衬底温度对低功率直流磁控溅射ZnO薄膜特性的影响

采用低功率直流反应磁控溅射法,在Si衬底上成功制备出了具有高c轴择优取向的ZnO薄膜,利用X射线衍射仪、荧光分光光度计研究了沉积温度对ZnO薄膜微观结构及光致发光特性的影响.结果表明,合适的衬底温度有利于提高ZnO薄膜结晶质量;在室温下测量样品的光致发光谱(PL),观察到波长位于440nm左右和485nm左右的蓝色发光峰及527nm左右微弱的绿光峰,随衬底温度升高,样品的PL谱中蓝光强度都明显增大,低功率溅射对其蓝光发射具有很重要的影响.综合分析得出440nm左右的蓝光发射应与Zni有关,485nm附近的蓝光发射是由于氧空位形成的深施主能级上电子跃迁到价带顶的结果,而527nm左右的较弱的绿光发射主要来源于导带底到氧错位缺陷能级的跃迁.生长温度主要是通过改变薄膜中缺陷种类及浓度而影响着ZnO薄膜的发光特性的.     

Cu掺杂ZnO的光致发光光谱

ZnO是宽禁带半导体,室温下禁带宽度为3.37eV,激子束缚能高达60meV,是制备光电器件的优选材料。然而,p型掺杂仍是亟待解决的问题。ⅠB元素Cu被认为在ZnO中产生受主能级,可以实现ZnO的p型掺杂。综述了各种制备方法、制备条件和激发条件下得到的Cu掺杂ZnO薄膜、纳米线和纳米棒的光致发光谱和机理,总结出Cu掺杂ZnO光致发光谱的带边发射会因为Cu的掺杂强度降低,或出现发射中心红移等现象。可见光区域由于Cu掺杂会产生新的蓝光、绿光和橙光发射峰,蓝光发射峰可能与Cu2+-Cu+跃迁或VZn和Zni有关;绿光发射峰可能与Cu杂质或VO-VZn跃迁有关,Cu掺杂还可能引入非辐射复合的点缺陷中心;橙光发射峰则可能由于Cu杂质受主能级向深施主能级跃迁而产生。     

Sn掺杂ZnO半导体纳米线的制备、表征及光学性能

采用化学气相沉积法获得了Sn掺杂含量约为2.4%(原子分数)的Sn掺杂ZnO半导体纳米线。X射线衍射结果表明,Sn的掺杂并没有改变ZnO的纤锌矿结构。掺杂纳米线的室温光致发光光谱在409.2nm和498.0nm处出现了蓝绿光发光峰。探讨了其发光机制,认为前者可能来源于从导带到Zn空位形成的浅受主能级的跃迁以及从氧空位形成的浅施主能级到价带的跃迁;而后者来源于从氧空位形成的浅施主能级到锌空位浅受主能级的跃迁。     

Ce掺杂ZnO纳米晶的光致发光特性

以 Zn(NOs)3·6H2O、Ce(NO3)3·6H2O为原料,明胶为模板分散剂,采用凝胶模板燃烧法制备纯ZnO和ZnO:Ce纳米晶,利用XRD、TEM和PL谱研究样品的结构和性能.结果表明:产物粒子形状基本为球形,结晶良好,属六方晶系结构;随着掺杂量的增加,粒子尺寸逐渐减小,说明Ce掺杂能够有效地抑制ZnO晶粒生长.在310nm光的激发下,观察到480～500nm强而宽的可见发射,在此背景上出现487nm和494nm的蓝绿光子发射峰,掺杂样品的发光强度显著增强.蓝光发射主要是由于氧空位与间隙氧之间的跃迁,绿光发射是由于材料表面离子化氧空位中的电子与价带中光激发的空穴之间的复合.     

Zn缓冲层对氧化锌薄膜的结构和光学特性的影响

采用射频磁控溅射法在玻璃衬底上制备了具有高c轴择优取向的不同Zn缓冲层厚度的ZnO(ZnO/Zn)薄膜。利用X射线衍射(XRD)法、扫描电子显微镜(SEM)技术和光致荧光(PL)发光谱(PL)等表征了ZnO/Zn薄膜的微观结构和发光特性。XRD的分析结果显示,随着缓冲层厚度的增加,(002)衍射峰的半高宽(FWHM)逐渐变小,表明薄膜的结晶质量得到改善。通过对样品PL谱的研究,发现分别位于435(2.85eV)和480nm(2.55eV)的蓝光双峰以及530nm(2.34eV)的绿光峰,且缓冲层沉积时间为10min时,样品的单色性最好。推测位于435nm的蓝光发射主要来源于电子从锌填隙缺陷能级到价带顶的跃迁所致,而绿光峰的发光机制与氧空位有关。     

Ge掺杂ZnO薄膜光学特性的研究

采用射频磁控共溅射法在硅基片上沉积了Ge掺杂ZnO薄膜,所制备的样品具有强蓝光发射和弱黄光发射.通过分析Ge掺入量和退火温度对发光谱的影响,并与相同条件下所沉积的纯ZnO薄膜的发光特性进行比较,结果表明,蓝光发射可能与Ge杂质形成的施主能级有关,弱黄峰可能源于Ge替代Zn空位形成的杂质能级到价带的跃迁复合.     

Co掺杂量对ZnO薄膜结构及光学特性的影响

采用脉冲激光沉积法(PLD)在SiO2村底上成功制备了具有c轴择优生长特性的Zn1-xCoxO(x=0.05、0.1、0.2、0.3)系列薄膜.通过X射线衍射和能谱仪研究了Co掺杂量对薄膜晶体结构和成分的影响;同时利用光致发光谱(PL)和透过率研究了薄膜的光学特性.结果表明,当掺杂浓度为10%时,薄膜生长最好,c轴择优生长最为显著;Co元素的掺入改变了薄膜的紫外、绿光和蓝光发射,分析认为主要是Co元素的掺入量改变了薄膜的禁带宽度、氧错位缺陷浓度和锌填隙缺陷的浓度;Co元素掺杂浓度为5%时,薄膜的透过率超过90%.此外,探讨了不同波段光发射的可能机理.     

锑掺杂对二氧化锡薄膜结构及发光性质的影响

采用射频磁控溅射方法在石英玻璃衬底上制备了SnO2:Sb薄膜.所制备的薄膜为四方金红石结构的多晶薄膜.PL谱表明,样品在396、450、500nm附近存在室温光致发射峰,发光峰的起因分别与SnO2薄膜中的氧空位缺陷及掺杂所致的施主一受主对之间的跃迁以及电子由其激发态向基态能级跃迁等因素有关.     

微纳结构ZnO荧光薄膜的电沉积及其物理特性研究

采用阴极电沉积法,以Zn(NO3)2水溶液为电解液,在透明导电玻璃ITO衬底上制备了ZnO薄膜,用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分析了ZnO薄膜的微纳结构和表面形貌.用Fluoromax-P型荧光光谱仪测量了样品的室温光致发光光谱,观察到550hm处的黄绿光发射峰,认为与样品中由导带到氧填隙引起的浅受主能级的电子跃迁有关.对样品进行500℃真空退火,研究了退火前后薄膜的结构及导电性能的变化.结果表明,退火处理使薄膜的均匀性和结晶质量得到改善,导电性明显增强.此外,还观察了薄膜的阴极射线发光.     

氧化锆(ZrO_2)的电、光性质与应用

重点分析了ZrO2的电子结构与能带特点、光学吸收、发射谱等,介绍了第一原理法计算不同晶相ZrO2的能带结构和电子能量状态密度图(DOS)的结果,在计算能级结构的基础上,归纳了不同晶相的ZrO2在禁带附近可能的电子跃迁机理及其相应的能量,说明了无论是高纯ZrO2还是掺杂ZrO2,在室温下均表现出高的绝缘性能。分析了高温下ZrO2导电能力提高的原因,高温导电性可应用于氧传感器和燃料电池中的电极隔膜材料。掺杂后的ZrO2晶体的透光性非常好,且在较高温度的环境中,如果不发生晶体结构转变或失透等,则温度对提高晶体的折射率有积极的作用。ZrO2粉体的白色外观是由于粉体的表面对可见光的散射以及晶体内部的大量缺陷对光的散射作用。介绍了纯ZrO2材料的发光效应来源在于捕获了电子的氧空位形成的新能级与基态能级间的跃迁,氧空位形成的F-色心或缔合中心而产生。指出ZrO2可以作为发光离子基质的原因在于作为宽禁带的ZrO2的声子能量较低,可为发光中心的稳定发光提供刚性场所。     

Structural, Morphological and Optical Properties of ZnO Thin Films Grown on γ-LiAlO2 Substrate by Pulsed Laser Deposition

ZnO thin films were deposited on the substrates of (100) γ-LiAlO2 at 400, 550 and 700℃ using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400℃, the grain size of the film is less than 1 μm observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550℃, highly-preferred c-orientation and high-quality ZnO film can be attained.While the substrate temperature rises to 700℃, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430 nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on γ-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.     

过渡金属(Mn2+、Ni2+、Fe3+、Cu2+)掺杂ZnO基稀磁半导体的制备及性质

利用溶液腐蚀法制备了Mn2+、Ni2+、Fe3+、Cu2+离子掺杂的ZnO基稀磁半导体。XRD表明掺杂后的ZnO仍然保持单一的纤锌矿结构,没有任何杂质相产生。由紫外-可见光反射谱可知掺杂后吸收边发生了红移。掺杂前ZnO的带隙为3.20eV,对样品分别掺入Mn、Ni、Fe和Cu后的带隙分别为3.19eV、3.15eV、3.08eV和3.17eV。掺杂后样品的室温PL谱除了紫外发射峰外,对于Mn掺杂的样品还在蓝光区域出现了2个分别位于424nm和443nm的发射峰,Fe掺杂的样品出现了一个位于468nm的微弱发射峰,Cu掺杂的样品出现了位于469nm及535nm的很宽的发射峰。室温磁滞回线显示掺杂后样品有明显的铁磁性,掺入Mn、Ni、Fe和Cu样品的剩余磁化强度(Ms)分别为0.3902×10-3emu/cm3、0.454emu/cm3、0.372emu/cm3和0.962×10-3emu/cm3,矫顽力分别为47Oe、115.92Oe、99.33Oe和23Oe。经分析室温铁磁性来源于缺陷调制的Mn2+-Mn2+长程铁磁交换相互作用。     

Influence of incorporation of Al3+ ions on the structural, optical and AC impedance characteristics of spin coated ZnO thin films

Aluminium doped zinc oxide thin films were deposited onto glass substrate using spin coating technique. The effects of Al doping on structural, optical and electrical properties of these films were investigated. X-ray diffraction analysis showed that all the thin films were of polycrystalline hexagonal wurtzite structure with (002) as preferential orientation except 2 at.% of Al doped ZnO films. The optical band gap was found to be 3.25 eV for pure ZnO film. It increases up to 1.5 at.% of Al doping (3.47 eV) and then decreased slightly for the doping level of 2 at.% (3.42 eV). The reason for this widening of the optical band gap up to 1.5 at.% is well described by Burstein–Moss effect. The photoluminescence spectra of the films showed that the blue shift and red shift of violet emission were due to the change in the radiative centre between zinc vacancy and zinc interstitial. Variation in ZnO grain boundary resistance against the doping concentration was observed through AC impedance study.     

Magnetic and optical properties of Mn doped ZnO nanocrystalline films

We have investigated the properties of Mn-doped ZnO nanocrystalline film growing on zinc foil by the hydrothermal method. X-ray photoelectron spectroscopy shows that the manganese ions exist as Mn2+ in the film. From UV-vis spectra, we observe a red shift in wavelength of absorption and greater reflectivity due to the Mn ion incorporation in ZnO lattices. The photoluminescence spectrum of the Mn-doped ZnO film shows two strong new blue peaks centered at 424 nm and 443 nm, besides the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902 x 10(-3) emu/cm3 and a coercive field of 47 Oe. We suggest that the blue emission of the Mn-doped ZnO film corresponds to the electron transition from the level of interstitial Zn and Mn to the valence band. The defects brought about by Mn ion incorporation are the main cause of the room temperature ferromagnetic property.     

Mg-Al共掺杂ZnO薄膜的制备及其光学特性

采用溶胶-凝胶（sol—gel）旋涂法在载玻片上制备了不同A1掺杂量的Mg—Al共掺杂ZnO薄膜．在室温下利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和光致发光（PL）谱仪等手段分析了Mg—Al共掺杂Zn0薄膜的微结构、形貌和发光特性．XRD结果表明Mg．AI＆掺杂zn0薄膜具有六角纤锌矿结构;随着Al掺杂量的增加,共掺杂薄膜呈C轴取向生长．由SEM照片可知薄膜表面形貌随Al掺杂量的增加由颗粒状结构向纳米棒状结构转变．透射光谱表明共掺杂薄膜在可见光区内的透射率大于50％,紫外吸收边发生蓝移．在室温下的PL谱表明Mg—Al共掺杂zn0薄膜的紫外发射峰向短波长方向移动：Al掺杂摩尔分数为1％和3％的Mg—Al共掺杂ZnO薄膜的可见发射峰分别为596nm的黄光和565nm的绿光．黄光主要与氧间隙有关,而绿光主要与氧空位有关．     

Ni2+掺杂ZnO薄膜及粉体的结构和发光性能研究

采用激光脉冲沉积法,用XeCl准分子激光器在Si (100)基片、真空和5Pa氧气气氛下制备了Ni2+(0.8％(原子分数))掺杂的呈六角纤锌矿结构的ZnO薄膜.氧气气氛下制备的薄膜沿(002)取向生长,表面比较平整,平均颗粒尺寸为80nm.真空条件下制备的薄膜出现Zn2SiO4杂相,平均颗粒尺寸为150nm.和真空条件下制备的薄膜相比,氧气气氛下制备的薄膜具有较强的ZnO本征发光,在425nm附近出现由于填隙Zn缺陷引起的较宽的蓝光发光带,并且在482nm处出现了由于氧空位和氧间隙间的转换引起的较强的蓝光发光峰,同时由于氧缺陷引起的449nm附近的蓝光发光峰强度明显降低.     

Structural and optical properties of La-doped ZnO films prepared by magnetron sputtering

La-doped ZnO films were prepared by RF magnetron sputtering using different composition powder compacted targets (0, 1, 2, 3 and 5 at.%). All films show a preferred c-axis growth orientation. Furthermore, the (002) diffraction peak shifts to a small angle and the full-width at half-maximum augments with increasing La concentration up to 2 at.%, which indicate that a small quantity of La atoms are incorporated into the ZnO lattice. The average transmittance in the visible range is over 80%, and a blue shift of the absorption edge is observed. With increasing La concentration, the band gap of ZnO films evaluated by the linear fitting linearly increases from 3.270 to 3.326 eV. In the photoluminescence spectra, a strong violet emission peak and a weak green emission band can be observed. The former is due to the electron transition between the defect energy levels, associated with the interfacial traps existing at the ZnO grain boundaries, and valence band. The latter could be ascribed to crystal defects related to oxygen vacancies.     

Cl~-,S~(2-)共掺杂氧化锌荧光粉的制备及发光性能

在空气气氛中,以NH_4Cl为助剂,通过热氧化硫化锌,制备出Cl~-,S~(2-)共掺杂氧化锌荧光粉,激发和发射光谱随氧化温度的变化而变化.在350nm激发下,氧化锌荧光粉的发射光谱只有510nm绿色峰,并有黄色区拖尾现象.绿色峰强度随煅烧温度的变化而变化.绿色峰归因与一价氧空位中的电子和价带中光生空穴的复合.氧化锌荧光粉的光致发光谱的变化是Cl~-,S~(2-)共掺杂的结果.     

直流磁控溅射ZnO薄膜的结构和室温PL谱研究

ZnO是一种新型的宽带化合化半导体材料 ,对短波长的光电子器件如UV探测器 ,LED和LD有着巨大的潜在应用。本实验研究采用直流反应磁控溅射法在硅衬底上沉积C轴择优取向的ZnO晶体薄膜 ,薄膜呈柱状结构 ,晶粒大小约为 10 0nm ,晶粒内为结晶性能完整的单晶 ,但晶粒在C轴方向存在较大的张应力。ZnO薄膜在He Cd激光器激发下有较强的紫外荧光发射 ,应力引起ZnO禁带宽度向长波方向移动 ,提高衬底温度有利于降低应力和抑制深能级的绿光发射