N2流量对GaN的形貌及光学和电学性能的影响

采用化学气相沉积法(CVD)在Si(100)衬底上以Ni为催化剂, 金属Ga和NH₃为原料合成了GaN微纳米结构, 并研究了N₂流量对产物GaN的形貌及光学和电学性能的影响。利用场发射扫描电子显微镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、X-ray能谱仪(EDS)、光致发光谱(PL)和霍尔效应测试仪(HMS-3000)等测试手段对样品的形貌、结构、成分、光学和电学性能进行了分析。结果表明, 随着N₂流量的增加, 产物GaN的形貌发生了由微米棒到蠕虫状线再到光滑纳米线的转变;生成的GaN均为六方纤锌矿结构;样品均表现出383 nm的近带边紫外发射峰和470 nm左右的蓝光发射峰;所有样品均为n型;并对产物GaN的形貌转变机理进行了分析。     

不同金属缓冲层对GaN薄膜的光学及电学性能的影响

本文以金属Ga和NH3为原料,Al、Ni和Fe为金属缓冲层,采用化学气相沉积法(CVD)在Si(100)衬底上合成了GaN微米薄膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能量弥散X射线谱(EDS)、光致发光光谱(PL)和霍尔效应测试仪(HMS-3000)等对GaN微米薄膜进行表征。结果表明,所有样品均为六方纤锌矿结构;样品均出现了很强的近带边紫外发射峰和半峰宽较大的中心波长为672 nm红光发射峰;不同样品的电学性能差异较大。最后对合成的GaN微米薄膜的可能形成机理进行了简单分析。     

不同金属缓冲层对GaN薄膜的光学及电学性能的影响

本文以金属Ga和NH₃为原料,Al、Ni和Fe为金属缓冲层,采用化学气相沉积法(CVD)在Si(100)衬底上合成了GaN微米薄膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能量弥散X射线谱(EDS)、光致发光光谱(PL)和霍尔效应测试仪(HMS-3000)等对GaN微米薄膜进行表征。结果表明,所有样品均为六方纤锌矿结构;样品均出现了很强的近带边紫外发射峰和半峰宽较大的中心波长为672nm红光发射峰;不同样品的电学性能差异较大。最后对合成的GaN微米薄膜的可能形成机理进行了简单分析。     

GaN薄膜的两步法制备及其物性转变的研究

本实验通过水浴加热和简单化学气相氨化两步法,在旋涂有ZnO的Si衬底上成功合成了由排列整齐纺锤体形貌的GaOOH构成的薄膜,然后在950℃下对样品进行氨化得到由排列整齐纺锤体组成的GaN薄膜。然后对氨化前后样品的形貌,结构和光学性能分别通过FESEM、EDS、TEM、XRD和PL谱进行了表征。结果表明:水热生成的GaOOH薄膜是由纺锤体形状GaOOH紧密排列形成,该纺锤体形状GaOOH有直径大约600 nm,长约为1.5~2μm。氨化前后样品的形貌没发生太大的变化;但晶体结构由正交晶系相GaOOH转变为六方纤锌矿GaN;而且发光峰也由较宽的绿光峰转变为中心为365 nm的蓝光峰,这主要是由于样品由正交晶系相GaOOH转变为六方纤锌矿GaN引起的。最后对排列整齐的锤体形构成的GaOOH薄膜的形成机理以及GaOOH向GaN的转变过程发生的化学反应做了简单的探讨和分析。     

Ag作催化剂制备的GaN的形貌及其性能

用化学气相沉积法(CVD)在Si(100)衬底上以Ag纳米颗粒为催化剂制备了微纳米结构的GaN,原料是熔融态的金属Ga和气态的NH3。采用X射线衍射仪(XRD)、透射电镜(TEM)、X-ray能谱仪(EDS)、场发射扫描电子显微镜(SEM)、光致发光能谱(PL)和霍尔效应测试对样品进行了结构、成分、形貌和发光、电学性能分析。结果表明:生成的自组装GaN为六方纤锌矿的类似小梯子的微纳米单晶结构,且在不同的温度下,GaN的发光性能和电学性能也有所不同,相对于强的紫外发光峰,其它杂质发光峰很微弱,且均呈p型导电。对本实验所得到的GaN微纳米结构的可能形成机理进行了探讨。     

GaN纳米带、纳米环和Z字结构纳米线在金属镓颗粒上的原位生长及其发光性质

在1050℃氨气和氢气混合气氛中加热金属镓,在镓颗粒表面原位生长出了GaN纳米带、纳米环和Z字结构纳米线．利用激光拉曼光谱仪、扫描电子显微镜和透射电子显微镜对产物进行了表征,结果表明,所得不同形貌GaN纳米结构均为单晶六方纤锌矿结构,纳米带宽度在20～300nm,长达30gm;纳米环直径在5-8gm;Z字结构纳米线的直径约为160nm．研究了反应温度和时间对产物形貌和结构的影响,提出了不同形貌GaN纳米结构的可能形成机理．从GaN纳米结构的发光光谱中观察到了发光峰位于361nm强的紫外光发光和456nm弱的蓝光发光,这两种发光分别起源于GaN宽带隙带边的激子发射和浅的给体向深的局域受体的跃迁．     

利用Pd催化合成单晶GaN纳米线的光学特性(英文)

基于金属元素钯具有的催化特性,采用射频磁控溅射方法,在Si(111)衬底上沉积Pd:Ga2O3薄膜,然后在950℃下对薄膜进行氨化,制备出大量GaN纳米线.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等技术手段对样品的结构、形貌和成分进行分析.结果表明,制备的样品为具有六方纤锌矿结构的单晶GaN纳米线,直径在20-60nm范围内,长度为几十微米,表面光滑无杂质,结晶质量较高.用光致发光光谱对样品的发光特性进行测试,分别在361.1、388.6和426.3nm处出现三个发光峰,且与GaN体材料相比近带边紫外发光峰发生了较弱的蓝移.对GaN纳米线的生长机制也进行了简单的讨论.     

扩镓Si基溅射Ga2O3氮化反应生长GaN薄膜

采用射频磁控溅射在扩镓硅基上溅射Ga2O3氮化反应生长GaN薄膜。用X射线衍射(XRD)、扫描电镜(SEM)、选区电子衍射(SAED)、光电能谱(XPS)和荧光光谱(PL)对样品进行结构、形貌、组分和发光特性的分析。XRD、SAED和XPS分析证明,采用此方法得到六方纤锌矿结构的GaN多晶膜。SEM显示薄膜由均匀、结合紧密的纳米微晶粒组成,其直径约为50～100nm。PL发光谱显示位于344nm处,相对于365nm明显蓝移的带边峰,此发光峰应归功于自由载流子的复合。     

双盘状ZnO的可控制备

采用水热法制备了形貌可控、 尺寸均一的双盘状ZnO. X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等测试结果表明, 制备的ZnO具有六方纤锌矿结构, 由2个直径约为4 μm, 厚度约为600 nm的圆盘复合而成. 考察了反应温度和乙酸锌与柠檬酸钾的摩尔比对产物形貌与尺寸的影响, 实现了双盘状ZnO的可控合成, 并初步探讨了其形成机理. 荧光光谱显示, 双盘状ZnO的紫外发射峰半高宽约为10 nm, 比块体ZnO的紫外发射峰半高宽(18 nm)窄, 表明双盘状ZnO具有更好的光学特性.     

ZnO纳米片/微棒复合体的制备、结构及光学性能

以十六烷基三甲基溴化铵(CTAB)为表面活性剂,以氯化锌和氢氧化钠为原料,在低温水热条件下制备出具有纳米片状接枝结构的ZnO微棒。通过扫描电镜(SEM)、X射线衍射(XRD)、透射电镜(TEM)、光致发光(PL)和拉曼光谱(Raman)对产物的形貌、晶体结构和光学性能进行了表征。结果表明,表面活性剂CTAB对产物最终形貌的形成具有重要作用;微棒表面所接枝的薄片为多晶结构;产物光致发光峰是较少见的弱蓝光发射与强红光发射;同时对这种ZnO微棒的生长机理进行了探讨。     

不同形貌Bi4Ti3O12粒子的可控合成及光催化性能

研究了用一步水热法制备的不同形貌的钛酸铋(Bi₄Ti₃O₁₂, BIT)粒子的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. XRD结果表明, 所制备的BIT 样品为层状钙钛矿结构. FESEM结果表明, 通过控制水热过程的反应参数可以得到不同形貌的纳米粒子. 紫外-可见漫反射光谱(UV-Vis DRS)表明BIT 样品的带隙能约为2.88-2.93 eV. 利用可见光(λ>420 nm)照射下的甲基橙(MO)降解实验评价了BIT 样品的光催化性能. 结果表明, BIT 的光催化活性比掺氮TiO₂ (N-TiO₂)高得多. 研究了形貌对BIT 光催化性能的影响. 所制备的BIT纳米带光催化效率最高, 经可见光照射360 min, 甲基橙溶液的降解率可达到95.0%.     

Hydrothermal synthesis of cobalt carbonates using different counter ions: An efficient precursor to nano-sized cobalt oxide (Co3O4)

Synthesis of submicrometer crystalline particles of cobalt carbonate was achieved hydrothermally using different cobalt salts and urea with a molar ratio from 1:3 to 1:20 (cobalt salt:urea) in aqueous solutions at 160 °C for 24-36 h, in the presence of cetyltrimethylammonium bromide (CTAB) as a surfactant. Nanoparticles of Co₃O₄, with an average size from 30 to 39 nm, were obtained by thermal decomposition of CoCO₃ samples at 500 °C for 3 h in an electrical furnace. The as-synthesized products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis spectra and thermal analysis. Studying the optical properties of the as-prepared cobalt oxide nanoparticles showed the presence of two band gaps, the values of which confirmed the semiconducting properties of the prepared Co₃O₄.     

Hydrothermal synthesis, characterization, and photocatalytic properties of Zn2SnO4

Nanosized Zn₂SnO₄ (ZTO) particles were successfully synthesized by a simple hydrothermal process in water/ethylene glycol mixed solution using amines (ethylamine, n-butylamine, n-hexylamine, and n-octylamine) as mineralizer. The products were characterized by X-ray diffractions (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption. The results indicated that the hydrothermal conditions, such as alkaline concentration (n-butylamine), reaction temperature, solvent composition, and the kind of amines, had an important influence on the composition, crystallinity, and morphology of the product. The as-synthesized ZTO samples exhibited high activities and durabilities for photodegradation of methyl orange and the activities were mainly affected by the crystallinities of the samples. A hexagonal-shaped ZTO (H-ZTO) sample was prepared in 0.53 M of n-butylamine solution at 180 °C for 20 h and its optical properties were characterized by UV-Vis diffuse reflectance and Photoluminescence (PL) spectra. Furthermore, the photocatalytic H₂ evolution reaction from ethanol aqueous solution over H-ZTO was also investigated.     

溶剂热方法合成Cu2ZnSnS4空心球

以氯化亚铜,硝酸锌,氯化锡和硫脲作为反应前驱体,聚乙二醇作为模板,利用溶剂热方法合成Cu₂ZnSnS₄中空球。其中,聚乙二醇对于产物的最终形成起到关键作用。文章讨论了Cu₂ZnSnS₄中空球的生长机制,并通过X射线衍射(XRD)、拉曼光谱、场发射电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线能量色散谱(EDX)、X射线光电子谱(XPS)、选区电子衍射谱(SAED)和紫外-可见光分光光度计(UV-Vis)等技术对样品的微结构以及光学性质进行了表征和分析。结果显示Cu₂ZnSnS₄中空球为四方晶体,尺寸为600 nm。其禁带宽度为1.52 eV,适用于制作光伏器件。     

Catalytic Performance of Spherical MCM-41 Modified with Copper and Iron as Catalysts of NH3-SCR Process

Spherical MCM-41 with various copper and iron loadings was prepared by surfactant directed co-condensation method. The obtained samples were characterized with respect to their structure (X-ray diffraction, XRD), texture (N₂ sorption), morphology (scanning electron microscopy, SEM), chemical composition (inductively coupled plasma optical emission spectrometry, ICP-OES), surface acidity (temperature programmed desorption of ammonia, NH₃-TPD), form, and aggregation of iron and copper species (diffuse reflectance UV-Vis spectroscopy, UV-Vis DRS) as well as their reducibility (temperature programmed reduction with hydrogen, H₂-TPR). The spherical MCM-41 samples modified with transition metals were tested as catalysts of selective catalytic reduction of NO with ammonia (NH₃-SCR). Copper containing catalysts presented high catalytic activity at low-temperature NH₃-SCR with a very high selectivity to nitrogen, which is desired reaction products. Similar results were obtained for iron containing catalysts, however in this case the loadings and forms of iron incorporated into silica samples very strongly influenced catalytic performance of the studied samples. The efficiency of the NH₃-SCR process at higher temperatures was significantly limited by the side reaction of direct ammonia oxidation. The reactivity of ammonia molecules chemisorbed on the catalysts surface in NO reduction (NH₃-SCR) and their selective oxidation (NH₃-SCO) was verified by temperature-programmed surface reactions.