分子束外延生长的极性与非极性BeZnO薄膜的比较研究

采用分子束外延设备在不同晶面蓝宝石衬底上(c面,a面,r面)生长BeZnO薄膜。使用复合缓冲层生长得到了高质量的BeZnO薄膜,X射线衍射半高宽达到600 arcsec。在c面与a面蓝宝石衬底上生长得到了极性BeZnO薄膜,在r面蓝宝石上生长得到了非极性BeZnO薄膜。共振拉曼光谱测试结果表明薄膜中的Be含量在同一水平。相对于c面与a面蓝宝石上的极性BeZnO薄膜,生长在r面蓝宝石衬底上的非极性BeZnO薄膜具有较大的表面粗糙度以及较大的半高宽,但是其光致发光谱中的紫外发光峰远远强于极性BeZnO薄膜,并且黄绿光发光峰弱于极性BeZnO薄膜。     

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。     

MOCVD方法生长ZnO微米柱的结构与光学性质

通过X射线衍射、扫描电子显微镜和变温光致发光光谱对MOCVD方法生长在蓝宝石衬底上的ZnO微米柱材料的结构及发光特性进行了表征.X射线衍射结果表明,ZnO具有良好的c轴择优取向,扫描电子显微镜图中可观察出ZnO微米在呈六角结构生长,半径约为0.5～1.5μm.样品的发光光谱通过He-Cd激光器的325nm线激发,从光谱中发现低温(81K)下出现极强的与激子相关的带边发光峰,温度升高到360K时与自由激子相关的紫外发射峰仍然是清晰可见.     

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。     

非掺杂ZnO薄膜中紫外与绿色发光中心

用直流反应溅射方法在硅衬底上淀积了ZnO薄膜,测量它们的光致发光(PL)光谱,观察到两个发光峰,峰值能量分别为3.18(紫外峰,UV)和2.38eV(绿峰).样品用不同温度分别在氧气、氮气和空气中热处理后,测量了PL光谱中绿峰和紫外峰强度随热处理温度和气氛的变化,同时比较了用FP-LMT方法计算的ZnO中几种本征缺陷的能级位置.根据实验和能级计算的结果,推测出ZnO薄膜中的紫外峰与ZnO带边激子跃迁有关,而绿色发光主要来源于导带底到氧错位缺陷(O_Zn)能级的跃迁,而不是通常认为的氧空 关键词： ZnO薄膜 热处理 光致发光光谱 缺陷能级     

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。     

Na-Mg共掺杂ZnO薄膜的结构和光学性质

利用溶胶-凝胶法,在普通载玻片上使用旋转涂膜技术制备了具有c轴择优取向生长的Na-Mg共掺杂的ZnO薄膜。用XRD、SEM、光致发光(PL)及透射光谱对薄膜样品进行了表征。结果表明:Na-Mg共掺杂有利于ZnO薄膜的c轴择优取向生长,并且随着Na+掺杂浓度的增加,晶粒尺寸先增大后减小;通过比较不同掺杂浓度ZnO薄膜的PL谱,推测发光峰值位于380nm的紫外发射与ZnO的自由激子复合有关;发现掺入Mg的确能使ZnO禁带宽度增大,掺杂组分为Na0.04Mg0.2Zn0.76O时,其PL谱只有一个很强的紫光发射峰,其近带边紫外光发射强度较未掺杂的ZnO增强了近10倍,极大地提高了薄膜紫外发光性能;并且随Na+浓度增加薄膜透光性减弱。     

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     

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     

ZnO薄膜近带边紫外发光的研究

用ZnO陶瓷靶,采用脉冲激光沉积(PLD)技术在c-Al₂O₃衬底上制备了ZnO薄膜。通过不同温度下光致发光(PL)光谱的测量,对样品的紫外发光机理进行研究。 在较低温度(10 K)下的PL光谱中,观测到一个位于3.354 eV处的束缚激子(D⁰X)发射,随着温度的升高(~50 K),在D⁰X的高能侧观测到了自由激子的发射峰。在10 K温度下,3.309 eV处出现了一个较强的发光带A,此发光带强度随着温度升高先增大然后减小,并且一直延续到室温。重点讨论了此发光带的起源,并认为A带可归属于自由电子-受主之间的复合发射。     

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)。     

Structural and optical properties of ZnO film by plasma-assisted MOCVD

High quality ZnO film was deposited by plasma-assisted metal-organic chemical vapor deposition (MOCVD). We observed a dominant peak at 34.6° due to (0 0 2) ZnO, which indicated that the growth of ZnO film was strongly C-oriented. The full-width at half-maximum (FWHM) of the -rocking curve was 0.56° indicating relatively small mosaicity. Photoluminescence (PL) measurement was performed at both room temperature and low temperature. Ultraviolet (UV) emission at 3.30 eV was found with high intensity at room temperature while the deep level transition was weakly observed at 2.513 eV. The ratio of the intensity of UV emission to that of deep level emission was as high as 193, which implied high quality of ZnO film. From PL spectrum at 10 K, we observed A-exciton emission at 3.377 eV and D°X bound exciton transition at 3.370 eV. The donor–acceptor transition and LO phonon replicas were observed at 3.333 and 3.241 eV respectively. Raman scattering was performed in back scattering at room temperature. The E₂, A_1(LO) and A_1(TO) mode was seen at 437.6, 575.8 and 380 cm^–1 respectively. In comparison with Raman spectrum of ZnO powder, we found that ZnO film was nearly free of strain, which indicated high crystal quality.     

The photoluminescence characterization of the N-doped ZnO films produced by wet chemical deposition

The ZnO:N films are prepared by a wet chemical method. The temperature-dependent photoluminescence (PL) is used to investigate those ZnO: N films. Due to the introduction of nitrogen atoms into ZnO film, another phase appears in the ZnO film, which can release the stress and improve the film quality. As a result, a neutral donor-bound exciton (D⁰X) emission peak is shown in low temperature PL spectrum. With the increasing temperature, the D⁰X line gradually loses its intensity and shifts to 3.30 eV, which is consistent with the well-known conversion from bound exciton to free exciton at elevated temperatures. Then, due to the thermal quenching effect, the D⁰X line vanishes in room temperature. In addition, no shift is shown in the location of visible band emission and only the intensity decreases with the increasing temperature.     

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.     

衬底温度对ZnO薄膜的结构和光学特性的影响

利用等离子体辅助分子束外延(P-MBE)设备在蓝宝石衬底上通过改变生长温度,制备了不同的ZnO样品.研究了衬底温度对ZnO的结构、光学和电学性质的影响.样品的晶体结构利用X射线衍射谱进行表征.X射线衍射谱表明,所有的ZnO样品都是(002)取向的六角纤锌矿结构.随着生长温度的升高,X射线的(002)衍射峰的半峰全宽逐渐...     

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。     

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.