PIXE analysis of Fe content in Fe-implanted GaN film

The diluted magnetic semiconductors (DMSs) were achieved by the ion implantation. Fe+ ions (250 keV) were implanted into n-type GaN at room temperature with doses ranging from 8 X 10(15) cm(-2) to 8 X 10(16) cm(-2) and subsequently rapidly annealed at 800 degrees C for 5 m in N-2 ambient. PIXE was employed to determine the Fe-implanted content. The magnetic property was measured by the Quantum Design MPMS SQUID magnetometer. No secondary phases or clusters are detected within the sensitivity of XRD. Apparent ferromagnetic hysteresis loops measured at 10 K were presented. The relationships between the Fe-implanted content and the ferromagnetic property are discussed. (c) 2006 Elsevier B.V. All rights reserved.

Anisotropic strain relaxation of thin Fe film on c(4 x 4) reconstructed GaAs (001) surface

National Natural Science Foundation of China 60836002 10674130 60521001;Major State Basic Research of China 2007CB924903;Chinese Academy of Sciences KJCX2.YW.W09-1

Fe-diffusion-induced defects in InP annealed in iron phosphide ambient

Photoluminescence (PL) and photo induced current transient spectroscopy (PICTS) have been used to study deep levels in semi-insulating (SI) InP prepared by annealing undoped InP in pure phosphorus (PP) and iron phosphide (IP) ambient. Defects are much fewer in IP SI-InP than in PP SI-InP. Deep-level-related PL emission could only be detected in IP SI-InP. The results indicate that Fe diffusion inhibits the thermal formation of a number of defects in annealed InP. A complex defect has been formed in the annealing process in the presence of Fe.

Creation and suppression of point defects through a kick-out substitution process of Fe in InP

Indium antisite defect In-P-related photoluminescence has been observed in Fe-diffused semi-insulating (SI) InP. Compared to annealed undoped or Fe-predoped SI InP, there are fewer defects in SI InP obtained by long-duration, high-temperature Fe diffusion. The suppression of the formation of point defects in Fe-diffused SI InP can be explained in terms of the complete occupation by Fe at indium vacancy. The In-P defect is enhanced by the indium interstitial that is caused by the kick out of In and the substitution at the indium site of Fe in the diffusion process. Through these Fe-diffusion results, the nature of the defects in annealed undoped SI InP is better understood. (C) 2002 American Institute of Physics.

Mechanical alloying of Fe-Mn and Fe-Mn-Si

The ball milling of Fe-24Mn and Fe-24Mn-6Si mixed powders has been performed by the high energy ball milling technique. By employing X-ray diffraction and Mossbauer measurements, the composition evolution during the milling process has been investigated. The results indicate the formation of paramagnetic Fe-Mn or Fe-Mn-Si alloys with a metastable fee phase as final products, which imply that the Fe and Mn proceed a co-diffusion mechanism through the surface of fragmented powders. The thermal stability and composition evolution of the as-milled alloys were discussed comparing with the bulk alloy. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Mossbauer spectroscopy study of Fe-57 in R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

Fe-57 Mossbauer spectra for the Fe atoms in the R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb, Dy; T=V, Cr) compounds were collected at 4.2 K. The analysis of Mossbauer spectra was based on the results of magnetization and neutron powder diffraction measurements. The average Fe magnetic moments at 4.2 K, deduced from our data, are in accord with magnetization measurements. The average hyperfine field of Tb3Fe29-xCrx (x=1.0, 1.5, 2.0, and 3.0) decreases with increasing Cr concentration, which is also in accordance with the variation of the average Fe magnetic moment in the Tb3Fe29-xCrx compounds.

Analysis of the interfaces of [NiFe/Mo](30) and [Fe/Mo](30) multilayers

The interface states of [NiFe/Mo](30) and [Fe/Mo](30) multilayers have been investigated by x-ray small angle reflection and diffuse scattering. Significant interface roughness correlation was observed in both ultrathin [NiFe/Mo](30) and [Fe/Mo](30) multilayers. An uncorrelated roughness of about 27-3.1 Angstrom was revealed in the [NiPe/Mo](30) multilayers, which is explained as originating from a transition layer between the NiFe and the Mo layers. By the technique of diffuse scattering, it is clearly indicated that the interfacial roughness of NiFe/Mo is much smaller than that of Fe/Mo although the lattice mismatch is the same in both multilayers.

Synthesis Gas Generation by Chemical-Looping Reforming Using Ce-Based Oxygen Carriers Modified with Fe, Cu, and Mn Oxides

Chemical-looping reforming (CLR) is a technology that can be used for partial oxidation and steam reforming of hydrocarbon fuels. It involves the use of a metal oxide as an oxygen carrier, which transfers oxygen from combustion air to the fuel. Composite oxygen carriers of cerium oxide added with Fe, Cu, and Mn oxides were prepared by co-precipitation and investigated in a thermogravimetric analyzer and a fixed-bed reactor using methane as fuel and air as oxidizing gas. It was revealed that the addition of transition-metal oxides into cerium oxide can improve the reactivity of the Ce-based oxygen carrier. The three kinds of mixed oxides showed high CO and H-2 selectivity at above 800 degrees C. As for the Ce-Fe-O oxygen carrier, methane was converted to synthesis gas at a H-2/CO molar ratio close to 2:1 at a temperature of 800-900 degrees C; however, the methane thermolysis reaction was found on Ce-Cu-O and Ce-Mn-O oxygen carriers at 850-900 degrees C. Among the three kinds of oxygen carriers, Ce-Fe-O presented the best performance for methane CLR. On Ce-Fe-O oxygen carriers, the CO and H-2 selectivity decreased as the Fe content increased in the carrier particles. An optimal range of the Ce/Fe molar ratio is Ce/Fe > 1 for Ce-Fe-O oxygen carriers. Scanning electron microscopy (SEM) analysis revealed that the microstructure of the Ce-Fe-O oxides was not dramatically changed before and after 20 cyclic reactions. A small amount of Fe3C was found in the reacted Ce-Fe-O oxides by X-ray diffraction (XRD) analysis.

全固态电流型氧传感器及Pt-Fe复合催化剂的研究

控制电位电解型即电流型气体传感器由于具有检测气体种类多、浓度范围宽、体积小、价格低、测量精度高、可用于现场直接检测等优点，在环境监测与安全生产等领域中得到了广泛应用。本文论述了纳米级铂、碳纳米管负载铂及铂铁催化剂的合成方法，并对其进行了物理化学表征和电化学研究，主要结果如下： 采用柠檬酸钠还原的方法，合成了纳米级铂催化剂。TEM和XRD测试表明，该球形多晶铂的粒径为2－5nm。用此种铂催化剂制备了离子交换膜电极复合体，并组装了全固态电流型氧传感器；在对低浓度氧气进行测试时，具有高的灵敏度、较短的响应时间、较低的底电流和噪声，且响应信号与氧气的浓度呈良好的线性关系。 1．利用空气氧化和硝酸相结合对多壁碳纳米管进行了纯化，并利用1:1的H2SO4-HNO3混酸使其表面羧基化，TEM和CV测试表明多壁碳纳米管达到了纯化和表面官能团化的目的。 2．利用喷雾冷却法制备了多壁碳纳米管负载的铂及铂铁合金纳米级催化剂复合体，并利用TEM、EDS、XRD、ICP等进行了表征；在循环伏安扫描中，铂铁合金催化剂呈现较高的比表面积。将多壁碳纳米管负载的铂及铂铁合金纳米级催化剂应用于C1有机小分子的电化学氧化研究中发现，铂铁合金催化剂具有较高的催化活性.

[PMMA-b-PAN］-Fe络合物制备有机一无机杂化薄膜

本论文通过聚甲基丙烯酸甲酯-b-聚丙烯睛嵌段共聚物同铁（III）离子络合物（［PMMA-b-PAN］-Fe）制备有机一无机杂化薄膜，并利用妨M对薄膜的表面形态进行了表征。结果表明，通过控制［PMMA-b-PAN］-Fe络合物溶液热处理时间（T=120℃）及络合物溶液中精基同铁＜III）离子的摩尔比率，可以得到不同表面形态的有机一无机杂化薄膜。并借助抑S对［PMMA-b-PAN〕-Fe络合物配位作用进行了研究，发现铁（III）离子与PMMA-b-PAN嵌段共聚物中的睛基配位。此外，对掺杂有FeSO4·7H2O 的均聚甲基丙烯酸甲酷（PMMA）溶液、均聚丙烯睛(PAN)溶液和FeSO4·7H2O（溶解在DMF中）溶液经不同时间热处理（T=120℃）后的薄膜表面形态进行了研究，结果发现，掺杂有FeSO4·7H2O 的PMMA 溶液经20in热处理后，薄膜的表面形态与FeS04·7H2O。溶液经20in热处理后薄膜的表面形态基本相同，而掺杂有FesO4·7H2O的PAN溶液经不同时间热处理后，薄膜的表面形态没有明显的变化。与此同时，对匡[PMMA-b-PAN]-Fe络合物高温热解制备碳材料进行了初步的研究，研究结果表明，利用PMMA-b-PAN］-e杂化薄膜炭化制备具有纳米尺寸孔洞的碳薄膜是可能的，但控制好热解条件至关重要。