掺杂氧化锌纳米棒阵列材料的制备及光学性能研究

通过低温化学方法在多孔硅柱状阵列(NSPA)衬底上制备得到铕掺杂ZnO(ZnO∶Eu)纳米棒阵列结构。实验方法简单、条件温和,有效地实现了ZnO纳米棒和铕离子之间的能量转移,丰富了ZnO纳米半导体材料体系的发光。X射线衍射以及X射线光电子能谱证实铕离子成功掺杂进了ZnO晶体中。室温荧光光谱测试结果表明:ZnO∶Eu纳米棒阵列可实现从紫外光到蓝-绿光的宽谱带发射,其中发光中心位于～380 nm的紫外光源于ZnO的带边发射,位于450～570 nm的蓝-绿光源于ZnO的本征缺陷发光,而位于～615 nm的红光发光则源于铕离子核外电子4f壳层结构。同时借助于能带示意图对光致发光机理进行了分析。     

多孔硅光致发光峰半峰全宽的压缩

硅发光对于在单一硅片上实现光电集成是至关重要的.目前已有的使硅产生发光的方法有:掺杂深能级杂质、掺稀土离子、多孔硅、纳米硅以及Si/SiO₂超晶格.声空化所引发的特殊的物理、化学环境为制备光致发光多孔硅薄膜提供了一条重要的途径.实验表明,声化学处理对于改善多孔硅的微结构,提高发光效率和发光稳定性都是一项非常有效的技术.超声波加强阳极电化学腐蚀制备发光多孔硅薄膜,比目前通用的常规方法制备的样品显示出更优良的性质.这种超声波的化学效应源于声空化,即腐蚀液中气泡的形成、生长和急剧崩溃.在多孔硅的腐蚀过程中,由于超声波的作用增加了孔中氢气泡的逸出比率和塌缩,有利于孔沿垂直方向的腐蚀,使多孔硅光致发光峰的半峰全宽压缩到了3.8nm.     

The investigation of photoluminescence centers in porous alumina membranes

To investigate the origin of blue photoluminescence (PL) in porous alumina membrane, we have prepared an anodic aluminum oxide film with a pore diameter of 40 nm in oxalic acid solution by a two-step anodization process. Our results show that the as-prepared alumina membrane is amorphous and exhibits a broad emission band peaking at around 452 nm with two sub-peaks located at 443 nm and 470 nm. As indicated by the PL excitation spectra, there are two excitation peaks which can account for the sub-peaks observed in the PL emission band. We have proposed that the broad emission band with two sub-peaks can be attributed to two luminescence centers in porous alumina membranes, namely, oxygen defects and oxalic impurities. Furthermore, we have rationalized that the two emission centers show similar influence on the PL band in the blue region based on a simple model. PACS 81.07.-b; 81.16.Dn; 79.60.Jv     

Effects of Fe doping on crystalline and optical properties of yttria-stabilized zirconia

Yttria-stabilized zirconia (YSZ) samples with different Fe concentrations were prepared to study the effects of Fe doping on crystalline and optical properties of YSZ. The former properties were determined by X-ray diffraction, while the latter properties were determined by diffuse reflectance (DR) and photoluminescence (PL) spectroscopies. Lattice contraction of YSZ caused by the Fe doping was observed. We revealed that the DR spectra of the 3 and 6 mol% Fe-doped YSZ samples originate from the Fe ions dissolved and undissolved in the YSZ, respectively. Moreover, two PL bands centered around 440 and 530 nm were observed for the YSZ sample, whereas one PL band centered around 440 nm was observed for the Fe-doped YSZ samples. The Fe doping reduced the PL intensity of YSZ and quenched the PL band around 530 nm. This could be explained by considering that the concentration of Fe ions near the surface of YSZ is much larger than that in the bulk of YSZ or by considering that the Fe doping enhances surface band bending of YSZ.     

Cu掺杂氧化锌薄膜的发光特性研究

通过射频反应溅射法在Si（111）衬底上制备了不同Cu掺杂量的ZnO薄膜.室温下测量了样品的光致发光（PL）谱，所有样品的PL谱中均观察到435?nm左右的蓝光发光带，该发光带的强度与Cu掺杂量和溅射功率有关.当溅射功率为150?W，Cu掺杂量为2.5%时，ZnO薄膜的PL谱中出现了较强的蓝光双峰，而溅射功率为100?W，Cu掺杂量为1.5%时，出现了位于437nm（2.84eV）处较强的蓝光峰，后者的取向性较好.还研究了掺杂量和溅射功率对发光特性的影响，并对样品的蓝光发光机制进行了探讨. 关键词： ZnO薄膜 Cu掺杂 光致发光谱 射频反应共溅射     

Influence of excitation light wavelength on the photoluminescence properties for ZnO films prepared by magnetron sputtering

Highly orientated polycrystalline ZnO films were deposited on sapphire, silicon and quartz substrates at room temperature by r.f. magnetron sputtering. Different photoluminescence (PL) spectra were observed when excited with different wavelength light. A UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates, and only the 446 nm blue emission appeared for the films on glass substrates when the wavelength of the excitation light was 270 nm. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 488 and 516 nm, respectively. When the wavelength of the excitation light increased to 398 nm, the PL spectrum becomes a wide band that is consistent with three emission peaks.     

Optical properties of silicon microcolumn grown by nanosecond pulsed laser irradiation

We have investigated the optical properties of silicon pillars formed by cumulative nanosecond pulsed excimer laser irradiation of single-crystal silicon in vacuum created under different repetition rates. The changes in optical characteristics of silicon pillar were systematically determined and compared as the number of KrF laser shots was increased from 1 to 15,000.The results show that silicon pillar PL curves exhibit a blue band around 430 nm and an ultraviolet band peaking at 370 nm with the vanishing of the green emission at 530 nm. A correlation between the intensity of the blue PL band and the intensity of the Si-O absorption bands has been exploited to explain such emission, whereas, the origin of the ultraviolet band may be attributed to different types of defects in silicon oxide.     

Blue luminescent silicon nanocrystals prepared by short pulsed laser ablation in liquid media

The pulsed laser processing in liquid media is an attractive alternative to produce room temperature luminescent silicon nanocrystals (Si-ncs). We report on a blue luminescent Si-ncs preparation by using nanosecond pulsed laser (Nd:YAG, KrF excimer) processing in transparent polymer and water. The Si-ncs fabrication is assured by ablation of crystalline silicon target immersed in liquids. During the processing and following aging in liquids, oxide based liquid media, induce shell formation around fresh nanocrystals that provides a natural and stable form of surface passivation. The stable room temperature blue-photoluminescent Si-ncs are prepared with maxima located around ∼440 nm with corresponding optical band gap around ∼2.8 eV (∼430 nm). Due to the reduction of surface defects, the Si-ncs preparation in water, leads to a narrowing of full-width-half-maxima of the photoluminescence spectra.     

Aging effect on blue luminescent silicon nanocrystals prepared by pulsed laser ablation of silicon wafer in de-ionized water

Blue luminescent colloidal silicon nanocrystals (Si-ncs) were synthesized at room temperature by nanosecond pulsed laser ablation of a single-crystal silicon target in de-ionized water. Irregular Si-nc fragments obtained by laser ablation are stabilized into regularly shaped, spherical, and well-separated aggregates during the aging process in water. Aging in de-ionized water for several weeks improved the photoluminescence (PL) intensity. At least two weeks of aging are necessary for observation of broad blue room temperature PL with a maximum centered at 420 nm. Detailed structural analysis revealed that agglomerates after aging for several months contain Si-ncs with irregular shape smaller than the quantum confinement limit (<5 nm). These blue luminescent Si-ncs dispersed in de-ionized water exhibited a PL decay time of 6 ns, which is much faster than that of Si-ncs prepared in traditional ways (usually on the order of microseconds). The oxidized Si-ncs with quantum confinement effects are responsible for a PL band around 400 nm visible to the naked eye at room temperature.     

飞秒脉冲激光辐照下硅表面光致荧光特性(英文)

采用钛宝石飞秒脉冲激光对单晶硅在空气中进行辐照,研究了硅表面在不同扫描速度和能量密度下的光致荧光特性。光致荧光谱(PL)测量表明,在样品没有退火处理的情况下,激光扫描区域观察到橙色荧光峰(603nm)和红色荧光带(680nm附近)。扫描电子显微镜(SEM)测量显示,在飞秒脉冲激光辐照硅样品的过程中硅表面沉积了大量的纳米颗粒。利用傅里叶变换红外光谱仪(FT-IR)检测到了低值氧化物SiOx(x2)的存在,并且结合能谱仪(EDS)检测结果发现氧元素在光致发光中起着重要作用。研究表明:603nm处橙色荧光峰来自微构造硅表面低值氧化物SiOx,680nm附近红色荧光带来自量子限制效应。同时样品表面硅纳米颗粒的尺寸和氧元素的浓度分别决定了红色荧光带和橙色荧光的强度,通过调节飞秒激光脉冲的扫描速度和能量密度,可以有效地控制样品的荧光强度。     

Photoluminescence excitation properties of porous silicon with and without Er-Yb-containing complex

Two bands in the photoluminescence excitation spectra have been studied for the red, blue, and IR emission of oxidized porous silicon (PS) and PS with Er³⁺- and Yb³⁺-containing gadolinium oxychloride complex (PS:Er,Yb), introduced by thermal diffusion. These two spectral bands were shown to reflect contributions of two different mechanisms of excitation-emission processes. The UV band for the IR emission of PS:Er,Yb rose sharply at about 290 nm and was explained by the direct photoemission of carriers from the valence band of Si crystallites into the conduction band of the oxide shell. The second band was found to be common for the red and blue emission and assosiated with the carriers photoexcitation inside the Si crystallites. Lifetimes for both bands were measured and the structure of the blue emission from PS:Er,Yb with peaks at 416, 440, 466, and 500 nm from PS:Er,Yb was observed.     

Comparative investigation of photoluminescence of silicon wire structures and silicon oxide films

Photoluminescence spectra and their dependence on temperature as well as Raman scattering spectra and Atomic Force Microscopy investigations have been used to study the peculiarities of the red photoluminescence band in low-dimensional Si structures, such as porous silicon and silicon oxide films. It has been shown that the red photoluminescence band of porous silicon is complex and can be decomposed into two elementary bands. It was discovered that elementary band intensities depend very much on surface morphology of porous silicon. The same positions of the photoluminescence bands are also observed in silicon oxide films for different oxide composition. Comparative investigation of the PL temperature dependences in porous silicon and silicon oxide films indicates that silicon-oxide defect related mechanisms of some elementary photoluminescence bands are involved.