Modifications in thin film structures by swift heavy ions

We review older and more recent work concerning modification of thin films during irradiation with heavy ions in the electronic energy deposition regime: loss of H₂ and N₂ from the bulk of several thin film materials, electronic sputtering of SiO₂ and oxygen diffusion across an interface in SiO₂.     

Mixing induced by swift heavy ion irradiation at Fe/Si interface

The present work deals with the mixing of metal and silicon by swift heavy ions in high-energy range. Threshold value for the defect creation in metal Fe calculated was found to be ∼ 40 keV/nm. A thin film of Fe (10 nm) was deposited on Si (100) at a pressure of 4 × 10⁻⁸ Torr and was irradiated with 95 MeV Au ions. Irradiation was done at RT, to a dose of 10¹³ ions/cm² and 1 pna current. The electronic energy loss was found to be 29.23 keV/nm for 95 MeV Au ions in Fe using TRIM calculation. Compositional analysis of samples was done by Rutherford backscattering spectroscopy. Reflectivity studies were carried out on the pre-annealed and post-annealed samples to study irradiation effects. Grazing incidence X-ray diffraction was done to study the interface. It was observed that ion beam mixing reactions at RT lead to mixing as a result of high electronic excitations.     

二极溅射沉积Fe-N-O薄膜的形貌与结构分析

利用二极溅射的方法在不同衬底上沉积了Fe N O薄膜。通过扫描电子显微镜(SEM)、光电子能谱(XPS)和透射电子显微镜(TEM)等先进实验分析手段对二极溅射沉积Fe N O薄膜的形貌与结构进行了分析。XPS和TEM的结果表明,薄膜的主要成分为FeO和少量的Fe16N2多晶体组成,生长上存在择优取向;表面均匀、致密、平整,晶粒大小在50nm左右。     

Influence of 150 MeV Ni swift heavy ion irradiation on CuFe2O4 thin films prepared by radio frequency magnetron sputtering: Modification on structure and surface morphology

The bulk copper ferrite nanomaterials are synthesized by co-precipitation technique. The vibrating sample magnetometer measurement for bulk CuFe₂O₄ reveals its unsaturated superparamagnetic behavior. The crystallites of the synthesized nanomaterial are in cubic form having an average size of ~ 100 Å and are used as target to prepare thin films of various thicknesses (600, 900 and 1100 nm) by radio frequency magnetron sputtering technique. X-ray peaks arise only when films are annealed at 1200 °C and also they are found to be in tetragonal structure. The magnetic characteristics of 900 nm unirradiated CuFe₂O₄ thin film exhibit superparamagnetic behavior and have an unsaturated magnetic moment at high field. Magnetic force microscopy images of unirradiated CuFe₂O₄ thin films confirm the soft nature of the magnetic materials. The 150 MeV Ni¹¹⁺ swift heavy ion irradiation on these thin films at the fluence of 1 × 10¹⁴ ions/cm² modifies the polycrystalline nature due to electron-phonon coupling. Atomic force microscopy image shows that the swift heavy ion irradiation induces agglomeration of particles in 600 and 900 nm thin films and increases rms surface roughness from 33.43 to 39.65 and 69.7 to 102.46 nm respectively. However, in 1100 nm film, holes are created and channel-like structures are observed along with a decrease in the rms surface roughness from 75.12 to 24.46 nm. Magnetic force microscopy images of 900 nm irradiated thin film explain the formation of domains on irradiation and are also supported by the ferromagnetic hysteresis observed using vibrating sample magnetometer.     

Amorphous/crystalline Fe55Ni20Cu5P10Si5B5 composite produced by two-component melt–spinning

ABSTRACT

This work presents unique microstructure and thermal properties of the Fe₅₅Ni₂₀Cu₅P₁₀Si₅B₅ alloy produced by novel modification of the melt-spinning method, where two precursor alloys are simultaneously ejected i.e. Fe₄₀Ni₄₀P₁₀Si₅B₅ and Fe₇₀Cu₁₀P₁₀Si₅B₅, forming a composite ribbon. The investigation of melting the precursors by differential scanning calorimetry confirms the liquid miscibility of the Fe₇₀Cu₁₀P₁₀Si₅B₅ alloy. The two-component melt-spun composite obtained from the two alloys is compared to the alloys produced from a homogeneous liquid. The electron microscopy, X-ray diffraction and differential scanning calorimetry show different microstructure of the composite in comparison with the traditionally melt-spun alloys and our results reveal that the composite alloy inherits the thermal properties of the precursors.

This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys.     

Structural and spectroscopic modifications of nanocrystalline zinc oxide films induced by swift heavy ions

Structural and spectroscopic modifications of nanocrystalline (nc) ZnO films induced by Swift heavy ion (SHI) irradiation is reported. Films were irradiated at incremented ion fluences. Structural study reveals that the nanocrystals become more oriented at low fluences, while a release of strain and decrease in grain size is observed at high fluence. The surface morphology study also shows a decrease in crystallite size and agglomeration of grains at high fluence. On the other hand micro-Raman and Fourier transform infrared (FTIR) results show that the longitudinal optical (LO) mode is strengthened and red shifted, while the transverse optical (TO) mode get dampened at high fluence. But the amorphization of crystallites was not observed under the used irradiation conditions. The observed structural and spectroscopic modifications are explained in terms of high density of lattice defects and disorder created by dense electronic excitations induced by SHI irradiation.     

Structural and spectroscopic modifications of nanocrystalline zinc oxide films induced by swift heavy ions

Structural and spectroscopic modifications of nanocrystalline (nc) ZnO films induced by Swift heavy ion (SHI) irradiation is reported. Films were irradiated at incremented ion fluences. Structural study reveals that the nanocrystals become more oriented at low fluences, while a release of strain and decrease in grain size is observed at high fluence. The surface morphology study also shows a decrease in crystallite size and agglomeration of grains at high fluence. On the other hand micro-Raman and Fourier transform infrared (FTIR) results show that the longitudinal optical (LO) mode is strengthened and red shifted, while the transverse optical (TO) mode get dampened at high fluence. But the amorphization of crystallites was not observed under the used irradiation conditions. The observed structural and spectroscopic modifications are explained in terms of high density of lattice defects and disorder created by dense electronic excitations induced by SHI irradiation.     

Determination of the composition of binary systems by the ratio method employing SEM-EDAX

By employing x-ray emission in a scanning electron microscope (SEM), it has been shown that compositions of binary systems such as As-Se glasses, Al-Zn alloys and copper sulphides can be determined.     

催化裂解聚苯乙烯制备碳纳米管的研究

通过在60℃氮气气氛中催化裂解聚苯乙烯,制备了大量管径为5～40nm的高质量的碳纳米管.利用扫描电子显微镜、透射电子显微镜和拉曼光谱对所制备的碳纳米管进行了表征.研究表明,所制备的碳纳米管石墨化程度高,在碳纳米管的管壁上仅有少量的无定形碳存在.催化裂解聚苯乙烯制备碳纳米管是一种有前途、低成本的绿色化学方法.     

Calibration of High-Resolution X-Ray Tomography With Atomic Force Microscopy

For two-dimensional x-ray imaging of thin films, the technique of scanning transmission x-ray microscopy (STXM) has achieved images with feature sizes as small as 40 nm in recent years. However, calibration of three-dimensional tomographic images that are produced with STXM data at this scale has not yet been described in the scientific literature, and the calibration procedure has novel problems that have not been encountered by x-ray tomography carried out at a larger scale. In x-ray microtomography, for example, one always has the option of using optical imaging on a section of the object to verify the x-ray projection measurements; with STXM, on the other hand, the sample features are too small to be resolved by light at optical wavelengths. This fact implies that one must rely on procedures with higher resolution, such as atomic force microscopy (AFM), for the calibration. Such procedures, however, generally depend on a highly destructive sectioning of the sample, and are difficult to interpret because they give surface information rather than depth information. In this article, a procedure for calibration is described that overcomes these limitations and achieves a calibration of an STXM tomography image with an AFM image and a scanning electron microscopy image of the same object.A Ge star-shaped pattern was imaged at a synchrotron with a scanning transmission x-ray microscope. Nineteen high-resolution projection images of 200 × 200 pixels were tomographically reconstructed into a three-dimensional image. Features in two-dimensional images as small as 40 nm and features as small as 80 nm in the three-dimensional reconstruction were resolved. Transverse length scales based on atomic force microscopy, scanning electron microscopy, x-ray transmission and tomographic reconstruction agreed to within 10 nm. Toward the center of the sample, the pattern thickness calculated from projection images was (51 ± 15) nm vs (80 ± 52) nm for tomographic reconstruction, where the uncertainties are evaluated at the level of two standard deviations.     

Structural damage in ZnO bombarded by heavy ions

The effect of implantation parameters on damage build-up in ZnO bombarded with Bi and Er ions is studied by Rutherford backscattering/channelling spectrometry. The results show that the damage accumulation behaviour in ZnO is different dramatically from that in other semiconductors. In particular, a variation of implantation parameters, such as collision cascade density, sample temperature and ion flux, has only a minor influence on the damage accumulation in the crystal bulk for the case of such heavy ions. Moreover, an intermediate damage peak, between the surface and bulk defect peaks, is observed for all the irradiation conditions studied. The cascade density affects the behaviour of this intermediate peak with increasing ion dose.     

Enhanced Vertical Charge Transport of Homo- and Blended Semiconducting Polymers by Nanoconfinement

The morphology of conjugated polymers has critical influences on electronic and optical properties of optoelectronic devices. Even though lots of techniques and methods are suggested to control the morphology of polymers, very few studies have been performed inducing high charge transport along out-of-plane direction. In this study, the self-assembly of homo- and blended conjugated polymers which are confined in nanostructures is utilized. The resulting structures lead to high charge mobility along vertical direction for both homo- and blended conjugated polymers. Both semicrystalline and amorphous polymers show highly increased population of face-on crystallite despite intrinsic crystallinity of polymers. They result in more than two orders of magnitude enhanced charge mobility along vertical direction revealed by nanoscale conductive scanning force microscopy and macroscale IV characteristic measurements. Moreover, blends of semicrystalline and amorphous polymers, which are known to show inferior optical and electrical properties due to their structural incompatibility, are formed into harmonious states by this approach. Assembly of blends of semicrystalline and amorphous polymers under nanoconfinement shows charge mobility in out-of-plane direction of 0.73 cm² V⁻¹ s⁻¹ with wide range of absorption wavelength from 300 to 750 nm demonstrating the synergistic effects of two different polymers.     

Transdermal delivery of car vedilol in rats: probing the percutaneous permeation enhancement mechanism of soybean extract–chitosan mixture

Background: This study was designed for investigating the effect of soybean (SS) extract and chitosan (CTN) in facilitating the permeation of carvedilol (CDL) across rat epidermis. Method: Transdermal flux of carvedilol through heat-separated rat epidermis was investigated in vitro using vertical Keshary–Chien diffusion cells. Biophysical and microscopic manifestations of epidermis treated with SS-extract, CTN, and SS extract–CTN mixture were investigated by using DSC, TEWL, SEM, and TEM. Biochemical estimations of cholesterol, sphingosine, and triglycerides were carried out for treated excised as well as viable rat epidermis. The antihypertensive activity of the patches in comparison to that after oral administration of carvedilol was studied in deoxycorticosterone acetate-induced hypertensive rats. Results: The solubility of CDL was found to be maximum in the presence of 1% (w/v) SS extract. The K_IPM/PB of CDL decreased with increase in concentration of SS extract. The in vitro permeation of CDL across rat epidermis increased and was maximum with combination of SS extract and chitosan (CTN). Biochemical and microscopic studies revealed the initiation of reversal of barrier integrity after 12 hours. Furthermore, the application of patches containing SS extract–CTN mixture resulted in sustained release of carvedilol, which was able to control the hypertension in deoxycorticosterone acetate (DOCA) induced hypertensive rats through 24 hours. CTN was found to potentiate the permeation enhancing activity of SS extract. Conclusion: The developed transdermal patches of CDL containing SS extract–CTN mixture exhibited better performance as compared to oral administration in controlling hypertension in rats.     

Formulation by design of felodipine loaded liquid and solid self nanoemulsifying drug delivery systems using Box–Behnken design

Objective: To design and develop liquid and solid self-nanoemulsifying drug delivery systems (SNEDDS and S-SNEDDS) of felodipine (FLD) using Box–Behnken design (BBD).

Methods: Solubility study was carried out in various vehicles. Ternary phase diagram was constructed to delineate the boundaries of the nanoemulsion domain. The content of formulation variables, X1 (Acconon E), X2 (Cremophor EL) and X3 (Lutrol E300) were optimized by assessment of 15 formulations (as per BBD) for mean globule sizes in Millipore water (Y1), 0.1?N?HCl (Y2), phosphate buffer (pH 6.4) (Y3); emulsification time (Y4) and T_85% (Y5). The responses (Y1–Y5) were evaluated statistically by analysis of variance and response surface plots to obtain optimum points. The optimized formulations were solidified by adsorption to solid carrier technique using Aerosil 200 (AER).

Results and discussion: Transmission electron microscopy images confirmed the spherical shape of globules with the size range concordant with the globule size analysis by dynamic light scattering technique (<60?nm). The surface morphology of S-SNEDDS (before release) by scanning electron microscopy and atomic force microscopy indicated that SNEDDS are adsorbed uniformly on the surface of AER. The dried residue of S-SNEDDS (after release) revealed the presence of nanometric pores vacated by the previously adsorbed SNEDDS onto AER. Differential scanning calorimetry and X-ray powder diffraction studies illustrated the change of FLD from crystalline to amorphous state.

Conclusion: This study indicates that owing to nanosize, SNEDDS and S-SNEDDS of FLD have potential to enhance its absorption and may serve an efficient oral delivery.     

Investigation of the growth of In2O3 on Y-stabilized ZrO2(100) by oxygen plasma assisted molecular beam epitaxy

Thin films of In₂O₃ have been grown on Y-stabilised ZrO₂(100) substrates by oxygen plasma assisted molecular beam epitaxy over a range of substrate temperatures between 650 °C and 900 °C. Growth at 650 °C leads to continuous but granular films and complete extinction of substrate core level structure in X-ray photoelectron spectroscopy. However with increasing substrate temperature the films break up into a series of discrete micrometer sized islands. Both the continuous and the island films have excellent epitaxial relationship with the substrate as gauged by X-ray diffraction and selected area electron diffraction and lattice imaging in high resolution transmission electron microscopy.     

Transient thermal process induced by swift heavy ions: Defect annealing and defect creation in Fe and Ni

In the present paper, a method is proposed to quantitatively estimate the nuclear defect annealing by the electronic stopping powerS _e. The spatial distribution of defects created in metals by nuclear collisions is known from numerical calculation based on the binary collisions with screened Coulomb potential. In the framework of the thermal spike model,S _e induced annealing of nuclear defects is simulated without considering athermal recombination. These calculations are applied to iron and nickel. The agreement between experiment and simulation in iron allows to determine the electron-phonon coupling value for iron. The defect creation byS _e arises when the energy deposited on the atoms overcomes the energy necessary to melt the matierial.     

电子显微分析技术在奥氏体合金应力腐蚀开裂研究领域中的应用

奥氏体合金广泛应用于核电领域。应力腐蚀开裂是核电材料主要的失效形式之一,奥氏体合金的应力腐蚀开裂关系到核电站的安全运行。综述了评估应力腐蚀开裂的试样方法以及运用现代电子显微分析技术表征应力腐蚀开裂的方法。对这些电子显微分析技术的优点进行了总结,并指出未来电子显微分析技术在应力腐蚀开裂研究中的发展方向。     

Sculpting the Plasmonic Responses of Nanoparticles by Directed Electron Beam Irradiation

Spatial confinement of matter in functional nanostructures has propelled these systems to the forefront of nanoscience, both as a playground for exotic physics and quantum phenomena and in multiple applications including plasmonics, optoelectronics, and sensing. In parallel, the emergence of monochromated electron energy loss spectroscopy (EELS) has enabled exploration of local nanoplasmonic functionalities within single nanoparticles and the collective response of nanoparticle assemblies, providing deep insight into associated mechanisms. However, modern synthesis processes for plasmonic nanostructures are often limited in the types of accessible geometry, and materials and are limited to spatial precisions on the order of tens of nm, precluding the direct exploration of critical aspects of the structure-property relationships. Here, the atomic-sized probe of the scanning transmission electron microscope is used to perform precise sculpting and design nanoparticle configurations. Using low-loss EELS, dynamic analyses of the evolution of the plasmonic response are provided. It is shown that within self-assembled systems of nanoparticles, individual nanoparticles can be selectively removed, reshaped, or patterned with nanometer-level resolution, effectively modifying the plasmonic response in both space and energy. This process significantly increases the scope for design possibilities and presents opportunities for unique structure development, which are ultimately the key for nanophotonic design.     

有关电子显微技术的几个实验和建议

本文涉及两个和电子显微技术有关的问题：豆．透射电子显微镜试样薄片表面沉淀相颗粒存在状况的实验观察．２．扫描电子显微镜背反射电子象用作定量金相测定的建议。