The Rectification Studies on the P -Ion Implanted C60/Si Films

N-type doping of the C₆₀ films deposited on Si substrates has been achieved by 80 keV P⁺-ion implantation with doses of 2×10¹⁴ cm^-2 at room temperature. The heterostructures composed of the n-type doped C₆₀ films and n- or p-type Si(111), Si(100) substrates are studied in view of semiconductor heterojunctions. The rectification and other electrical characteristics of the P⁺-ion implanted n-C₆₀/n-(p-)Si heterostructures are disclosed by the current-voltage (I-V) measurements at room temperature. The n-C₆₀/p-Si heterostructures show stronger rectification than n-C₆₀/n-Si heterostructures and Si(111) substrates are found to be more suitable for forming n-C₆₀/Si heterostructures than Si(100) substrates.     

A three-step process for epitaxial growth of (111)-oriented C60 films on alkali–halide substrates

Epitaxial (111)-oriented C₆₀ films have been grown on alkali–halide substrates, KCl (100), KBr (100) and NaCl (100) by a three-step process: (1), substrate surface cleaning by high temperature heating; (2), initial deposition with a low deposition rate to grow two or three monolayers (ML); and (3), deposition with a high deposition rate to grow a film with expected thickness. It was found that (111)-oriented epitaxial C₆₀ films could be grown at low temperatures in a wide temperature range, from 40 to 120°C. By this three-step process, we can also grow epitaxial C₆₀ films at deposition rates as high as 35 Å/min.     

Preparation and characterization of C60S16 and C70S48 thin films

In this study, we have investigated different methods for preparation of thin films of C₆₀ and C₇₀-sulfur compounds. Films of good quality were obtained by reaction of amorphous C₆₀ and C₇₀ films with a saturated sulfur solution in toluene at 40°C or with saturated sulfur vapour at a temperature of 140°C for several hours. The quality of the fullerene-sulfur films were strongly dependent on the microstructure of the initially deposited fullerene film and the synthesis temperature. X-ray diffraction analyses showed that both methods lead to the formation of films consisting of C₆₀S₁₆ and C₇₀S₄₈ (space groups C 2/c and Amm2, respectively). C₆₀S₁₆ films synthesised on Al₂O₃(012) and Si(100) substrates were texture-free while C₇₀S₄₈ films typically exhibited a preferential (100) orientation. The films were also characterised by Raman and IR- spectroscopy, which confirmed that the interactions between the fullerene molecules and the S₈ rings are weak. The fullerene-sulfur compounds were found to be unstable at high vacuum conditions. Both materials C₆₀S₁₆ and C₇₀S₄₈ are non-conductive at room temperature with conductivities less then 10⁻⁵ (Ω/cm).     

Ni2O3对C3S形成过程的影响及其固溶效应

C3S是水泥熟料中最重要的矿物,杂质离子固溶进入C3S晶格并促进其单斜型或三方型稳定存在,研究离子在C3S中的固溶作用机理,能更深入了解阿利特的微结构及性质。利用化学分析、XRD、DTA及相图分析,研究Ni2O3对C3S形成过程的影响及其固化效应。结果表明:Ni2O3主要以+2价的形式在CaO-Si O2二元体系中存在,因其优先与Si O2反应形成固溶体,f-CaO随Ni2O3掺量递增而增大;当Ni2O3掺量大于其CaO-Si O2二元体系固溶极限时,f-CaO变化趋势呈相反趋势,且促进C3S形成效应明显。通过最小二乘法及Ni2O3固溶度的精确界定,可推导出Ni2O3在C3S中的固溶反应分子式为:(Ca3-0.53xNi0.53x)(Si1-0.47xNi0.47x)O5(x=0.0442)。     

Characterization of intermetallic phases and oxides formed in annealed Ni/Al multilayer structures

Two different multilayer structures composed of ten alternating Ni and Al thin films were sputter deposited on Si (111) substrates. These multilayers with individual Ni and Al thin film thicknesses of about 25 nm and 38 nm and of 25 nm and 13 nm, respectively, have the average compositions of Ni_0.50Al_0.50 and Ni_0.75Al_0.25. The samples were heat treated in a differential scanning calorimeter instrument with a constant heating rate of 40 °C min ⁻¹ in Ar from room temperature to 550 °C. The compositions of as-deposited and heat-treated samples were studied with high-resolution Auger electron spectroscopy (AES) rotational depth profiling. X-ray photoelectron spectroscopy (XPS) analyses show an excess of Ni in both annealed samples. X-ray diffraction measurements of annealed multilayers show the formation of Ni₂Al₃ and NiAl₃ phases in the Ni_0.50Al_0.50 sample and the presence of Ni₃Al and Ni A1₃ phases with some excess of Ni in the Ni_0.75Al_0.75 sample. AES and XPS investigations of the reacted layers after 15 min annealing in air at 500 °C disclose considerably different surface oxide thin films: on the Ni_0.50Al_0.50 layer the oxide thin film consists of Al₂O₃ with a small amount of NiO, whereas that on the top of the Ni_0.75Al_0.25 layer is thicker and consists of NiO on top and some Al₂O₃ below.     

Stacking Defects in C60 Films

The structure of pollycrystalline C₆₀ films prepared by sublimation from 99.9% pure C₆₀ powder and from graphite soot was investigated by X-ray diffraction. A complex fcc (111) line was found in the former samples. Comparison of experimental and simulated (111) profiles allowed to assess quantitatively the degree of stacking disorder introduced during the growth of the film. Probabilities could be derived for continuation of already started fcc and hep sequences, thereby characterizing the statistical microstructure of the C₆₀ films. Also, the relative magnitudes of inter- and intra-layer disorder can be estimated. The films deposited from graphite soot show a high structural disorder.     

First principles calculations of iron-doped heterofullerenes

We present results of first principles calculations of the geometric and electronic structure of the networked iron fullerene C₅₉Fe. This heterofullerene is obtained from C₆₀ by replacing a C atom with a Fe atom and relaxing self-consistently the structure to the local minimum. The C₅₉Fe molecule has a closed-cage structure reminiscent of that of C₆₀, but locally deformed in the vicinity of the Fe dopant atom. On the other hand, in-cage doping with iron leads to an electronic structure considerably modified with respect to that of C₆₀. The Kohn–Sham energy diagram of this new iron coordination compound is presented and features characterizing the Fe–C bonding in this system are discussed.     

Excitons in self-organized layered perovskite films prepared by the two-step growth process

Thin films of microcrystalline (C₈H₁₇NH₃)₂PbBr₄ were prepared by a two-step growth process as follows: (1) deposition of PbBr₂ films on substrates and (2) self-organized growth of layered perovskite compounds by exposing the PbBr₂ film to C₈H₁₇NH₃Br vapor in a vacuum chamber. As-synthesized (C₈H₁₇NH₃)₂PbBr₄ films were characterized by using X-ray diffraction, temperature dependence in optical absorption and photoluminescence spectra. (C₈H₁₇NH₃)₂PbBr₄ films created by this synthesis approach were found to microcrystalline form, single phase and highly oriented with a c-axis perpendicular to the substrate surface. (C₈H₁₇NH₃)₂PbBr₄ films showed clear exciton absorption and photoluminescence even at room temperature in the near-ultraviolet region. Exciton binding energy of (C₈H₁₇NH₃)₂PbBr₄ was estimated about 200 meV.     

Investigation and Manipulation of C60 on a Si Surface Using a Scanning Tunneling Microscope

We have demonstrated that the tip of a scanning tunnelling microscope (STM) may be used to position individual C₆₀ molecules on a Si(111) surface. This work is reviewed together with more recent results on STM modification of C₆₀multilayers. The chemical passivation of Si(111) by a C₆₀ monolayer is also discussed.     

Study of microstructure of epitaxial fullerenes films

A comprehensive study was made on the structure of epitaxial thin films of C₆₀ and C₇₀ by means of transmission electron microscopy. Both the films show similar face-centered cubic structure and are epitaxial on (001) mica with close-packed plane parallel to the substrate surface. Two main kinds of defects-stacking faults and twins-were observed and are discussed. The effect of the remaining C₇₀ impurity on the crystal orientation of C₆₀ films was studied by comparing different samples made from high-purity fullerene and C₆₀/C₇₀ mixtures. The results show that there is a higher density of planar defects in the films containing larger amounts of impurities: moreover, some faint anomalous reflections located at so-called 2a₀ fcc reciprocal lattice points were also detected, probably as a result of C₇₀ contamination. Finally, it is found that stacking disorders can be easily increased by keeping the high-quality pure C₆₀ film in air at room temperature for a few weeks, implying the instability of the crystal orientation of the epitaxial fullerene films.     

DIAMOND FILMS FROM CH3OH SYSTEMS

Polycrystalline diamond films were obtained on silicon (111) substrates by the microwave plasma-assisted chemical-vapour-deposition (CVD) method from theCH₃OH+H₂ systems.When CH₃OH,CH₃COCH₃, H₂ were used as the source gases.the diamond epitaxial films were obtained on the synthesized single-crystal diamond (100), (110) and (111) substrates too. From the experimental results, we could discover that: CH₃OH, CH₃COCH₃ and other hydrocarbon gases could also be used as suitable source gases for the growth of diamond films.     

C60 Films Formed by Ionized Cluster Beam Deposition: Structure and Doping by Ion Implantation

C₆₀ films were formed on a variety of substrates by ionized cluster beam (ICB) technique. Their structure was found to depend on the acceleration voltages and substrate. Then the Coo films were implanted by P⁺-ions with doses from 0—2×10¹⁴ ion/cm². The in situ measurement of electrical conductivity revealed an abrupt decrease of three orders in resistance. The temperature coefficient of resistivity of the P⁺-ion implanted C₆₀ film remained in a negative value.     

Bromination of [60]Fullerene. II. Crystal and Molecular Structure of [60]Fullerene Bromides, C60Br6, C60Br8, and C60Br24

The crystal and molecular structures of the bromofullerene solvates C₆₀Br₆·0.5C₆H₅Cl·0.5Br₂, C₆₀Br₈·1.5(o-C₆H₄Cl₂), C₆₀Br₈·Br₂, C₆₀Br₈·0.5C₆H₅Br·0.5Br₂, and C₆₀Br₂₄·2Br₂ have been determined by single crystal X-ray diffraction. The molecular species C₆₀Br₆, C₆₀Br₈, and C₆₀Br₂₄ which have idealized C_s, C_2v , and T_h symmetries, respectively, have several different types of C-Br and C-C bonds. A comparison between different solvates of the same bromofullerenes revealed a larger stability of the packing modes for the C₆₀Br₆ and C₆₀Br₂₄ solvates, whereas the C₆₀Br₈ solvates showed different packing motifs dependent on the nature and amount of the solvent molecules.     

Structure of C60 Thin Films Formed by Ionized Cluster Beam Deposition

C₆₀ thin films were formed on cleaved NaC1 substrates at room temperature and their crystallinity and crystal orientation were found to be controlled by acceleration and ionization voltages of ionized cluster beam (ICB) technique.     

Crystal texture selection in epitaxies of orthorhombic antiferromagnetic YMnO3 films

The orthorhombic phase of YMnO₃ has been epitaxially stabilized on SrTiO₃ single crystal substrates. Changing the substrate orientation, the out-of-plane orientation of the epitaxial films can be tuned to (001), (101), or (100). Depending on the orientation, the films present varied crystal domain structures and lattice strains. Single domain YMnO₃(100) films have been grown on SrTiO₃(110) substrates, whereas they present two and three crystal variants on SrTiO₃(001) and SrTiO₃(111), respectively. Epitaxial stress in each domain is anisotropic, tensile in one direction and compressive in the other. It has consequences in the texture selection when domains with different out-of-plane orientation can grow epitaxially. Antiferromagnetism of YMnO₃ films has been confirmed by measuring the exchange bias field induced in an underlying ferromagnetic SrRuO₃ layer.     

Electron Microscopic Investigations of Transformations from C60 to Diamond, Filament and Microcapillary

We report the transformation of C₆₀ into diamond by electron beam pulse annealing of flash evaporated films (at 10^-6 torr) of C,₆₀, or by direct evaporation of C₆₀ in helium (100 torr) atmosphere. The formation of filament and microcapillaries (tubulene-like structures) by electron beam annealing of the C₆₀ deposit is also reported.     

Structure and surface termination of ZnO films grown on (0001)- and (112¯0)-oriented Al2O3

We have studied the surface termination of ZnO(0001¯) films grown on Al₂O₃ substrates with high epitaxial quality. The structural properties of the ZnO films were investigated by X-ray scattering, revealing a predominant (0001¯)ZnO out-of-plane texture with the [112¯0]_ZnO[0001]_Al2O3 and [112¯0]_ZnO[101¯0]_Al2O3 azimuthal orientations for (112¯0)Al₂O₃ and(0001)Al₂O₃ substrates, respectively. The surface termination was determined by X-ray photoemission spectroscopy (XPS) via pyridine (C₅H₅N) adsorption at the ZnO surface. XPS data recorded at different temperatures after exposure to pyridine revealed that for both orientations of the Al₂O₃ substrates the deposited ZnO films were terminated by oxygen atoms, i.e. corresponding to a ZnO (0001¯) surface.     

Investigations of the Interaction of Nickel and Carbon Monoxide with Solid Films of C60 and C70 by UV and X-Ray Photoelectron Spectroscopy

Based on UV and X-ray photoelectron spectroscopy, it is shown that nickel metal clusters deposited on solid C₆₀ and C₇₀ films cause marked changes in the valence band spectra. In addition, the C 1s core-level of the fullerenes shift to lower binding energies while the Ni 2p_3/2 core level shifts towards higher binding energies, especially at small metal coverages. These observations signify the occurrence of charge-transfer from the nickel metal to the fullerene. We also show that CO adsorbs weakly on C₆₀ and C₇₀ surfaces.     

45钢表面Ni/WC复合熔覆层的形成机制

采用真空熔覆技术在45钢表面制备Ni +WC复合熔覆层并进行阶段性取样,研究镍基复合涂层的形成机制。结果表明：在45钢表面生成与基体冶金熔合、WC硬质颗粒分布均匀的Ni基复合熔覆层。整个熔覆层由4 mm厚的复合层、1 mm厚的过渡层、20 μm厚的扩散熔合区以及250 μm厚的扩散影响区组成。复合层区由WC和分解形成的富W复相碳化物包围在Ni颗粒周围组成;复合熔覆层的主要组成相有γ-Ni固溶体、Cr₇C₃、Ni_2.9Cr_0.7Fe_0.36、Cr₂₃C₆、Ni₃Fe、Ni₃Si、Ni₃B、W₂C以及C等;真空熔覆过程包括：镍基合金颗粒达到熔点(900℃)前升温阶段颗粒间微烧结颈的形成、升温达到熔点(1020℃)开始的镍基合金颗粒熔融以及保温阶段(1060℃)的熔合扩散与WC颗粒微区位置的调整。     

GROUP TRANSFER AND DIMERIZATION PROCESSES OF C60(CN)2 UNDER ATMOSPHERIC PRESSURE IONIZATION CONDITIONS

Neutral and anionic C₆₀(CN)₂ were investigated with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectrometry. It was observed that its anions underwent cyano- group and oxygen transfer, and dimerization processes in ESI conditions to form C₆₀(CN)₃H^-, C₆₀(CN)₂(OH₂)^-, [C₆₀(CN)₃H]^-₂, [C₆₀(CN)₂(OH₂)]^-₂ and [(C₆₀)₂(CN)₂(OH)]^-. Meanwhile, neutral C₆₀(CN)₂, for which no signal was observed in ESIMS, showed a base peak corresponding to C₆₀(CN)₂Cl^- in APCIMS spectra with CHCl₃ used as solvent, while only a molecular ion peak corresponding to C₆₀(CN)^-₂ was observed for the toluene solution of neutral C₆₀(CN)₂ in the same conditions. Possible mechanisms for group transfer and dimerization were proposed based on these observations.