Graphene synthesis by ion implantation

We demonstrate an ion implantation method for large-scale synthesis of high quality graphene films with controllable thickness. Thermally annealing polycrystalline nickel substrates that have been ion implanted with carbon atoms results in the surface growth of graphene films whose average thickness is controlled by implantation dose. The graphene film quality, as probed with Raman and electrical measurements, is comparable to previously reported synthesis methods. The implantation synthesis method can be generalized to a variety of metallic substrates and growth temperatures, since it does not require a decomposition of chemical precursors or a solvation of carbon into the substrate.     

Effect of ion irradiation on internal stress of amorphic carbon films produced by pulsed laser

Amorphic carbon films either 50 or 160 nm thick were deposited on Si(100) and glass substrates at room temperature in a high-vacuum environment using a Q-switched Nd-YAG pulse laser focused on a graphite target. These films were irradiated with Ti⁺ or C⁺ ions having kinetic energies of 35 and 75 keV, and the changes in internal stresses of the films with varying ion influence were investigated by measuring substrate bending using stylus profilometry. The ion energy and the film thickness were chosen such that the ion penetration depth, R_p, corresponded to either the film thickness or one half of the film thickness. The results indicate that there is an optimum ion fluence leading to a stress-free film for a given ion species and energy. Interpretation of the resulting stress behavior from ion irradiation was made based on the relaxation resulting from damage inside the film together with interfacial mixing. The scanning electron microscopy pictures and surface roughness measurements showed a very smooth surface for both as-deposited and ion-irradiated films. The ion-irradiated films had a Vickers hardness greater than 22 GPa, and were adherent to both Si and glass substrates. An investigation of the film characteristics using Raman scattering and electron-energy loss spectra has revealed that high-energy ion irradiation of an intermediate ion fluence can be utilized successfully to deposit an adherent and hard carbon film with controlled internal stress without changing the film structure significantly.     

Chemical surface treatment of silicone for inducing its bioactivity

It has been confirmed that the apatite nucleation is induced by silanol (Si–OH) groups formed on the surfaces of materials and/or silicate ions adsorbed on them.It was previously shown that apatite nuclei are formed on organic polymers when the polymers are placed on CaO, SiO2-based glass particles soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma, and that they grow spontaneously to form a dense and uniform apatite layer together with high adhesive strength to the substrates when the polymers are soaked in another solution with ion concentrations 1.5 times the SBF. In the present study, silanol groups bonded covalently to the surface of the silicone substrate were formed and its apatite-forming ability was examined. When silicone substrates were treated with 5 or 10 M NaOH with pH 7.25 at 36.5°C for more than 3 h, silanol groups were formed on the surfaces of the substrates. When thus NaOH-treated substrates were soaked in 1.5SBF at 36.5°C, a bone-like apatite was formed on the substrates in a short period. © 1998 Chapman & Hall.     

Metallization of polytetrafluoroethylene substrates by ion plating

The paper deals with the adhesion of copper films deposited using the ion plating technique onto polytetrafluoroethylene (PTFE) substrates. The substrates were biased by an r.f. voltage; copper was evaporated by electron bombardment. The results showed that careful sputter cleaning in an argon-oxygen (or helium- oxygen) mixture is essential to achieve good adhesion.Diagnostics by IR spectroscopy indicated that sputter cleaning in pure argon induced some damage at the substrate surface and that PTFE chains were broken. Microscopic inspection gave evidence that sputter cleaning in an argon-oxygen mixture increased the roughness of the substrate surface. Results of adhesion strength measurements for silver films on PTFE substrates after reactive sputter cleaning are presented and discussed. The formation of CuOCbonds at the interface is assumed to play an essential role.     

Study of the substrate treatment effect on initial growth of indium tin-oxide films on polymer substrate using in situ conductance measurement

Changes in the initial growth mode of ion beam sputtered indium tin oxide (ITO) films on polycarbonate (PC) substrates were investigated by an in situ measurement of electrical conductance. The PC substrates were irradiated with l keV Ar ions in an oxygen environment (ion assisted reaction: IAR), prior to the film deposition for changing the surface energy. The electrical conduction modes in ITO films were discussed in terms of the film thickness and the surface energy of PC substrates. It was found that, in the initial part of the film growth, ITO nucleation density increased with the increase of the surface energy of PC. The change of the growth mode was discussed in both viewpoints of thermodynamics and atomic kinetics theories and verified by AFM (atomic force microscope) observations. Thermal stability of ITO films was investigated to observe the effect of the growth mode change by IAR pre-treatment of polymer substrate.     

Modification of the shape of large germanium nanoislands on silicon surface by low-energy ion bombardment

Germanium nanoislands on silicon substrates were irradiated by hydrogen and argon ions with energies below 350 eV. In the initial stage, ion bombardment leads to the division of large islands into several small islands irrespective of the ion type. The resulting surface is more homogeneous than the initial and is stable with respect to further ion irradiation.     

Surface modification of poly(ethylene terephthalate) polymeric films for flexible electronics applications

The production of Flexible Electronic Devices (FEDs) by roll-to-roll large-scale manufacturing processes is a rapidly growing sector and the development of functional (inorganic and/or organic) thin layers onto flexible polymeric substrates represents one of the key issues for the low cost production of FEDs. However, the flexible substrates should meet advanced demands, as high optical transparency, high barrier properties and increased adhesion of the subsequent functional layers, which will have a major affect on their performance, efficiency and lifetime. Plasma treatment can be successfully employed for the improvement of the bonding structure and surface properties of flexible polymeric substrates. In this work, we report on the effect of Pulsed DC N⁺ ion bombardment using different ion energies, on the bonding structure, electronic and optical properties and surface nanotopography of Poly(Ethylene Terephthalate) (PET) substrates. For the investigation of the optical properties, we have used in-situ and real-time Spectroscopic Ellipsometry from the IR to Vis-farUV spectral region, in combination to advanced modeling procedures, whereas Atomic Force Microscopy has been employed for surface nanotopography investigation. As it has been found, the N⁺ bombardment leads to the appearance of new chemical bonds (C-N or C-O bonds in Φ-NH₂, Φ-NHR, C(O)-NHR, Φ-OH, or (CO)-OH), as well as partial disappearing of the C-O bond of ester group, on a surface layer of PET.     

The effects of pre-implantation of steel substrates on the structural properties of TiN coatings

We have studied the effects of nitrogen pre-implantation of AISI C1045 steel substrates on the microstructure and microhardness of deposited TiN coatings. The substrates were implanted at 40 keV, to the fluences from 5 × 10¹⁶ to 5 × 10¹⁷ ions/cm², which was followed by deposition of 1.3-μm thick TiN coatings by reactive sputtering. Structural characterization of the samples was performed by standard and grazing incidence X-ray diffraction analysis, Rutherford backscattering spectroscopy and transmission electron microscopy. Microhardness was measured by the Vicker’s method. Nitrogen implantation up to 2 × 10¹⁷ ions/cm² induces the formation of Fe₂N phase in the near surface region of the substrates, which becomes more pronounced for higher fluences. Microstructure of the deposited TiN coatings shows a strong dependence on ion beam pre-treatment of the substrates. The layers grown on non-implanted substrates have a (200) TiN preferential orientation, and those grown on implanted substrates have (111) TiN preferential orientation. The change in preferred orientation of the layers is assigned to a developed surface topography of the substrates induced by ion implantation, and possible effects of distorted and altered crystalline structure at the surface. Ion implantation and deposition of TiN coatings induce an increase of microhardness of this low performance steel for more than eight times.     

Experimental factors controlling analyte ion generation in laser desorption/ionization mass spectrometry on porous silicon

Desorption/ionization on porous silicon (DIOS) is a relatively new laser desorption/ionization technique for the direct mass spectrometric analysis of a wide variety of samples without the requirement of a matrix. Porous silicon substrates were fabricated using the recently developed nonelectrochemical H2O2-metal-HF etching as a versatile platform for investigating the effects of morphology and physical properties of porous silicon on DIOS-MS performance. In addition, laser wavelength, mode of ion detection, pH, and solvent contributions to the desorption/ionization process were studied. Other porous substrates such as GaAs and GaN, with similar surface characteristics but differing in thermal and optical properties from porous silicon, allowed the roles of surface area, optical absorption, and thermal conductivities in the desorption/ionization process to be investigated. Among the porous semiconductors studied, only porous silicon has the combination of large surface area, optical absorption, and thermal conductivity required for efficient analyte ion generation under the conditions studied. In addition to these substrate-related factors, surface wetting, determined by the interaction of deposition solvent with the surface, and charge state of the peptide were found to be important in determining ion generation efficiency.     

Inhomogeneous character of the initial stage of ion beam deposition of ultrathin gold films

Gold films with thicknesses ranging from below 1 nm to 3 nm have been simultaneously deposited by the ion beam sputter technique onto the surface of glass substrates smooth on a subnanometer level and onto Si(001) substrates with nanodimensional inhomogeneities in the form of germanium atomic islands. Irrespective of the substrate surface nature, gold deposition initially leads to the formation of a stable layer with a thickness of several atomic monolayers. The gold films with thicknesses above 2 nm are continuous and homogeneous. Terminated in an intermediate stage, the sputter deposition of gold may result in the formation of an inhomogeneous layer of the island type. The results are interpreted taking into account the well-known fact that a high-energy component is present in the flux of the ion beam sputtered target material.     

Alignment of Semiconductor Nanowires Using Ion Beams

Gallium arsenide nanowires are grown on 〈100〉 GaAs substrates, adopting the epitaxial relation and thus growing with an angle around 35° off the substrate surface. These straight nanowires are irradiated with different kinds of energetic ions. Depending on the ion species and energy, downwards or upwards bending of the nanowires is observed to increase with ion fluence. In the case of upwards bending, the nanowires can be aligned towards the ion beam direction at high fluences. Defect formation (vacancies and interstitials) within the implantation cascade is identified as the key mechanism for bending. Monte Carlo simulations of the implantation are presented to substantiate the results.     

Effect of ion bombardment on the initial stages of thin film growth

The influence of ion bombardment on the initial stages of silver deposition onto amorphous substrates was investigated. Pronounced adatom-depleted zones arise around larger crystallites, and coalescence begins earlier in the deposition process. A defined crystal orientation appears from the beginning of the condensation. The results are explained using the assumption of enhanced surface mobilities of both adatoms and crystallites. The possibility of application of ion bombardment for surface decoration is qualitatively investigates and discussed.     

Temperature behaviour of the substrate surface during growth of nanocrystalline silicon carbide films by deposition of 120 eV carbon and silicon ions

Changes in the temperature of nanocrystalline SiC film surface were measured during film growth by direct deposition of carbon and silicon ions onto substrates at ∼800 °С. It has been found that the initial stage of the film growth is characterized by uncontrolled variations of the surface temperature, which are observed for constant values of the deposition parameters. The energy components of the temperature balance on the film surface during its growth under conditions of direct ion deposition are analyzed. It is shown that magnitudes of temperature variations depend on the energy and current density of the deposited ions and on the ratio of the emissivity coefficients of the substrate material and silicon carbide. If this ratio is 1:6, the temperature rise at the initial growth stage reaches 160 °С when using 120 eV ion energy. For ion deposition onto silicon carbide substrates these uncontrolled temperature deviations at the initial stage of film growth were not observed.     

Low energy Ar+ ion beam irradiation effects on Si ripple pattern

Etching of surfaces by ion beam sputtering is widely used to pattern surfaces. Recent studies using the high-spatial-resolution capability of the scanning tunneling microscope, atomic force microscope and SEM (Scanning Electron Microscopy) disclose in fact that ion bombardment creates repetitive structures at micro-nanometre scale, waves (ripples), checkerboards or pyramids. The phenomenon is related to the interaction between ion erosion and diffusion of adatoms (vacancies), which causes surface re-organization. In this paper we investigated the ripple pattern formation on Si substrates by low energy Ar+ ion bombardment and the dose effect on ripple size. We also briefly discussed the irradiation effects (at normal incidence) on ripple pattern for different irradiation time. Finally, based on Bradley and Harper (BH) theory we proposed a model to understand the mechanism of ripple pattern change due to Ar+ ion beam irradiation.     

Application of high-density plasma to sputtering and reactive sputtering processes

An investigation of thin-film preparation processes by sputtering technique has been carried out utilizing the high-density plasma induced by the microwave power coupled in the surface wave mode. The high sputtering rate arising from the high ion current to the target is expected to be advantageous for processes of nitride surface and compounds. An independent control of the external bias potential to the target and of the gas mixture ratio is demonstrated to be possible by the mode-locking mechanism. Ferromagnetic films of FeNi alloy were deposited on glass substrates. Films of TiN and of AlN were produced on plastic substrates and on glasses.     

Fabrication of discrete gallium nanoislands on the surface of a Si(001) substrate using a focused ion beam

A gallium focused ion beam (FIB) has been used to implant Ga at specific sites on the surface of undoped Si(001) substrates. Upon annealing at 600?°C, discrete nanoscale surface islands form within the FIB patterned regions when the total Ga ion dose, or fluence, is greater than 1.0 × 10(16) ions cm( - 2). The number of islands depends on the size of the irradiated region and a single island can be achieved for a FIB milled region that is 100 nm × 100 nm. The average sizes of the islands were found to range from 24.5 nm when exposed to a total ion dose of 1.2 × 10(16) ions cm( - 2) to 45 nm for a dose of 3.0 × 10(16) ions cm( - 2). We have confirmed that these surface islands are metallic Ga by performing a selective chemical etch that removes the islands and by transmission electron microscopy characterization. These patterned Ga surface templates could serve as nucleation sites for the lateral arrangement of discrete quantum dot structures.     

Microstructure of interface for high-adhesion DLC film on metal substrates by plasma-based ion implantation

The diamond-like carbon (DLC) film was prepared on various metal substrates with a plasma-based ion implantation and deposition using superimposed RF and negative high-voltage pulses. The adhesion strength of DLC film was enhanced above the epoxy resin strength by implantation of carbon ions or mixed ions of carbon and silicon to the substrate surface before DLC deposition. In order to clarify the mechanism for improvement in adhesive strength, the microstructure of an interface between DLC film and substrate was examined in detail by transmission electron microscopy (TEM) observations in combination with EDS analysis. As a result, the enhancement in adhesion strength of DLC film by C ion implantation resulted from the formation of amorphous-like phase in the ion-implanted region of substrate, the production of carbon-component graded interface, the destruction of the oxide layer on the top surface of substrate, and the reduction of residual stress in DLC film by ion implantation during the deposition. The production of stress-free DLC film allowed us to demonstrate a supra-thick DLC film of more than 400 μm in thickness.     

Nitrogen beam bombardment induce polarity of carbon nanotubes

The multiwalled carbon nanotubes (MWCNTs) were prepared on SiO₂ substrates using chemical vapor deposition (CVD). N ion beam bombardment to MWCNTs was performed at different beam currents of 5–15 mA in an ion-beam-assisted deposition (IBAD) system. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) proved no significant crack and surface morphological change for MWCNTs after N ion beam bombardment. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometry (FTIR), and Raman studies indicated that higher N ion beam current (15 mA) or N atomic concentration (8.6%) induced formation of polar N-containing functional groups of N–C and N–H bonds on the surfaces of MWCNTs. The content of N–C and N–H bonds increased with N ion beam current.     

溅射与沉积过程的计算机模拟

应用TRIM和TRIDYN程序模拟氮化硼材料的溅射率与Ar 入射角的关系，Ar 辅助沉积氮化础薄膜与硅基片的界面结构，铜基片溅射率与入射能量的关系，以及Ar 以垂直于表面方向轰击非晶硅产生的溅射速率。铜基片溅射率的计算结果与已有的实验数据相比较表明，两者吻合得很好。硅片的溅射速率与应用38－cm宽束离子源设备的实验结果之间也吻合比较好。     

Effects of metal nanoparticles on the secondary ion yields of a model alkane molecule upon atomic and polyatomic projectiles in secondary ion mass spectrometry

A model alkane molecule, triacontane, is used to assess the effects of condensed gold and silver nanoparticles on the molecular ion yields upon atomic (Ga(+) and In(+)) and polyatomic (C60(+) and Bi3(+)) ion bombardment in metal-assisted secondary ion mass spectrometry (MetA-SIMS). Molecular films spin-coated on silicon were metallized using a sputter-coater system, in order to deposit controlled quantities of gold and silver on the surface (from 0 to 15 nm equivalent thickness). The effects of gold and silver islets condensed on triacontane are also compared to the situation of thin triacontane overlayers on metallic substrates (gold and silver). The results focus primarily on the measured yields of quasi-molecular ions, such as (M - H)(+) and (2M - 2H)(+), and metal-cationized molecules, such as (M + Au)(+) and (M + Ag)(+), as a function of the quantity of metal on the surface. They confirm the absence of a simple rule to explain the secondary ion yield improvement in MetA-SIMS. The behavior is strongly dependent on the specific projectile/metal couple used for the experiment. Under atomic bombardment (Ga(+), In(+)), the characteristic ion yields an increase with the gold dose up to approximately 6 nm equivalent thickness. The yield enhancement factor between gold-metallized and pristine samples can be as large as approximately 70 (for (M - H)(+) under Ga(+) bombardment; 10 nm of Au). In contrast, with cluster projectiles such as Bi3(+) and C60(+), the presence of gold and silver leads to a dramatic molecular ion yield decrease. Cluster projectiles prove to be beneficial for triacontane overlayers spin-coated on silicon or metal substrates (Au, Ag) but not in the situation of MetA-SIMS. The fundamental difference of behavior between atomic and cluster primary ions is tentatively explained by arguments involving the different energy deposition mechanisms of these projectiles. Our results also show that Au and Ag nanoparticles do not induce the same behavior in MetA-SIMS of triacontane. The microstructures of the metallized layers are also different. While metallic substrates provide higher yields than metal islet overlayers in the case of silver, whatever the projectile used, the situation is reversed with gold.