SIMS在碲镉汞红外焦平面探测器工艺中的应用

文章介绍了二次离子质谱仪的结构及其基本工作原理,并通过对典型应用的分析,介绍了二次离子质谱分析技术在高灵敏度碲镉汞红外焦平面探测器材料和器件制备工艺中的作用,特别是在结探监测和微量杂质监控方面所发挥的重要作用。     

High‐Performance Alkaline Polymer Electrolyte for Fuel Cell Applications

Although the proton exchange membrane fuel cell (PEMFC) has made great progress in recent decades, its commercialization has been hindered by a number of factors, among which is the total dependence on Pt‐based catalysts. Alkaline polymer electrolyte fuel cells (APEFCs) have been increasingly recognized as a solution to overcome the dependence on noble metal catalysts. In principle, APEFCs combine the advantages of and alkaline fuel cell (AFC) and a PEMFC: there is no need for noble metal catalysts and they are free of carbonate precipitates that would break the waterproofing in the AFC cathode. However, the performance of most alkaline polyelectrolytes can still not fulfill the requirement of fuel cell operations. In the present work, detailed information about the synthesis and physicochemical properties of the quaternary ammonia polysulfone (QAPS), a high‐performance alkaline polymer electrolyte that has been successfully applied in the authors' previous work to demonstrate an APEFC completely free from noble metal catalysts (S. Lu, J. Pan, A. Huang, L. Zhuang, J. Lu, Proc. Natl. Acad. Sci. USA 2008 , 105, 20611), is reported. Monitored by NMR analysis, the synthetic process of QAPS is seen to be simple and efficient. The chemical and thermal stability, as well as the mechanical strength of the synthetic QAPS membrane, are outstanding in comparison to commercial anion‐exchange membranes. The ionic conductivity of QAPS at room temperature is measured to be on the order of 10^?2 S cm^?1. Such good mechanical and conducting performances can be attributed to the superior microstructure of the polyelectrolyte, which features interconnected ionic channels in tens of nanometers diameter, as revealed by HRTEM observations. The electrochemical behavior at the Pt/QAPS interface reveals the strong alkaline nature of this polyelectrolyte, and the preliminary fuel cell test verifies the feasibility of QAPS for fuel cell applications.     

Evidence for Chemicals Intermingling at Silicon/Titanium Oxide (TiOx) Interface and Existence of Multiple Bonding States in Monolithic TiOx

Metal oxides (MOs) are used in photovoltaics and microelectronics as surface passivating layers and gate dielectrics, respectively. The effectiveness of MOs predominantly depends on their structure and the nature of the semiconductor/MO (S/MO) interface. While some efforts are made to analyze interface behavior of a few MOs, greater fundamental understanding on the interface and structural behaviors of emerging MOs is yet to be established for enhanced scientific and technological developments. Here, the structure of atomic layer deposited titanium oxide (TiO_x) and the nature of the c‐Si/TiO_x interface on the atomic‐ to nanoscale are probed. A new breed of mixed oxide (SiO_x+TiO_x) interfacial layer with a thickness of ≈1.3 nm at the c‐Si/TiO_x interface is discovered, and its thickness further increases to ≈1.5 nm after postdeposition annealing. It is observed that both as‐deposited and annealed monolithic TiO_x films comprise multiple bonding states at varying film thickness, with an oxygen‐deficient TiO_x layer located close to the mixed oxide/TiO_x interface. The stoichiometry of this layer improves when reaching the middle and near surface regions of the TiO_x layer, respectively. This work uncovers several critical structural and interface aspects of TiO_x, and thus creates opportunities to control and design improved photovoltaic and electronic devices for future development.     

SIMS characterization of HgCdTe and related II-VI compounds

The production of consistent high purity materials is critical for improvement in performance and sensitivity of II-VI photovoltaic and photoconductive devices. Information regarding the energy band structure and impurity or defect levels present in the material is essential to understand and enhance the performance of current detectors along with the development of future novel devices. Secondary ion mass spectrometry (SIMS) is capable of providing information of purity, junction depths, dopant distribution, and stoichiometry in the material. SIMS techniques can achieve high detection sensitivities in very small analytical volumes and for a wide range of elements (almost the entire periodic table). SIMS analysis also provides unique capabilities for localizing atomic distribution in two and three dimensions. Ion images can be obtained by registering the positions of mass selected ions formed in the sputtering process. The combination of excellent detection sensitivity, high mass resolution, depth profiling capability, and high resolution image acquisition on a wide spectrum of elements by a SIMS instrument is not matched by any other instrumentation technique.     

Band gap measurement of Bi2MoxW1-xO6 by low loss electron energy loss spectroscopy

This work shows the comparison of high-resolution electron energy loss spectra (HR-EELS) in the low loss region (0−15 eV) to investigate the electronic structure from koechilinite Bi₂MoO₆ to rusellite Bi₂WO₆ varying the stoichiometric relation Bi₂Mo_xW_1−xO₆. The effect of the Mo to W ratio on the bandgap energy was evaluated on individual particles. Two approximations were considered in order to determine the band gap energy value, the first one was a linear fit and the second one was a mathematical fit. Both analyses are in agreement with those ones collected and analyzed by UV–Vis characterization. Our results suggest a direct electronic transition that increases from about 2.53 eV to about 3 eV as the W content increase from 0% to 100% wt. X-ray diffraction was used to corroborate the crystal structure and crystal size; transmission electron microscopy was used to monitor the morphology evolution and UV–Vis spectroscopy in diffuse reflectance mode to determine the Eg. These techniques complement the characterization of these materials.     

砷离子注入体材料碲汞的二次离子质谱分析

用二次离子质谱（ＳＩＭＳ）分析了低能注放（１５０ｋｅＶ）砷在体材料碲镉汞中的分布和注入砷原子在碲镉汞中的热扩散情况,砷在碲镉汞中的分布表现出复杂的多元扩散机制。在缺陷密度（ＥＰＤ）比较低的碲镉汞材料中,砷扩散的主体符合恒定扩散系数的有限源扩散模型,呈现出浓度随深度的高斯分布。而在缺陷密度比较大的碲镉汞材料中,砷的分布呈多段指数型分布,表面出更复杂的多机制扩散特性。     

InP/In_xGa_(1-x)As异质结构中Zn元素的扩散机制

采用闭管扩散方式实现了Zn元素在晶格匹配InP/In_(0.53)Ga_(0.47)As及晶格失配InP/In_(0.82)Ga_(0.18)AS两种异质结构材料中的P型掺杂,利用二次离子质谱(SIMS)以及扫描电容显微技术(SCM)对Zn在两种材料中的扩散机制进行了研究.SIMS测试表明:Zn元素在晶格失配材料中的扩散速度远大于在晶格匹配材料中的扩散速度,而SCM测试表明:两种材料中的实际PN结深度与SIMS测得的Zn扩散深度之间存在一定的差值,这是由于扩散进入材料中的Zn元素并没有被完全激活,而晶格失配材料中Zn的激活效率相对更低,使得晶格失配材料中Zn元素扩散深度与PN结深度的差值更大.SCM法是一种新颖快捷的半导体结深测试法,对于半导体器件工艺研究具有重要的指导意义.     

Characterization of CdTe for HgCdTe surface passivation

The objectives of this work are to study the physical and chemical structure of CdTe films using secondary ion mass spectrometry (SIMS) and atomic force miroscopy (AFM) and to demonstrate the usefulness of these analytical techniques in determining the characteristics of CdTe-passivation films deposited by different techniques on HgCdTe material. Three key aspects of CdTe passivation of HgCdTe are addressed by different analytical tools: a) morphological microstructure of CdTe films examined by atomic force microscopy; b) compositional profile across the interface determined by Matrix (Te)—SIMS technique; c) concentration of various impurities across the CdTe/HgCdTe structure profiled by secondary ion-mass spectrometry.     

Mercury interstitial generation in ion implanted mercury cadmium telluride

Junction formation and stability in ion implanted mercury cadmium telluride critically depend on the ability to generate Hg interstitials. The creation of Hg interstitials is found to strongly depend on the preferred lattice position of the element implanted. Elements that substitute onto the cation sublattice create significantly more Hg interstitials than elements that sit interstitially or on the anion sublattice. Recoils from implant damage also contribute to Hg interstitial formation in heavier mass implants (Z ≥ of mass Zn), but appear to have negligible influence on interstitial generation in implants of lighter ions. The combination of implanting ions of large mass and high solubility on the cation sublattice produces strong Hg interstitial sources. Implants with these ions can form deep junctions even in heavily doped substrates. Junction stability is also improved with the stronger interstitial source.     

Study of high-quality epitaxial YBCO thin films grown directly on Y-Cut LiNbO3

Pulsed laser deposition was used to deposit high-quality YBa₂Cu₃O_7-δ (YBCO) thin films directly on y-cut LiNbO₃ substrates. The as-deposited YBCO films had a high degree of in-plane orientation and showed superconducting transition temperature (T_co) at 91K with a transition width of less than IK. Transport critical current densities were found to be ∼10⁶ A/cm² at 77K and zero field. An ion beam minimum channeling yield of 16% was obtained for YBCO films, indicating high crystallinity. High-resolution transmission electron microscopy studies showed that the interface between the film and the substrate was quite smooth and free from interfacial interdiffusion. The defects in thin films are also identified. The work showed that high-quality high T_c thin films can be deposited directly on LiNbO₃. Novel devices based on the properties of both YBCO and LiNbO₃ could be realized based on these results.     

Resonance lonization spectroscopy for quantitative and sensitive surface and bulk measurements of impurities in II-VI materials

We have applied resonance ionization spectroscopy for the first time on II-VI materials, Cd, Te, CdZnTe, and HgCdTe for the measurement of trace impurities. It is an analytical technique with extremely high sensitivity, selectivity, dynamic range, and quantitation accuracy. The technique provides virtual freedom from matrix effects and minimizes isobaric and other mass interferences, known to be the shortcomings in secondary ion mass spectroscopy and other mass spectroscopic measurements. Quantitative analysis of Cu in bulk CdZnTe boules has shown Cu concentration in the range low 10¹⁴ to low 10¹⁵ cm^-3 with an average copper content in four different boules near 2 x 10¹⁴ cm^-3. High Cu concentration (1-2 x 10¹⁷ cm^-3) measured in some HgCdTe epitaxial layers correlated with lower Hall mobility in the layer, and in one case the intentionally In-doped, n-type HgCdTe layer turned p-type.     

基于硼酸溶液处理的GaAs/InP低温晶片键合技术

提出了一种基于硼酸溶液的GaAs/InP低温晶片键合技术,实现了GaAs/InP基材料间简单、无毒性的高质量、低温(290℃)晶片键合。GaAs/InP键合晶片解理截面的扫描电子显微镜(SEM)图显示,键合界面整齐,没有裂缝和气泡。通过键合过程,InP上的In0.53Ga0.47As/InP多量子阱结构转移到了GaAs基底上。X射线衍射及荧光谱显示,键合后的多量子阱晶体质量未变。二次离子质谱(SIMS)和Raman光谱图显示,GaAs/InP键合晶片的中间层厚度约为17 nm,界面处B元素有较高的浓度,键合晶片的中间层很薄,因此可以得到较好的电学、光学特性。     

Microanalysis for microelectronics

Microanalytical methods are powerful tools for the diagnosis and elimination of failures in materials and components in microelectronics. Because of the very small structure dimensions, especially methods with extremely high spatial resolution were used for characterization of microstructure details or for identification and quantitative estimation of chemical composition in very small areas or very thin layers. In this publication a short overview of the most important microanalytical methods is given and particle beam methods are described in more detail. Their principles are explained and their performance is described with examples of analytic problems of development and production of microelectronic components.     

Ion beam mixing characteristics of MOCVD grown InGaAs/GaAs superlattices

The ion beam mixing behavior of InGaAs/GaAs strained layer superlattice structures grown by metalorganic chemical vapor deposition was studied using secondary ion mass spectroscopy and Rutherford backscattering channeling. The fluence dependence of intermixing by MeV Kr⁺ irradiation has been investigated. Significant intermixing occurs for fluences much lower than for similar intermixing in other superlattice systems (i.e. ALAs/GaAs). The intermixing exhibits no temperature dependence for fluences of 2 x 10¹⁵ to 5 x 10¹⁵ cm⁻² which sharply contrasts with the behavior of the AlAs/GaAs superlattice system which shows a strong temperature dependence, including a miscibility gap, in the temperature range 523 to 973K. Samples irradiated at 573K retain a high degree of crystallinity when compared to lower temperature irradiations indicating that the InGaAs/GaAs superlattice can be disordered and still retain crystallinity.     

SIMS analysis of nitrided oxides grown on 4H-SiC

This paper shows for the first time, physical evidence of nitrogen incorporation at the oxide-SiC interface as a result of post-oxidation annealing in nitric oxide (NO). Using secondary ion mass spectroscopy (SIMS) analysis, the location and shape of the nitrogen profile is seen to be almost identical to that found in oxide-silicon interfaces. Close examination of oxygen and carbon SIMS profiles and atomic force microscope scans also indicate a sharper interface when annealing is done using NO compared to inert gases such as N₂ or argon, possibly due to the removal of carbon clusters which form at the interface during oxidation. As in the case of silicon, NO annealing shows great promise as a processing step in the production of device quality gate oxides on SiC.     

Thermal stability of heavily tellurium-doped InP grown by metalorganic molecular beam epitaxy

The thermal stability of tellurium in InP has been examined in samples doped with Te up to an electron concentration of 1.4 × 10²⁰ cm⁻³. Annealing was conducted using rapid thermal annealing for a period of one minute at temperatures over the range 650–800°C. Secondary ion mass spectroscopy analysis showed virtually no change in the Te profile before and after annealing, even at the highest annealing temperatures. High resolution x-ray diffraction and Hall measurements revealed a general decrease in the lattice strain and carrier concentration for annealing temperatures above 650°C. No evidence of strain relief was found in the form of cross-hatching or through the formation of a dislocation network as examined by scanning electron microscopy or transmission electron microscopy (TEM). These results are most likely due to the formation of Te clusters, though such clusters could not be seen by crosssectional TEM.     

Understanding Degradation Mechanisms in SrIrO3 Oxygen Evolution Electrocatalysts: Chemical and Structural Microscopy at the Nanoscale

Designing acid-stable oxygen evolution reaction electrocatalysts is key to developing sustainable energy technologies such as polymer electrolyte membrane electrolyzers but has proven challenging due to the high applied anodic potentials and corrosive electrolyte. This work showcases advanced nanoscale microscopy techniques supported by complementary structural and chemical characterization to develop a fundamental understanding of stability in promising SrIrO₃ thin film electrocatalyst materials. Cross-sectional high-resolution transmission electron microscopy illustrates atomic-scale bulk and surface structure, while secondary ion mass spectrometry imaging using a helium ion microscope provides the nanoscale lateral elemental distribution at the surface. After accelerated degradation tests under anodic potential, the SrIrO₃ film thins and roughens, but the lateral distribution of Sr and Ir remains homogeneous. A layer-wise dissolution mechanism is hypothesized, wherein anodic potential causes the IrO_x-rich surface to dissolve and be regenerated by Sr leaching. The characterization approaches utilized herein and mechanistic insights into SrIrO₃ are translatable to a wide range of catalyst systems.     

Atmosphere‐Induced Reversible Resistivity Changes in Ca/Y‐Doped Bismuth Iron Garnet Thin Films

Bismuth iron garnet Bi₃Fe₅O₁₂ (BIG) is a multifunctional insulating oxide exhibiting remarkably the largest known Faraday rotation and linear magnetoelectric coupling. Enhancing the electrical conductivity in BIG while preserving its magnetic properties would further widen its range of potential applications in oxitronic devices. Here, a site‐selective codoping strategy in which Ca²⁺ and Y³⁺ substitute for Bi³⁺ is applied. The resulting p‐ and n‐type doped BIG films combine state‐of‐the‐art magneto‐optical properties and semiconducting behaviors above room temperature with rather low resistivity: 40 Ω cm at 450 K is achieved in an n‐type Y‐doped BIG; this is ten orders of magnitude lower than that of Y₃Fe₅O₁₂. High‐resolution electron spectromicroscopy unveils the complete dopant solubility and the charge compensation mechanisms at the local scale in p‐ and n‐type systems. Oxygen vacancies as intrinsic donors play a key role in the conduction mechanisms of these doped BIG films. On the other hand, a self‐compensation of Ca²⁺ with oxygen vacancies tends to limit the conduction in p‐type Ca/Y‐doped BIG. These results highlight the possibility of integrating n‐type and p‐type doped BIG films in spintronic structures as well as their potential use in gas sensing applications.     

A study of chemical beam epitaxy of GaAs using tris-dimethylaminoarsenic

The growth of GaAs by chemical beam epitaxy using triethylgallium and trisdimethylaminoarsenic has been studied. Reflection high-energy electron diffraction (RHEED) measurements were used to investigate the growth behavior of GaAs over a wide temperature range of 300–550°C. Both group III- and group Vinduced RHEED intensity oscillations were observed, and actual V/III incorporation ratios on the substrate surface were established. Thick GaAs epitaxial layers (2–3 μm) were grown at different substrate temperatures and V/III ratios, and were characterized by the standard van der Pauw-Hall effect measurement and secondary ion mass spectroscopy analysis. The samples grown at substrate temperatures above 490°C showed n-type conduction, while those grown at substrate temperatures below 480°C showed p-type conduction. At a substrate temperature between 490 and 510°C and a V/III ratio of about 1.6, the unintentional doping concentration is n ∼2 × 10¹⁵ cm⁻³ with an electron mobility of 5700 cm²/V·s at 300K and 40000 cm²/V·s at 77K.     

Analysis of V/III incorporation in nonstoichiometric GaAs and InP films using SIMS

Using secondary ion mass spectrometry (SIMS), we have investigated the excess group V content in GaAs and InP films grown by molecular beam epitaxy at low temperature. Using the inherent depth profiling capability of SIMS, we investigated the V/III ratio in films grown at nominally constant temperatures and also in films grown with stepped temperature profiles. Thickness profiles of the V/III ratio show the effects of intentional temperature changes and of an unintentional drift in the actual substrate temperature during growth. The ability to measure as little as 0.1% excess As and about 0.2% excess P indicates excellent measurement resolution. SIMS analysis is also used to identify a narrow growth temperature range over which InP can be grown with appreciable nonstoichiometry yet remain monocrystalline.