XPS characterisation of plasma treated and zinc oxide coated PET

At first, X-ray photoelectron spectroscopy (XPS) analyses of reference and carbon dioxide plasma treated polyethylene terephthalate (PET) were carried out. Significant chemical modifications were outlined in the treated PET surface in comparison with the reference one. The formation of new oxygenated groups was evidenced. These modifications heighten the level of interactions between the polymer substrate and the deposited coating.In a second stage, zinc oxide thin films were elaborated by r.f. magnetron sputtering from a ceramic target and with a reactive gas (mixture of argon-1% oxygen) under optimised conditions on CO₂ plasma treated PET. The interfacial chemistry between the plasma treated PET and the zinc oxide was also studied by XPS. The line shape changes in the high-resolution core level spectra of carbon C1s, oxygen O1s, and zinc (Zn2p3/2, Zn3p), with the progressive deposition of zinc oxide coatings being recorded. The obtained spectra were fitted to mixed Gaussian-Lorentzian components using XPS CASA software.An interaction scheme between the zinc oxide thin layer and its polymer substrate, in the first stage of deposition, was proposed and checked by corroborating the findings of the different XPS spectra and their decompositions. It suggests the formation of ZnOC complexes at the interface, which are promoted by an electron transfer from zinc to oxygen in oxygenated species, mainly alcohol groups, generated by the CO₂ plasma treatment of PET.     

XPS and SRUPS study of oxygen adsorption on Cd0.9Zn0.1Te (1 1 1)A surface

Synchrotron radiation ultraviolet photoemission spectroscopy (SRUPS) and X-ray photoelectron spectroscopy (XPS) have been applied to investigate oxygen adsorption on a cadmium zinc telluride (CZT) (1 1 1)A surface. The surface chemical composition and the surface oxidation process were monitored by recording the Te 3d, O 1s, Zn 2p, Cd 4d core level peaks, and the Cd MNN Auger peak. The CZT (1 1 1)A surface was effectively oxidized by dosing oxygen directly. The typical surface state of the clean CZT (1 1 1)A surface was identified. After oxygen exposure, this surface state disappeared and a signal due to the formation of O–CZT appeared. In addition, the work function of CZT decreased with the increasing oxygen exposure.     

Photoemission studies of initial oxidation for ultra-thin zinc film on 6H-SiC(0 0 0 1) surface with synchrotron radiation

The thermal oxidation process of metallic zinc on 6H-SiC(0 0 0 1) surface has been investigated by using atomic force microscopy (AFM), synchrotron radiation photoelectron spectroscopy (SRPES) and XPS methods. The AFM images characterize the surface morphology of ZnO film formed during the thermal oxidation and SRPES record the valence band, Si 2p and Zn 3d spectra at different stages. The O 1s peak is recorded by XPS because of the energy limit of the synchrotron radiation. Our results reveal that the silicon oxides layer of SiC substrate can be reduce by hot metallic zinc atom deposition. The oxygen atoms in the silicon oxides are captured by the zinc atoms to form ZnO_x at the initial stage and as a result, the oxidized SiC surface are deoxidized. After the zinc deposition with the final thickness of 2.5 nm, the sample is exposed in oxygen atmosphere and annealed at different temperatures. According to the evolution of peaks integrated intensities, it is considered that the Zn/SiC system will lose zinc atoms during the annealing in oxygen flux at high temperature due to the low evaporation temperature of pure zinc. After further annealing in oxygen flux at higher temperature, the substrate is also oxidized and finally the interface becomes a stable SiC-SiO_x-ZnO sandwich structure.     

Refractive index dispersion in thin ZnGa2O4 films

We have studied refractive index dispersion in thin ZnGa₂O₄ films obtained by high-frequency RF ion plasma sputtering. We have established that the spectral dependence of the refractive index in the visible region of the spectrum is mainly determined by transitions from the band including 2p states of the oxygen and 3d states of the zinc, forming the highest occupied level of the valance band, to the bottom of the conduction band formed by the 4s4p states of the zinc. For the studied films, we have determined the parameters of the single-oscillator approximation, the dispersion energy, the chemical bond ionicity, and the coordination number.     

直接沉淀法中不同晶型钛酸锌的X射线粉末衍射研究

以Ti(SO₄)₂和Zn(NO₃)₂·6H₂O为原料,碳酸铵为沉淀剂,采用直接沉淀法制备了钛酸锌的粉体。探讨了反应条件对所得钛酸锌晶体结构的影响,并对样品进行了XRD和TG-DTA等分析。钛酸与碳酸锌分子生成的先后顺序影响得到的钛酸锌的结构。在钛酸优先生成的体系中,碳酸锌分子生成之后与周围足量的钛酸分子发生碰撞反应,由于钛酸优先生成且沉淀剂足量,碰撞反应充分且在碰撞反应中钛酸保持过量,反应生成了亚钛酸锌(Zn₂Ti₃O₈)。在碳酸锌优先生成的体系中,钛酸分子生成之后与周围足量的碳酸锌分子发生碰撞反应,由于碳酸锌优先生成且沉淀剂足量,碰撞反应充分且在碰撞反应中碳酸锌保持过量,反应生成了正钛酸锌(Zn₂TiO₄)。另外,沉淀剂用量和反应温度都影响着最终产物的种类和晶型。沉淀剂用量越多、反应温度越高,越易于生成Zn₂Ti3O₈或Zn₂TiO₄。只有在沉淀剂不足、反应温度较低的情况下,才能生成偏钛酸锌(ZnTiO₃)。     

掺锰氧化锌的结构和光学特性

采用直流反应磁控溅射的方法,在玻璃衬底上沉积了Zn0.93Mn0.07O薄膜,研究了氧分压对薄膜结构和光学特性的影响。X射线衍射测试结果显示,Zn0.93Mn0.07O薄膜都具有高度的c轴择优取向,在氧分压为0.4的时候,薄膜的衍射峰具有最小的半峰全宽,最大的晶粒尺寸。X射线光电子能谱测试结果表明:Mn2 离子已经取代了氧化锌晶格中的部分Zn2 ,但还掺杂有少量的MnO2分子;处在1 021 eV的Zn 2p3/2能级只有单一的Zn2 ;而O2 -则来自Zn-O和Mn-O。由于伯斯坦-莫斯效应,Zn0.93Mn0.07O薄膜光吸收跃迁过程只能在价带态和费密能级附近及以上的导带空态之间发生,其吸收谱线显示,与纯ZnO薄膜吸收谱线相比,产生了蓝移现象。同时还伴随有导带尾跃迁的发生,研究表明,这是由3d5多重能级的d-d跃迁而引起的。经过计算,在氧分压为0.4的时,Zn0.93Mn0.07O薄膜的禁带宽度是最大的,这可能是由交换作用的减弱而引起的。     

苯丙氨酸桥联金属双卟啉的诱导圆二色光谱研究

本文报道了邻位和对位桥联苯丙氨酸锌双卟啉的合成，考查了双卟啉的分子结构对诱导圆二色性的影响。结果表明，两个卟啉环之间的π－π堆积和手性激子偶合作用是影响此类双卟啉圆二色光谱的主要因素。     

Effect of isotopic mass on the photoluminescence spectra of zinc oxide

ZnO is a wurtzite-type semiconductor at ambient conditions whose natural composition consists of almost pure ¹⁶O and a mixture of 48.6% ⁶⁴Zn, 27.9% ⁶⁶Zn, 4.1% ⁶⁷Zn, 18.8% ⁶⁸Zn, and 0.6% ⁷⁰Zn. In this work, we report a photoluminescence study of different samples of isotopically pure and natural zinc oxide between 15 and 300 K. The isotopic coefficients of the bound exciton energy have been obtained and compared with previous values for the shift of the free A exciton energy. The isotopic coefficients of the bound exciton energy have allowed us to estimate the contribution of the zinc and the oxygen vibrations to the bandgap renormalization by electron-phonon interaction. A two-oscillator model based on the zinc and oxygen renormalization energies has been used to account for the temperature dependence of the bandgap in ZnO.     

Spectra of Zn XIX and Zn XX in the 20–50 Å region

We have analyzed the spectra of highly ionized zinc and identified twenty four new lines of Zn XIX and Zn XX in the 20–50 Å region. The lines in this region are principally due to the transitions of the type 3snp, 3pnd, ns and 3dnf, np where $\text{n ? 4}$. The spectra were excited by laser irradiation of zinc in a vacuum and the lines have been identified by extrapolating the published data for isoelectronic ions.     

Formation of nanoparticles containing zinc in Si(001) by ion-beam implantation and subsequent annealing

The formation of nanoparticles containing zinc in Si(001) substrates by the implantation of ⁶⁴Zn⁺ ions and subsequent annealing in dry oxygen at 800 and 1000°C for 1 h is studied. The structure of the samples is studied by high-resolution transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy. 20-nm zinc nanoparticles located at a depth of about 50 nm are revealed in the as-implanted sample. 10–20-nm pores are observed in the surface layer. Annealing leads to oxidation of the Zn nanoparticles to the Zn₂SiO₄ state. It is shown that the oxidation of Zn nanoparticles begins on their surface and at an annealing temperature of 800°C results in the formation of nanoparticles with the “соre–shell” structure. The X-ray diffraction technique shows simultaneously two Zn and Zn₂SiO₄ phases. ZnO nanoparticles are not formed under the given implantation and annealing conditions.     

Defects in room-temperature ferromagnetic Cu-doped ZnO films probed by x-ray absorption spectroscopy

We report a comprehensive study of the defects in room-temperature ferromagnetic (RTFM) Cu-doped ZnO thin films using x-ray absorption spectroscopy. The films are doped with 2 at.% Cu, and are prepared by reactive magnetron sputtering (RMS) and pulsed laser deposition (PLD), respectively. The results reveal unambiguously that atomic point defects exist in these RTFM thin films. The valence states of the Cu ions in both films are 2(+). In the film prepared by PLD, the oxygen vacancies (V(O)) form around both Zn ions and Cu ions in the hexagonal wurtzite structure. Upon annealing of the film in O(2), the V(O) population reduces and so does the RTFM. In the film prepared by RMS, the V(O)s around Cu ions are not detected, and the V(O) population around Zn ions is also smaller than in the PLD-prepared film. However, zinc vacancies (V(Zn)) are evidenced. Given the low doping level of spin-carrying Cu ions, these results provide strong support for defect-mediated ferromagnetism in Cu-doped ZnO thin films.     

磷酸锌水合物的光谱性质及热稳定性

用XRD,Raman,FTIR研究了三种磷酸锌水合物的常温光谱,分析了图谱特征随结晶水的变化;用TG-DTA研究了四水磷酸锌的热稳定性,并确定了磷酸锌水合物的生成温度。结果显示结晶水含量的不同引起了磷酸锌水合物的X衍射2θ特征值和特征峰的变化;FTIR图谱反映了在1 640 cm-1处和3 400～3 550 cm-1范围对应的H—O—H,O—H键的伸缩振动形式和强度的区别;Raman光谱反映P—O键振动模式在400～700 cm-1区间的差异同时揭示了O—H键振动峰宽的差异。四水磷酸锌在90 ℃时开始失水,145 ℃完全脱去两分子结晶水生成二水物,195 ℃时变为一水物,273 ℃时脱去剩余的结晶水成为无水磷酸锌。     

L-苏糖酸及其金属化合物的红外光谱研究

制备了高纯度的L-苏糖酸及其与钙、镁、锰、钴、镍和锌的化合物,用化学分析和元素分析确定了它们的组成;通过红外光谱分析研究,确定金属离子与L-苏糖酸的羰基氧配位,同时与羧基脱质子配位,而醇羟基质子不解离,金属离子为sp~3杂化,配位数为4。     

Single violet luminescence emitted from ZnO films obtained by oxidation of Zn film on quartz glass

The photoluminescence (PL) emission properties of ZnO films obtained on quartz glass substrate by the oxidation of Zn films were studied. The strong single violet emission centering about 413-424 nm was observed in the room temperature PL spectra of the ZnO films. The intensity of violet emission increased and the peak position shift from 424 to 413 nm with increasing oxygen pressures. The violet emission was attributed to the electron transition from the valence band to interstitial zinc (Zn_i) level under low oxygen pressure conditions (50-500 Pa). Under high oxygen pressure conditions (5000-23,000 Pa), both interstitial zinc (Zn_i) and zinc Vacancy (V_Zn) were thought to be responsible for the violet emission.     

热蒸发法Zn／ZnO叶状微米结构自组装生长及其发光特性

采用热蒸发法在ZnO缓冲层覆盖着Si衬底上合成了2D叶状的Zn晶枝结构,Zn的晶枝长度约为几十微米,厚度约为200nm,随后Zn晶枝在O2的气氛下热处理,在晶枝表面获得纤细、均匀的ZnO纳米线。晶枝按照无催化、自组装、汽相生长模式生长,晶枝最快生长方向是沿着载气气流的方向释放凝固潜热,XRD分析结果结果显示了Zn纳米线具有六角纤锌矿结构,Zn/ZnO的发光谱显示,在380nm处有一弱的UV近带边发射和中心在505nm处的强绿光发射,绿光发射归因于施主/受主对之间的辐射跃迁。     

Structures and electrical properties of pure and vacancy-included ZnO NWs of different sizes

The structures and electronic properties of Zn O nanowires(NWs) of different diameters are investigated by employing the first-principles density functional theory. The results indicate that the oxygen vacancy(VO) exerts a more evident influence on the band gap of the Zn O NWs. However, the effect will be weakened with the increase of the diameter. In addition, the energy band shifts downward due to the existence of VOand the offset decreases with the reduction of the VOconcentration. As the concentration of surface Zn atoms decreases, the conduction band shifts downward, while 2p electrons are lost in the oxygen vacancy, resulting in the split of valence band and the formation of an impurity level. Our findings agree well with the previous observations and will be of great importance for theoretical research based on Zn O NWs.     

Surface nature of nanoparticle zinc-titanium oxide aerogel catalysts

Nanoparticle zinc-titanium oxide materials were prepared by the aerogel approach. Their structure, surface state and reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc titanate matrices. The 8-45 nm aerogel particles were evaluated as catalysts for methanol oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides with anion defects. Titanium based oxides exhibited a high selectivity to dimethyl ether, so that a strong Lewis acidic character suggested for the catalysts was associated primarily with the Ti⁴⁺ center. Both methanol conversion and dimethyl ether formation rates increased with increasing the zinc content added to the oxide support. Results demonstrate that cubic zinc titanate phases produce new Lewis acid sites having also a higher reactivity and that the nature of the catalytic surface transforms from Lewis acidic to basic characters due to the presence of reactive oxygen vacancies.     

Synthesis of dimension-tunable ZnO nanostructures via the design of zinc hydroxide precursors

A facile synthesis route is presented to achieve dimension-tunable ZnO nanostructures by the design of zinc hydroxide precursors under the surfactant-free condition. From three types of zinc hydroxide precursors, namely, crystalline Zn(OH)(NO₃)(H₂O) nanobelts, amorphous zinc hydroxides microparticles and soluble Zn(OH)^2-₄\mathrm{Zn}(\mathrm{OH})^{2-}_{4} species, the porous ZnO nanosheets, ZnO nanoparticles and ZnO nanowires can be achieved, respectively. The porous ZnO nanosheets exhibit large polar surface area. Thermal analysis indicates that the crystalline Zn(OH)(NO₃)(H₂O) nanobelts were converted to the porous ZnO nanosheets by in situ lattice reconstruction, which was attributed to the unique fibrous structure of Zn(OH)(NO₃)(H₂O) nanobelts. The as-prepared dimension-tunable ZnO nanostructures have potential applications in solar cells, photocatalysis, novel chemical and biological sensors, etc.     

光谱法研究Zn2+对枸杞超氧化物歧化酶JZ活力和结构的影响

针对提取的天然抗氧性物质超氧化物歧化酶量少,稳定性差等问题,实验以枸杞为原料,采用硫酸铵盐析分级分离方法提取了枸杞超氧化物歧化酶(superoxide disutase of lycium,SOD-LY),紫外光谱法确定了其类型;考察了不同种类的锌盐ZnSO4,ZnCl2,Zn(CH3COO)2和Zn(NO3)2对SOD-LY活力的影响,选择出能显著提高其活力的锌盐.采用傅里叶变换红外光谱、紫外光谱、荧光光谱法研究了最佳锌盐同SOD-LY分子的作用方式.结果表明,提取的SOD-LY 属于Cu/Zn-SOD类型.不同浓度锌盐的存在均可影响SOD-LY的活性.其中,Zn(NO3)2对SOD-LY活力影响最大;红外光谱表明,Zn(NO3)2使SOD-LY二级结构中β-片层、β-转角和β-反平行结构减少,α-螺旋和无规则卷曲结构增多.荧光光谱分析得出,Zn2+与SOD-LY之间的相互作用力主要为静电引力,有利于稳定SOD-LY的活性中心,使得SOD-LY活力增强.Zn2+与SOD-LY结合常数(KΛ)为1.666×103 L·mol-1,结合位点数(n)为1.238,结合距离(r0)为3.62 nm,该研究为提高SOD的活力、稳定性及扩展其应用提供理论帮助.     

Defect engineering of ZnO

The defect responsible for the transparent to red color change of nominally undoped ZnO bulk single crystals is investigated. Upon annealing in the presence of metallic Zn as reported by Halliburton et al. and also Ti and Zr a native defect forms with an energy level about 0.7 eV below the conduction band. This change is reversible upon annealing in oxygen. Optical transmission data along with positron depth profiles and annealing studies are combined to identify the defect as oxygen vacancies. Vacancy clustering occurs at about 500 °C if isolated zinc and oxygen vacancies. In the absence of zinc vacancies, clusters form at about 800 °C.