Polarization characteristics of surface plasmon resonance in SnO<Subscript>2</Subscript> nanocluster films

Internal reflection features caused by the surface plasmon resonance in nanoscale films containing defect tin dioxide clusters in the stoichiometric dielectric matrix are studied by the method of polarization modulation of electromagnetic radiation. The angular and spectral characteristics of reflectances R _s ² and R _p ² of s- and p-polarized radiation and their polarization difference ρ = R _s ² − R _p ² are measured in the wavelength range λ = 400–1600 nm. The experimental characteristics ρ(ϑ, λ) (ϑ is the radiation incidence angle) obtained represent the optical property features associated with the film structure and morphology. Surface plasmon polaritons and local plasmons excited by s- and p-polarized radiation are detected; their frequency and relaxation properties are determined. The structural sensitivity of the technique for studying the surface plasmon resonance for tin dioxide films is shown.     

Plasmonic Au/TiO2‐Dumbbell‐On‐Film Nanocavities for High‐Efficiency Hot‐Carrier Generation and Extraction

Plasmon‐induced hot carriers have vast potential for light‐triggered high‐efficiency carrier generation and extraction, which can overcome the optical band gap limit of conventional semiconductor‐based optoelectronic devices. Here, it is demonstrated that Au/TiO₂ dumbbell nanostructures assembled on a thin Au film serve as an efficient optical absorber and a hot‐carrier generator in the visible region. Upon excitation of localized surface plasmons in such coupled particle‐on‐film nanocavities, the energetic conduction electrons in Au can be injected over the Au/TiO₂ Schottky barrier and migrated to TiO₂, participating in the chemical reaction occurring at the TiO₂ surface. Compared with the same dumbbell nanostructures on an indium tin oxide (ITO) film, such nanocavities exhibit remarkable enhancement in both photocurrent amplitude and reaction rate that arise from increased light absorption and near‐field amplification in the presence of the Au film. The incident‐wavelength‐dependent photocurrent and reaction rate measurements jointly reveal that Au‐film‐mediated near‐field localization facilitates more efficient electron–hole separation and transport in the dumbbells and also promotes strong d‐band optical transitions in the Au film for generation of extra hot electrons. Such nanocavities provide a new plasmonic platform for effective photoexcitation and extraction of hot carriers and also better understanding of their fundamental science and technological implications in solar energy harvesting.     

Tin Dioxide Sensing Layer Grown on Tubular Nanostructures by a Non‐Aqueous Atomic Layer Deposition Process

A new atomic layer deposition (ALD) process for nanocrystalline tin dioxide films is developed and applied for the coating of nanostructured materials. This approach, which is adapted from non‐hydrolytic sol‐gel chemistry, permits the deposition of SnO₂ at temperatures as low as 75 °C. It allows the coating of the inner and outer surface of multiwalled carbon nanotubes with a highly conformal film of controllable thickness. The ALD‐coated tubes are investigated as active components in gas‐sensor devices. Due to the formation of a p‐n heterojunction between the highly conductive support and the SnO₂ thin film an enhancement of the gas sensing response is observed.     

Tin Dioxide Microspheres as a Promising Material for Phosphopeptide Enrichment Prior to Liquid Chromatography‐(Tandem) Mass Spectrometry Analysis

Functional materials are frequently used to identify and characterize proteins and their modifications in complex biological samples throughout the analytical workflow. Protein phosphorylation is a highly important post‐translational modification that is being examined with the help of diverse materials that exhibit affinity towards the phosphate group of phosphoamino acids. Titanium dioxide and zirconium dioxide particles are increasingly used to enrich phosphopeptides from proteolytic digests of protein mixtures, although specificity and recovery still leave room for improvement. Here, we present tin dioxide (SnO₂, stannia) microspheres as a new type of metal oxide material for phosphopeptide enrichment. The microspheres are produced by a nanocasting process, starting from silica particles as a template, which allows the tuning of material properties such as particle diameter and porosity of the microspheres in a straightforward manner. For the first time, we are able to show that tin dioxide can be used to enrich phosphopeptides from mixtures such as enzymatic digests of proteins, followed by analysis by liquid chromatography‐mass spectrometry (LC‐MS). For optimization of the enrichment protocol, we use synthetic phosphorylated and nonphosphorylated peptides, and test different solvent compositions for loading and washing steps to enhance the selectivity of the material without compromising phosphopeptide recovery. Furthermore, the selectivity and phosphopeptide binding properties of tin dioxide are compared to the established metal oxide materials, titanium dioxide and zirconium dioxide, using mixtures of model proteins. Even without the use of additional additives such as α‐hydroxy acids, which have been used to enhance the specificity of TiO₂‐based enrichment, we show that a comparably good performance can be achieved for the SnO₂ spheres.     

基于MSM结构的表面等离子体共振光纤折射率传感器

基于表面等离子体共振(SPR)效应,设计了一种基于多模-单模-多模(MSM)结构的光纤折射率传感器。采用光纤熔接的方式构成MSM结构,并且在单模光纤的表面涂覆二氧化钛/银(TiO2/Ag)复合膜构成传感单元。利用FDTD Solutions仿真分析了单模光纤长度与金属膜厚度对传感器性能的影响。结果表明:单模光纤长度越长,共振深度越深;TiO2/Ag复合膜中Ag膜厚度为50nm,TiO2膜厚度为20nm时,传感器性能最优,在1.33~1.41环境折射率范围内,传感器的灵敏度约为6 875nm/RIU。实验结果表明该光纤折射率传感器结构制作工艺简单、灵敏度高。     

Role of surface oxygen vacancies in photoluminescence of tin dioxide nanobelts

The role of surface oxygen vacancies in the optical properties of tin dioxide nanobelts is investigated in this paper. Using a first-principles approach, based on the density functional theory combined to a very accurate exchange correlation functional, we characterize SnO₂ (1 0 1), that is the nanobelt largest surface. We show that the presence of surface oxygen vacancies leads to the appearance of (i) occupied states located at about 1 eV above the valence band and (ii) unoccupied states lying in resonance with the conduction band. Photoluminescence characterization performed on samples of SnO₂ nanobelts at low temperature shows that the basic spectral features of luminescence are in excellent agreement with theoretical predictions.     

The effect of single-phonon and plasmon recombination on the lifetime in n-Hg1−xCdxTe with magnetically tuned bandgap

Theoretical investigations have predicted a great enhancement of electron-hole recombinations by adjusting the bandgap of narrow-gap semiconductors to the energy of elementary excitation in solids such as phonons or plasmons. Such an enhancement of the recombination rate of excess carriers is very important in constructing far-I.R. devices and might be used to generate high densities of LO-phonons and plasmons. We report experimental evidence of the influence of these recombination channels on the photoconductivity and the excess carrier lifetime in semimetallic n-Hg_1−xCd_xTe alloys, whose induced bandgap is magnetically tuned through the relevant energies of the elementary excitations. Both from a comparison of theoretically estimated lifetimes with Auger lifetimes and from experimental observations the new recombination channels prove to be very efficient and dominate the behaviour near their resonance with the band-gap.     

Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling

A novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ～1 to 21 nm and a thin Au film of ～25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 10⁴–8 × 10³ for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.     

Potential barrier and photovoltage at interfaces of hexadecafluoro-copper-phthalocyanine and copper phthalocyanine films on the surface of tin dioxide

Potential barrier formation during the deposition of ultrathin coatings of copper phthalocyanine (CuPc) and hexadecafluoro-copper-phthalocyanine (F₁₆CuPc) on the surface of polycrystalline tin dioxide and during the deposition of F₁₆CuPc coatings over a CuPc film is studied. A photoinduced change in the surface potential of the prepared structures upon exposure to light in the visible wavelength region is detected. The surface photovoltage of the studied organic films has a positive sign with respect to the substrate, its spectral dependences correspond to the absorption spectra of the organic materials CuPc and F₁₆CuPc. Surface potential measurements are performed using a probe beam of low-energy electrons, based on the total current spectroscopy technique. A total decrease in the work function by 0.2 eV is detected during the deposition of a CuPc film up to 8 nm in thickness on a SnO₂ substrate; in the case of the F₁₆CuPc/SnO₂ interface, an increase in the work function by 0.55 eV is detected. At the initial deposition stage, at organic film thicknesses of up to 1.5 nm, the interfacial potential barrier corresponded to electron density transfer from the organic film to the substrate in both cases of CuPc/SnO₂ and F₁₆CuPc/SnO₂. It is assumed that the photoinduced change in the surface potential is caused by charge-carrier separation in a boundary region up to 1.5 nm thick.     

Aqueous Deposition of Ultraviolet Luminescent Columnar Tin‐Doped Indium Hydroxide Films

Indium tin oxide (ITO) has attracted intense interest as the most important transparent conducting oxide (TCO) that sees wide use in many opto‐electronic and photo‐chemical devices. The goal of this study is to explore the possibility of depositing ITO thin films using a bioinspired aqueous deposition route as an alternative. On the surface of sulfonated‐self assembled monolayers, Sn‐doped indium hydroxide films are obtained via a hydrogen peroxide‐assisted method. As a result, the as‐deposited indium tin hydroxide films possess a single hexagonal phase of In(OH)₃· xH₂O (0 ≤ x ≤ 1) with Sn doping percentage of (1.7 ± 0.2) at % and a column‐like hierachical microstructure. Structural, compositional and property studies, including electron microscopy, X‐ray diffraction, photoelectron spectroscopy, optical transmittance, photoluminescence and four‐probe conductivity measurements, are conducted. The possible mechanism based on oriented attachment is discussed for the film growth. Strong room temperature photoluminescence within the near UV range is observed in the case of Sn‐doped, but not in the one of the pure In(OH)₃· xH₂O films. Annealing of the indium tin hydroxide films above 200 °C gives nanocrystalline Sn:In₂O₃ films with higher UV and visible transparency and electrical conductivity compared with those of pure In₂O₃ films. The influence of annealing atmosphere is investigated.     

Effect of Pt, Pd, Au additives on the surface and in the bulk of tin dioxide thin films on the electrical and gas-sensitive properties

The microstructure and properties of thin (??100 nm) SnO₂ films with noble metals Pt, Pd, Au additives, grown by dc magnetron deposition are studied. It is shown that the introduction of additives into the bulk and the deposition of dispersed catalysts on the semiconductor surface make it possible to control the sensor parameters in pure air and upon exposure to reduction (CO, H₂, CH₄) and oxidation (NO₂) gases. Possible mechanisms for the effect of Pt, Pd, Au on the bulk and surface properties of tin dioxide are discussed. The technological conditions for film growth, which provide the selective detection of low concentrations (10?C100 ppm) of CO and H₂, below-explosive concentrations (0.5?C2.5 vol %) of methane, and trace concentrations (0.05?C5 ppm) of NO₂ are determined.     

钝化层对声表面波滤波器的影响

为了研究钝化层对声表面波(SAW)滤波器性能的影响,以二氧化硅(SiO2)薄膜为钝化层,对厚度为12～80 nm的SiO2膜钝化层工艺数据进行分析.结果表明,当SiO2膜钝化层覆膜厚度大于25 nm时其膜层质量均匀性好,致密度高.同时SiO2膜钝化层厚度对膜层间的粘性、传播损耗、自身的质量负载及谐振峰处的频率均有影响,...     

干冰微粒喷射法清洗ITO玻璃及其对有机电致发光器件性能的影响

采用干冰微粒喷射法对ITO玻璃表面进行了清洁处理,并与浸泡式低频超声波湿法清洗的ITO玻璃进行了对比测量,结果表明:干冰微粒喷射法处理后,ITO薄膜表面的接触角减小,表面污染物颗粒数量下降,ITO薄膜表面上碳的含量较之未处理时降低了48.5%,锡、铟的含量分别增加了533.33%和267.57%,说明干冰微粒法对ITO薄膜表面的有机污染物和杂质颗粒的清洗效果超过了超声波湿法。此后,制备了干冰微粒法清洗ITO阳极的有机电致发光器件(OLED)器件,以及结构相同但ITO电极是用超声波湿法清洗的OLED器件,对这两种器件的参数进行了测量,其结果表明:干冰微粒喷射法清洗器件的启亮电压、亮度和电流效率与超声波湿法清洗的相比较均有所改善。     

Oxidation Behavior of Molten Tin Doped with Phosphorus

The oxidation process of molten tin in air at 280°C was studied. We found that a trace addition of phosphorus to the tin reduced the surface oxidation greatly by forming a protective film. The total thickness of the oxide film formed on the molten Sn-0.007wt.%P alloy was about 36 nm, which was composed of a layer of 6 nm SnO₂, 10–15 nm (Sn, P)O, and a transition layer. This oxide film was approximately a quarter of the thickness that formed on pure tin. The oxidized surfaces of different tin alloys were studied by scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Much higher segregation of phosphorus was observed on the subsurface of the oxide film, and the concentration of phosphorus in the oxide film was about 500 times greater than that of the bulk concentration. Based on this result, the segregation of phosphorus on the molten surface could result in the formation of a new protective (Sn, P)O film on the subsurface of the molten tin. It is also suggested that the crystal structure of the oxide film should be studied in the future to confirm the mechanism.     

Preparation and Memory Performance of a Nanoaggregated Dispersed Red 1‐Functionalized Poly (N‐vinylcarbazole) Film via Solution‐Phase Self‐Assembly

A nanoaggregated dispersed red 1‐grafted poly(N‐vinylcarbazole) (abbreviated PVDR) is self‐assembled via π–π stacking interactions of the carbazole groups in the polymer system after adding a solution of PVDR in N,N‐dimethylformamide to dichloromethane. Upon self‐assembly, the nanoaggregated PVDR film displays helical columnar stacks with large grain sizes, whereas a non‐aggregated PVDR film exhibits an amorphous morphology with smaller grain size. A write‐once read‐many‐times (WORM) memory device is shown whereby a pre‐assembled solution of PVDR is spin‐coated as the active layer and is sandwiched between an aluminum electrode and an indium‐tin‐oxide (ITO) electrode. This device shows very good memory performance, with an ON/OFF current ratio of more than 10⁵ and a low misreading rate through the precise control of the ON and OFF states. The stability of the nanoaggregated PVDR device is much higher than that of the non‐nanoaggregated PVDR device. This difference in device stability under constant voltage stress can be mainly attributed to the difference in the film crystallinity and surface morphology. No degradation in current density was observed for the ON‐ and OFF‐states after more than one hundred million (10⁸) continuous read cycles indicating that both states were insensitive to the read cycles. These results render the nanoaggregated PVDR polymer as promising components for high‐performance polymer memory devices.     

采用SiO2/SixNy双材料微桥测试结构测量PECVD富硅氮化硅薄膜的导热系数

In order to balance the compressive stress of a silicon dioxide film and compose a steady MEMS structure, a silicon-rich silicon nitride film with tensile stress is deposited by plasma enhanced chemical vapor deposition process. Accurately measuring the thermal conductivity of the film is highly desirable in order to design, simulate and optimize MEMS devices. In this paper, a Si02/SixNy bimaterial microbridge structure is presented to measure the thermal conductivity of the silicon-rich silicon nitride film by single steady-state measurement. The thermal conductivity is extracted as 3.25 W/（m-K）. Low thermal conductivity indicates that the silicon-rich silicon nitride film can still be utilized as thermally insulating material in thermal sensors although its thermal conductivity is slightly larger than the values reported in literature.     

Mechanism of Crystal Formation in Ruddlesden–Popper Sn‐Based Perovskites

Knowledge of the mechanism of formation, orientation, and location of phases inside thin perovskite films is essential to optimize their optoelectronic properties. Among the most promising, low toxicity, lead‐free perovskites, the tin‐based ones are receiving much attention. Here, an extensive in situ and ex situ structural study is performed on the mechanism of crystallization from solution of 3D formamidinium tin iodide (FASnI₃), 2D phenylethylammonium tin iodide (PEA₂SnI₄), and hybrid PEA₂FA_n?1Sn_nI_3n+1 Ruddlesden–Popper perovskites. Addition of small amounts of low‐dimensional component promotes oriented 3D‐like crystallite growth in the top part of the film, together with an aligned quasi‐2D bottom‐rich phase. The sporadic bulk nucleation occurring in the pure 3D system is negligible in the pure 2D and in the hybrid systems with sufficiently high PEA content, where only surface crystallization occurs. Moreover, tin‐based perovskites form through a direct conversion of a disordered precursor phase without forming ordered solvated intermediates and thus without the need of thermal annealing steps. The findings are used to explain the device performances over a wide range of composition and shed light onto the mechanism of the formation of one of the most promising Sn‐based perovskites, providing opportunities to further improve the performances of these interesting Pb‐free materials.     

High efficiency polymer solar cells with wet deposited plasmonic gold nanodots

We report the enhanced performance of poly(3-hexylthiophene)/[6,6]-phenyl-C₆₁ butyric acid methyl ester (P3HT/PCBM) bulk heterojunction solar cells with wet deposited interfacial gold nanostructures on their indium tin oxide (ITO) surfaces. To produce localized surface plasmons at the ITO surfaces, gold nanostructures were fabricated through the layer-by-layer deposition of gold nanorods onto the ITO substrates and transformed into nanodots through a thermally induced shape transition. The incorporation of plasmonic gold nanodots on the ITO surface was found to result in an increase in the power conversion efficiency from 3.04% to 3.65%, which is due to the presence of the resulting plasmon field.     

In Situ Growth of Mesoporous SnO2 on Multiwalled Carbon Nanotubes: A Novel Composite with Porous‐Tube Structure as Anode for Lithium Batteries

A novel mesoporous‐nanotube hybrid composite, namely mesoporous tin dioxide (SnO₂) overlaying on the surface of multiwalled carbon nanotubes (MWCNTs), was prepared by a simple method that included in situ growth of mesoporous SnO₂ on the surface of MWCNTs through hydrothermal method utilizing Cetyltrimethylammonium bromide (CTAB) as structure‐directing agents. Nitrogen adsorption–desorption, X‐ray diffraction and transmission electron microscopy analysis techniques were used to characterize the samples. It was observed that a thin layer tetragonal SnO₂ with a disordered porous was embedded on the surface of MWCNTs, which resulted in the formation of a novel mesoporous‐nanotube hybrid composite. On the base of TEM analysis of products from controlled experiment, a possible mechanism was proposed to explain the formation of the mesoporous‐nanotube structure. The electrochemical properties of the samples as anode materials for lithium batteries were studied by cyclic voltammograms and Galvanostatic method. Results showed that the mesoporous‐tube hybrid composites displayed higher capacity and better cycle performance in comparison with the mesoporous tin dioxide. It was concluded that such a large improvement of electrochemical performance within the hybrid composites may in general be related to mesoporous‐tube structure that possess properties such as one‐dimensional hollow structure, high‐strength with flexibility, excellent electric conductivity and large surface area.     

Plasmon–phonon coupling in the infrared reflectance spectra of Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> films

The results of studies of optical reflection in the far- and mid-infrared spectral regions are reported. The reflectance of five Bi₂Se₃ topological insulator films grown by molecular-beam epitaxy on Si(111) substrates is measured. The characteristic parameters of phonons and plasmons are determined by means of dispersion analysis for multilayer structures. It is found that the plasma frequency in a layer close to the Si–film interface is noticeably higher than that in the film bulk. Calculations of the loss function show that plasmon–phonon coupling plays an important role in Bi₂Se₃ films. The attenuated total internal reflection method is used to determine the frequency of the surface plasmon–phonon mode.