纳米ZnO薄膜的激子光致发光特性

报道了纳米ZnO薄膜激子光致发光(PL)与温度的关系。首先利用低压金属有机化学气相沉积(LPMOCVD)技术生长ZnS薄膜,然后将ZnS薄膜在氧气中于800℃下热氧化2h获得纳米ZnO薄膜。X射线衍射(XRD)结果表明,纳米ZnO薄膜具有六角纤锌矿多晶结构且具有择优(002)取向。室温下观察到一束强的紫外(326eV)光致发光(PL)和很弱的深能级(DL)发射。根据激子峰的半高宽(FWHM)与温度的关系,确定了激子纵向光学声子(LO)的耦合强度(ГLO)。     

磁控溅射制备ZnO薄膜的受激发射特性的研究

用射频磁控反应溅射法在二氧化硅衬底上制备ZnO薄膜。得到了在不同温度下ZnO薄膜的吸收与光致发光。观测到了纵光学波 (LO)声子吸收峰与自由激子吸收峰 ;室温 (30 0K)下 ,PL谱中仅有自由激子发光峰。这些结果证实了ZnO薄膜具有较高的质量。探讨了变温ZnO薄膜的发光特性。研究了ZnO薄膜的受激发射特性。     

离子注入Zn的Si(001)基片热氧化制备纳米ZnO团簇及其生长行为研究

采用离子注入技术将Zn离子注入Si（001）基片,并在大气环境下加热氧化制备了ZnO纳米团簇.利用电子探针、薄膜X射线衍射仪、原子力显微镜和透射电子显微镜,对注入和热氧化后的薄膜成分、表面形貌和微观结构进行表征,探讨了热氧化温度以及注入剂量对纳米ZnO团簇的成核过程及生长行为的影响.结果表明,Zn离子注入到Si基片表面后形成了Zn纳米团簇,热氧化过程中Zn离子向表面扩散,在表面SiO₂非晶层和Si基片多晶区的界面处形成纳米团簇.热氧化温度是影响ZnO纳米团簇结晶质量的一个重要参数.随着热氧化温度的升高,金属Zn的衍射峰强度逐渐变弱并消失,而ZnO的（101）衍射峰强度逐渐增强.当热氧化温度高于800 ℃以后,ZnO与SiO₂之间开始发生化学反应形成Zn₂SiO₄. 关键词： ZnO纳米团簇 离子注入 微观结构 形貌分析     

生长条件对Ga掺杂ZnO薄膜微观结构及光致发光性能的影响

利用热氧化法在不同参数条件下生长了Ga掺杂范围较宽的ZnO薄膜, 研究了ZnO薄膜的表面微观结构和光致发光性能. 研究表明: Ga以Ga³⁺存在并掺入ZnO晶格取代Zn²⁺, Ga的掺入改变了ZnO薄膜中的缺陷类型及浓度、化学计量比、薄膜表面结晶质量, 进而影响了薄膜的光致发光性能. 随着热氧化温度升高, Ga掺杂量增大, ZnO薄膜的晶粒尺寸增大, 尺寸更均一, 紫外光与可见光强度比增大. 随着热氧化时间延长, Ga掺杂量降低, ZnO薄膜的晶粒尺寸均一性变差, 紫外光与可见光强度比减小.     

高质量ZnO及BeZnO薄膜的发光性质

用分子束外延设备插入缓冲层在c面蓝宝石上生长得到高质量ZnO和BeZnO薄膜。XRD测试显示薄膜具有六方结构和c轴取向,并具有良好的晶体质量,其中ZnO薄膜的半高宽仅为108 arcsec,Be_xZn_1-xO薄膜的半高宽小于600 arcsec。对ZnO和BeZnO薄膜的拉曼光谱进行对比研究发现,随着Be元素的掺入,A₁(LO)、A₁(2LO)声子模频率往大波数方向移动,并且首次发现了与Be元素掺杂有关的局域振动模。利用变温光致发光光谱研究了薄膜的发光性质,结果显示ZnO薄膜室温光致发光只出现一个紫外发发光峰(378 nm),而低温光谱(80 K)则出现了很强的自由激子发光峰。随着温度的升高,束缚激子发光逐渐湮灭向自由激子发光转变,并且峰值位置红移。相对于ZnO薄膜,BeZnO薄膜的紫外发光主峰位置蓝移,并且由于Be元素的掺入导致薄膜晶体质量下降,在低温(80 K)光致发光光谱中没有出现强的自由激子发光峰。另外,在低温光致发光及拉曼光谱中,主峰位置在100~200 K之间有局部最大值,推测为由于合金晶格热膨胀系数失配而引起的应力效应。     

氧和氩等离子辅助电子束蒸发制备高质量ZnO薄膜

采用等离子辅助电子束蒸发技术制备高纯金属锌膜，然后在氧气气氛下经高温热处理得到氧化锌的多晶薄膜。X射线衍射谱的结果表明：未经热氧化样品由金属锌和氧化锌纳米晶组成，随着热氧化温度的升高氧化锌纳米晶粒长大，形成纳米氧化锌多晶薄膜且薄膜结晶性增强；光致发光谱表明：样品均具有较强的紫外自由激子发光。由于未经热氧化样品中氧化锌纳米晶粒较小，具有较强的量子限域效应，因而经高温氧化后样品发光峰有较大红移。随着热氧化温度的进一步升高，束缚激子发射随热氧化温度升高而减弱，且发光峰位随热氧化温度升高出现蓝移；变温光致发光谱表明：紫外发光主要来自自由激子发射。     

MBE生长ZnO薄膜的结构和光学特性的研究

用等离子体源辅助分子束外延(P-MBE)方法在蓝宝石(0001)面上生长出了高质量的ZnO薄膜,并对其结构和发光特性进行了研究。在XRD中只观察到ZnO薄膜的(0002)衍射峰,其半高宽(FWHM)值为0.18°;而在共振Raman散射光谱中观测到1LO(579 cm-1 )和2LO(1 152 cm-1 )两个峰位,这些结果表明ZnO薄膜具有单一c轴取向和高质量的纤维锌矿晶体结构。在吸收光谱中观测到自由激子吸收和激子-LO声子吸收峰,这表明在ZnO薄膜中激子稳定的存在于室温,并且两峰之间能量间隔为71.2 meV,与文献上报道的ZnO纵向光学声子能量(71 meV)相符。室温下在光致发光光谱(PL)中仅观测到位于376 nm处的自由激子发光峰,而没有观测到与缺陷相关的深能级发射峰,表明ZnO薄膜具有较高的质量和低的缺陷密度。     

退火温度对ZnO薄膜结构和发光特性的影响

采用反应射频磁控溅射法在 Si(100)基片上制备了高c轴择优取向的ZnO薄膜，研究了退火温度对ZnO薄膜的晶粒尺度、应力状态、成分和发光光谱的影响，探讨了ZnO薄膜的紫外发光光谱和可见发光光谱与薄膜的微观状态之间的关系.研究结果显示,在600—1000℃退火温度范围内，退火对薄膜的织构取向的影响较小，但薄膜的应力状态和成分有比较明显的变化.室温下光致发光光谱分析发现，薄膜的近紫外光谱特征与薄膜的晶粒尺度和缺陷状态之间存在着明显的对应关系；而近紫外光谱随退火温度升高所呈现的整体峰位红移是各激子峰相对比例变 关键词： ZnO薄膜 退火 光致发光 射频反应磁控溅射 可见光发射     

非晶态Nb氧化物纳米薄膜可见光区的光玫发光

在低真空及亚高温(200～300℃)下.通过热氧化法在Si单晶基底上合成了呈准直阵列的椎形结构的氧化铌(NbOx)非晶结构纳米薄膜,薄膜经热处理后室温下在可见光区具有很好的光致发光.实验研究了退火温度与发光强度规律,对铌氧化物纳米薄膜的光致发光(PL)机制进行了初步分析和讨论.变功率光致发光(PL)实验有力地支持了初步讨论结果.     

退火对多晶ZnO薄膜结构与发光特性的影响

用射频反应溅射法在Si（111）衬底上制备了C轴取向的多晶ZnO薄膜，通过不同温度的退火处理，研究了退火对多晶ZnO薄膜结构和发光特性的影响.由x射线衍射得知，随退火温度的升高，晶粒逐渐变大，薄膜中压应力由大变小至出现张应力.光致发光测量发现，样品在430nm附近有一光致发光峰, 峰的强度随退火温度升高而减弱，联合样品电阻率随退火温度升高而逐渐变大的测量及能级图，推测出ZnO薄膜中的蓝光发射主要来源于锌填隙原子缺陷能级与价带顶能级间的跃迁. 关键词： ZnO薄膜 退火 光致发光 射频反应溅射     

Temperature dependence of excitonic luminescence from nanocrystalline ZnO films

The properties of the excitonic luminescence for nanocrystalline ZnO thin films are investigated by using the dependence of excitonic photoluminescence (PL) spectra on temperature. The ZnO thin films are prepared by thermal oxidation of ZnS films prepared by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The X-ray diffraction (XRD) indicates that ZnO thin films have a polycrystalline hexagonal wurtzite structure with a preferred (0 0 2) orientation. A strong ultraviolet (UV) emission peak at 3.26 eV is observed, while the deep-level emission band is barely observable at room temperature. The strength of the exciton-longitudinal-optical (LO) phonon coupling is deduced from the temperature dependence of the full-width at half-maximum (FWHM) of the fundamental excitonic peak, decrease in exciton-longitudinal-optical (LO) phonon coupling strength is due to the quantum confinement effect.     

纳米ZnO薄膜可见发射机制研究

利用溶胶－凝胶法 （Sol-Gel）制备了纳米ZnO薄膜,获得了高强的近紫外发射室温下测量了样品的光致发光谱(PL )、吸收谱(ABS)、X射线衍射谱(XRD).X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶态,具有六角纤锌矿结构和良好的C轴取向;发现随退火温度升高,（002）衍射峰强度显著增强,衍射峰的半高宽（FWHM）减小、纳米颗粒的粒径增大.由吸收谱(ABS)给出了样品室温下带隙宽度为3.30 eV.在PL谱中观察到二个荧光发射带,一个是中心波长位于392 nm附近强而尖的紫带,另一个是519 nm附近弱而宽的绿带研究了不同退火温度样品的光致发光峰值强度的变化关系,发现随退火温度升高,紫带峰值强度增强、绿带峰值强度减弱,均近似呈线性变化.证实了纳米ZnO薄膜绿光发射主要来自氧空位(Vo)形成的浅施主能级与锌空位(VZn)形成的浅受主能级之间的复合,或氧空位(Vo)形成的深施主能级上的电子至价带顶的跃迁;紫带来自于导带中的电子与价带中的空位形成的激子复合.     

Strong ultraviolet emission from zinc oxide thin films prepared by electrophoretic deposition

In this paper, we report a simple and efficient method to prepare high-quality nanocrystalline ZnO films by electrophoretic deposition. Absorption spectrum and transmission electron microscope image indicated that the average size of ZnO nanoparticles is about 9.5 nm. A strong ultraviolet emission peak at 384 nm is observed and the deep-level emission band is barely observed at room temperature. X-ray diffraction pattern revealed that the ZnO film has a polycrystalline hexagonal wurtzite structure. The Raman spectrum showed a typical resonant multi-phonon process within the ZnO film. The frequency shift of 1 LO phonon was about 583 cm⁻¹.     

Cesium doped and undoped ZnO nanocrystalline thin films: a comparative study of structural and micro‐Raman investigation of optical phonons

Undoped and cesium‐doped zinc oxide (ZnO) thin films have been deposited on sapphire substrate (0001) using the sol–gel method. Films were preheated at 300 °C for 10 min and annealed at 600 and 800 °C for 1 h. The grown thin films were confirmed to be of wurtzite structure using X‐ray diffraction. Surface morphology of the films was analyzed using scanning electron microscopy. The photoluminescence (PL) spectra of ZnO showed a strong ultraviolet (UV) emission band located at 3.263 eV and a very weak visible emission associated with deep‐level defects. Cesium incorporation induced a blue shift of the optical band gap and quenching of the near‐band‐edge PL for nanocrystalline thin film at room temperatures because of the band‐filling effect of free carriers. A shift of about 10–15 cm⁻¹ is observed for the first‐order longitudinal‐optical (LO) phonon Raman peak of the nanocrystals when compared to the LO phonon peak of bulk ZnO. The UV resonant Raman excitation at RT shows multiphonon LO modes up to fifth order. Copyright © 2010 John Wiley & Sons, Ltd.     

溶胶-凝胶法纳米ZnO薄膜的绿光发射

利用溶胶-凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)和X射线衍射谱(XRD),观测到中心波长在523 nm附近的绿色荧光发射,研究了纳米ZnO薄膜的绿光发射机制,证实了纳米ZnO薄膜绿光可见发射带来自氧空位(Vo)形成的浅施主能级和锌空位(Vzn)形成的浅受主能级之间的复合。     

Optical Analysis of Nanocrystalline ZnO Films Coated on Porous Silicon by Radio Frequency (RF) Magnetron Sputtering

Zinc oxide thin films have been deposited onto porous silicon (PSi) substrates at high growth rates by radio frequency (RF) sputtering using a ZnO target. The advantages of the porous Si template are economical and it provides a rigid structural material. Porous silicon is applied as an intermediate layer between silicon and ZnO films and it contributed a large area composed of an array of voids. The nanoporous silicon samples were adapted by photo electrochemical (PEC) etching technique on n-type silicon wafer with (111) and (100) orientation. Micro-Raman and photoluminescence (PL) spectroscopy are powerful and non-destructive optical tools to study vibrational and optical properties of ZnO nanostructures. Both the Raman and PL measurements were also operated at room temperature. Micro-Raman results showed that the A₁(LO) of hexagonal ZnO/Si(111) and ZnO/Si(100) have been observed at around 522 and 530 cm^–1, re- spectively. PL spectra peaks are distinctly apparent at 366 and 368 cm^–1 for ZnO film grown on porous Si(111) and Si(100) substrates, respectively. The peak luminescence energy in nanocrystalline ZnO on porous silicon is blue-shifted with regard to that in bulk ZnO (381 nm). The Raman and PL spectra pointed to oxygen vacancies or Zn interstitials which are responsible for the green emission in the nanocrystalline ZnO.     

纳米ZnO薄膜的光致发光性质

利用溶胶－凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)、吸收谱(ABS)、X射线衍射谱(XRD)．X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶状态,具有六角纤锌矿晶体结构和良好的C轴取向．观察到二个荧光发射带,中心波长分别位于395 nm的紫带、524 nm的绿带和450 nm附近的蓝带．证实了纳米ZnO薄膜绿光可见发射带来自氧空位(VO)形成的浅施主能级和锌空位(VZn)形成的浅受主能级之间的复合;450 nm附近的蓝带来自电子从VO的浅施主能级到价带顶或锌填隙(Zni) 到价带顶或导带底到VZn的浅受主能级的复合．