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。     

分子束外延生长的ZnO压电薄膜及其声表面波器件特性

用RF-MBE在蓝宝石(0001)衬底上引入MgO和低温ZnO双缓冲层生长了ZnO薄膜,并制备了声表面波器件。在ZnO薄膜中,仅观测到(0002)面的XRD,且衍射峰增强,半高宽减小,表明ZnO薄膜c轴取向性更好,晶体结构更优。室温下自由激子吸收峰更尖锐和吸收边更陡峭以及仅观测到自由激子发光,且发光线宽变窄、发光强度变大,表明ZnO薄膜缺陷密度减小,薄膜质量提高。测得该ZnO压电薄膜的电阻率高达4×10⁷ Ω·cm,其声表面波的速度高达5 010 m/s。     

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。     

高质量纳米ZnO薄膜的光致发光特性研究

报道了利用低压-金属有机物化学气相沉积技术生长纳米ZnS薄膜，然后，将ZnS薄膜在氧气中于800℃温度下进行热氧化制备高质量纳米ZnO薄膜.x射线衍射结果表明，纳米ZnO薄膜具有六角纤锌矿多晶结构.室温下观察到一束强的紫外(3.26 eV) 光致发光和很弱的深能级发射.根据激子峰的半高宽度与温度的关系确定了激子-纵向光学声子（LO）的耦合强度（ГLO）.由于量子限域效应使ГLO减少较多. 关键词： 光致发光 热氧化 激子 纳米ZnO薄膜     

全无机钙钛矿CsPbBr3微米棒的变温荧光特性

通过化学气相沉积法(CVD)在云母基底上制备得到CsPbBr_3微米棒,并使用扫描电子显微镜(SEM)、X射线衍射(XRD)对样品形貌和晶体结构进行表征。采用变温(10～290 K)荧光光谱研究了CsPbBr_3激子发光的温度依赖特性。实验发现,在室温下CsPbBr_3微米棒有两个发光峰,分别为位于2.357 eV、半宽为52 meV的自由激子发光及能量位于2.298 eV、半宽为73 meV的束缚激子发光。从10 K开始,随着温度升高,自由激子的峰位能量单调蓝移,束缚激子的峰位能量在120 K之前单调蓝移,其后趋于平缓。且激子峰半高宽随温度升高而逐渐增大。这种变温荧光特性主要是由于激子和纵向光学声子(LO)的相互作用引起的。本文有助于进一步理解CsPbBr_3光物理特性,对未来高性能光电子器件研究具有指导意义。     

全无机钙钛矿CsPbBr_(3)微米棒的变温荧光特性EI北大核心CSCD

通过化学气相沉积法(CVD)在云母基底上制备得到CsPbBr_(3)微米棒,并使用扫描电子显微镜(SEM)、X射线衍射(XRD)对样品形貌和晶体结构进行表征。采用变温(10~290 K)荧光光谱研究了CsPbBr_(3)激子发光的温度依赖特性。实验发现,在室温下CsPbBr_(3)微米棒有两个发光峰,分别为位于2.357 eV、半宽为52 meV的自由激子发光及能量位于2.298 eV、半宽为73 meV的束缚激子发光。从10 K开始,随着温度升高,自由激子的峰位能量单调蓝移,束缚激子的峰位能量在120 K之前单调蓝移,其后趋于平缓。且激子峰半高宽随温度升高而逐渐增大。这种变温荧光特性主要是由于激子和纵向光学声子(LO)的相互作用引起的。本文有助于进一步理解CsPbBr_(3)光物理特性,对未来高性能光电子器件研究具有指导意义。     

利用P-MBE制备高质量MgxZn1-xO的结构和光学特性

利用等离子体辅助分子束外延(P-MBE)的方法,在c平面的蓝宝石衬底上制备了高质量的MgxZn1-xO合金薄膜。通过改变Mg源的温度,得到了不同Mg组份的MgxZn1-xO合金薄膜;通过引入ZnO的低温缓冲层,有效地提高了MgxZn1-xO合金薄膜的结晶质量。随着Mg组份的增加,MgxZn1-xO的X射线衍射的(002)衍射峰逐渐向大角度方向移动。对样品进行光致发光(PL)谱的测量,在室温下观察到了较强的紫外发光。随Mg浓度的增加,紫外发光峰向高能侧移动,并且发光峰逐渐展宽。通过对x=0.15的样品进行变温光谱的测量研究了紫外发光峰起因,得到了MgxZn1-xO的发光是来自于自由激子的发光。自由激子束缚能为54meV。     

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)。     

离子注入及后退火方法制备SiO2基质中镶嵌ZnO纳米粒子的结构和光学性质

利用离子注入及后退火方法在光学纯的石英基片中注入3×1017cm-2剂量的Zn离子,然后在不同的退火条件下制备了高质量的镶嵌在SiO2基质中的ZnO纳米粒子.X射线衍射光谱的实验结果表明在氧气气氛、700℃退火温度和2小时退火时间条件下,得到了(002)择优取向镶嵌在SiO2基质中的ZnO纳米粒子;而在700℃退火温度、N2和O2气氛下顺次退火1小时,得到了比上述条件(002)择优取向更好的ZnO纳米粒子.室温下对用上述两种条件制备的镶嵌在SiO2基质中的ZnO纳米粒子观察到了自由激子吸收峰.室温光致发光谱中观察到了ZnO纳米粒子位于3.29eV处的强紫外发射,紫外发射强度与深能级发光强度之比为40,紫外发射峰的半高宽为96meV,晶体质量类似于分子束外延方法生长的ZnO.在低温(77K)光致发光谱中,较强的自由激子的紫外发光峰仍然存在.     

氟掺杂的氧化锌薄膜的结构和光学特性

通过热氧化氟化锌(ZnF2)薄膜的方法制备出氟掺杂的多晶ZnO薄膜,ZnF2薄膜是利用电子束蒸发方法沉积在Si(100)衬底得到的。利用X射线衍射和X射线电子能谱研究了ZnF2薄膜向ZnO的转变过程。实验结果表明,在400℃退火30min的条件下能够获得六方纤锌矿结构的ZnO：F薄膜。对ZnO：F薄膜的室温光致发光谱可以观察到位于379nm、半峰全宽为73meV的紫外发射峰,而相应于缺陷的深能级发射则完全猝灭。表明ZnO中残留的F能够有效地增强激子的发光,同时使缺陷发光强度明显降低。对F掺杂对ZnO的发光性能的影响进行了讨论。     

Photoluminescence and resonant Raman scattering in N-doped ZnO thin films

A combination of studies on photoluminescence and resonant Raman scattering in N-doped ZnO thin films were carried out at room temperature. In the photoluminescence spectra, a transformation of radiative recombination mechanism from free-exciton to donor-acceptor-pair transition was observed. An enhancement of resonant Raman scattering processes as well as longitudinal optical (LO) phonon overtones up to the sixth order were observed in the Raman spectra. Also, the nature of the 1LO phonon underwent a transformation from a pure A₁(LO) mode to a quasimode with mixed A₁ and E₁ symmetry. The underlying mechanisms accounting for the influences of N doping on the optical properties of ZnO were related to the incorporation of extrinsic defects in the crystal lattice.     

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.     

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.     

Photoluminescence studies of ZnO thin films on R-plane sapphire substrates grown by sol–gel method

Zinc oxide (ZnO) thin films on R-plane sapphire substrates were grown by the sol–gel spin-coating method. The optical properties of the ZnO thin films were investigated using photoluminescence. In the UV range, the asymmetric near-band-edge emission was observed at 300 K, which consisted of two emissions at 3.338 and 3.279 eV. Eight peaks at 3.418, 3.402, 3.360, 3.288, 3.216, 3.145, 3.074, and 3.004 eV, which respectively correspond to the free exciton (FX), bound exciton, transverse optical (TO) phonon replica of FX recombination, and first-order longitudinal optical phonon replica of FX and the TO (1LO+TO), 2LO+TO, 3LO+TO, 4LO+TO, and 5LO+TO, were obtained at 12 K. From the temperature-dependent PL, it was found that the emission peaks at 3.338 and 3.279 eV corresponded to the FX and TO, respectively. The activation energy of the FX and TO emission peaks was found to be about 39.3 and 28.9 meV, respectively. The values of the fitting parameters of Varshni's empirical equation were α=4×10^?3 eV/K and β=4.9×10³ K, and the S factor of the ZnO thin films was 0.658. With increasing temperature, the exciton radiative lifetime of the FX and TO emissions increased. The temperature-dependent variation of the exciton radiative lifetime for the TO emission was slightly higher than that for the FX emission.     

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.     

Optical properties of ZnO thin films on SiO2 substrates deposited by radio frequency magnetron sputtering

The optical properties of both the annealed and as-deposited ZnO thin films by radio frequency (RF)magnetron sputtering on SiO2 substrates were studied. In the annealed films, two pronounced well defined exciton absorption peaks for the A and B excitons were obtained in the absorption spectra, a strong free exciton emission without deep-level emissions was observed in the photoluminescence (PL) spectra at room temperature. It was found that annealing the films in oxygen dramatically improved the optical properties and the quality of the films.     

扩散掺杂的p型ZnO薄膜的光学性质研究

采用原子层沉积技术(atomic layer deposition)在InP衬底上生长ZnO薄膜,并在不同温度下(500和700 ℃)进行热退火处理,将P掺杂进入ZnO,得到p型ZnO薄膜。样品的光学特性通过光致发光光谱(photoluminescence, PL)来测定,得出热退火温度是影响P扩散掺杂的重要因素,低温PL光谱中,700 ℃热退火1 h样品的光谱展现出四个与受主相关的发射峰：3.351,3.311,3.246和3.177 eV,分别来自受主束缚激子的辐射复合(A°X)、自由电子到受主的发射(FA)、施主受主对的发射(DAP)以及施主受主对的第一纵向声子伴线(DAP-1LO),计算得到受主束缚能为122 meV,与理论计算结果一致。通过热扩散方式实现了ZnO薄膜的p型掺杂,解决了制约ZnO基光电器件发展的主要问题, 对ZnO基半导体材料及其光电器件的发展有重要意义。