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     

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     

用电泳法制备ZnxMg1-xO薄膜及其特性研究

用电泳法制备了一系列ZnxMg1-xO薄膜. 对ZnxMg1-xO薄膜的光致发光研究表明，在薄膜发射谱的紫外区域有两个显著的峰，分别对应自由激子和激子间碰撞的发光. 在可见光区域，发射谱的强度基本保持恒定，没有发现通常报道的绿光发射，说明生长的薄膜中氧与其他元素保持很好的 化学配比，抑制了基于氧空位的绿带发射机理. 另一方面，薄膜成分中Mg含量的变化和退火 温度的变化对薄膜的发射谱有显著的影响，表现在ZnxMg1-xO的紫 外发射峰随Mg含量的增加向短波方向移动，同时峰强度随退火温度的升高显著增加. 关键词： 发射谱 x射线衍射 电泳法 ZnMgO薄膜     

用电泳法制备ZnxMg1-xO薄膜及其特性研究

用电泳法制备了一系列ZnxMg1 -xO薄膜 .对ZnxMg1 -xO薄膜的光致发光研究表明 ,在薄膜发射谱的紫外区域有两个显著的峰 ,分别对应自由激子和激子间碰撞的发光 .在可见光区域 ,发射谱的强度基本保持恒定 ,没有发现通常报道的绿光发射 ,说明生长的薄膜中氧与其他元素保持很好的化学配比 ,抑制了基于氧空位的绿带发射机理 .另一方面 ,薄膜成分中Mg含量的变化和退火温度的变化对薄膜的发射谱有显著的影响 ,表现在ZnxMg1 -xO的紫外发射峰随Mg含量的增加向短波方向移动 ,同时峰强度随退火温度的升高显著增加     

CdSe/CdZnSe超晶格的激子光学性质的研究

用分子束外延法在GaAs衬底上生长了CdSe/Cd0.65Zn0.35Se超晶格结构。利用X射线衍射（XRD）、77K下变密度激发的光致发光光谱和变温度光致发光光谱研究了CdSe/CdZnSe超晶格结构和激光复合特性，在该材料中观测到激子－激子散射发射峰，变密度激发光致发光光谱和谱温度光致发光光谱证实了这一现象，激子发射峰的线宽随着温度的升高而展宽，低温时发光峰的宽度主要是由合金组分和阱垒起伏引起的，没温时激子线宽展宽是由于激子与纵光学声子和离化的施主杂质间的散射作用引起的，光致发光的强度随着温度的升高而降低，这主要是由激子的热离化造成的，也就是说，热激发使得电子或空穴由阱中跃迁至垒上。     

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。     

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。     

退火对ZnO:Al薄膜光致发光性能的影响

 采用溶胶-凝胶工艺在石英衬底上制备ZnO:Al（AZO）薄膜，通过不同温度的退火处理，研究了退火对AZO薄膜结构和光致发光特性的影响。XRD图谱表明：所制备的薄膜具有c轴高度择优取向，随着退火温度的升高，(002)峰的强度逐渐增强，同时(002)峰的半高宽逐渐减小,表明晶粒在不断增大。未退火样品的光致发光（PL）谱由361 nm附近的紫外带边发射峰和500 nm附近的深能级发射峰组成。样品经退火后，以500 nm为中心的绿带发射逐渐减弱，而带边发射强度有所增强,并且逐渐红移到366 nm附近，与吸收边移动的测试结果相吻合。对经过不同时间退火的样品分析表明，AZO薄膜的发光特性与退火时间也有很大关系，时间过短可见波段的发射较强，但时间过长会使晶粒发生团聚，导致紫外发射峰强度减弱。     

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.     

MgxZn1-xO单晶薄膜的结构和光学性质

用等离子辅助分子束外延(P-MBE)的方法,在蓝宝石c平面上外延生长了MgxZn1-xO合金薄膜。在0≤x≤0．2范围内薄膜保持着ZnO的纤锌矿结构不变。X射线双晶衍射谱的结果表明生长的样品是单晶薄膜。据布喇格衍射公式计算得到,随着Mg含量的增加,薄膜的品格常数C由0．5205nm减小到0．5185nm。室温光致发光谱出现很强的紫外近带发射(NBE)峰,没有观察到深能级(DL)发射,且随着Mg的掺入量的增加,紫外发射峰有明显的蓝移。透射光谱的结果表明,合金薄膜的吸收边随着Mg离子的掺入逐渐向高能侧移动,这与室温下光致发光的结果是相吻合的,并计算出随着x值增加,带隙宽度从3．338eV逐渐展宽到3．682eV。通过研究Mg0.12Zn0.88O样品的变温光谱,将紫外发射归结为束缚在施主能级上的束缚激子发射。并详细地研究了在整个温度变化过程中,束缚激子的两个不同的猝灭过程以及谱线的半峰全宽与温度变化的关系。     

硅基锗薄膜的红外吸收谱和电学特性

为了解退火对硅基锗薄膜的质量、红外吸收、透射率和电学性质的影响,采用分子束外延方法用两步法在硅基上生长锗薄膜。将生长后的样品分成两部分,其中一部分进行了退火处理。对退火前后的样品用高分辨X射线双晶衍射仪测量了(400)晶面的X射线双晶衍射摇摆曲线,用傅里叶红外光谱仪测量了红外透射率和吸收谱,并用霍尔效应仪测量了退火前后样品的载流子浓度、迁移率、电阻率、电导率和霍尔系数。结果表明,退火后的薄膜质量明显提高。退火后大部分区域吸收增大,透射率明显减小,615~3 730 cm-1区间的透射率均比退火前降低了20%以上。退火后的体载流子浓度增大到退火前的23.26倍,迁移率增大到退火前的27.82倍。     

Jumplike microdeformation of nanostructured metals

The parameters of microdeformation jumps for copper, aluminum, titanium, and Armco iron with the initial (annealed) structure and after equal-channel angular pressing are investigated in a creep mode under low compressive stresses. The strain rate is measured with a laser interferometer in 0.15-μm linear displacements. It is demonstrated that the values of the microstrain rate and the mean sizes of jumps for the annealed metals are larger than those for the metals subjected to severe deformation. It is revealed that there is a correlation between the jumps of microplastic deformation and the size of nanometal grains. The inference is made that, for nanostructured metals, as for other materials, the structural heterogeneity is one of the factors responsible for the jumplike deformation.     

On the origin of intrinsic donors in ZnO

As-grown undoped zinc oxide (ZnO) films have been annealed in zinc-rich, oxygen-rich and vacuum ambient, and the electron concentration varied greatly after the annealing process. It decreased nearly two orders of magnitude after the sample was annealed in oxygen, while increased nearly three times after annealed in metallic zinc ambient, and increased slightly after annealed in vacuum. It was found that the variation trend of the electron concentration is always the same with the expected variation of oxygen vacancy (V_O) under the three investigated conditions, it is thus speculated that V_O may be the dominant donor source in ZnO. By supplying more oxygen during the growth process to suppress V_O, ZnO films with lower electron concentration were obtained, which verifies the above speculation.     

InGaN/GaN多量子阱热退火的拉曼光谱和荧光光谱

通过拉曼光谱及荧光光谱测量研究了采用低压金属有机化学沉积(MOCVD)方法生长的InGaN／GaN多量子阱高温快速热退火处理对量子阱光学性质的影响。观测到退火后InGaN／GaN量子阱的拉曼光谱E2,A1(LO)模式的峰位置出现了红移,而且该振动峰的半高宽也有微小变化。温度升高退火效果更明显。退火使量子阱内应力部分消除,同时In,Ga原子扩散出现相分离使拉曼谱表现出变化。在常温和低温下的光荧光谱表明,退火处理的量子阱发光主峰都出现了红移;而且低温退火出现红移,退火温度升高相对低温退火出现蓝移;同时在低温荧光光谱里看到经过退火处理后原发光峰中主峰旁边弱的峰消失了。讨论了退火对多量子阱光学性质的影响。     

Investigation of the inhibiting outdiffusion of erbium atoms to a silicon-on-insulator surface after annealing at high temperature

The annealing behaviour of 400 keV Er ions at a fluence of 2×1015 cm-2 implanted into silicon-on-insulator(SOI) samples is investigated by Rutherford backscattering spectrometry of 2.1 MeV He2+ ions with a multiple scattering model.It is found that the damage close to the SOI surface is almost removed after being annealed in O2 and N2 atmospheres,successively,at ℃,and that only a small number of the Er atoms segregated to the surface of the SOI sample,whereas a large number of Er atoms diffused to a deeper position because of the affinity of Er for oxygen.For the SOI sample co-implanted with Er and O ions,there is no evident outdiffusion of Er atoms to the SOI surface after being annealed in N2 atmosphere at ℃.     

Effect of post-thermal annealing on the structural and optical properties of ZnO thin films prepared from a polymer precursor

ZnO thin films were synthesised by a new method which uses polyvinyl alcohol (PVA) as the polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and time. All the films possess tensile strain, which relaxes as the annealing temperature and time increase. The photoluminescence (PL) spectra contain only ultraviolet (UV) peaks at low temperature, but as the annealing temperature and time increase, we observe peaks at the blue and green regions with a variation in the intensities of these peaks with annealing temperature and time.     

Effect of post thermal annealing on the structural and optical properties of ZnO thin films prepared from polymer precursor

ZnO thin films were synthesised by a new method which uses polyvinyl alcohol (PVA) as polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and annealing time. All the films possess tensile strain which relaxes as the annealing temperature and the annealing time increases. The photoluminescence (PL) spectra contain only ultraviolet (UV) peaks at low temperature, but as the annealing temperature and time increase we observe peaks at blue and green regions with variation of the intensities of these peaks with annealing temperature and annealing time.     

Optical studies on the red luminescence of InGaN epilayers

Photoluminescence, photoluminescence excitation and time-resolved photoluminescence studies were performed in a partially relaxed InGaN epilayer, and exhibiting a 3D growth mode at the surface. Two emission bands, a red (centred at 1.88 eV) and a blue (centred at 2.58 eV) were observed. In order to investigate their origin and their relation with the strain relaxation along the growth direction, the sample was etched. After etching, only an asymmetrical broad emission band centred at 2.15 eV was observed.The decrease of decay time and the increase of the band edge absorption energy with increasing monitored photon energy, along the red emission, are assigned to the effect of localization of excitons at potential minima, originated in compositional and strain inhomogeneities of the sample. Therefore, the blue shift observed on this band with an increase in temperature, is caused by the population of higher energy states. The large difference between the luminescence intensities, decay times and the thermal quenching of the red and blue (centred at 2.58 eV) band is also accounted for by the localization model. It is demonstrated that the luminescence observed after etching is a superposition of two bands, one originated from the InGaN film, and the other from the GaN underlayer. The large difference between absorption and emission energies, compared with those measured in the as-grown sample, within the same spectral region, indicates that this emission has a different origin. It is suggested that deep levels might be responsible for the luminescence observed after etching.     

Effect of annealing time on properties of spinel LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> high-voltage lithium-ion battery electrode materials prepared by co-precipitation method

In this wok, a series of LiNi_0.5Mn_1.5O₄ (LNMO) samples with an octahedral shape entirely composed of (111) crystal planes were prepared by calcining the mixture of the precursor Ni_0.25Mn_0.75(OH)₂ and LiOH·H₂O at 800 °C for 15 h in air, followed by annealing them at 600 °C for different dwelling times. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and several electrochemical technologies were used to investigate the effect of annealing time on properties of the LNMO samples. XRD analysis indicates that the lattice parameters of the LNMO samples show a decreasing trend with increasing of annealing time, and the impurity peaks become less apparent for the sample annealed for 6 h and almost disappear for the samples annealed for 9 and 24 h. SEM results show that the annealing time has no obvious influence on the morphologies of the LNMO samples. Electrochemical measurements show that the electrochemical performances (capacity, cycle life, and rate capability) of the samples annealed for 6, 9, and 24 h are better than those of the unannealed sample, and the sample annealed for 9 h shows the best electrochemical properties among them due to its superior electrochemical kinetics of Li⁺ insertion/desertion.     

The effect of hydrogen stoichiometry on palladium strain and resistivity

The strain and the electrical resistivity of a Pd sample stressed by a constant tension have been investigated through a series of hydrogenation cycles in a continuous H stoichiometry [0?x?0.8] range. The isotropic lattice expansion for both “as drawn” and “annealed” Pd sample reveals a strain of only 1% from pure Pd to PdH_0.8 in disagreement with literature data available; the measured effect is minimum at x=0.13 (α+β phase) and then from x=0.6 (β phase) it has an exponential increase. The contribution of the mechanical tensile stress on the total relative elongation of the wire is also investigated. An increase of the Pd sample tensile strain after each hydrogenation cycle is reported for “as drawn” samples, while for “annealed” samples the reverse behaviour is observed. Moreover, annealed samples show considerably higher value of tensile strain compared to “as drawn”. The variation of mechanical strain versus H content, for both “annealed” and “as drawn”, has a maximum at x=0.52. Strain variation and resistivity variation versus H content exhibit similar behaviour.