镍钝化多孔硅表面形貌的控制和光致发光性能的改善

利用水热技术制备了系列镍钝化多孔硅样品,并对其表面形貌和光致发光谱进行了研究。实验表明,样品的表面形貌与其光致发光特性之间存在强烈的关联:采用具有较低Ni~(2 )浓度的腐蚀液所制备的样品表面形貌更为均匀,并具有相对较强的发光和较窄的发光峰。初步探索了通过对样品表面形貌的控制来改善样品发光性能的有效途径。     

钝化多孔硅光致发光谱的时间演化特性

通过改变溶液的组成成份,用水热腐蚀技术原位制备出具有不同表面钝化状况的四类多孔硅样品.将上述样品室温下存放于空气中,其光致发光谱的时间演化特性差异很大.其中,氢钝化多孔硅的发光强度衰减最快,峰位蓝移量也最大,而铁钝化多孔硅的发光强度和峰位则几乎不发生变化.红外吸收谱实验揭示出这种差异可能来源于样品表面钝化成份的不同.此发现为一步原位制取具有稳定发光性能的多孔硅提供了新的思路.     

Blue emission from hydrogen-containing a-Si：H／SiO2 multilayers and the investigation of its mechanism

A series of hydrogen-containing a-Si:H/SiO2 multilayers with different a-Si:H sublayer thickness were fabricated by layer-by-layer deposition and in situ plasma oxidation in a plasma-enhanced chemical vapor deposition system (PECVD). Optical induced blue emission from the samples was observed by the naked eye at room temperature, which has never been reported in the luminescence study of Si/SiO2 multilayers up to now. Both the photoluminescence (PL) peak and the absorption edge show a blue shift as the a-Si:H sublayer thickness decreases. The origin of the blue emission and the effect of hydrogen are discussed.     

氧对纳米ZnO薄膜晶体结构和光致发光的影响

ZnO是一种直接带半导体材料，在光电领域中和GaN一样受到关注．ZnO不仅有与GaN相似的晶体结构，而且它的激子结合能高达60meV，是GaN的2．4倍．采用射频(RF)磁控溅射法在n-Si(001)衬底上生长ZnO薄膜，XRD谱测量显示出氧压对ZnO薄膜的晶体结构有显著影响，用波长为325nm的激光激发，观察到在445nm处有一强的光致发光峰，它来自于氧空位浅施主能级上的电子跃迁到价带，分析了发光峰与氧压的关系以及退火对它的影响。     

Progress of Si-based nanocrystalline luminescent materials

Si-based nanomaterials are some new photoelctronic and informational materials developed rapidly in recent years, and they have potential applications in the light emitting devices, e. g. Si light emitting diode, Si laser and integrated Si-based photoelectronics. Among them are nanoscale porous silicon (ps), Si nanocrystalline embedded SiO₂ (SiO_x, x < 2.0) matrices, Si nanoquantum dot and Si/SiO₂ superlattice, etc. At present, there are various indications that if these materials can achieve efficient and stable luminescence, which are photoluminescence (PL) and electroluminescence (EL), it is possible for them to lead to a new informational revolution in the early days of the 21st century. In this article, we will mainly review the progress of study on Si-based nanomaterials in the past ten years. The involved contents are the fabricated methods, structural characterizations and light emitting properties. Finally, we predicate the developed tendency of this field in the following ten years.     

Fe(NO_3)_3浓度对水热法腐蚀多孔硅的影响

用水热腐蚀法,通过改变腐蚀液中Fe(NO3)3的浓度,制备多孔硅样品.用扫描电子显微镜、荧光分光光度计和傅立叶红外光谱仪对样品微结构和光学特性进行检测,并结合Islam-Kumar模型对检测结果进行分析.结果表明,增大腐蚀液中Fe(NO3)3浓度,可加快腐蚀速度,并使多孔硅中纳米硅尺寸减小,比表面积增大,从而引起样品发射峰发生蓝移,且对应于Si‖O键的红外吸收增强.     

Blue photoluminescence from nanocrystalline porous silicon structure fabricated by high-current pulsed electron beam irradiation

N-type Si （111） wafers have been processed by high-current pulsed electron beam （HCPEB） treatment with an increasing number of irradiation （1, 10 and 20 pulses）. The results of this work show that a highly porous nanostructure was formed after irradiation. Moreover, the high-density Si nanocrystals （Si-ncs） about 3 nm were distributed on the surface of Si wafers and exhibited 3.02 eV Photoluminescence （PL） emission in blue band. The PL intensity increases with the increase in the Si-ncs＇ density in accordance with the quantum confinement model, which can be ascribed to the different pulse time of HCPEB treatment. The possible formation mechanisms of micropores and Si-ncs are discussed.     

掺铕(铽)多孔硅的制备及其光致发光

采用了一种新的掺杂方法——溶胶-凝胶法将稀土配合物掺入多孔硅中．研究结果表明：“溶胶-凝胶法”可有效地把稀土掺入多孔硅中,所制得的杂化材料中,观察到Eu^3＋、Tb^3＋特征的橙红色、绿色室温光致发光．而且,通过SiO2对掺入稀土的包裹作用和对多孔硅层的覆盖,提高了多孔硅的稳定性,部分减少了多孔硅的发光猝灭．     

碳化硅薄膜的光学特性研究

采用螺旋波等离子体增强化学气相沉积(HW-PECVD)技术制备了纳米晶碳化硅(nc-SiC)薄膜,利用傅立叶红外吸收谱(FTIR)、X射线衍射谱(XRD)、紫外-可见透射光谱(UV-Vis)和光致发光谱(PL)对薄膜的结构、光学带隙、发光特性等进行了测量和分析.结果表明,所沉积薄膜主要以Si-C键合结构存在,薄膜中包含有立方结构的3C-SiC晶粒,光学带隙2.59 eV,室温下薄膜表现出强的可见蓝色光致发光,发光峰位随氙灯激发波长的增加呈现红移现象,并将此发光归因于量子限制效应作用的结果.     

无掩模选择性制备硅纳米线阵列及其光致发光

基于金属辅助硅化学刻蚀发展了一种无掩模选择性区域制备硅纳米线阵列的方法, 并利用该方法成功制备了图形化的硅纳米线阵列. 扫描电子显微镜(scanning electron microscope, SEM) 分析表明, 所制备的硅纳米线阵列是高质量的多孔微纳米结构, 并利用拉曼光谱仪研究了室温下硅纳米线阵列的光致发光特性. 结果表明, 硅纳米线阵列可实现有效的光发射, 发光波峰为663 nm. 该方法工艺简单、有效, 可潜在地应用于构筑硅基光电集成器件.     

多孔硅发光特性的研究

在以氢氟酸为基本组份的腐蚀液中,以单晶硅为阳极采用横向阳极氧化方法,制备了具有光致发光特性的多孔硅,系统地研究了多孔硅薄膜的光学性质;x光衍射分析表明样品具有良好的晶体质量;测量了样品的变波长激光喇曼光谱,光致发光峰值波长和半峰高宽度对电解液组份、电解电流密度及电解时间等量的依赖关系;利用二维量子尺寸效应对上述物理现象作了定性的解释.     

Eu~(3+)和Yb~(3+)掺杂的近红外发光材料的制备及荧光性能

采用溶胶-凝胶法制备了系列近红外发光材料Y_(1.98-x)Yb_xEu_(0.02)O_3(其中x=0,0.01,0.02,0.04,0.06,0.10),并采用X射线衍射仪(XRD)、荧光光谱(PL)等测试方法、技术对样品的物相结构和发光特性进行了表征及测试.结果表明:Eu~(3+)和Yb~(3+)掺杂的荧光粉中,Eu~(3+)和Yb~(3+)部分取代了Y~(3+),并占据其晶格位置,而对Y_2O_3的立方相晶体结构未产生显著影响;在466 nm波长(Eu~(3+)的特征激发峰)激发下,在可见光区及近红外光区可观察到较强的发射光谱,其中,Y_(1.94)Yb_(0.04)~(3+)Eu_(0.02)~(3+)O_3在近红外光区发光效率最高.采用溶胶-凝胶法制备出Eu~(3+)和Yb~(3+)掺杂的新型荧光材料,可将硅太阳能电池吸收较弱的高能光子转换成吸收较好的近红外光子,可有效解决太阳光谱与硅太阳能电池光电响应之间存在的光谱失配问题.     

BaAl2S4:Eu溅射靶材合成方法研究

采用放电等离子烧结(SPS)方法和粉末烧结法制备BaAl2S4:Eu溅射靶材,分析了靶材成分和结构特性以及利用靶材制备薄膜的发光特性.实验结果表明,SPS烧结的BaAl2S4:Eu溅射靶材的纯度高,无其它硫化物形成,被氧化的可能性小,靶材致密,气孔少;形成薄膜的PL谱主要是470nm处的蓝光发射.粉末烧结法制备的Ba-Al2S4:Eu溅射靶材的纯度低,靶材被氧化的几率大,气孔多,不致密,呈三维网状结构;在470nm处的蓝光发射峰值相对较弱.放电等离子烧结方法更适合制备BaAl2S4:Eu溅射靶材.     

C60偶联多孔硅系统的蓝光发射

用G60作为表面钝化剂，与多孔硅进行偶联．发现当C60偶联多孔硅系统在空气中存储一年后，能够发射460nm左右的强烈蓝光．经过系统的测量和分析，认为蓝光起源的发光中心与SiO2体材料中的“自捕获激子”模型类似．它是由一个氧空位和一个间隙氧组成的，间隙氧同时和相邻的晶格氧形成过氧连接．光激发载流子来自于Si纳米晶粒的核心，辐射复合过程则在多孔硅表面的发光中心进行．进一步的电子束辐照和臭氧辐照实验证明了这个发光中心的存在．从FTIR谱的分析，推测是样品表面Si=O双键的缓慢变化促使了蓝光中心的自发产生．     

S引入ZnO的水热生长及其微观发光特性研究

利用单步水热法制备了纯ZnO和S引入的双棒状ZnO（S-ZnO）孪晶结构,并系统研究了掺杂对ZnO结构、形貌及荧光发光特性的影响。X射线衍射的实验结果表明,在引入S的ZnO样品中没有出现可以检测的新物相,S在样品中主要以杂质的形式存在。荧光光谱数据表明,在低温下纯ZnO样品无可见光发光,但S-ZnO样品出现了较强的绿光发光峰;室温下两个样品均出现了可见光发光：ZnO样品的发光峰位于橙光区（570 nm附近）,而S-ZnO位于绿光区（500 nm附近）。微区阴极荧光谱的数据表明,ZnO样品的橙光发光非常弱,几乎不可探测;S-ZnO样品的绿光发光则很强,要远远超过带边发光。本研究结果为进一步理解S在ZnO中引入的缺陷及其发光机理起到重要的作用,对增强ZnO的可见光发光特性进行了有益的探索。     

3C—SiC晶体薄膜的退火特性及其光荧光

采用HFCVD技术,通过两步CVD生长法,以CH4＋SiH4＋H2混合气体为生长源气,在Si衬底上生长3C－SiC晶体薄膜。对所制备的样品薄膜在氮气气氛中分别采取了快速退火和慢速退火处理,并对退火前后的样品进行了光荧光（PL）分析。结果显示,未经退火处理的样品其PL谱为一覆盖整个可见光区域展宽光谱线,主峰位置在520nm附近;经快速退火处理后样品的PL谱在450nm位置附近出现了又一较强峰,再经慢速退火处理后此峰基本消失,但室温PL峰发生红移。比较结果说明快速退火处理极易给3C－SiC晶体薄膜造成应力损伤。     

The pl “violet shift” of cerium dioxide on silicon

CeO₂ thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied from tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of “violet shift” was observed.     

铒离子注入氮化镓的光学活性与缺陷掺杂变化

对100keV、1×1015cm-2的Er离子注入的GaN 退火样品的各项性质进行研究,采取光致发光(室温)、拉曼光谱和卢瑟福背散射对不同的退火样品的微观结构和光学性质进行研究.在退火样品中,均观测到了在1539nm 附近的PL峰.随着退火温度的升高,PL峰强在900℃时达到最大值.RBS结果显示随着温度的升高,Er离子不断扩散,且有部分在表面析出,导致在光学活性位置上的Er离子减少,使PL强度在更高温度下减弱.      

退火温度对ZnO/SiO_2复合薄膜结构及光学性能的影响

采用溶胶-凝胶(sol-gel)法在玻璃衬底上制备ZnO/SiO2(ZSO)复合薄膜,并采用扫描电子显微镜(SEM)、X射线衍射(XRD)、紫外-可见分光光度计(UV-Vis)和光致发光(PL)谱对样品的形貌、晶体结构、透过率及光致发光性能进行表征.SEM结果表明,样品为双层结构,随着退火温度的升高,颗粒变大,并产生团聚现象;XRD结果表明,样品经退火处理后生成六方纤锌矿型ZnO,衍射峰强度和晶粒尺寸随退火温度的升高而增大;UV-Vis结果表明,样品同时具有ZnO和SiO2特征吸收边,双层复合薄膜中ZnO和SiO2两种不同材料的能带不连续导致360nm附近的曲线不平滑,并使能带蓝移,经400℃退火处理后的样品透过率较高;PL谱结果表明,在355nm波长激发下,样品分别在紫外区和蓝光区域产生发射峰,随着退火温度的升高,样品内缺陷密度减小,由缺陷引起的发光强度减弱.     

Effect of sintering on the optical properties of SiO2 colloidal crystal multilayers

High-quality SiO2 colloidal crystal multilayers were fabricated from ethanol solutions by the vertical deposition method and the effect of sintering on the optical properties of the samples was investigated. Optical properties,which are determined by the photonic band structure, weres tudied by means of light transmission and reflection measurements. The morphology of the samples was characterized by scanning electron microscopy (SEM). SEM images illustrate the ordered close package of the spherical colloids in planes parallel to the substrate surface. In addition, the sampie is crackless as a result of an appropriate drying rate. It is shown that with the increase of the sintering final temperature, though the depth and the width of the peak of Bragg diffraction of the sample vary vastly, the peak produces few blue shifts. Optical measurement results were compared favorably to the microstructural properties of the colloidal crystal multilayers.