四角状氧化锌纳米结构的发光特性研究

The tetrapod ZnO nanostructures are synthesized on the Si （100） substrates using the chemical va- por deposition （CVD） method at 1000 ℃. Each nanostructure has four arms which are about 3-10 μm in length and 0.2-1.5 μm in diameter. Further analyses on structure demonstrate that the tetrapod ZnO nanostructures have single crystalline wurtzite hexagonal structure preferentially oriented in c-axis. The photoluminescence （PL） mea- surements of the tetrapod ZnO nanostructures revealed a UV peak at 382 nm corresponding to the free exciton emission, and a green peak at 523 nm arising from deep level emission. For comparative analysis, cathodolumines- cence （CL） spectra obtained from different regions of an individual tetrapod are investigated. Moreover, a possible growth mechanism of the tetrapod ZnO nanostructures is also discussed based on the experimental results.     

Luminescence Properties of Nanometer Si with Embedded Structure

Blue luminescence at about 431 nm is obtained from epitaxial silicon after C^＋ implantation, annealing in hydrogen ambience and chemical etching sequentially. With increase of chemical etching, the blue peak is enhanced at first, then decreased and substituted by a red peak at last. C=O compounds are introduced during C^＋ implantation and embedded in the surface of nanometer Si formed during annealing, and at last is formed nanometer silicon with embedded structure, which contributes to the blue emission. Presented is the possible mechanism of photoluminescence.     

Fluorescent emission characteristics of polycrystalline diamond film prepared by direct current jet CVD

The free-standing diamond films are deposited on molybdenum substrate by direct current jet chemical vapor deposition （DCJCVD）. X-ray diffraction, Raman spectroscopy and cathodoluminescence （CL） measurement are used to investigate the films structure and defects related to electron transition properties of the diamond films. The X-ray diffraction spectrum reveals that the diamond films have the polycrystalline cubic structure with diffraction peaks at 43.88° and 75.24°. A sharp peak at 1331.8 cm^-1 and a broad band at about 1250-1550 cm^-1 from Raman spectrum are attributed to diamond phase and sp2-type carbons, respectively. Two emission peaks at 440 nm and 530 nm, associated with dislocation defects and nitrogen and vacancy complexes respectively, are observed in cathodoluminescence spectrum. In addition, in order to understand both emission processes, a simple energy level scheme is suggested.     

Luminescent Properties of Nanometer Si with Embedded Structure

Blue luminescence at about 431nm is obtained from epitaxial silicon after C^ implantation,annealing in hydrogen ambience and chemical etching sequentially. When annealed in nitrogen ambience and etched accordingly, there is a much narrower peak at about 430nm. During C^ implantation,C=O compounds are introduced into and embedded in the surface of nanometer Si formed during annealing,at last, nanometer silicon with embedded structure is formed,which contributes to the blue emission.     

Effects of post-annealing treatment on the structure and photoluminescence properties of CdS/PS nanocomposites prepared by sol-gel method

CdS nanocrystals have been successfully grown on porous silicon (PS) by sol-gel method. The plan-view field emission scanning electron microscopy (FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of CdS are broadly distributed on the surface of PS substrate. With the increase of annealing time, the CdS nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of ZnO/PS show that CdS nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence (PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of CdS/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.     

Electrodeposition and Characterization of ZnO Thin Films

Thin films of ZnO were electrodeposited from an aqueous solution of Zn（NO3 ）2 on indium tin oxide（ITO）-covered glass substrate. The analysis of X-ray diffraction（XRD） and scanning electron micrograph （SEM） indicated that the obtained ZnO films had a compact hexagonal wurtzite type structure with preferable （002） growth direction. A sharp near-UV emission peak located at 380 nm and a strong orange-red emission peak located at 593 nm were observed in the photoluminescence, when excited with 325 nm wavelength at room temperature. Then the prepared ZnO films were introduced as anode phosphors into the field emission test. It was found that orange-red cathode-luminescence was observed and the luminescent brightness was enhanced by annealing. When annealing temperature increased about 600 ℃, the photoluminescence with peak of 531 nm and the green cathode-luminescence were observed. The tests showed that the brightness of about 2 × 102 cd/m^2 was obtained at electric field of 2 V/μm for annealed sample. The results revealed that the film could be a good kind of low-voltage drived cathode-luminescence phosphor.     

Photolumincscent Properties of Polyacetylenes Carbazole

The optical properties of one mono-substituted polyacetylene and two di-substituted polyacetylenes have been investigated. Each of the substituted polyacetylenes bears a carbazole unit in the side chain. In spite of the differences in their molecular structures, the dilute solutions（about 1 × 10^-6 M） of these substituted polyacetylenes exhibit the same absorptions and deep-blue emissions （about 360 nm）. Interestingly, the absorption and emission spectra of these substituted polyacetylenes are similar to those of the small molecule carbazole. As the concentration of the substituted polyacetylenes increases to about 1 × 10^-6 M, we have detected intense blue emissions at about 475 nm. Our results indicate that the absorption, the deep-blue emission（about 360nm） and the intense blue emission （about 475nm） originate from the carbazole chromophores in the side chain.     

Fluorescence enhancement of single-phase red-blue emit-ting Ba_3MgSi_2O_8:Eu~(2 ),Mn~(2 ) phosphors via Dy~(3 ) addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba3MgSi2O8:Eu2 ,Mn2 phosphors for plant cultivation has been investigated by Dy3 addition.The Ba3MgSi2O8:Eu2 ,Mn2 ,Dy3 (BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm.The two emission bands are coincident with the absorption spectrum for photosynthesis of plants.An obvious enhancement effect has been observed upon addition of Dy3 with amount of 0.03 mol%,in which the intensities of both blue and red bands reach a maximum.The origin of red and blue emission bands is analysed.The photochromic parameters of the samples at the nearly UV excitation are tested.This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation.     

Design and research of quasi-planar self-aligned silicon avalanche electron emission array

The device structure and technical processings of quasi-planar self-aligned silicon avalanche electron emission array arc introduced. The processing step at the edge of electron emission region is about 10nm only and the width of self-aligned current channel of shallow As implantation is about 3μm. Its I-V characteristics show a larger linear region and lower series resistance than that of the previous silicon avalanche electron emission devices. Some of the electron emission characteristics are also discussed in this paper.     

Properties of Light Emission Spectrum of Double-barrier Tunnel Junction

Fabricated are the double-barrier light emission tunnel junctions successfully. Introduced are the fabrication process and light emission characteristics. The spectra of the junctions are measured and analyzed especially. Their spectrum wavelength including main wave peak（locates at 450 nm～500 nm） of the double- barrier junction shows a ＂blue shift＂ in comparison with that of the single-barrier Metal/Insulator/ Semiconductor（MIS） or Metal/Insulator/Metal（MIM） junction（wave peak locates at 620 nm-740 nm）. This phenomenon should be due to the occurrence of the electron resonant tunneling in the double-barrier junction.     

Investigation of luminescence properties of ZnO nanowires at room temperature

The controllable growth processes of ZnO nanowires by evaporation of metal zinc with high purity and its luminescence properties have been investigated in detail. Firstly, the power of ZnO nanowires with high yield and homogeneous dimension was synthesized using the special quartz boat at 600 °C. Then, the oriented ZnO nanowires with about 20 nm diameter were synthesized by using a 90 nm-thick layer of ZnO nanocrystals on the Si substrate as the seed layer. Both fabrication processes are repeatable and no catalysts are necessary. Finally, photoluminescence (PL) spectroscopy for ZnO nanowires using an He-Cd laser line of 325 nm as the excitation source were measured at room temperature and both samples showed a sharp strong ultraviolet (UV) near-band edge emission. However, different UV peak positions (385 nm for ZnO nanowire powder, 377 nm for ZnO nanowire array) can be observed. The size confinement effect for excitons and carriers is proposed to explain the blue shift of the near-band edge emission with decreasing size and the native defects are responsible for the green emission.     

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。     

Effects of the Cr doping on structure and optical properties of ZnO thin films

Cr-doped ZnO thin films are prepared on glass substrates by the magnetron sputtering technique. An X-ray diffraction (XRD) is used to analyze the structural properties of the thin films. It indicates that all the thin films have a preferential c-axis orientation. The peak position of the (002) plane shifts to the higher 2θ value, and the peak intensity decreases with the increase of Cr doping. The results of the scanning electron microscopy (SEM) show that the surface morphology becomes loose with the incre...     

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。     

Eu3+,Li+共掺杂ZnO薄膜结构与发光性质的研究

为了研究Eu3+,Li+共掺杂的ZnO薄膜结构与发光性质,采用脉冲激光沉积方法在P型单晶Si（111）衬底上制备了Eu3+,Li+共掺杂的ZnO薄膜,其中,Eu3+作为发光中心,而Li+作为低价电荷的补偿离子和发光敏化剂。分别对样品进行了X射线衍射谱测试和光致发光谱分析。得出的数据中X射线衍射谱显示,Eu3+,Li+共掺杂的ZnO薄膜具有c轴择优取向,X射线衍射谱中除ZnO晶向以外没有出现其它结晶峰;Eu3+,Li+共掺杂的ZnO薄膜的光致发光谱与ZnO纯晶体薄膜的发射光谱基本相似,但是掺杂ZnO薄膜的紫外发光峰却出现红移现象,峰值位于382nm处,且发光峰也不尖锐。当以395nm的激发光照射样品时,在光致发光光谱中观察到了稀土Eu3+在594nm,613nm附近的特征发光峰。结果表明,掺杂元素Eu3+,Li+均已进入到ZnO晶格中,形成了以Eu3+为发光中心的ZnO纤锌矿结构。     

纳米ZnO光学性质研究进展

介绍了纳米ZnO常见发光谱的发光机制。在室温光致发光谱(PL)中,一般在380 nm处出现紫外发光,也有报道在357和377 nm处的紫外发光,列举了几种不同的发光解释。对于深能级发光,一般在400～550 nm出现连续的发光带,也有观察到深能级的声子伴线和声子复制现象。在低温光致发光谱的紫外发射中,一般观察到由自由激子发射(FX)、中性施主束缚激子发射(D0X)、施主-受主对跃迁峰(DAP)、中性施主束缚激子对应的双电子卫星峰(TES)以及声子伴线。综述了纳米ZnO的喇曼光谱、透射光谱、电致发光谱(EL)的特征,最后展望了纳米ZnO的光学性能研究前景。     

氧化锌薄膜的电化学沉积法制备及受激发射研究

采用一种简单的电化学沉积法，在三电极化学池中，以单一的硝酸锌水溶液作为电沉积液，制备了高光学质量的半导体ZnO薄膜。透射光谱测量表明其光学带隙为3．35eV，400～2000nm波段的光学透过率大于80％。X射线衍射(XRD)和原子力显微镜(AFM)研究表明，ZnO薄膜为纤锌矿结构的无序多晶颗粒膜，微晶尺寸小于250nm。当用355nm的皮秒脉冲激光作为抽运源垂直入射薄膜表面时，可以检测到400nm附近的近紫外受激发射光，其强度随入射强度呈超线性增长关系，阈值在196．8kW／cm^2处，并且激光发射是多模的和各个方向的，还与被激发的面积有关，表现为随机激光发射机制。     

电泳法制备ZnO纳米薄膜研究

报导了一种简单而有效的制备ZnO纳米薄膜的方法。以纳米ZnO和Mg(NO3).6H2O的异丙醇溶液作为电泳膜的沉积液,采用电泳法在ITO衬底玻璃上制备了高质量的ZnO纳米薄膜,并用透射电镜(TEM)、X射线衍射(XRD)、Raman谱和光致发光(PL)谱等对所制得的薄膜进行了表征。XRD表明,ZnO电泳膜是多晶膜且具有纤维锌矿结构;Raman谱和PL谱表明,ZnO纳米薄膜具有较强的紫外发射,其峰值波长为384 nm,而它的可见发射几乎观察不到,表明ZnO电泳膜是高质量的。     

Effect of growth conditions on zinc oxide nanowire array synthesized on Si (100) without catalyst

A uniformly distributed ZnO nanowire array has been grown on silicon (100) substrates by catalyst-free chemical vapor transport and condensation. The effect of growth conditions including source heating temperature, substrate temperature, and gas flow rate on growth properties of ZnO nanowire arrays are studied. Scanning electron microscopy, X-ray diffraction, and room temperature photoluminescence are employed to study the structural features and optical properties of the samples. The results show a correlation among experimental growth parameters. There is a zone for substrate temperature, by controlling gas flow rate, that uniformly distributed and well aligned ZnO nanowire arrays can be grown. Also, experiments indicate that ZnO nanowire arrays with different diameter along their length have been formed under various growth conditions in the same distance from source material. It is found that supersaturation is a crucial parameter determining the growth behavior of ZnO nanowire arrays. The growth mechanism of ZnO nanowires is discussed. The room temperature photoluminescence spectrums of ZnO nanowire array show two emission bands. One is the exciton emission band (centered at 380 nm) and the other is a broad visible emission band centered at around 490 nm. As the substrate temperature decreases, the intensity of UV emission increases while the intensity of visible emission peak decreases.