Synthesis of silicon carbide films by combined implantation with sputtering techniques

Silicon carbide (SiC) films were synthesized by combined metal vapor vacuum arc (MEVVA) ion implantation with ion beam assisted deposition (IBAD) techniques. Carbon ions with 40 keV energy were implanted into Si(1 0 0) substrates at ion fluence of 5 × 10¹⁶ ions/cm². Then silicon and carbon atoms were co-sputtered on the Si(1 0 0) substrate surface, at the same time the samples underwent assistant Ar-ion irradiation at 20 keV energy. A group of samples with substrate temperatures ranging from 400 to 600 °C were used to analyze the effect of temperature on formation of the SiC film. Influence of the assistant Ar-ion irradiation was also investigated. The structure, morphology and mechanical properties of the deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nanoindentation, respectively. The bond configurations were obtained from IR absorption and Raman spectroscopy. The experimental results indicate that microcrystalline SiC films were synthesized at 600 °C. The substrate temperature and assistant Ar-ion irradiation played a key role in the process. The assistant Ar-ion irradiation also helps increasing the nanohardness and bulk modulus of the SiC films. The best values of nanohardness and bulk modulus were 24.1 and 282.6 GPa, respectively.     

Observation of ferromagnetism at room temperature for Cr ions implanted ZnO thin films

Single crystalline ZnO films were grown on c-plane GaN/sapphire (0 0 0 1) substrates by molecular beam epitaxy. Cr⁺ ions were implanted into the ZnO films with three different doses, i.e., 1 × 10¹⁴, 5 × 10¹⁵, and 3 × 10¹⁶ cm⁻². The implantation energy was 150 keV. Thermal treatment was carried out at 800 °C for 30 s in a rapid thermal annealing oven in flowing nitrogen. X-ray diffraction (XRD), atomic force microscopy, Raman measurements, transmission electron microscopy and superconducting quantum interference device were used to characterize the ZnO films. The results showed that thermal annealing relaxed the stress in the Cr⁺ ions implanted samples and the implantation-induced damage was partly recovered by means of the proper annealing treatment. Transmission electron microscopy measurements indicated that the first five monolayers of ZnO rotated an angle off the [0 0 0 1]-axis of the GaN in the interfacial layer. The magnetic-field dependence of magnetization of annealed ZnO:Cr showed ferromagnetic behavior at room temperature.     

Effect of swift heavy ion irradiation on photoluminescence properties of ZnO/PMMA nanocomposite films

We report a study on the SHI induced modifications on structural and optical properties of ZnO/PMMA nanocomposite films. The ZnO nanoparticles were synthesized by the chemical route using 2-mercaptoethanol as a capping agent. The structure of ZnO nanoparticles was confirmed by XRD, SEM and TEM. These ZnO nanoparticles were dispersed in the PMMA matrix to form ZnO/PMMA nanocomposite films by the solution cast method. These ZnO/PMMA nanocomposite films were then irradiated by swift heavy ion irradiation (Ni⁸⁺ ion beam, 100 MeV) at a fluence of 1×10¹¹ ions/cm². The nanocomposite films were then characterized by XRD, UV-vis absorption spectroscopy and photoluminescence spectroscopy. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. Enhanced green luminescence at about 527 nm and a less intense blue emission peak around 460 nm were observed after irradiation with respect to the pristine ZnO/PMMA nanocomposite film.     

Ferromagnetism in ZnO doped with Co by ion implantation

The importance of doping ZnO with magnetic ions is associated with the fact that this oxide is a good candidate for the formation of a magnetic-diluted semiconductor. Most of the studies reported in Co-doped ZnO were carried out in thin films, but the understanding of the modification of the magnetic behaviour due to doping demands the study of single-crystalline samples. In this work, ZnO single crystals were doped at room temperature with Co by ion implantation with fluences ranging between 2×10¹⁶ and 1×10¹⁷ ions cm⁻² and implantation energy of 100 keV. As implanted samples show a superparamagnetic behaviour attributed to the formation of Co clusters, room temperature ferromagnetism is attained after annealing at 800 °C, but no magnetoresistance was detected in the temperature range from 10 to 300 K.     

Change of sheet resistance of high purity alumina ceramics implanted by Cu and Ti ions

High purity alumina ceramics (99% Al₂O₃) was implanted by copper ion and titanium ion in a metal vapour vacuum arc (MEVVA) implanter, respectively. The influence of implantation parameters was studied varying ion fluence. The samples were implanted by 68 keV Cu ion and 82 keV Ti ion with fluences from 1 × 10¹⁵ to 1 × 10¹⁸ ions/cm², respectively. The as-implanted samples were investigated by scanning electron microscopy (SEM), glancing X-ray diffraction (GXRD), scanning Auger microscopy (SAM), and four-probe method. Different morphologies were observed on the surfaces of the as-implanted samples and clearly related to implantation parameters. For both ion implantations, the sheet resistances of the alumina samples implanted with Cu and Ti ion fluences of 1 × 10¹⁸ ions/cm², respectively, reached the corresponding minimum values because of the surface metallization. The experimental results indicate that the high-fluence ion implantation resulted in conductive layer on the surface of the as-implanted high purity alumina ceramics.     

Synthesis of molybdenum silicide by both ion implantation and ion beam assisted deposition

Two groups of Mo/Si films were deposited on surface of Si(1 0 0) crystal. The first group of the samples was prepared by both ion beam assisted deposition (IBAD) and metal vapor vacuum arc (MEVVA) ion implantation technologies under temperatures from 200 to 400 °C. The deposited species of IBAD were Mo and Si, and different sputtering Ar ion densities were selected. The mixed Mo/Si films were implanted by Mo ion with energy of 94 keV, and fluence of Mo ion was 5 × 10¹⁶ ions/cm². The second group of the samples was prepared only by IBAD under the same test temperature range. The Mo/Si samples were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), sheet resistance, nanohardness, and modulus of the Mo/Si films were also measured. For the Mo/Si films implanted with Mo ion, XRD results indicate that phase of the Mo/Si films prepared at 400 and 300 °C was pure MoSi₂. Sheet resistance of the Mo/Si films implanted with Mo ion was less than that of the Mo/Si films prepared without ion implantation. Nanohardness and modulus of the Mo/Si films were obviously affected by test parameters.     

Crystalline quality of 3C-SiC formed by high-fluence C-implanted Si

Carbon ions at 40 keV were implanted into (1 0 0) high-purity p-type silicon wafers at 400 °C to a fluence of 6.5 × 10¹⁷ ions/cm². Subsequent thermal annealing of the implanted samples was performed in a diffusion furnace at atmospheric pressure with inert nitrogen ambient at 1100 °C. Time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) was used to investigate depth distributions of the implanted ions. Infrared transmittance (IR) and Raman scattering measurements were used to characterize the formation of SiC in the implanted Si substrate. X-ray diffraction analysis (XRD) was used to characterize the crystalline quality in the surface layer of the sample. The formation of 3C-SiC and its crystalline structure obtained from the above mentioned techniques was finally confirmed by transmission electron microscopy (TEM). The results show that 3C-SiC is directly formed during implantation, and that the subsequent high-temperature annealing enhances the quality of the poly-crystalline SiC.     

Creation of nanoparticles and luminescence in Al2O3 crystal by Zn ion implantation

Single crystal α-Al₂O₃ wafers were implanted with 45 keV Zn ions up to a fluence of 1×10¹⁷ ions/cm², and were then subjected to furnace annealing in oxygen atmosphere at different temperatures. Various techniques have been applied to study the creation of nanoparticles (NPs), defects and their thermal evolutions, as well as their effects on optical properties of Al₂O₃. Our results clearly show that Zn NPs have been synthesized in the as-implanted sample and they begin to be oxidized at 500 °C. Two broad photoluminescence bands appear in the Zn ion-implanted samples and their intensities depend on the annealing temperatures. The results have been interpreted in view of creation of the defects and NPs, Zn atoms diffusion as well as their thermal evolution during annealing.     

Ferromagnetism and microstructure in Fe-implanted ZnO

Fe ions were implanted into ZnO single crystals with multiple energies between 50 and 380 keV up to a total fluence of 12.5×10¹⁷ cm⁻². The crystal quality of Fe⁺ implanted ZnO was investigated by X-ray diffraction 2θ scans and ω-rocking curve measurements. The appearance of Fe related diffraction peaks after C annealing of the implanted sample indicates possibly formation of Fe nanoparticles. Superconducting quantum interference device measurements revealed ferromagnetic behavior below 250 K for both the as-implanted and post-annealed ZnO. Photoluminescence and Raman scattering as well as X-ray rocking curve measurements all indicate introduction of structural defects after Fe implantation. Some of the defects act as nonradiative recombination centers, and suppress the visible and ultraviolet (UV) emission in ZnO. These defects also break the Raman selection rule, and lead to the activation of some silent phonon modes. Annealing of the implanted sample at C causes partial recovery of the defects, however, the X-ray diffraction results of the anneal ZnO show even an improvement of the crystal quality compared with the un-implanted one. This could be attributed to the recovery of the grown-in defects in ZnO.     

Engineering of hydrophilic and plasmonic properties of Ag thin film by atom beam irradiation

Hydrophilic Ag nanostructures were synthesized by physical vapour deposition of 5 nm Ag thin films followed by irradiation with 1.5 keV Ar atoms. Optical absorbance measurements show a characteristic surface plasmon resonance absorption band in visible region. A blue-shift in absorbance from 532 to 450 nm is observed with increasing fluence from 1 × 10¹⁶ to 3 × 10¹⁶ atoms/cm². Atomic force microscopy was performed for the pristine and irradiated samples to study the surface morphology. The atom beam irradiation induced sputtering and surface diffusion lead to the formation of plasmonic surface. Rutherford backscattering spectroscopy of the pristine and irradiated film indicates that metal content in the film decreases with ion fluence, which is attributed to the sputtering of Ag by Ar atoms. The contact angle measurement demonstrates the possibility of engineering the hydrophilicity by atom beam irradiation.     

Structural and optical properties of Au-implanted ZnO films

The structural and luminescence related optical behaviours of Au ion implanted ZnO films grown by magnetic sputtering and their post implantation annealing behaviours in the temperature range of 100-700 °C have been investigated. Optical absorption and transmittance spectra of the films indicate that band edge of Au-implanted ZnO has shifted to high energy range and optical band gap has increased, because the sharp difference of thermal expansion induces the lattice mismatch between ZnO and SiO₂. PL spectra reveal that UV and visible luminescence bands of ZnO films can be improved after thermal annealing due to recovery of defects and Au ions incorporation. Importantly, green luminescence band of 530 nm has been only observed in the Au-implanted and subsequently annealed ZnO films and it enhances with the increasing annealing temperature, which can be related to Au atoms or clusters in ZnO films. Furthermore, X-ray photoelectron spectroscopy measurements reveal that the Au⁰ is dominant state in Au implanted and annealed ZnO films. Possible mechanisms, such as optical transitions of Au atoms or clusters and deep level luminescence of ZnO, have been proposed for green emission.     

Optical properties of ZnO and Al2O3 implanted with silver ions

ZnO and Al₂O₃ samples implanted with 30-keV silver ions with fluences in the interval (0.25–1.00) × 10¹⁷ ions/cm² are studied by the method of optical photometry in the visible part of the spectrum. The optical transmission spectra of the implanted samples exhibit a selective band associated with surface plasmon resonance absorption of silver nanoparticles. The intensity of this band nonmonotonically depends on the implantation fluence. The silver ion depth distribution in the samples is calculated. It is shown that the non-monotonicity observed in experiments is due to an increase in the substrate sputtering ratio with increasing implantation fluence. It is found that vacuum thermal annealing of the implanted Al₂O₃ layers up to 700°C causes a considerable narrowing of the plasmon absorption bandwidth without a tangible change in its intensity. At higher annealing temperatures, the plasmon absorption band broadens and its intensity drops. Annealing of the ZnO films under such conditions causes their complete vaporization.     

SiO2 film electret with high surface potential stability

The plasma surface treatment and ion implantation were utilized to improve the stability of charge storage in the SiO₂ film electret. It was found that the SiO₂ films treated by argon plasma with the arcing at 700 V for 15 min, or implanted by 150 keV (kilo electron volt) Ar⁺ with a dose of 2 × 10¹¹ cm⁻², after being negatively charged, showed a remnant negative potential as large as 90% of the primary value after being stored in a glass container with desiccant for 10 days. It was also found that after being negatively charged at room temperature and aged at 200-350 °C for several times, the SiO₂ films implanted by 150 keV Ar⁺ had a relatively high remnant potential and it did not decay significantly even after being heated at the aging temperature of 200-350 °C in room atmosphere for 60 min.     

Conductivity modification of ZnO film by low energy Fe ion implantation

In this paper we report the structural, optical and electrical behaviours of ZnO films implanted with 300 keV Fe¹⁰⁺ ions. From UV-vis spectroscopy it is observed that the band gap of the films decreases after implantation. Photoluminescence yield seems to increase in the implanted samples. From Hall measurements it is observed that the unimplanted sample shows n-type conductivity for the entire temperature range (100-300 K), whereas after implantation the samples show p-type conductivity for ≤200 K. The DC resistivity of the implanted samples is found to be lower than that of the unimplanted sample. We have found that the magnetoresistance of our samples is positive in the temperature range 200-300 K, but it becomes negative below 200 K.     

Processing for optically active erbium in silicon by film co-deposition and ion-beam mixing

Techniques of film deposition by co-evaporation, ion-beam assisted mixing, oxygen ion implantation, and thermal annealing were been combined in a novel way to study processing of erbium-in-silicon thin-film materials for optoelectronics applications. Structures with erbium concentrations above atomic solubility in silicon and below that of silicide compounds were prepared by vacuum co-evaporation from two elemental sources to deposit 200-270 nm films on crystalline silicon substrates. Ar⁺ ions were implanted at 300 keV. Oxygen was incorporated by O⁺-ion implantation at 130 keV. Samples were annealed at 600 °C in vacuum. Concentration profiles of the constituent elements were obtained by Rutherford backscattering spectrometry. Results show that diffusion induced by ion-beam mixing and activated by thermal annealing depends on the deposited Si-Er profile and reaction with implanted oxygen. Room temperature photoluminescence spectra show Er³⁺ transitions in a 1480-1550 nm band and integrated intensities that increase with the oxygen-to-erbium ratio.     

The study of ion mixed amorphous carbon films on single crystal silicon by C ion implantation

Amorphous-carbon (a-C) films were deposited on a single-crystal silicon substrate by vacuum vapor deposition system and these amorphous carbon films were implanted with 110 keV C⁺ at fluences of 1 × 10¹⁷ ions/cm². The effect of ion mixing on the surface morphology, friction behavior and adhesion strengths of amorphous carbon films was examined making use of atomic force microscopy (AFM), ball-on-disk reciprocating friction tester, nano-indentation system and scanning electron microscope (SEM). The changes in chemical composition and structure were investigated by using X-ray photoelectron spectroscopy (XPS). The results show that the anti-wear life and adhesion of amorphous carbon films on the Si substrates were significantly increased by C ion implantation. The SiC chemical bonding across the interface plays a key role in the increase of adhesion strength and the anti-wear life of amorphous carbon film. The friction and wear mechanisms of amorphous carbon film under dry friction condition were also discussed.     

Luminescence properties of Tb implanted ZnO

ZnO [0 0 0 1] crystals were irradiated at room temperature with Tb⁺ ions of 400 keV with fluences from 1×10¹⁶ to 2×10¹⁷ cm⁻². The implanted layer was examined by several methods, including radioluminescence (RL), Rutherford backscattering spectrometry (RBS) and optical spectroscopy. The optical extinction spectra were simulated using Mie scattering theory. Absorption spectra predicted by Mie theory for particles of decreasing diameter were compared with those obtained experimentally. Some qualitative agreement between theoretical and experimental data was achieved. It was also shown that the intensities of the characteristic green emission bands associated with Tb produced by ⁵D₄→⁷F_j=5,4 transitions have increased about 8 times after annealing. Optical spectroscopy and radioluminescence data have revealed that the ion implantation is a promising tool for synthesizing Tb nanoparticles in the ZnO surface. The Tb nanoparticles exhibit a rather weak plasma resonance.     

Effect of copper ions implantation on corrosion behavior of zircaloy-4 in 1 M H2SO4

In order to study the effect of copper ion implantation on the aqueous corrosion behavior, samples of zircaloy-4 were implanted with copper ions with fluences ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc source (MEVVA) operated at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircaloy-4 in a 1 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-4 implanted with copper ions when the fluence is smaller than 5 × 10¹⁶ ions/cm². The corrosion resistance of implanted samples declined with increasing the fluence. Finally, the mechanism of the corrosion behavior of copper-implanted zircaloy-4 was discussed.     

离子注入ZnO薄膜的拉曼光谱研究

室温下,用80 keV N⁺和400 keV Xe⁺离子注入ZnO薄膜,注入剂量分别为5.0×10¹⁴—1.0×10¹⁷/cm²和2.0×10¹⁴—5.0×10¹⁵/cm².利用拉曼散射技术对注入前后的ZnO薄膜进行光谱测量和分析,研究了样品的拉曼光谱随离子注入剂量的变化规律.实验结果发现,未进行离子注入的样品在99,435 cm<     

Iron nanoparticles in amorphous SiO<Subscript>2</Subscript>: X-ray emission and absorption spectra

The local structure of the chemical bond of iron ions implanted into SiO₂ glasses (implantation energy, 100 keV; fluence, 1 × 10¹⁶ cm^?2) is investigated using x-ray emission and absorption spectroscopy. The Fe L x-ray emission and absorption spectra are analyzed by comparing them with the corresponding spectra of reference samples. It is established that iron nanoparticles implanted into the SiO₂ vitreous matrix are in an oxidized state. The assumption is made that the most probable mechanism of transformation of iron nanoparticles into an oxidized state during implantation involves the breaking of Si-O-Si bonds with the formation of Si-Si and Fe-O bonds.