表面等离子体共振增强ZnO/Ag薄膜发光特性研究

为了提高氧化锌光致发光强度,以磁控溅射氧化锌/银复合薄膜为研究对象,系统地研究了氧化锌薄膜的光学性质。实验中首先在硅衬底上用射频磁控溅射的方法沉积氧化锌/银复合薄膜,作为对比,同时沉积了一层氧化锌薄膜。通过扫描电子显微镜和原子力显微镜对样品的形貌及成份进行表征,并且在室温下测试样品在300~800 nm波长范围内的光致发光光谱。实验结果表明:所制得样品为均匀分布的氧化锌纳米薄膜,纯氧化锌光致发光光谱结果显示有波长位于378 nm左右的紫光、470 nm左右的蓝色发光峰存在,加入银薄膜后,氧化锌可见光区和紫外光区的光致发光光谱强度均有所增强,而且紫外光峰位出现了红移。实验结果结合样品吸收谱对光致发光机理的分析作了进一步的分析。     

Si衬底上MgxZn1-xO薄膜发光特性研究

采用射频磁控溅射（RFMS）法，在Si衬底上生长出具有（002）择优取向的MgxZn1-xO薄膜。透射光谱结果表明，与ZnO相比，MgxZn1-xO薄膜的吸收带边从378nm蓝移至308nm，这说明MgxZn1-xO薄膜的带隙随着Mg组分的增加而加宽。扫描电镜（SEM）能谱分析表明，薄膜中的Mg含量比靶源中的高。用不同波长的光激发得到的光致发光（PL）潜显示，在不同波长的光激励下，只出现单色蓝或绿发光峰，其它的发光峰消失，而且随着激发光波长从260nm、280nm到300nm的增加，发光峰位置分别从431nm、459nm红移至489nm，发光强度也显著增强。分析表明，这些发光峰与O空位有关。     

Spectroscopic studies of sol–gel grown CdS nanocrystalline thin films for optoelectronic devices

CdS is one of the highly photosensitive candidate of II–VI group semiconductor material. Therefore CdS has variety of applications in optoelectronic devices. In this paper, we have fabricated CdS nanocrystalline thin film on ultrasonically cleaned glass substrates using the sol–gel spin coating method. The structural and surface morphologies of the CdS thin film were investigated by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) respectively. The surface morphology of thin films showed that the well covered substrate is without cracks, voids and hole. The round shape particle has been observed in SEM micrographs. The particles sizes of CdS nanocrystals from SEM were estimated to be～10–12 nm. Spectroscopic properties of thin films were investigated using the UV–vis spectroscopy, Photoluminescence and Raman spectroscopy. The optical band gap of the CdS thin film was estimated by UV–vis spectroscopy. The average transmittance of CdS thin film in the visible region of solar spectrum found to be～85%. Optical band gap of CdS thin film was calculated from transmittance spectrum ～2.71 eV which is higher than bulk CdS (2.40 eV) material. This confirms the blue shifting in band edge of CdS nanocrystalline thin films. PL spectrum of thin films showed that the fundamental band edge emission peak centred at 459 nm also recall as green band emission.     

覆膜浸渍扩散阴极表面微区电子发射像研究

覆膜对浸渍扩散热阴极表面电子发射的影响一直是热阴极研究领域的重点课题。该文采用最新研制的深紫外激光光发射电子显微镜/热发射电子显微镜(DUV-PEEM/TEEM),对一半覆膜、另一半未覆膜的浸渍扩散阴极试样作了1150 ℃×2 h激活,并对其表面微区的热电子发射像及其随温度的变化作了比较。结果发现,两种阴极的热电子发射均主要位于孔隙及其邻近颗粒边缘;随温度升高,未覆膜阴极发射主要集中于孔隙内及周边有限区域内,发射面积增量较小,覆膜则使阴极有效发射区域得以由孔隙及其边缘向距孔隙更远的区域延伸,发射面积大幅增加。上述结果首次给出了覆膜浸渍扩散阴极微区的电子发射特征,对于理解该类型阴极发射机理有一定参考价值。     

ZnO:Ag薄膜的制备及其光学性能研究

采用蒸镀与氧化二步法,以高纯混合金属Zn:Ag作蒸发源,在石英衬底上沉积Zn:Ag金属薄膜,经不同热氧化处理生长Ag掺杂ZnO薄膜。结果显示,以Ag含量为质量分数3%的蒸发源沉积的Zn:Ag薄膜经500℃氧化后,生成的ZnO:Ag薄膜在380 nm附近出现很强的近带边紫外发光峰,在438~470 nm附近出现较弱的深能级缺陷发光峰,该薄膜在360 nm有接近垂直的吸收边,其载流子浓度为1.810×1021cm–3,表现出p型导电特性和较好的光学质量。     

Synthesis and characterization of phosphorus-doped ZnO and (Zn,Mg)O thin films via pulsed laser deposition

The transport and optical properties of phosphorus-doped (Zn,Mg)O thin films grown via pulsed laser deposition (PLD) are studied. The carrier type of as-deposited (Zn,Mg)O:P films converts from n-type to p-type with increasing oxygen partial pressure. All the films exhibit good crystallinity with c-axis orientation. This result indicates the importance of oxidation conditions in realizing p-type (Zn,Mg)O:P films. The as-deposited ZnO:P film properties show a strong dependence on the deposition ambient at different growth temperatures. The resistivity of the samples deposited in O₃/O₂ mixture is two orders of magnitude higher than the films grown in oxygen and O₂/Ar/H₂ mixture. The room-temperature photoluminescence (PL) of the as-deposited films has been shown that growing in the O₂/Ar/H₂ mixture ambient significantly increases the band edge emission while inhibiting the visible emission. The enhanced ultraviolet (UV) emission in the films grown in O₂/Ar/H₂ mixture may result from hydrogen passivation of the deep level emission centers. The annealed ZnO:P films are n-type with nonlinear dependence of resistivity on annealing temperature. The resistivity increases in the films with annealing at 800°C while decreasing with further increasing annealing temperature. Strong visible light emission is observed from the ZnO:P films annealed in oxygen.     

Ag纳米颗粒有机薄膜受激辐射增强研究

为进一步降低有机半导体材料的激射阈值,文章研究利用银纳米颗粒的表面等离子体共振效应来实现对有机半导体薄膜受激辐射的增强.将制备好的Ag纳米溶液旋涂于玻璃基底上,然后在其上再旋涂PS:Alq3:DCJTB有机薄膜发光层,构成平面波导结构.用355nm波长的YAG激光泵浦样品.实验发现:相比于无Ag纳米颗粒情况,有Ag纳米...     

表面覆盖退火对ZnO薄膜光学性质的影响

研究了暴露在空气中退火和表面覆盖蓝宝石基板退火对MOCVD生长的ZnO薄膜光学性质的影响.研究发现,暴露在空气中退火虽可以去除薄膜中的氢杂质,并在低温光致发光(PL)谱中观察到与氢相关的束缚激子峰消失,但是退火后样品室温PL谱中可观察到很强的可见光发射,表明样品中引入了大量的深能级,样品的自由激子发光没有增强.而表面覆盖蓝宝石基板退火的样品,有效去除了氢杂质,但没有观察到可见光发射,说明表面覆盖蓝宝石基板退火可以有效地保护ZnO表面不分解,不生成深能级中心.由于激子束缚中心的减少,表面覆盖退火样品的自由激子发射大大增强.     

热氧化法制备ZnO薄膜及其特性研究

用热氧化金属Zn膜的方法在Si(111)衬底上制备ZnO薄膜。X射线衍射结果表明,500℃氧化的样品的结晶性能最好。随氧化温度的升高,薄膜内的应力方向在450~500℃之间发生转变,从沿c轴的张应力变为压应力。500℃氧化的样品的室温光致发光(PL)谱中,紫外峰的半高宽为94.8meV,其强度与深能级发射强度之比高达162。氧化温度超过700℃后,样品的PL谱以深能级发射为主,对此现象产生的原因进行了讨论。     

脉冲激光沉积法制备氧化锌薄膜

ZnO是一种新型的Ⅱ-Ⅵ族半导体材料,具有优良的晶格、光学和电学性能,其显著的特点是在紫外波段存在受激发射。利用脉冲激光沉积法(PLD)在氧气氛中烧蚀锌靶制备了纳米晶氧化锌薄膜,衬底为石英玻璃,晶粒尺寸约为28-35 nm。X射线衍射(XRD)结果和光致发光(PL)光谱的测量表明,当衬底温度在100-250℃范围内时,所获得的ZnO薄膜具有c轴的择优取向,所有样品的强紫外发射中心均在378-385 nm范围内,深能级发射中心约518-558 nm,衬底温度为200℃时,得到了单一的紫外光发射(没有深能级发光)。这归因于其较高的结晶质量。     

金刚石薄膜的形成及其场发射特性研究

研究了金刚石聚晶碳膜的生长过程,以及不同生长阶段碳膜的场发射性能。通过磁控溅射法在陶瓷上镀一层金属钛作为制备碳膜的衬底,将衬底放入微波等离子体化学气相沉积腔中,经过不同的沉积时间制备出一系列的碳膜。利用SEM、Raman光谱仪、X射线衍射仪等仪器,对碳膜进行了形貌与成分分析,最后利用二极结构场发射装置,测试了碳膜的场发射性能。着重讨论了金刚石聚晶碳膜生长过程中的变化,并且对金刚石聚晶碳膜的场发射机理进行了深入研究。     

On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking

The green emission of poly(9,9′′‐dioctylfluorenyl‐2,7′′‐diyl), end‐capped by polyhedral oligomeric silsequioxanes, (PFO‐POSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green‐to‐blue emission intensity ratio, used to assess the emission properties of thin (90 nm) films, was 3.70, 4.35, and 1.54 for an air‐annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5–6 μm) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl‐to‐aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting.     

Electromigration and electrochemical reaction mixed failure mechanism in gold interconnection system

Power bipolar devices with gold metallization experience high failure rates. The failures are characterized as shorts, detected during LSI testing at burn-in. Many of these shorted locations in the chip are the same for the failed devices. From a statistical analysis for wafer lots, it is found that the short failure rate is higher for the lots with thinner SiON interlayer dielectric films. Cracks are commonly observed in the SiON films at step edge portions of the device. The SiON film is locally turned to Au–Si eutectic at short positions by the reaction of Au with the SiON film and the reaction is only generated at specific step edge portions, i.e., at step edge on emitter electrodes in driver transistors and/or at cross-points of power lines. Based upon these results, a new electromigration and electrochemical reaction mixed failure mechanism is proposed for the failure.     

退火过程对c轴择优取向的ZnO薄膜的光学性质的影响

利用溶胶凝胶法在石英衬底上采用旋涂法制备出ZnO薄膜,通过X射线衍射仪发现不同的退火温度对ZnO薄膜的择优取向有很大影响;通过紫外可见分光光度计和室温发光谱可以看出,制备的薄膜有很好的光学透过性和很强的紫外发光特性,而不同的退火温度对其光学性质有很大的影响。实验发现采用此种方法在650℃左右退火是一个合适的退火温度,结构特性和光学性质都相对较好;采用热分析方法可知ZnO将在375℃左右从非晶转向结晶状态,因而在常规ZnO薄膜制备方法中增加一步500oC的热处理将有助于提高ZnO薄膜的结晶质量。     

应用于FED的金刚石薄膜的光学和结构分析

本文比较研究了不同晶粒大小和结构的金刚石薄膜的场发射性质,这些金刚石薄膜通过热丝辅助化学气相沉积法(HFCVD)获得.研究结果表明纳米尺寸效应对金刚石薄膜的场发射性能有非常重要的影响,通过比较不同晶粒尺寸的金刚石薄膜发现纳米金刚石薄膜相对于大晶粒金刚石薄膜(比如微米级的金刚石薄膜)有更好的场发射性能.从拉曼光谱得到,含有一定量非金刚石相的金刚石薄膜有更好的场发射能力和更低的开启电场(E0).另外,具有(111)定向的金刚石薄膜比起其他结构的金刚石薄膜,它的电子发射能力更强.     

AZO种子层朝向对ZnO纳米棒形貌和发光特性的影响

在水平管式炉中,采用热蒸发锌粉的方法,在镀有掺铝氧化锌(AZO)薄膜的石英基片上制备了大量高密度的ZnO纳米棒,AZO膜面分别正对和背对锌源。利用扫描电子显微镜、X射线衍射仪以及荧光光谱仪分析AZO膜面朝向对ZnO纳米棒的形貌、微结构及光学性能的影响。结果表明,不同朝向的AZO膜面上所生长的纳米棒具有相似的形貌和微结构。保温时间10min样品的氧空位的缺陷态发光为绿光,强度较强;保温时间15min样品的纳米棒长度较长、相对垂直衬底,其近带边发光较强,氧间隙的缺陷态发光较弱。正对锌源衬底上且保温时间15min样品的近带边发光最强,且缺陷态发光最弱。     

退火温度对生长在TiO2缓冲层上的ZnO薄膜的影响

采用电子束蒸发技术在TiO2缓冲层上沉积了ZnO薄膜,研究了不同的退火温度对薄膜晶化质量及发光性质的影响.利用X射线衍射仪和扫描探针显微镜分析了薄膜样品的结构性质,利用荧光光谱仪研究了薄膜样品的光致发光性质.分析结果表明,退火处理后的ZnO薄膜都沿c轴择优牛长.在600℃下退火的样品具有最强的(002)衍射峰、最强的紫外发射和最弱的可见光发射,其晶粒大小均匀.紧密堆积.而对于在500和700℃下退火的样品,其可见光发射较强.这表明在600℃下退火的样品具有最好的晶化质量.     

Enhanced Vertical Charge Transport in a Semiconducting P3HT Thin Film on Single Layer Graphene

The crystallization and electrical characterization of the semiconducting polymer poly(3‐hexylthiophene) (P3HT) on a single layer graphene sheet is reported. Grazing incidence X‐ray diffraction revealed that P3HT crystallizes with a mixture of face‐on and edge‐on lamellar orientations on graphene compared to mainly edge‐on on a silicon substrate. Moreover, whereas ultrathin (10 nm) P3HT films form well oriented face‐on and edge‐on lamellae, thicker (50 nm) films form a mosaic of lamellae oriented at different angles from the graphene substrate. This mosaic of crystallites with π–π stacking oriented homogeneously at various angles inside the film favors the creation of a continuous pathway of interconnected crystallites, and results in a strong enhancement in vertical charge transport and charge carrier mobility in the thicker P3HT film. These results provide a better understanding of polythiophene crystallization on graphene, and should help the design of more efficient graphene based organic devices by control of the crystallinity of the semiconducting film.     

Short‐Wavelength Lasing‐Spasing and Random Spasing with Deeply Subwavelength Thin‐Film Gain Media

Lasing‐spasers are subwavelength‐sized metal/dielectric structures that emit light via stimulated emission of surface plasmons. Here, it is demonstrated that silver nanoparticles combined with deeply subwavelength, blue‐emitting conjugated polymer thin films can function as room‐temperature lasing‐spasers and random spasers with quality factors up to 250. In contrast to other thin‐film‐based spaser and plasmonic random laser studies, which have used gain films ranging from ≈200 nm to 500 nm in thickness and which monitor emission guided to the sample edges, in this study, the thickness of the thin‐film gain medium ranges from 30 nm to 70 nm and emission is collected normal to the plane of the film. This eliminates effects that arise from optical trapping of scattered emission within the gain medium that is typically associated with plasmonic random lasing. The use of the conjugated polymer thin‐film gain medium allows higher chromophore densities compared to organic dye‐doped layers, which enables spasing using deeply subwavelength gain layers. Samples implementing gold nanoparticles and the conjugated polymer gain medium do not exhibit stimulated emission, demonstrating that it is the spectral overlap between the silver nanoparticle's surface plasmon resonance and the gain medium's emission that is necessary for observation of stimulated emission from this material system.     

Improving the emission characteristics of a carbon nanotube film in NaCl electrolyte

Screen printing is undoubtedly the most cost-effective process for the fabrication of large-sized carbon nanotube field emission display (CNT-FED). A novel post-treatment method in NaCl electrolyte was presented to solve the problem of poor field emission characteristics of printed CNT films. Compared to those of untreated films, the turn-on electric field of the treated film decreased from 2.4 to 1.4 V/μm and the total emission current of the treated film that has the same printing area as the untreated one increased from ∼100 to ∼1800 μA. Scanning electron microscope (SEM) and Raman spectrum study revealed that field emission characteristics are enhanced by two factors. Firstly, the NaCl electrolyte treatment appeared to render the CNT surfaces more activey by exposing more CNTs from the CNT film. Secondly, the numerous defects of CNTs of the CNT film were increased by electrical current energy.