Luminescence of Thin Films of Lead and Bismuth Tungstates

The luminescence spectra of thin films of PbWO₄ and Bi₂WO₆ were investigated. It is shown that these spectra are similar and that they consist of three individual bands in the blue (2.80 eV PbWO₄ and 2.93 eV Bi₂WO₆), green (2.35 eV PbWO₄ and Bi₂WO₆), and red (1.75 eV PbWO₄ and 1.90 eV Bi₂WO₆) spectral regions. The differences in the nature of the absorption centers of excitation energy are established. The distinguishing features displayed by the temperature dependences of the individual emission bands in the PbWO₄ films are explained by energy migration between emission centers via transfer of free carriers through the conduction and valence bands.     

Light Dispersion in Bismuth Germanate Crystals and Bismuth Oxide Films

The dispersion of light in Bi₄Ge₃O₁₂ and Bi₁₂GeO₂₀ single crystals and thin Bi₂O₃ films with a monoclinic structure was investigated in the visible spectral region. The parameters of a single-oscillator approximation have been found. It is established that in Bi₄Ge₃O₁₂ crystals the absorption band caused by the O2p–Bi6p transitions makes the main contribution to the dispersion curve in the visible region, whereas in Bi₁₂GeO₂₀ crystals this is made by transitions from the hybrid O2p–Bi6p states to the conduction band. The dispersion energy, the degree of the ionicity of binding, and the coordination number of the first coordination sphere of the Bi³⁺ cation have been determined.     

Luminescence of Thin Bi2W2O9 Films

The luminescence spectra of thin Bi₂W₂O₉ films have been investigated. The spectra were separated into elementary components by the Alentsev–Fock method. The radiation band with a maximum at 2.43 eV in the luminescence spectrum of Bi₂W₂O₉ has been assigned to the Frenkel autolocalized excitons. The luminescence bands with maxima at 2.10 and 1.90 eV have been assigned to the emission of the centers whose energy levels are located in the forbidden band. The luminescence of the Bi₂W₂O₉ films is due to the emission of the WO₆ complex.     

Influence of Oxygen Vacancies on the Luminescence Spectra of Thin Bi4Ge3O12 Films

Luminescence spectra of thin Bi₄Ge₃O₁₂ films annealed in air and in vacuum have been investigated. It has been established that the luminescence spectra for different forms of excitation consist of three bands with maxima at 2.70, 2.40, and 2.05 eV. The relation of the bands with maxima at 2.40 and 2.05 eV to the centers that incorporate an oxygen vacancy has been shown. The separated emission bands have been interpreted.     

X‐Ray Luminescence of Thin Oxide Films Containing Lead and Bismuth

We obtained thin films of the Bi₄Ge₃O₁₂, Bi₄Si₂O₁₂, PbWO₄, and Bi₂WO₆ scintillators and investigated their luminescence properties on xray excitation. We measured the xray luminescence spectra and established the linear character for the dependence of the luminescence intensity on the power of the dose of xray irradiation within the limits of up to 3·10^–3 A/kg. We investigated the radiation stability of the films obtained. The possibility of their application for detecting ionizing radiation is investigated. The films based on Bi₄Ge₃O₁₂ with an admixture of the Ge and Si or Mn activator of up to 1.5 mol.% are most suitable.     

Influence of Oxygen Vacancies on the Luminescence Spectra of Y2O3 Thin Films

Luminescence spectra of Y₂O₃ thin films annealed in air and in vacuum are investigated. It is established that the presence of oxygen vacancies leads to a decrease in the intensity of the luminescence band with a maximum at 3.4 eV (related to emission of selflocalized Frenkel excitons describing the excited state of a molecular ion (YO₆)^9–) and of the luminescence band with a maximum at 2.9 eV (related to the anion sublattice). It is revealed that the oxygen vacancies also lead to a decrease in the luminescence intensity in the 2.60, 2.35, 2.10. 1.90, and 1.70 eV bands that are related to radiative recombination in the donor–acceptor Y³⁺–O^2– pairs. The donor–acceptor distances are calculated.     

碲化铋薄膜载能粒子相互作用的超快研究

碲化铋禁带宽度非常窄而具有高电导率和塞贝克系数,同时具有低热导率,成为已知室温下优值系数最高的热电材料。已有研究表明,纳米薄膜和超晶格是进一步提高材料热电性能的可行途径。因此超快研究碲化铋纳米薄膜中载能子间的相互作用过程对开发高性能热电材料有重要意义。本文采用飞秒激光泵浦-探测技术,实验研究了沉积在硅基底上厚度为100 nm碲化铋薄膜中各载能粒子的相互作用过程。通过改变延迟时间步长,分别观察到价带电子被光子激发跃迁至导带,激发电子在导带内与声子的能量弛豫及导带电子与空穴复合跃迁至价带,并将能量传递给声子导致声子温度升高的过程。此外,还观察到热应力产生的声波,并据此得到了碲化铋薄膜中纵波声速为2649 m s^-1。     

IR Reflection of Thin Bi4Ge3O12 Films

The spectra of IR reflection of the systems thin Bi₄Ge₃O₁₂ film–substrate made of molten -SiO₂ quartz in the region 10–1600 cm^–1 at 295 K are investigatedterpretation of fundamental vibrations in the region 10–800 cm^–1 and two phonon processes in the region 800–1600 cm^–1 are considered.     

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)。     

Luminescence of Bismuth‐Activated Ceramics of Yttrium and Scandium Oxides

The luminescence spectra of Y₂O₃:Bi and Sc₂O₃:Bi ceramics have been investigated. The spectra have been resolved into elementary components by the Alentsev–Fock method. It has been established that the luminescence is attributed to emission centers of three types, two of which are due to the replacement of Y³⁺ (or Sc³⁺) by Bi³⁺ at the nodes of the crystal lattice of Y₂O₃ (or Sc₂O₃) with the point symmetry C ₂ and C _3i . The emission center Bi³⁺ in the position C_3i leads to the appearance of blue luminescence with maxima at 3.03 eV for Y₂O₃:Bi and at 3.05 eV for Sc₂O₃:Bi; this luminescence is attributed to the transition ³ P ₁–¹ S ₀. The emission center Bi³⁺ in the position C ₂ initiates green luminescence (which is also related to the ³ P ₁–¹ S ₀ transition in Bi³⁺) with a maximum in the region of 2.40 eV in Y₂O₃:Bi and in the region of 2.46 eV in Sc₂O₃:Bi. The red luminescence band with maxima at 1.85 eV in Y₂O₃:Bi and at 1.95 eV in Sc₂O₃:Bi is related to the presence of structural defects.     

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     

磁控溅射制备ZnO薄膜的结构及发光特性研究

采用射频反应磁控溅射法在玻璃衬底上制备出具有c轴高择优取向的ZnO薄膜,利用X射线衍射、扫描探针显微镜及荧光分光光度法研究了生长温度对ZnO薄膜微观结构及光致发光特性的影响。结果表明,合适的衬底温度有利于提高ZnO薄膜的结晶质量;在室温下测量样品的光致发光谱(PL),观察到波长位于400 nm左右的紫光、446 nm左右的蓝色发光峰及502 nm左右微弱的绿光峰,随衬底温度升高,样品的PL谱中紫光及蓝光强度逐渐增大,同时,绿光峰的强度也表现出一定程度的增强。经分析得出紫光应是激子发光所致,而锌填隙则是引起蓝光发射的主要原因,502 nm左右的绿光峰应该是氧的深能级缺陷造成的。此外,还测量了样品的吸收谱,并结合样品吸收谱的拟合结果对光致发光机理的分析作了进一步的验证。     

Energy Levels in the Forbidden Band of the Bi4Ge3O12 Ceramics

Thermally stimulated luminescence in the Bi₄Ge₃O₁₂ ceramics and also in the ceramics of the parent components Bi₂O₃ and GeO₂ is investigated. The similarity of the curves of the thermally stimulated luminescence in bismuth germanate with the structure of eulytine Bi₄Ge₃O₁₂ and sillenite Bi₁₂GeO₂₀ is explained. The relation of the thermally stimulated luminescence band in Bi₄Ge₃O₁₂ (with a maximum at 143 K) to the disruptions in the germanium sublattice and of the thermally stimulated band (with a maximum at 187 K) to the recombination processes in the bismuth sublattice is shown. It has been established that the light sum in the Bi₄Ge₃O₁₂ ceramics is stored most effectively upon excitation by light in an energy region of 4.4 eV.     

Thermally stimulated luminescence of bismuth germanate ceramics with the benitoite,eulitine, and sillenite structures

Thermally stimulated luminescence (TSL) of Bi₂Ge₃O₉, Bi₄Ge₃O₁₂, and Bi₁₂GeO₂₀ and the primary components Bi₂O₃ and GeO₂ was studied under x-ray excitation. Thermal activation energies and frequency factors of trapping centers in the studied ceramics were determined. The relationships of TSL bands of the studied ceramics with maxima at 141–145 and 166–170 K and damage to the Ge sublattice and of TSL bands with maxima at 104–110 and 180–190 K and recombination processes in the Bi sublattice were demonstrated. Recombination processes causing luminescence upon nonequilibrium charge carrier release from trapping centers occur in structural complexes of similar configuration that contain the Bi ion in a nearest environment of O atoms. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 359–364, May–June, 2008.     

氧化锌可见区发光机制

探究与缺陷相关的氧化可见区发光机制对获得高效激子发光和实现紫外激光有重要的意义，也是该领域研究的基本问题之一，本文用X射线衍射、X射线光电子能谱，电子顺磁共振和光致发光谱研究了ZnO:Mn纳米薄膜的结构和发光性质，证明了氧空位或缺陷分布于纳米晶表面，提出了可见发光中心是Vo^**和[Vo^*,electron]或[Vo^**,two electrons]复合体的发光模型。     

PLD制备的Cu掺杂SnS薄膜的结构和光学特性

利用脉冲激光沉积(PLD)在玻璃衬底上制备了Cu掺杂SnS薄膜.靶材是由SnS和Cu₂S粉末混合压制而成(Cu和Sn的量比分别为0%、2.5%、5%、7.5%和10%).利用X射线衍射(XRD)、拉曼光谱仪(Raman)、原子力显微镜(AFM)、紫外-可见-近红外分光光度计(UV-Vis-NIR)、Keithley 4200-SCS半导体参数分析仪研究了Cu掺杂量对SnS薄膜的晶体结构、表面形貌、光学性质和电学性能的影响.结果表明:所制备的SnS薄膜样品沿(111)晶面择优取向生长, SnS :5%Cu薄膜的结晶质量最好且具有SnS特征拉曼峰.随着Cu掺杂量的增大, 平均颗粒尺寸逐渐增大.不同Cu掺杂量的薄膜在可见光范围内的吸收系数均为10⁵ cm^-1数 量级.SnS :5%Cu薄膜的禁带宽度E_g为2.23 eV, 光暗电导率比值为2.59.同时, 在玻璃衬底上制备了p-SnS :Cu/n-ZnS 异质结器件, 器件在暗态及光照的条件下均有良好的整流特性, 并具有较弱的光伏特性.     

光学薄膜及其进展

对光学薄膜的性能及制备技术等方面进行了简要的评述,并指出随着科学技术的进步,光学薄膜及相关技术不论从广度还是深度来看都得到了显著发展.     

富硅氮化硅薄膜的荧光发射

室温下在3．45eV的激光激发下,对950℃温度下淀积的LPCVD富硅的SiNx薄膜中,观测到5个高强度的可见荧光的发射。其峰位位置分别为2．7,2．69,2．4,2．3,2．1eV。通过TEM、IR、XPS等的分析研究表明,该样品为纳米硅镶嵌结构的a-SiNx：H复合膜,分析了其微结构的成因及其与膜内应力之间的相互关系。经过1000～1200℃快速退火(RTA)处理,原PL谱蓝移并只出现了峰位为3．0,2．8eV的两个紫蓝色荧光的发射,用能隙态模型对此结果做了初步的分析和讨论。认为薄膜中纳米硅团簇的密度、尺寸的变化和亚稳态缺陷态对其PL峰以及膜应力起着十分重要的作用。     

All-Optical Bistabilities in Reflection and Luminescence of Thin ZnSe Films

First reports of absorptive all-optical bistabilities in reflectance and luminescence of a Fabry-Perot cavity consisting of thin (0.70 μm) ZnSe film are presented. We demonstrate that the observation of bistability in the reflected beam does not require necessarily the appearance of bistability in the transmitted beam. Luminescence bistabilities, however, are observed both in the light captured from the incident side of the film and in the light emitted from the transmission side. The bistabilities in reflection and luminescence are explained quite satisfactorily by the principle of increasing absorption due to photo-irradiation and the dependence of the luminescence intensity on a photo-thermally induced temperature change, respectively. All experiments were carried out at room temperature with the 488 nm line of an argon laser.     

沿膜厚方向的簿膜非均匀折射率及其色散测量

以传统的光学监控法与石英晶体振荡法为基础,在薄膜沉积过程中,同时测量膜片的透过率及膜层的厚度,以及与它们对应的控制波长,并根据三者与折射率之间的关系,由计算机反解出不同膜厚处的折射率——非均匀折射率及不同厚度、不同波长处的薄膜折射率——非均匀色散。同时给出了硫化锌薄膜在水晶石薄膜的测量实例,并进行了分析与讨论。