氧化锌复合纳米微粒的发光特性研究

最近，通过对有机表面活性剂包覆的氧化锌纳米微粒ZnO／ST作强热表面化学修饰，我们得到了核心／壳层结构的红色氧化锌复合纳米微粒．与以往的无色氧化锌纳米微粒的性质相比，这种复合微粒具有独特的光学和非线性光学性质．1）复合氧化锌纳米微粒的光学带隙发生了很大红移．同体相带队相比（Eg=3．4eV），新的光学带隙出现在2．5eV左右，而且其光学带隙随着热处理温度的升高而向更长波方向移动．透射电子衍射成像和选区衍射实验表明，这种颜色变红的样品在粒径上（～8nm）与热处理前的无色样品相比没有明显的变化，且具有同体相氧化锌相…     

纳米6H-SiC薄膜的等离子体化学气相沉积及其紫外发光

采用螺旋波等离子体化学气相沉积技术在Si(100)衬底上制备了具有纳米结构的碳化硅(SiC)薄膜.通过X射线衍射、傅里叶红外吸收和扫描电子显微镜等技术对所制备薄膜的结构、形貌以及键合特性进行了分析,利用光致发光技术研究了样品的发光特性.分析表明,在500℃的衬底温度和高氢气稀释条件下,所制备的纳米SiC薄膜红外吸收谱主要表现为SiC TO声子吸收,X射线衍射显示所制备的纳米SiC薄膜为6H结构.采用氙灯作为激发光源,不同氢气流量下所制备的样品在室温下呈现出峰值波长可变的紫外发光.     

无催化剂气相沉积法直接制备用于紫外光检测的氧化锌纳米线网

对于环境检测和高速光通信而言,高性能紫外光电探测器是关键。利用气相沉积法在无催化剂条件下制备氧化锌纳米线网,在纳米线网上直接制备光电器件的性能得到了提高。结果显示,纳米线网光电探测器的光电流为60 A,大约是单根纳米线光电器件光电流的15倍。详细讨论纳米线网光电探测器的响应机制发现,在纳米线网内,纳米线与纳米线之间的结势垒高度决定了纳米线内部载流子的传输。当紫外光照射纳米线网光电探测器时,纳米线与纳米线之间结势磊高度的快速变低,从而提高光电器件的性能。     

均匀沉淀法制备纳米氧化锌研究

以六水硝酸锌为锌源、氢氧化钠为碱源、甲醇溶液作为溶剂,采用均匀沉淀法合成了纳米氧化锌.实验结果表明制备出的纳米氧化锌为纯相六角纤锌矿结构氧化锌.通过X-射线衍射(XRD),扫描电镜(SEM)等测试手段对所得产物的组成、形貌、结构进行了研究.该方法制备的纳米氧化锌平均粒径在11 nm左右.     

以ZnS为源用化学气相沉积法在硅衬底上生长ZnO纳米颗粒

首次以ZnS为源,采用化学气相沉积法在抛光的Si单晶片衬底上生长晶态的ZnO纳米颗粒,其形貌、尺寸和密度都与气体流量、衬底温度、生长时间以及有无催化剂等生长条件密切相关．在没有Au催化的条件下,ZnO颗粒呈圆形颗粒,直径多在30-200nm之间,密度为10^4-10^9cm^-2;有Au催化的条件下,ZnO纳米颗粒呈六边形,平均尺寸明显变小,在10—100cm之间,而密度显著提高,为10^8-10^10cm^-2所制备的纳米ZnO颗粒在497nm和376nm附近分别有很强和较弱的光致发光．     

a—Si3N4纳米粒子的能级结构研究

用激光化学气相沉积法制备出平均粒径为10nm的a-Si     

Si基异质结构发光的研究现状

综述了Ｓｉ 基异质结构发光研究的现状。介绍了Ｓｉ 材料本身的本征发光、激子发光、杂质发光等特性,描述了掺Ｅｒ－ Ｓｉ 的发光、Ｓｉ 基量子结构（ 量子阱、量子点） 的光发射,重点研究ＳｉＧｅ／Ｓｉ 异质结构的发光性质。同时还对多孔Ｓｉ 发光、Ｓｉ 基发光二极管（ＬＥＤ） 与Ｓｉ 双极晶体管（ＢＪＴ） 集成、Ｓｉ 基上垂直腔面发射激光器（ＶＣＳＥＬ） 与微透镜的混合集成作了简要的介绍。     

纳米结构洋葱状富勒烯的CCVD法制备

纳米结构洋葱状富勒烯(NSOFs)是准球体同心壳层形状的碳笼构成的富勒烯分子，由于其独特的结构及性能，具有极富潜力的应用前景。现有的制备洋葱状富勒烯的方法有高能电子束辐照含碳物质、水中电弧放电法、纳米金刚石粉热处理和射频等离子CVD等。但由于上述种种方法的制备条件苛刻，不适合工     

生长时间对氧化锌纳米棒发光性能的影响

为了研究氧化锌纳米棒的生长机理,先用脉冲激光沉积方法在玻璃衬底上制备一层氧化锌薄膜作为种子层,然后用水热法在种子层上生长氧化锌纳米棒,研究了不同反应时间对其结构、形貌及发光特性的影响。利用X射线衍射仪和扫描电子显微镜测定样品的结构和形貌,用自组建的光致发光系统对样品的光致发光光谱进行了测量。结果表明,氧化锌纳米棒沿c轴高度取向并呈六角纤锌矿结构;随着生长时间的增加,氧化锌纳米棒结晶质量明显改善,纳米棒均匀、致密性和取向性均提高,样品的缺陷发光增强而激子发光减弱。     

多糖绿色合成纳米氧化锌的研究

利用一种高分子多糖——葡聚糖作为稳定剂和软模板,通过一条绿色途径合成了粒径为70nm左右的纳米氧化锌,发现其在380nm处有一个强烈的吸收峰。通过SEM,TEM等测试手段,研究了葡聚糖分子以及热处理对纳米氧化锌形貌和粒径的影响,并探讨了纳米氧化锌的形成机理。此种方法也可拓展到其它纳米氧化物的合成领域。     

四脚针状ZnO纳米结构的制备及表征

采用以Zn粉、C粉为原料,采用热蒸发法,在没有任何载气和700℃下制备了四脚针状ZnO纳米结构。C粉起到了催化剂的作用但产物却不存在催化剂去除的问题,同时C粉氧化生成的CO/CO2还起到了载气的作用。扫描电镜(SEM)表明,四脚针状ZnO具有很细的尖端,直径为50 nm。X射线衍射(XRD)、微区拉曼图谱的特征峰表明,四脚针状ZnO是高纯的六角纤锌矿结构。光致发光(PL)谱在403 nm附近有微弱的紫光发射峰,而在510 nm附近出现了很强的绿光发射峰。     

Evolution of ZnO nanostructures on silicon substrate by vapor-solid mechanism: Structural and optical properties

ZnO nanostructures with different morphologies and sizes were synthesized on silicon substrate simply by the thermal evaporation of high-purity metallic zinc powder in the presence of oxygen without the use of any catalyst or additives. It was observed that the substrate temperature and the distance of the substrate from the source material play a critical role to determine the morphologies and sizes of the deposited structures. Scanning electron microscopic observations revealed that different types of nano- and microstructures, such as ZnO pyramid-shaped nanotowers, nanowires attached with the sheet-like structures, nanorods, microcages, and microtubes were obtained at different temperature zones with specific distances of the substrate from the source material. High-resolution transmission electron microscopy and x-ray diffraction studies confirm that the deposited products are single crystalline with wurtzite hexagonal structures. The room-temperature photoluminescence spectra of all the deposited structures displayed a strong near-band-edge emission with negligible green emission.     

ZnO纳米管的制备及光学特性研究

ZnO nanotubes have been fabricated through a carbon thermal reduction deposition process. Structure characterization results show that the ZnO nanotubes have a single crystalline wurtzite hexagonal structure pref- erentially oriented in the c-axis. The diameters of ZnO nanotubes are in the range of 90-280 nm and the wall thickness is about 50-100 nm. Room-temperature photoluminescence measurements of the ZnO nanotubes exhibit an intensive ultraviolet peak at 377 nm and a broad peak centered at about 517 nm. The UV emission is caused by the near band edge emission while the green emission may be attributed to both oxygen vacancy and the surface state. Raman and cathodoluminescence spectra are also discussed. Finally, a possible growth mechanism of the ZnO nanotubes is proposed.     

Measuring the optical properties of a trapped ZnO tetrapod

We report the onset of lasing from an electrodynamically trapped ZnO tetrapod. Each of the four legs of such an isolated tetrapod behaves as a single nanowire, where light is guided along the length of the wire and the necessary resonant feedback for lasing is provided at the two end facets. A diluted solution of ZnO tetrapods in methanol was sprayed in the form of a charged mist into a chamber containing the electrodynamic endcap trap. The quick evaporation of methanol assisted in trapping a single charged ZnO tetrapod. The trapped tetrapod is optically pumped with pulses from a Q-switched laser at a wavelength of 355 nm and emits light at 390 nm. For increasing pump fluences above 15 mJ/cm², a superlinear increase in intensity and a narrowing in the spectral width of the photoluminescence were observed, indicating lasing.     

Sb掺杂ZnO电子结构和光学性质

为了研究ZnO掺Sb后电子结构和光学性质的变化,采用基于密度泛函理论对纯净ZnO和Sb掺杂ZnO两种结构进行第一性原理的计算。计算结果表明：随着Sb的掺入,体系的晶格常数变大,键长增加,体积变大,系统总能增大。能带中价带和导带数目明显变密,费米能级进入导带,体系逐渐呈金属性,带隙明显展宽。在光学性质方面,主吸收峰的左边出现了新的吸收峰,是由导带上的Zn-4s和Sb-5p轨道杂化电子跃迁所致;同时介电函数虚部波峰发生一定程度的升高,实部静态介电常数也明显增大。     

The sprayed ZnO films: nanostructures and physical parameters

We synthesized the pure and indium-doped (IZO) ZnO films with a facile composition control spray pyrolysis route. The substrate temperature (T_s) and In-doping effects on the properties of as-grown films are investigated. The X-ray pattern confirms that the as-synthesized ZnO phase is grown along a (002) preferential plane. It is revealed that the crystalline structure is improved with a substrate temperature of 350 ℃. Moreover, the morphology of as-grown films, analyzed by AFM, shows nanostructures that have grown along the c-axis. The (3 × 3μm²) area scanned AFM surface studies give the smooth film surface RMS < 40 nm. The UV-VIS-IR measurements reveal that the sprayed films are highly transparent in the visible and IR bands. The photoluminescence analysis shows that the strong blue and yellow luminescences of 2.11 and 2.81 eV are emitted from ZnO and IZO films with a slight shift in photon energy caused by In-doping. The band gap is a bit widened by In-doping, 3.21 eV (ZnO) and 3.31 eV (IZO) and the resistivity is reduced from 385 to 8 Ω ·m. An interesting result is the resistivity linear dependence on the substrate temperature of pure ZnO films.     

Studies on the properties of sputter-deposited Ag-doped ZnO films

Ag-doped ZnO films were prepared by simultaneous rf magnetron sputtering of ZnO and dc magnetron sputtering of Ag on glass substrate. The influences of dopant content and substrate temperature on the properties of the as-grown films were investigated. Several analytical tools such as X-ray diffraction, spectrophotometer, atomic force microscopy, scanning electron microscopy and four-point probe were used to explore the possible changes in electrical and optical properties. The as-grown film has a preferred orientation in the (0 0 2) direction. As the amounts of the Ag dopant were increased, the crystallinity as well as the transmittance and optical band gap were decreased while the electrical resistivity increased. However, as the substrate temperature was increased, the crystallinity and the transmittance were increased. A small amount of Ag (<1 at%) lowered the resistivity by 30% with only a slight decrease in the visible transparency.     

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。     

Rapid synthesis of ZnO dandelion-like nanostructures and their applications in humidity sensing and photocatalysis

In this study, ZnO dandelion-like nanostructures were rapidly synthesized on Si substrates using a two-step thermal oxidation approach. The ZnO nanostructures were grown at various thermal oxidation temperatures ranging from 400 °C to 700 °C. These nanostructures were then applied to humidity sensing and photocatalysis. The ratio of measured resistances in the humidity sensors for relative humidity (RH) levels of 11% and 95% at room temperature (RT) were found to rise from 10² to 10⁵ times for humidity sensors constructed with the nanostructures grown at temperatures from 400 °C to 700 °C, respectively, and sensor response time decreased from 15 s to 5 s. These results show that the proposed ZnO dandelion-like nanomaterial shows promise as a candidate for fabricating high-performance humidity sensors when the nanostructures are grown at 700 °C. In addition, the photocatalytic effect of the nanostructures was tested with a decomposition of methyl orange (MO) dye under UV illumination. Experimental results show that the ZnO dandelion-like nanomaterial grown at a thermal oxidation temperature of 700 °C exhibits an excellent photocatalytic effect, which degrades to almost 90% of the MO activity over 120 min.     

Growth-temperature-dependent optical and acetone detection properties of ZnO thin films

Zinc oxide (ZnO) thin films were prepared onto glass substrates at moderately low growth temperature by two-stage spray pyrolysis technique. The effects of growth temperature on structural, optical and acetone detection properties were investigated with X-ray diffractometry, a UV-visible spectrophotometer, photoluminescence (PL) spectroscopy and a homemade gas sensor testing unit, respectively. All the films are polycrystalline with a hexagonal wurtzite phase and exhibit a preferential orientation along [002] direction. The film crystallinity is gradually enhanced with an increase in growth temperature. The optical measurements show that all the films are physically highly transparent with a transmittance greater than 82% in the visible range. The band gap of the film is observed to exhibit a slight red shift with an increasing growth temperature. The PL studies on the films show UV/violet PL band at ～ 395 nm. Among all the films investigated, the film deposited at 250 ℃ demonstrates a maximum sensitivity of 13% towards 20 ppm of acetone vapors at 300 ℃ operating temperature.