MgxZn1-xO单晶薄膜和MgZnO/ZnO异质结构的光学性质

报道了利用等离子辅助分子束外延技术,在蓝宝石c平面上外延生长的MgxZn1-xO单晶薄膜以及MgZnO/ZnO异质结构的光学性质.室温下随着Mg浓度增加,合金薄膜样品的发光峰与吸收边均向高能侧移动.研究了样品紫外发光的起因,将MgxZn1-xO合金薄膜的发光归结为束缚激子的复合.在Mg0.08Zn0.92O/ZnO样品中,观察到了分别来自于ZnO层和MgZnO盖层的发光和吸收,并将其归因于来自ZnO层的自由激子和MgZnO盖层的束缚激子发射.     

氧压与ZnO薄膜发光特性的关系研究

在不同的环境氧压下用脉冲激光沉积方法在Si(111)衬底上生长了ZnO薄膜,以325 nm He-Cd激光器为激发源获得了薄膜的荧光光谱以研究其发光特性,用X射线衍射仪(XRD)和原子力显微镜(AFM)研究了薄膜的晶体结构和表面形貌,结果表明氧压在20 Pa和50Pa之间制备的ZnO薄膜具有良好的紫外发光特性和较好的晶体质量.分析了ZnO薄膜的发光机理,认为薄膜紫外峰源自自由激子复合发光,绿光峰的发光机制与锌位氧OZn关系密切,氧空位是蓝光发射的重要原因.     

紫外发光的半导体MgxZn1-xO薄膜制备与性质

利用ZnO微晶粉末以化学电泳法成功地在导电玻璃上制备了不同x值的紫外发光的宽禁带氧化物半导体三元化合物MgxZn1-xO薄膜.电子显微镜和X 射线衍射研究显示,薄膜由MgxZn1-xO微晶组成,薄膜中微晶大小的分散度比ZnO粉末有所减小,并更具择优取向的趋势.室温下光致发光测量给出,MgxZn 1-xO薄膜在小于380nm的紫外波段出现较强的半宽小于20nm的激子性发光峰,而且带边峰的半宽以及带边峰与杂质缺陷峰强度之比均较原始的ZnO粉末有明显改善,表明这种MgxZn1-xO薄膜具有优良的紫外发光特性.     

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。     

电化学方法生长有序纳米柱阵列的发光性质

采用电化学方法在磁控溅射方法生长的ZnO薄膜上生长垂直于衬底排列的ZnO纳米柱.ZnO薄膜的作用主要是为ZnO纳米柱的生长提供同质外延层.电化学生长的ZnO纳米柱具有良好的晶体质量和发光性能.通过研究其变温发光光谱可以确定其紫外发光峰来自于带边激子的辐射复合.此种方法生长的ZnO纳米柱在场发射显示、蓝紫色和白光发光二极管方面有潜在的应用前景.     

两步法生长ZnO纳米棒的结构及其发光特性

应用两步法在玻璃衬底上制备了高度取向的ZnO纳米棒,并研究了衬底和反应时间等参数对其结构及发光特性的影响。从样品的扫描电镜(SEM)图中发现,利用脉冲激光沉积(PLD)方法在玻璃衬底上生长一层ZnO薄膜作为修饰层,可以明显提高水热法生长的ZnO纳米棒的结晶质量。样品的SEM和光致发光(PL)谱表明,在有ZnO修饰层的玻璃衬底上生长的ZnO纳米棒分布均匀,排列致密,取向性好;缺陷发光的发光强度约是激子发光峰的2倍,且随着反应时间增长,样品的缺陷发光增强而激子发光减弱。     

900℃空气退火对L-MBE生长的ZnO薄膜发光特性的影响

采用激光分子束外延法在蓝宝石衬底(0001)上生长了高度c轴择优取向的高质量ZnO薄膜,在空气中对生长的薄膜进行900℃退火处理,并对退火前后样品的结晶质量、发光特性采用X射线衍射(XRD)、变温光致发光(PL)研究.退火处理后的ZnO薄膜(0002)面XRDθ-2θ扫描曲线强度明显增强.在光致发光实验中,观测到薄膜分别在3.352,3.309和3.237eV附近有3个明显的近紫外发光峰,分别对应自由激子发射、中性施主或受主束缚激子I9及其声子伴线1Lo.随着温度升高,峰位逐渐向长波方向移动(即所谓"红移"),半高宽(FWHM)逐渐展宽;在发光谱中,来自于晶体缺陷的深能级(DL)区发光强度极小.     

900℃空气退火对L-MBE生长的ZnO薄膜发光特性的影响

采用激光分子束外延法在蓝宝石衬底(0001)上生长了高度c轴择优取向的高质量ZnO薄膜,在空气中对生长的薄膜进行900℃退火处理,并对退火前后样品的结晶质量、发光特性采用X射线衍射(XRD)、变温光致发光(PL)研究.退火处理后的ZnO薄膜(0002)面XRDθ-2θ扫描曲线强度明显增强.在光致发光实验中,观测到薄膜分别在3.352,3.309和3.237eV附近有3个明显的近紫外发光峰,分别对应自由激子发射、中性施主或受主束缚激子I9及其声子伴线1Lo.随着温度升高,峰位逐渐向长波方向移动(即所谓"红移"),半高宽(FWHM)逐渐展宽;在发光谱中,来自于晶体缺陷的深能级(DL)区发光强度极小.     

Mn掺杂浓度对ZnO纳米薄膜的结构和光致发光的影响

Mn掺杂的ZnO基稀磁半导体材料由于具有独特的特性而受到人们广泛的关注。ZnO的激子束缚能高达60meV,具有优良的光学性质。因此,Mn掺杂的ZnO材料研究在磁性半导体领域广泛开展起来。文章采用溶胶-凝胶法制备了Mn掺杂的ZnO纳米晶,讨论了不同Mn含量对材料结构和光致发光的影响。XRD结果表明,所有的样品均具有六角纤锌矿结构,并且随着引入Mn含量的增加,样品的晶格常数增大。光致发光结果显示,随Mn含量的增加,样品的紫外发光峰先红移后蓝移。光致发光谱也显示,适量的Mn掺杂可以钝化样品的可见区发射,提高样品的光学质量。     

热氧化法制备ZnO纳米针的微结构与场发射性质研究

ZnO是一种重要的宽禁带半导体材料，室温下带隙宽3.37eV，激子结合能高达60meV，在短波激光器、太阳能电池、压电材料、发光照明材料等方面具有广泛的应用前景。一维ZnO纳米材料具有高的长径比、良好的物理化学等性能，其合成备受关注。     

Mapping of two-photon luminescence amplification in zinc-oxide microstructures

The mapping of two-photon excited luminescence in aggregations of free-standing zinc oxide microrods has been carried out at room temperature. Two-photon luminescence spectra in the excitonic region for individual microrods have been recorded. The luminescence intensity exhibits a power-law dependence on the optical pump power with the exponent n > 2. This fact, along with the existence of a threshold power above which the dependence in the exciton region deviates from a quadratic one, indicates the onset of light amplification in individual ZnO microrods and the conditions preceding laser oscillation.     

Spontaneous and stimulated UV luminescence of ZnO:N at 77 K

The spontaneous and stimulated UV luminescence spectra of ZnO:N samples possessing different nitrogen contents are measured at a temperature of 77 K. Luminescence peaks resulting from bound and free excitons, biexcitons, and electron recombination via the nitrogen acceptor level are identified. The optical depth (123 meV) of the N_O impurity acceptor level is determined. It is established that stimulated UV luminescence originating from inelastic exciton interaction sets in as the optical pump power increases.     

Interaction of coherent confined optical modes in neighboring 3D cylindrical ZnO microcavities

Luminescent properties of pairs of neighboring variously spaced 3D cylindrical ZnO microcavities 1.8 μm in diameter, produced by electron-beam lithography and reactive ion etching, are studied. Narrow luminescence peaks in the ZnO exciton spectral region, related to single-mode lasing, were observed. The energy of exchange interaction of coupled modes of two microcavities was calculated as a function of the intercavity distance. Broadening of the line of stimulated UV luminescence associated with coupled photonic modes of two microcavities was observed as the intercavity distance decreased.     

Effects of Chemical Treatment on the Luminescence of ZnO

The effects of chemical treatment on the luminescence of ZnO were investigated by cathodoluminescence. For this purpose, ZnO ceramics and O- and Zn-terminated faces of ZnO single crystals were studied. The samples were dipped in KOH and HCl solutions as well as pure H₂O for 3 min. H₂O and HCl treatments of ZnO ceramics can increase or decrease the initial ultraviolet (UV) intensity depending on the location examined, and induce an increase of the UV intensity under e-beam irradiation. HCl treatment of the Zn-face of ZnO single crystals slightly affects the surface morphology and the luminescence. HCl treatment of the O-face etches the surface to hexagonal pyramidal features. In addition, the initial UV intensity is always lower for the HCl-treated than for the untreated O-face, while the UV intensity increases at the beginning of e-beam irradiation. These results suggest that the UV intensity is influenced by the surface and bulk reactions of H⁺ with ZnO.     

衬底温度对脉冲激光沉积制备ZnO性能的影响

本文采用脉冲激光沉积（PLD）(KrF准分子激光器：波长248 nm,频率5Hz,脉冲宽度20 ns）方法在氧气气氛中以高纯Zn（99.999%）为靶材、在单晶硅和石英衬底表面成功生长了ZnO薄膜。通过X射线衍射仪、表明轮廓仪、荧光光谱仪、紫外可见分光光度计对合成薄膜材料的晶体结构、厚度、光学性质等进行了研究,分析了衬底温度变化对其性能的影响。实验结果表明我们使用PLD法在室温下可以制备出了高度结晶取向、高透过率和近带边发射的高质量ZnO薄膜。     

Optical properties of ZnO thin films prepared by sol-gel process

The present study focused on ZnO thin films fabricated by sol-gel process and spin coated onto Si (1 0 0) and quartz substrates. ZnO thin films have a hexagonal würtzite structure with a grain diameter about 50 nm. Optical properties were determined by photoluminescence (PL) and absorption spectroscopy. The absorption spectrum is dominated by a sharp excitonic peak at room and low temperatures. At room temperature, two transitions were observed by PL. One near to the prohibited energy band in ultraviolet (UV) region and the other centered at 640 nm, characteristic of the electronic defects in the band-gap. The spectrum at 6 K is dominated by donor-bound exciton lines and donor-acceptor pair transition. LO-phonon replica and two-electron satellite transitions are also observed. These optical characteristics are a signature of high-quality thin films.     

溶液浓度对ZnO纳米棒形貌和发光的影响

为了获取高质量、高取向排列规则的ZnO纳米棒,玻璃衬底预先用脉冲激光沉积方法制备一层ZnO薄膜作为籽晶层,应用水热法在玻璃衬底上生长ZnO纳米棒。探究了籽晶层及不同溶液浓度对ZnO纳米棒结构和发光的影响,用扫描电子显微镜和X射线衍射仪测量样品的形貌和结构,用组建的光致发光测试系统对样品的室温光致发光光谱进行测定。结果表明,ZnO纳米棒具有高度取向且分布致密均匀;光致发光光谱显示ZnO的近带边发射比深能级发光略低;随着溶液浓度的增加,近带边发光和深能级发光相对强度的比值依次降低。     

The study on mechanism of ultraviolet laser emission at room temperature from nanocrystal thin ZnO films grown on sapphire substrate by L-MBE

ZnO nanocrystal thin films were fabricated on sapphire substrates by laser molecular beam epitaxy. The structure and optical properties of the films were investigated experimentally. The film having small nanocrystal size of about 50-200 nm shows optically pumped ultraviolet laser emission at room temperature. This paper discussed the theoretical mechanism of excitonic radiative recombination in relation with the nanocrystal structure on ZnO film ultraviolet laser research. It is concluded that the experimental results are consistent with the theoretical analysis.