Direct Beam Deposition Research Articles

Ion beam-treated space polymers: long-term stability in GEO-simulated environments

As part of a large program conducted between years 2010 and 2018, a number of ion beam surface treatments and proprietary coatings formed on advanced space polymers by direct ion beam deposition were developed at Integrity Testing Laboratory (ITL) Inc, in Canada. This technology allowed producing surfaces with controlled surface resistivity in a wide range of charge dissipation values, with negligibly low additional RF losses and other important functional properties, that allowed using such treated materials and products in modern space antennae, solar arrays and other external applications on spacecrafts in GEO environment. This paper will present an overview of results achieved throughout the years on enhancement of radiation stability of space polymers that were ion beam treated and coated with special multifunctional thin coatings by direct ion beam deposition. The treated/coated subjects have been ground-based tested in a range of radiation conditions, simulating the GEO radiation environment, conducted in three world-recognized GEO simulation facilities.

Oxygen doping effect on wettability of diamond-like carbon films

DLC films were deposited on Ge substrates using direct ion beam deposition method, followed by investigating the influence of O2 doping on their morphological, electrical, and structural properties. The films were doped with oxygen under flow rates of 5, 10, 20, and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. The hydrophilicity of the layers was analyzed by the contact angle measuring experiment. The results showed that by increasing the O2 flow ratio from 5 to 40 sccm, the percentage of O2 increases from 1.1 to 3.9%. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°.

Direct ion-beam deposition of Ag nanoparticles using a solid-state silver ion source

Ion beam technology has shown itself worth to be an efficient method to produce nanoparticles embedded in dielectrics for photoelectronic devices. However, direct ion-beam deposition of nanoparticles (NPs) on the surface of dielectrics is rarely reported because the conventional metal ion source runs into difficulties to generate low energy (<10 keV) ion-beams. Herein, Ag NPs are directly deposited on the surface of Si substrates using the recently developed solid electrolyte ion source (SEIS), which possesses advantages of compactness, simple working conditions, and ability of emitting ion-beam at an energy of few keV. The composition, morphology and size of the synthesized Ag NPs are studied. Precise control of the NPs size including in-plane diameter and height is achieved by a modulation of the ion implantation dose. Localized maskless deposition of metal films on semiconductor surface is also expected using the SEIS device.

Modification of optical and mechanical properties of nitrogen doped diamond-like carbon layers

We have deposited diamond-like carbon (DLC) films on glass and Si substrates with direct ion beam deposition technique and investigated the effect of N2 doping on their structural, mechanical, and optical properties. The DLC coatings were doped with nitrogen under different flow rates of 5, 10, 20, 40, and 50 sccm. Morphological characteristics investigation of the prepared samples showed decrement in their average roughness from 4.1 to 0.68 nm. Raman studies showed that the number of graphitic sp2 bonding increased with N doping. By increasing the N2 content, the graphite cluster size increased. FTIR measurement revealed the functional groups available in the prepared samples. UV–Vis analysis showed that the optical transmission of nitrogen-doped DLC (N-DLC) coatings decreased when N2 content increased from 5 to 40 sccm followed by decrement in both the optical band gap and the internal stress. Finally, the mechanical properties such as hardness and elastic modulus decreased by increasing N2 content from 5 to 40 sccm.

Effect of ion energy on microstructure and adhesion of diamond-like carbon on Ti6Al4V by ion beam deposition

The microstructure and adhesion of diamond-like carbon (DLC) thin films on Ti6Al4V substrates were investigated using direct ion beam deposition with ion energy varying from 65eV to 90eV. The samples prepared were characterized by Raman spectroscopy, synchrotron near-edge X-ray absorption fine structure spectroscopy, scanning electron microscopy, and X-ray diffraction. Indentation testing by Vickers hardness tester was used for adhesion evaluation. The results show that the adhesion of DLC thin films on Ti6Al4V substrates mainly depends on ion energy used in the deposition process. Higher ion energy results in higher sp3 concentration in DLC thin films, which firstly increases then decreases the adhesion of DLC on Ti6Al4V substrate depending on the sp3 fractions and ion energy of 70eV provides the highest adhesion on both the bare and diamond nanoparticle coated Ti6Al4V.

Ultra-smooth diamond-like carbon coatings with high elasticity deposited at low temperature by direct ion beam deposition

Diamond-like carbon (DLC) coatings were fabricated under high vacuum at low temperature using a direct ion beam deposition technique based on a Penning ion source. Post-acceleration and electrostatic scanning were applied to form adhesive and laterally homogenous coatings across 50mm using ion energies from 3.0 to 10.5kV. The deposition rate was set to 0.4nms−1 to prevent heating of the coating and substrate. Structural, physical and chemical analyses revealed the formation of atomically flat hydrogenated amorphous carbon (a-C:H) coatings with a sp3 content of typically 20%. RBS measurements show that coatings produced at high acceleration voltage have impurities of carbon in the near-surface region of the silicon substrate as well as silicon impurities in the DLC coating at the interface. The penetration depth of the impurities is energy dependent. Nanoindentation measurements provided hardness figures of up to 18GPa combined with high elasticity values of 90%. Hardness and elasticity values and the sp3 content were measured to be proportional to the acceleration energy. An interface layer was observed with transmission electron microscopy indicating atomic interlocking between the carbon coating and the silicon substrate. The results highlight the opportunity to produce a-C:H coatings with high elasticity by direct ion deposition at low temperature.

Luminescence properties of thin nanocrystalline silicon-carbide films fabricated by direct-beam ion deposition

Nanocomposite films containing nanocrystals of silicon and silicon carbide are fabricated by direct ion-beam deposition onto silicon substrates. The films obtained are by Raman spectroscopy and the photoluminescence method. It is found that the samples under study exhibit two photoluminescence bands, in the “red” and near-infrared (IR) (600–1000 nm) and “blue” (400–550 nm) spectral ranges, which are accounted for by, respectively, the radiative recombination of excitons in silicon nanocrystals and radiative transitions between levels related to local centers (defects) on the surface of silicon nanocrystals and in the surrounding matrix. Short-duration treatment of the films in a solution based on hydrofluoric acid leads to modification of the emission spectrum and to an increase in the intensity of the exciton band due to the passivation of defects on the surface of silicon nanocrystals.

Robust plasmonic substrates

Robustness is a key issue for the applications of plasmonic substrates such as tip-enhanced Raman spectroscopy, surface-enhanced spectroscopies, enhanced optical biosensing, optical and optoelectronic plasmonic nanosensors and others. A novel approach for the fabrication of robust plasmonic substrates is presented, which relies on the coverage of gold nanostructures with diamond-like carbon (DLC) thin films of thicknesses 25, 55 and 105 nm. DLC thin films were grown by direct hydrocarbon ion beam deposition. In order to find the optimum balance between optical and mechanical properties of the considered robust plasmonic substrates, nanoindentation and wear resistance experiments as well as ablation experiment were performed. The mechanical properties of the layered substrates are tested via atomic force microscopy, evaluating spatially resolved threshold loads both for plastic deformation and breaking. DLC coating with thicknesses between 25 and 105 nm is found to considerably increase the mechanical strength of the substrates while at the same time ensuring conservation of sufficient field enhancements of the gold plasmonic substrates.

Polyvinylpyrrolidone surface modification with SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx films using Hall-type closed drift ion beam source

In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films.

Adhesion enhancement of diamond-like carbon thin films on Ti alloys by incorporation of nanodiamond particles

Coating adherent diamond-like carbon (DLC) thin films directly on Ti alloys is technologically difficult. This research incorporates nanodiamond particles to form a diamond/DLC composite interlayer to enhance the adhesion of DLC thin films on Ti6Al4V substrates. Initially, nanodiamond particles were deposited on Ti6Al4V substrates by microwave plasma enhanced chemical vapor deposition from a methane–hydrogen gas mixture. A DLC thin film was then deposited, on top of the nanodiamond particles, by direct ion beam deposition. Scanning electron microscopy, Atomic force microscopy, X-ray Diffraction and Raman spectroscopy were used to characterize the microstructure and chemical bonding of the deposited particles and films, and Rockwell indentation testing was used to evaluate the adhesion of the deposited films. The results indicate that the pre-deposited nanodiamond particles significantly enhance the interfacial adhesion between the DLC thin film and the Ti6Al4V substrate, possibly by enhanced interfacial bonding, mechanical interlocking, and stress relief.

Deposition of polycrystalline Si thin films on glass substrates by direct negative Si ion beam deposition

Polycrystalline Si (Poly-Si) thin films were deposited on a glass substrate by direct negative Si (Si −) ion beam deposition. The glass substrate temperature was kept constant at 500 °C for all depositions. Prior to deposition, the ion energy spread and ion-to-atom arrival ratio were evaluated as a function of the ion beam energy. The Si − ion energy spread was less than 10% regardless of the ion energy, while the ion-to-atom arrival ratio increased proportionally from 1.3 to 1.6 according to the ion beam energy. Atomic force microscopy images showed that a relatively rough surface was obtained at 50 eV of Si − ion energy and it is also concluded that the Si − ion beam irradiation at 50 eV is effective to deposit Si thin film with small grains as shown in Fig. 3.

Ion beam deposition of amorphous hydrogenated carbon films on amorphous silicon interlayer: Experiment and simulation

A thick layer of amorphous silicon (a-Si) was deposited on industrial grade crystalline n-Si < 111 > substrate by means of electron beam evaporation. On top of a-Si layer, amorphous hydrogenated carbon (a-C:H) film was grown by direct ion beam deposition from acetylene precursor gas. In order to study on atomic level the a-C:H film growth on amorphous silicon, a theoretical model was developed in a form of reaction rate (kinetic) equations. Numerical simulation using this model has revealed that the ratio of sp 3/sp 2 content in the film is heavily influenced by relaxation rate of the carbon atoms in a sub-surface region of the film that were activated by ion irradiation. The final structure of a-C:H film does not depend much on elemental composition and structure of amorphous Si coating, provided that deposition procedure is not terminated at its initial stage but continues for more than 60 s. It became evident, therefore, that the use of a-Si interlayer with a-C:H films could be particularly beneficial when a need arises to minimize or eliminate the effect of the substrate. As one of such cases, a poor adhesion of amorphous carbon on steel and other ferrous alloys could be mentioned.

Refractive index sensor based on the diamond like carbon diffraction grating

In this work we present an optical refractive index (RI) sensor based on the spectral analysis of anomalies in the optical response from the diffraction grating employing polarized polychromatic light. The sensor consists of holographic diffraction grating (period 423.5 nm) coated with a thin (110 nm) SiO x doped diamond like carbon film (DLC) that defines sensitivity of the sensor as well as the range of the spectral analysis. The deposition of the DLC film (synthesized by the direct ion beam deposition from the hydrocarbon source) has influence on the shape but not on the position of the anomalies observed in the specular reflection spectrum. From the reflection spectra the RI dispersion curve of liquid analyte–water was obtained.

Optical properties of diamond‐like carbon films irradiated by X‐ray photons

AbstractAmorphous diamond like carbon (DLC) films deposited at room temperature on quartz glass wafer by means of direct ion beam deposition method from acetylene gas or hexamethyldisiloxane (HMDSO) vapour mixture with hydrogen and nitrogen gas were irradiated by high energy X‐ray photon and the optical properties of irradiated DLC films were investigated. Ionizing radiation induced modification of optical properties of the DLC films of different type were studied using UV–VIS spectrometry, laser ellipsometry, Raman and IR spectroscopy, and interpreted on the basis of the obtained results. It was found, that the irradiation of amorphous hydrogenated DLC films introduced significant changes in the investigated structures; however the properties of SiOx containing DLC films remained almost stable after their exposure with high energy X‐ray photons. The influence of film deposition conditions and co‐doping on the optical properties of irradiated DLC films and the role of hydrogen in the films are discussed. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Radiation induced changes in amorphous hydrogenated DLC films

Amorphous hydrogenated diamond-like carbon (DLC) films synthesized at room temperature from acetylene gas on quartz glass wafers by means of the direct ion beam deposition method and irradiated with X-ray photons of different energy were investigated. Ionizing radiation induced changes of bonding structure in a-C:H films of different thickness and different density were studied using Raman and infrared spectroscopy and atomic force microscopy. Optical transmittance spectra of the DLC films in UV–vis range were measured as well. The influence of technological deposition characteristics on the optical properties of irradiated amorphous DLC films and the role of the hydrogen in the DLC films were estimated and discussed with the purpose to assess possible application of amorphous hydrogenated DLC films as the protective coatings in radiation detectors. All investigated DLC films showed some increasing tendency of the optical transmittance in the visible and infrared range after the irradiation. Low density PLCH films irradiated with high energy X-ray photons were highly transparent in the whole UV–vis range and indicated possible changes in the bonding structure of the irradiated samples, which have been discussed on the basis of the results obtained during this investigation.

Characterization of electrospray ion-beam-deposited CdSe/ZnS quantum dot thin films from a colloidal solution

Colloidal semiconductor quantum dot (QD) nanocrystals can be deposited in the form of inorganic thin films using the ion beam direct deposition method. To simultaneously preserve the nanocrystal configuration and remove the organics derived from the ligand and solvent, the authors used an electrospray technique and an ion beam technique. These techniques provided a soft-ionization process to obtain nanocrystalline ions and a collision process to attain a nonequilibrium state of the deposits, respectively. Because of the nature of the soft-ionization process, the electrospray phenomenon resulted in various forms of QD ions that depended on the preparation of the colloidal solution source and spraying conditions. The authors concentrated on finding operational conditions of the system that deposited thin films with reduced organics concentrations by examining the correlation between fast Fourier transform infrared absorption spectroscopy and photoluminescence intensity. The morphology of the deposited films was observed using an atomic force microscope.

Electrical properties of the diamond like carbon films irradiated with high energy photons

SiOx—containing amorphous diamond like carbon (DLC) is very attractive material for a number of practical applications. DLC films are possible candidates for the formation of passive layers in electronic devices and are used as protective coatings. Both applications are interesting for the construction of medical radiation detectors. Radiation induced structural changes and electrical properties of DLC: SiOx films (undoped and co-doped) synthesized at room temperature by means of direct ion beam deposition method were investigated after their irradiation with high energy (Emax = 15 MeV) X-ray photons. It was found that transparency of the irradiated DLC films was not changed significantly, as compared to initial samples, stating only small increase of the optical band gap in DLC films. However radiation induced changes were dependent on co-doping and film deposition conditions which were responsible for the sp3/sp2 ratio and hydrogen content in the investigated films. Analysis of U-I characteristics showed decreasing tendency of the leakage current in the range 0–20 V and especially high dependency of breakdown voltage on the deposited contact area in irradiated films as compared to initial samples. Possible mechanism of radiation induced changes in irradiated DLC films is discussed on the basis of the results of Raman and Infrared spectroscopy.

Hydrogen influence on the structure and properties of amorphous hydrogenated carbon films deposited by direct ion beam

The present work provides results for amorphous hydrogenated carbon (a-C:H) films grown by direct ion beam deposition method. Acetylene and its mixtures with hydrogen were used. The films were characterized by Rutherford backscattering spectrometry, elastic recoil detection, Raman spectroscopy, ellipsometry, infrared spectroscopy, and microhardness measurements. These techniques indicated that an admixture of hydrogen yields a lower deposition rate, a higher content of total and bounded hydrogen in the a-C:H films, and a lower film density. The optical and mechanical properties depend on both, hydrogen concentrations in the gas phase and in the films, and show a strong diamond-like component, which reaches maximum at 34 at.% of hydrogen. Further hydrogen dilution enhanced only sp 2 clustering and possible reduced a number of both sp 3 and C–C sp 3 bonds. We suppose that these effects (in the high hydrogen concentration range) are not only related to the ion irradiation difference between the light hydrogen and the much heavier carbon but also to the diffusion in the a-C:H films.

Graphitization of amorphous diamond-like carbon films by laser irradiation

Amorphous diamond-like hydrogenated carbon, or a-C:H, films were deposited on Si wafers by means of direct ion beam deposition from acetylene or from a gaseous mixture of acetylene and hydrogen. The samples were irradiated by the second harmonic (λ=532nm) of a Q-switched YAG:Nd laser. The effect of laser irradiation was studied with Raman and infrared spectroscopy and spectroscopic ellipsometry. Changes in the optical spectra of samples of various H content were investigated depending on laser intensity. Experimental data were interpreted taking into account the structural transformations of a-C:H films.

Hydrophobic properties of the ion beam deposited DLC films containing SiO x

Diamond like carbon (DLC) films received considerable interest due to outstanding mechanical and tribological properties as well as chemical inertness and hydrophobicity. That combination is particularly interesting for possible application of the DLC as anti-sticking layers in novel lithographic techniques such as nanoimprint lithography, because Si, quartz and Ni – the most often used materials for imprint stamp formation – have high surface energy and, as a result, bad anti-adhesive properties. In present study, SiO x containing DLC thin films were synthesized from hexamethyldisiloxane vapor and hydrogen gas mixture by direct ion beam deposition. Anti-sticking properties of the grown DLC thin films were evaluated measuring surface contact angle with water. Chemical composition and structure of the deposited films were investigated by X-ray photoelectron spectroscopy and FTIR spectrometry. Morphology of the films was measured by atomic force microscopy. Effects of hexamethyldisiloxane flux on structure, anti-sticking properties and surface morphology of the SiO x containing DLC thin films were defined.