Surface and Interface Analysis

Graphene and carbon nanotubes/fibers (CNT/CNF) hybrid structures are emerging as frontier materials for high‐efficiency electronics, energy storage, thermoelectric, and sensing applications owing to the utilization of extraordinary electrical and physical properties of both nanocarbon materials. Recent advances show a successful improvement in the structure and surface area of layered graphene by incorporating another dimension and structural form—three‐dimensional graphene (3DG). In this study, vertically aligned CNFs were grown using plasma enhanced chemical vapor deposition on a relatively new form of compressed 3DG. The latter was synthesized using a conventional thermal chemical vapor deposition. The resulting free‐standing hybrid material is in‐situ N doped during synthesis by ammonia plasma and is produced in the form of a hybrid paper. Characterization of this material was done using electrochemical and spectroscopic measurements. The N doped hybrid showed relatively higher surface area and improved areal current density in electrochemical measurements than compressed pristine 3DG, which makes it a potential candidate for use as an electrode material for supercapacitors, sensors, and electrochemical batteries.

A number of simple aliphatic hydrocarbon polymers have been studied by static SIMS. The low‐mass positive spectra reflect structural differences in the polymeric structure, which result in characteristic fingerprint spectra. Unsaturation and differences in branching lead to very distinct spectral features which show promise for the application of SIMS as an analytical technique in polymer‐related areas. An attempt is made to interpret the spectra in terms of molecular structure, fragmentation mechanisms and ion stabilities. The chemical nature of ion beam damage in PE and PP was studied to some extent.

Sunshield membranes made of germanium‐coated black polyimide (GBP) or Kapton are often used on the reflector/transmitter antenna of satellites for thermal control applications. However, the germanium top layer is prone to degrade during ground storage and implementation. Hence, vacuum/inert gas‐sealed packaging is required for storing the membranes, followed by a staggered fabrication schedule as the shelf‐life of the GBP is identified as only ~6 months. In the present study, microstructural, thermo‐optical, and electrical properties along with X‐ray photoelectron spectroscopy (XPS) studies for evaluating oxidation states of the as‐received and degraded GBP films have been investigated thoroughly. The radio frequency (RF) loss behavior of both the films has also been studied for S band (2.5–3.5 GHz), Ku band (10.5–14.5 GHz), and Ka band (30–35 GHz). Copyright © 2015 John Wiley & Sons, Ltd.

Despite the widely recognized importance of the several species of inositol polyphosphates in cell biology, inositol has not been successfully imaged and quantified inside cells using traditional spectrophotometry. Multi‐isotope imaging mass spectrometry (MIMS) technology, however, has facilitated direct imaging and measurement of cellular inositol. After pulsing cells with inositol labeled with the stable isotope Carbon‐13 (¹³C), the label was detected in subcellular volumes by MIMS. The tridimensional localization of ¹³C within the cell illustrated cellular distribution and local accumulation of inositol. In parallel, we performed control experiments with ¹³C‐glucose to compare a different ¹³C distribution pattern. Because many functions recently attributed to inositol polyphosphates are localized in the nucleus, we analyzed its relative nuclear concentration. We engineered yeast with human thymidine permease and viral thymidine kinase then fed them with ¹⁵N‐thymidine. This permitted direct analysis of the nuclear DNA through the detection of the ¹⁵N isotopic signal. We found practically no co‐localization between inositol signal (¹³C‐isotope) and nuclear signal (¹⁵N‐isotope). The ¹³C‐tag (inositol) accumulation was highest at the plasma membrane and in cytoplasmic domains. In time‐course labeling experiments performed with wild‐type (WT) yeast or modified yeast unable to synthesize inositol from glucose (ino1Δ), the halftime of labeled inositol accumulation was ~1 h in WT and longer in ino1Δ. These studies should serve as a template to study metabolism and physiological role of inositol using genetically modified yeasts. Copyright © 2014 John Wiley & Sons, Ltd.

The surface composition of CuInSe₂ thin films, made by co‐evaporation of the elements, has been shown to be strongly dependent on the bulk composition of the films. This is explained by the presence of a secondary phase, most likely Cu₂Se, on the surface of Cu‐rich films. The fast variation of the surface concentration is also found for films that, according to the equilibrium pseudobinary phase diagram (Cu₂SeIn₂Se₃), should be single‐phase chalcopyrite. An explanation, suggesting the presence of a Cu‐rich compound also on the surface of films with a composition in the single phase regions, is proposed.

Surface atomic concentrations have been shown to be modified in CuInSe₂ films by a 4.5 keV Ar⁺ sputter etch. Heating in vacuum at the film deposition temperature restores the surface atomic concentrations to an as‐deposited condition, with the exception of the selenium concentration. The missing selenium atoms are substituted by oxygen atoms still remaining in the film after sputtering and heating.

The possibility of obtaining a detailed picture of the electronic structure makes surface photovoltage spectroscopy (SPS) eminently suitable for bridging the gap between the chemical, physical, optical and electrical properties of semiconductors. In SPS, changes in band bending (both at the free semiconductor surface and at buried interfaces) are monitored as a function of external illumination. Surface photovoltage spectroscopy can provide detailed, quantitative information on bulk properties (e.g. bandgap and type, carrier diffusion length and lifetime) and can be used for complete construction of surface and interface band diagrams, including the measurement of energy levels in quantum structures. A particular strength is that a comprehensive analysis of surface and bulk defect state distributions and properties is made possible. Measurements using SPS are contactless and non‐destructive. In addition, they can be performed both in situ and ex situ, at any reasonable temperature, on any semiconducting material, at any ambient and at any lateral resolution down to the atomic scale. This review starts with an overview of SPS‐related surface and interface theory, describes the SPS experimental set‐up and presents applications for surface and interface characterization of a wide variety of materials and structures, cross‐correlating them with other methodologies. Copyright © 2001 John Wiley & Sons, Ltd.

Quang phổ electron đỉnh đàn hồi liên quan đến phổ của các electron thứ cấp trong khu vực gần E_p năng lượng chính và xác định chúng bằng đơn vị tuyệt đối dựa trên tỷ lệ phần trăm N_e của các electron phản xạ đàn hồi. Một quy trình được mô tả để đánh giá phổ đỉnh đàn hồi. Các kết quả thực nghiệm trên các mẫu polycrystalline như than chì, Si, Ge, thép không gỉ, Mo, W và Au được trình bày trong dải năng lượng trung bình (E_p = 1–3 keV). Các phổ được đo bằng một máy phân tích gương trụ hoạt động trong chế độ dòng điện một chiều. Đối với các nguyên tố (Si, Mo, v.v.), N_e chủ yếu được xác định bởi số nguyên tử Z, N_e(Z)∼(Z – 26)^0.65 được tìm thấy cho Z ≥ 26 và E_p = 3.1 keV. Sự phụ thuộc của N_e vào E_p có thể được ước lượng theo luật bậc N_e(E_p)∼E_p^−β(Z), với β(Z) dao động giữa 2 và 0.4 cho dải số nguyên tử Z = 4–79. Đỉnh đàn hồi bao gồm các electron thoát ra từ một lớp bề mặt được xác định bởi chiều dài tự do trung bình không đàn hồi của các electron chính. Sử dụng các giá trị của Seah và từ dữ liệu thực nghiệm N_e, crossection phản xạ ngược đã được xác định. Chúng thay đổi giữa 5 × 10⁻²⁰(C)−2.8 × 10⁻¹⁸ cm² (W, Au). Một số kết quả mới được trình bày về tổn thất plasmon thể tích. Trong Si và Ge, chiều dài tự do của các electron năng lượng trung bình được xác định bởi tổn thất plasmon thể tích đầu tiên, trong khi trong các kim loại, các đóng góp của các quá trình tổn thất khác là quan trọng. Thực tiễn sử dụng đỉnh đàn hồi và N_e như các tham chiếu cho các đỉnh Auger và tổn thất cho phép ước lượng các crossection ion hóa trong quang phổ electron Auger.

Hành vi oxi hóa anod của các lớp mỏng nitride titanium được phun phản ứng trên các nền silicon đã được nghiên cứu nhằm thu được các lớp oxynitride ở nhiệt độ phòng. Kết quả cho thấy, sự khác biệt nhỏ trong thành phần hóa học của các lớp nitride titanium có thể dẫn đến những thay đổi lớn trong khả năng phản ứng với oxy. Do đó, có một ảnh hưởng mạnh mẽ của tỷ lệ nguyên tử N/Ti đến động học oxi hóa. Phân tích các lớp mỏng bằng kỹ thuật tán xạ Rutherford và phổ khối ion thứ cấp cho thấy rằng cấu trúc oxide được hình thành bởi một lớp mỏng oxi hóa bên ngoài, bao gồm một hỗn hợp của TiO₂ + TiN_x, tiếp theo là một lớp dày hơn chứa các nguyên tử oxy hòa tan trong lớp nitride titanium đã được nạp trước đó. Sau khi oxi hóa kéo dài, không có nitơ nào được phát hiện trong lớp bề mặt, mà chỉ bao gồm TiO₂. Thú vị thay, độ dày của lớp ngoài gần như không phụ thuộc vào điện áp hình thành và dòng điện anod hóa.

In the mathematical formalism of quantitative AES and XPS, the elastic electron collisions are not taken into account. However, recent calculations have shown that the neglect of the elastic collisions may result in considerable errors. Theoretical analysis of the actual electron transport in a solid requires two major problems to be considered. (i) calculation of the differential elastic scattering cross‐sections for a given potential and electron energy and (ii) description of the multiple electron scattering. Both problems are extensively reviewed. The Monte Carlo method is usually used to describe the electron trajectories in a solid at energies of surface‐sensitive electron spectroscopies. Such simulations have indicated that the elastic collisions of photoelectrons affect considerably the angular distribution of the measured intensity and the photoelectron escape depth. The latter parameter may be diminished by > 30%. Elastic collisions of Auger electrons decrease the current recorded by the typical analysers and also considerably decrease the escape depth. Thus, the actual electron transport in a solid should be considered in calculations associated with determining the inelastic mean free path using the overlayer method or overlayer thickness measurements. The usual formalism of quantitative AES and XPS can be extended easily to account for the elastic electron collisions. The values of the corresponding correcting factors are extensively compiled. To check the validity of the Monte Carlo calculations, the results of simulations of forward electron scattering and electron back‐scattering are compared with the available experimental data. Excellent agreement between experimental and theoretical angular distributions of photoelectrons has been found. A very good agreement was also observed in the case of elastic electron back‐scattering from surfaces.

This standard is issued under the fixed designation E 673; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (ϵ) indicates an editorial change since the last revision or reapproval.