【作者】 杨峰；

【导师】 汪茫； 孙景志；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2008， 博士

【摘要】 氧化锌（ZnO）是一种重要的宽禁带半导体功能材料,室温下能带带隙为3.37eV,激子束缚能高达60 meV,远高于其它宽禁带半导体材料（如:GaN为25 meV,ZnSe为22 meV）的激子束缚能,是室温热能的2.3倍（26 meV）,因此ZnO中的激子能够在室温下稳定存在,另外由激子-激子散射诱发的受激辐射的阈值要比电子-空穴等离子体复合的受激辐射阈值低,ZnO有望用于在短波长发光二极管、半导体激光器、紫外探测器、太阳能电池、高频和大功率器件。另外,ZnO还具有制备工艺简单,能带及导电类型易调控和无毒无污染等优点。ZnO由于其晶体具有极性特征,导致了其丰富的纳米形态,诸如纳米线（棒）、纳米管、纳米带、纳米片、纳米环、纳米花、纳米螺旋结构等,不同的结构各有其特定的用途,使得ZnO的形貌和结构控制具有重要意义。ZnO与硫能产生强的相互作用,可以作为硫的吸附剂使用。本研究将含硫化合物应用到ZnO的制备过程中,不仅在一定程度上实现了对ZnO的形核、生长和形貌的控制,而且获得了一些新型的复合纳米结构,同时有针对性地对有关体系的荧光发射性能、表面光电压和光电流性能和电荷转移机理进行了研究,内容包括以下几方面:（一）、以十二烷基硫醇为代表研究了直链硫醇(C_nH_2n+1SH,n=5,6,8,10,12)在硝酸锌。六次甲基四胺水热合成ZnO过程中对形态结构的影响,用X-射线衍射、扫描电子显微镜和透射电子显微镜、荧光光谱等技术对得到的纳米结构进行了全面的表征。实验事实证明:在反应过程中反应体系分为两相,硫醇相和水溶液相。ZnO在水相中成核,与水相中溶解的十二烷基硫醇作用后因疏水作用而被萃取到硫醇相中,进而使ZnO的生长停止。通过高温烧结硫醇相中的ZnO前驱体,可以得到ZnO的纳米颗粒。减小硫醇的烷基链的长度,反应现象与采用十二烷基硫醇基本一致,但硫醇的疏水性降低,在水相中的溶解度增大,导致萃取过程变慢。采用戊硫醇时体系不再分相,反应得到了一种类八面体形的特殊结构单元。这是第一次在实验上捕获到八面体的ZnO结构单元的实例,对ZnO形貌的生成与演化的研究具有重要意义。在此基础上,本文研究了十二烷基硫醇对锌箔-甲酰胺反应体系的影响,发现在硫醇作用下,锌箔表面通过自组装的方式得到ZnO的纳米片状和鸟巢状纳米结构。高分辨电镜显示ZnO纳米片的表面由很多不同晶面的纳米颗粒组成。（二）、在水热合成条件下,利用硫代硫酸钠与锌箔反应,得到了硫掺杂的多孔弧形ZnO-S纳米线,纳米线的长度可达微米级。通过二次生长,硫代硫酸钠溶液将ZnO纳米棒阵列转变成了ZnO纳米叶阵列。通过改变锌源和反应条件,在较低温度下（65℃）得到了纤锌矿型的ZnS纳米颗粒,这是目前报道的在常压下得到纤锌矿结构ZnS的最低温度。在同样的反应体系中,通过改变反应条件可以实现对ZnS纳米颗粒的尺寸和晶相控制。通过表面光电压谱与相位的关系,判定纳米ZnS的导电类型为n-型;采用表面光电流谱与场诱导表面光电压谱相结合的研究手段,建立了光电流与场诱导表面光电压之间的内在联系。（三）、通过将巯基功能化的苝酰亚胺与ZnO原位组装,制备了苝酰亚胺/ZnO有序复合体系。表面光电压谱研究表明,复合体系可以显著提高载流子的分离效率,光伏响应呈数量级的增长。复合体系的荧光光谱测试发现苝酰亚胺的荧光显著淬灭,证明发生了从苝酰亚胺到ZnO的光致电荷转移。电子结构研究结果表明ZnO与巯基苝酰亚胺之间的能级匹配,有利于实现电荷转移。（四）、通过AAO模板制备了含ZnO相的锌铝水滑石,研究了模板孔径对水滑石形貌的影响。对得到的水滑石退火前后的表面浸润性进行了测试,发现接触角从122°减小到65°,研究表明层间阴离子的消失是浸润性发生显著变化的原因。光声光谱研究发现AAO模板的纳米孔隙对光声信号有明显的增强作用,增强作用与孔径成反比。更多还原

【Abstract】 Zinc oxide（ZnO）is an important oxide semiconductor,which has a wide band gap of 3.37eV at room temperature.Its exciton binding energy is 60 meV,much larger than that of other semiconductors such as GaN（25 meV）and ZnSe（22 meV）.This energy is 2.3 times of room temperature thermal energy（26 meV）,which besteads the excitons of ZnO with high stability.Furthermore,exciton-exciton scattering-induced stimulated emission occurs at a threshold lower than that for the electron-hole plasma recombination.These essences make ZnO have dramatic potential applications in the light emitting diodes,ultraviolet laser,detectors,solar cells and high-frequency and high-power devices.Due to the polar surface,ZnO presents in various nanostructures,including nanobelts,nanorings,nanowires（nanorods）,nanoflowers,nanotubes,nanosheets and nanohelixes.Different structures have found different applications.So,controllable synthesis of ZnO nanostructures is of great significance.It has been found that ZnO displays strong intereactions with S-species and acts as a well-known sulfur adsorbent. It is rational to make use of S-contained ligands for controllable growth of ZnO nanostructures.In this dissertation,thiols and Na₂S₂O₃ have been applied into the ZnO nanostructure fabrication,the main contents include the following parts.（1）ZnO nanostructures were synthesized in a controlled manner by using mercapto-compounds(C_nH_2n+1SH,n = 5,6,8,10 and 12)as ligands.With dodecylthiol as a representative example,the derived ZnO nanocrystals were characterized with X-ray diffraction,energy dispersion X-ray analysis, transmission electron microscopy,and photo-luminescence spectroscopy techniques.The experimental data confirmed the following mechanism.Heating the two phase system composing by thiol and aqueous solution of Zn（NO₃）₂ and hexamethyltetramine,primary ZnO clusters were generated and they were spontaneously capped by thiol molecules dissolved in the aqueous phase.When a critical size was reached,the thiol-capped particles transferred from aqueous to organic phase because of the hydrophobicity of the alkyl chains and their growth was stopped there.After calcining the thiol-capped precursor particles at elevated temperature,ZnO nanoparticles were obtained.The reaction system behaved differently from others in the case of n = 5,it changed from a two-phase to a uniform suspension after heating the mixture.A unique octahedron nanostrucutre was obtained,which was theoretically predicted as the intergradation of tetrapod ZnO nanocrystals but had never been observed before this report.This observation is helpful to the elucidation of the generation of ZnO nanostructures in various morphologies.Influence of dodecythiol on the system of zinc foil-formamide was studied.With the aid of dodecythiol,untra-thin ZnO nanosheets and unique bird-net structures were generated through self-assembling process on the surface of zinc foils.（2）Using a simple hydrothermal strategy,a novel porous arc-shaped S-doped ZnO nanowires were fabricated by reaction zinc foil in an aqueous solution of sodium hyposulfite at 65℃.The radius and length of nanowires were about 100 nm and 5μm, and diameter of nanopores on nanowires is about 10 nm.Through a two-step process, ZnO nanorods array was transferred to ZnO nanoleaves at mild conditions.Moreover, hexagonal form ZnS with wurtzite structure was obtained with a facile solution under 65℃.Surface photovoltage spectroscopy（SPS）and phase investigations indicated that the obtained ZnS was an n-type semiconductor,and the intrinsic relationship between the field-induced SPS（FISPS）and surface photocurrent spectroscopy（SPC） of ZnS nanoparticles was also established by combinational studis.（3）By in situ assmbling of ZnO nanorods and T-PTCDI[N,N-di（4-thiophenol）perylene-3, 4,9,10-tetracarboxylic diimide],ZnO/T-PTCDI hybrid was synthesized. SPS and FISPS measurement results showed that hybridization dramatically improved the disassociation of the photogenerated electron-hole pairs thereby the surface photovoltaic response enhanced by several tens times.The sufficient quenching of the fluorescence of the hybrids further confirmed the efficient photo-induced electron transfer from T-PTCDI to ZnO component.And the electronic structure data also suggested an energetically favorable electron transfer process.（4）Zinc-aluminum layered double hydroxide（Zn-A1 LDH）thin films were prepared by direct precipitation on the surface of porous anodic alumina oxide（AAO） template.The effects of nano-sized wall-edges on Zn-A1 LDH growth were studied and it was found that the Zn-A1 LDH films can be grown more efficiently on porous AAO membrane than those on flat bulk alumina oxide surface.The water contact angle of the as-prepared Zn-A1 LDH films was measured to be 122°,but after calcination at 600℃for 2h,it became 65°,indicating the surface transformed from a hydrophobic to a hydrophilic one,the thermal-induced reconstruction and the removal of inter-layer anions were ascribed to the changes of surface wettability.Photoacoustic properties were studied and the nanopores of AAO showed enhanced the photocoustic response,the enhancement was inversely proportional to the radius of nanopores of AAO template.更多还原