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。     

掺AlZnO纳米线阵列的光致发光特性研究

采用化学气相沉积方法，以金做催化剂，在Si (100)衬底上制备了掺AlZnO纳米线阵列.扫描电子显微镜(SEM)表征发现ZnO纳米线的直径在30nm左右.X射线衍射(XRD)图谱上只存在ZnO的(002)衍射峰，说明ZnO纳米线沿c轴择优取向.掺AlZnO纳米线阵列的室温光致发光(PL)谱中出现了3个带边激子发射峰：373nm，375nm，389nm.运用激子理论推算出掺AlZnO纳米线的禁带宽度为3.343eV ，束缚激子结合能为0.156eV；纯ZnO纳米线阵列PL谱中3个带边激子发射 关键词： 光致发光 化学气相沉积(CVD) 激子 ZnO纳米线阵列     

ZnCdse-ZnSe多量子阱中的激子发光

在77-300K温度下研究了Zn_1-xCd_xSe-ZnSe多量子阱(MQWs)的光致发光特性.首次在77K,Ar离子激光器的457.9nm激发下,在Zn_0.68Cd_0.32Se-ZnseMQWs中观测到5个发光带,其中三个发光带被归因于不同的激子发射:即n=1重空穴(HH)激子;n=l轻-重空穴(LH)激子和n=IHH激子同时发射两个纵光学声子的复合发光,并且n=1HH激子发光可延续至室温.     

利用离子激发发光研究低温条件下ZnO发光行为EI北大核心CSCD

离子激发发光(Ions beam induced luminescence,IBIL)可以实时原位分析不同温度、不同离子辐照条件下材料内部点缺陷的演变行为。本文利用2 MeV H^(+)研究了300,200,100 K温度下ZnO单晶内部点缺陷发光及其随注量的演变行为。实验中发现ZnO深能级发射和近带边发射,结合Voigt分峰与XPS实验结果,确定红光(1.75 eV)与V_(Zn)相关,橙红光(1.95 eV)来自Zn_(i)到O_(i)跃迁;对于与V_(O)相关的绿光(2.10 eV),其红移可能由于温度降低导致更多电子由导带释放到Zn_(i)。峰中心位于3.10 eV和3.20 eV近带边发射分别来自于Zn_(i)到价带的跃迁和激子复合,红移原因分别为Zn_(i)附近局域化能级和带隙收缩。利用单指数公式对发光强度进行拟合,获得的衰减速率常数(f)可以表征缺陷的辐射硬度,对比发现深能级发射峰在200 K时辐射硬度最大,而近带边发射峰在300 K时辐射硬度最大。     

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     

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.     

氢化后ZnO发光性质的变化

通过低温光致发光(PL)谱研究氢化对ZnO发光性质的影响。氢通过一个直流等离子体发生装置引入到ZnO晶体。研究发现氢的引入影响了束缚激子的相对发光强度,特别是I4峰(3.363eV)的强度增加和3.366eV峰出现。比较未氢化样品,氢化样品PL谱显示不同的温度依赖。     

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。     

CdSe/CdMnSe多量子阱的激子光学性质的研究

用分子束外延在GaAs衬底上生长了CdSe/CdMnSe多量子阱结构.利用X射线衍射(XRD)、变密度激发的PL光谱、变温度PL光谱和变密度激发的ps时间分辨光谱研究了CdSe/CdMnSe多量子阱结构和激子复合特性.讨论了随温度升高辐射线宽展宽和辐射复合效率降低的机理.发现不同激发密度下发光衰减时间不同,认为它的机理可能是无辐射复合引起的.在该材料中观测到激子激子散射发射峰,它被变密度激发和变温度PL光谱所证实. 关键词： CdSe/CdMnSe 量子阱 光学性质     

MOCVD法生长ZnO薄膜的结构及光学特性

采用MOCVD方法在c Al2 O3衬底上生长出了具有单一c轴取向的ZnO薄膜 ,采用X射线衍射 (XRD)、Raman散射、X射线光电子能谱 (XPS)及光致发光 (PL)谱等方法对ZnO薄膜的结构及光学特性进行分析测试。XRD分析只观察到ZnO薄膜 (0 0 0 2 )衍射峰 ,其FWHM数值为 0 1 84°。Raman散射谱中 ,4 35 32cm- 1 处喇曼峰为ZnO的E2 (high)振动模 ,A1 (LO)振动模位于 5 75 32cm- 1 处。XPS分析表明 :ZnO薄膜表面易吸附游离态氧 ,刻蚀后ZnO薄膜O1s光电子能谱峰位于 5 30 2eV ,更接近Zn—O键中O1s电子结合能 (5 30 4eV)。PL谱中 ,在3 2 8eV处观察到了自由激子发射峰 ,而深能级跃迁峰位于 2 5 5eV ,二者峰强比值为 4 0∶1 ,表明生长的ZnO薄膜具有较高的光学质量     

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)。     

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     

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.     

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.     

Effect of different annealing temperature on Sb-doped ZnO thin films prepared by pulsed laser deposition on sapphire substrates

Influence of annealing temperature on the properties of Sb-doped ZnO thin films were studied. Hall measurement results indicated that the Sb-doped ZnO annealed at 950 °C was p-type conductivity. X-ray diffraction (XRD) results indicated that the Sb-doped ZnO thin films prepared at the experiments are high c-axis oriented. It was worth noting that p-type sample had the worst crystallinity. The measurements of low-temperature photoluminescence (PL) spectra indicate that the sample annealed at the temperatures of 950 °C showed strong acceptor-bound exciton (A⁰X) emission, and confirmed that it is related to Sb-doping by comparing with the undoped ZnO low-temperature PL spectrum.     

Effect of annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films on sapphire (0 0 0 1) substrates by magnetron sputtering

ZnO thin films were epitaxially grown on sapphire (0 0 0 1) substrates by radio frequency magnetron sputtering. ZnO thin films were then annealed at different temperatures in air and in various atmospheres at 800 °C, respectively. The effect of the annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films are investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL). A strong (0 0 2) diffraction peak of all ZnO thin films shows a polycrystalline hexagonal wurtzite structure and high preferential c-axis orientation. XRD and AFM results reveal that the better structural quality, relatively smaller tensile stress, smooth, uniform of ZnO thin films were obtained when annealed at 800 °C in N₂. Room temperature PL spectrum can be divided into the UV emission and the Visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the Visible broad band emission can be ascribed to the deep level emissions (DLE). By analyzing our experimental results, we recommend that the deep-level emission correspond to oxygen vacancy (V_O) and interstitial oxygen (O_i). The biggest ratio of the PL intensity of UV emission to that of visible emission (I_NBE/I_DLE) is observed from ZnO thin films annealed at 800 °C in N₂. Therefore, we suggest that annealing temperature of 800 °C and annealing atmosphere of N₂ are the most suitable annealing conditions for obtaining high quality ZnO thin films with good luminescence performance.     

RF溅射钕掺杂ZnO薄膜的结构与发光特性

通过射频磁控溅射技术在Si(111)衬底上制备了未掺杂ZnO薄膜和Nd掺杂ZnO薄膜。应用XRD分析了ZnO:Nd薄膜的晶格结构,通过AFM观察了ZnO:Nd薄膜的表面形貌。结果表明,Nd掺入了ZnO晶格中,由于Nd原子半径大于Zn原子半径,Nd以替位原子的形式存在于ZnO晶格中。ZnO:Nd薄膜为纳米多晶薄膜,表面形貌粗糙。ZnO:Nd薄膜的室温光致发光谱表明,相同条件下制备的未掺杂ZnO薄膜和Nd掺杂ZnO薄膜都出现了395nm的强紫光带和495nm的弱绿光带。我们认为,紫光发射峰窄而锐且强度远大于绿光峰,源于薄膜中激子复合;绿光峰强度较弱,源于薄膜中的氧空位(VO)及氧反位锌缺陷(OZn)。Nd掺杂没有影响ZnO:Nd薄膜的PL谱的发射峰的峰位。由于Nd3 离子电荷数与Zn2 离子电荷数不相等,为了保持ZnO薄膜的电中性,间隙锌(VZn)可以作为Nd替位补偿性的受主杂质而存在,影响ZnO薄膜的激子浓度。同时,Nd掺入使ZnO的晶格畸变缺陷浓度改变增强,因而发射峰的强度随Nd掺杂浓度不同而变化。     

A simple growth route towards ZnO thin films and nanorods

Highly orientated ZnO thin films and the self-organized ZnO nanorods can be easily prepared by a simple chemical vapor deposition method using zinc acetate as a source material at the growth temperature of 180 and 320 °C, respectively. The ZnO thin films deposited on Si (100) substrate have good crystallite quality with the thickness of 490 nm after annealing in oxygen at 800 °C. The ZnO nanorods grown along the [0001] direction have average diameter of 40 nm with length up to 700 nm. The growth mechanism for ZnO nanorods can be explained by a vapor-solid (VS) mechanism. Photoluminescence (PL) properties of ZnO thin films and self-organized nanorods were investigated. The luminescence mechanism for green band emission was attributed to oxygen vacancies and the surface states related to oxygen vacancy played a significant role in PL spectra of ZnO nanorods.     

Pulsed laser deposited ZnO/ZnO:Li multilayer for blue light emitting diodes

Thin films of ZnO, Li doped ZnO (ZLO) and multilayer of ZnO and ZLO (ZnO/ZLO) were grown on silicon and corning glass substrates by pulsed laser deposition technique. Single phase formation and the crystalline qualities of the films were analyzed by X-ray diffraction and Li composition in the film was investigated to be 15 wt% by X-ray photoelectron spectroscopy. Raman spectrum reveals the hexagonal wurtzite structure of ZnO, ZLO and ZnO/ZLO multilayer and confirms the single phase formation. Films grown on corning glass shows more than 80% transmittance in the visible region and the optical band gaps were calculated to be 3.245, 3.26 and 3.22 eV for ZnO, ZLO and ZnO/ZLO, respectively. An efficient blue emission was observed in all films which were grown on silicon (1 0 0) substrate by photoluminescence (PL). PL measurements at different temperatures reveal that the PL emission intensity of ZnO/ZLO multilayer was weakly dependent on temperature as compared to the single layers of ZnO and ZLO and the wavelength of emission was independent of temperature. Our results indicate that ZnO/ZLO multilayer can be used for the fabrication of blue light emitting diodes.     

Photoluminescence study of Si doped and undoped Chalcopyrite CuGaSe2 thin films

Photoluminescence (PL) characteristics have been studied on undoped and Si-doped CuGaSe₂ single crystal thin films grown on GaAs (001) substrate by migration-enhanced epitaxy. Room temperature PL spectrum of an undoped layer clearly shows free excitonic emission bands related to the minimum band-edge and to the split-off valence band, but no discernible emission has been observed in the low energy area. At 4.2 K, the excitonic emission due to the split-off valence band disappears. Instead, two additional emissions appear at 1.68 and 1.715 eV which are attributed to the bound exciton and band-to-acceptor transition. The Si doping to CuGaSe₂ produces two additional PL bands around 1.61 and 1.64 eV. These PL bands are attributed to the donor acceptor pair emissions due to the doped Si impurity which probably occupies Cu or Ga sites and intrinsic Cu vacancy.