Ion Beam Assisted Sputter Deposition Research Articles

Structural and dielectric properties of ion beam deposited titanium oxynitride thin films

Titanium oxynitride ( $${\hbox {TiO}}_{x}{\hbox {N}}_{y}$$ ) thin films were fabricated by ion beam-assisted sputtering deposition. Effects of oxygen contribution, assisting ion energy ( $$E_{\mathrm{a}}$$ ), assisting ion beam current ( $$I_{\mathrm{a}}$$ ) on the microstructure and dielectric behavior of the films were analyzed. The results show that increasing O content made the films to turn from fcc-TiN (111)-oriented to fcc $${\hbox {TiO}}_{x}{{\hbox {N}}}_{y}$$ (220)-oriented. Proper $$E_{\mathrm{a}}$$ and low $$I_{\mathrm{a}}$$ can enhance the (220) orientation in $${\hbox {TiO}}_{x}{{\hbox {N}}}_{y}$$ thin films. The increase in oxygen content leads to the red-shift of plasmonic resonant frequency and makes the films more dielectric. Higher $$E_{\mathrm{a}}$$ and $$I_{\mathrm{a}}$$ make the $${\hbox {TiO}}_{x}{{\hbox {N}}}_{y}$$ films more metallic. Atomic composition is an important factor underlying the results. The study provides a method to control the plasmonic properties of oxynitride films in a wide range by atomic composition and assisting ions.

Effects of sputtering and assisting ions on the orientation of titanium nitride films fabricated by ion beam assisted sputtering deposition from metal target

Ion beam assisted titanium nitride (TiN) film has attracted much attention because its fast texture and high conductivity can be effectively applied in all-conductive superconducting coated conductor. In this work, TiN films were prepared by ion beam sputtering deposition from a metal titanium target. Effects of sputtering ion energy, assisting ion energy, assisting ion current and deposition temperature on the orientation and surface morphology were analyzed. The results indicate that assisting ion is an important factor in orientation selection, and high assisting ions and low assisting ion current could enhance the crystallinity. However, too high assisting ion energy and current can destroy the crystallinity in IBAD–TiN. This orientation selection can be attributed to the energy exchange between assisting ions and adatoms.

Ferroelectric polarization and resistive switching characteristics of ion beam assisted sputter deposited BaTiO3 thin films

In this work, 150nm thick polycrystalline BaTiO3 (BTO) films were deposited on Pt/TiO2/SiO2/Si substrate by ion beam assisted sputter deposition technique. The bias voltage dependent resistive switching (RS) and ferroelectric polarization characteristics of Au/BTO/Pt devices are investigated. The devices display the stable bipolar RS characteristics without an initial electroforming process. Fittings to current–voltage (I–V) curves suggest that low and high resistance states are governed, respectively, by filamentary model and trap controlled space charge limited conduction mechanism, where the oxygen vacancies act as traps. Presence of oxygen vacancies is evidenced from the photoluminescence spectrum. The devices also display P–V loops with remnant polarization (Pr) of 5.7μC/cm2 and a coercive electric field (Ec) of 173.0kV/cm. The coupling between the ferroelectric polarization and RS effect in BTO films is demonstrated.

Ion beam assisted sputter deposition of ZnO for silicon thin-film solar cells

Ion beam assisted deposition (IBAD) is a promising technique for improving the material quality of ZnO-based thin films. The operation of an auxiliary Ar+ ion source during deposition of ZnO : Ga thin films by dc magnetron sputtering led to an improvement in crystalline texture, especially at low temperatures due to momentum transfer from the ions to the growing film. Etching of IBAD-ZnO : Ga films in diluted HCl revealed crater-like surface structures with crater diameters of up to 600 nm. These structures are usually achieved after deposition at high substrate temperatures. This is an indication that the grain structure was remarkably changed by bombarding these films during deposition in terms of increasing the compactness of the ZnO : Ga films. Subsequent annealing procedures led to an improvement in the electrical and optical properties. Hydrogenated microcrystalline silicon (µc-Si : H) solar cells exhibited enhanced efficiency as compared to cells on other low-temperature sputtered reference ZnO films. This improvement was ascribed to light trapping by the modified etching behaviour of the IBAD-ZnO : Ga films as well as improved transparency after the vacuum annealing step.

Mechanical properties and thermal stability of SiBCN films prepared by ion beam assisted sputter deposition

The high hardness, exceptional high temperature stability, and oxidation resistance of bulk Si–B–C–N ceramics have led to the expectation that these materials will be good candidates for superior coating materials in high-temperature applications. In this study, SiBCN films were prepared using ion beam assisted sputter (IBAS) deposition, and the mechanical properties and thermal stabilities of the films at 600, 700, and 800°C in air were investigated. In particular, the effects of the ion beam assist on the properties of the SiBCN films were examined. The SiBCN films were deposited on Si plates by sputtering a target composed of Si+BN+C using a 2-keV Ar+ ion beam. A low-energy N2+ and Ar+ mixed ion beam irradiated the samples during the sputter deposition. The Si content in the SiBCN films was controlled by changing the Si/(BN+C) ratio of the target. BCN films were also deposited for comparison. The composition and chemical bonding structure of the prepared films were investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that c-BN bonds were formed in the ion-assisted BCN film. The oxide layer thickness on the SiBCN films after thermal annealing decreased due to the IBAS deposition and an increase in the Si content. Ion-assisted SiBCN films annealed at 800°C showed the highest hardness of 20GPa.

Effect of low energy ion bombardment on structure and photoluminescence characterization of Al-doped ZnO thin films

Al-doped zinc oxide (AZO) films are prepared by dual ion-beam assisted sputter deposition at room temperature. An assisting argon ion beam (ion energy Ei=0–300eV) directly bombards the substrate surface to modify the properties of the AZO films. The effects of assisting ion beam energy on the characteristics of AZO films were investigated based on transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and photoluminescence measurement. With increasing assisting ion beam bombardment, the crystalline quality of the AZO films was improved and the oxygen vacancies were increased observably. Two red emissions originating from the oxygen vacancies in the films appear at 1.71 and 1.64eV. This study suggests that wide-band-gap materials could act as effective visible light emitters and ion beam bombardment provides a simple route to synthesize such materials.

An orientation competition in yttria-stabilized zirconia thin films fabricated by ion beam assisted sputtering deposition

A previously found orientation competition in ion beam sputtered yttria-stabilized zirconia thin films was studied in detail. The effects of sputtering energy and deposition angle were analyzed in ion sputtered films without assisting ions bombardment. It is found that for normally deposited films, (001) and (011) orientations are favored at low and high sputtering energy respectively. For inclined substrate deposited films, as deposition angle increases, (001), (011) and (111) orientations are advantaged in turn. The results can be attributed to the in-plane energy exchange of deposition atom and adatoms. In ion beam assisting deposited YSZ films of low assisting ions energy and current, a (001) oriented biaxial texture is gradually induced as ion energy increased. In the case of ion beam assisted inclined deposition of 45°, (001) orientation is enhanced and two preferential in-plane orientations are found coexist.

Highly textured zinc oxide films by room temperature ion beam assisted deposition

AbstractA new ion beam assisted sputter deposition technique has been developed which facilitates room temperature fabrication of thin ZnO films with exceptional structural order. The well‐defined texture of these films is comparable to films deposited at elevated temperatures of typically 200–300 °C in standard sputter processes. Structural investigations reveal that the applied Xe+ ion bombardment mainly affects the nucleation of ZnO crystallites. The high structural order of the nucleation layer is maintained in subsequent stages of film growth. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation of nanocomposite thin films by ion beam and plasma based sputtering processes

Experimental results on nanocomposite TiN/Cu and TiN/Si thin films by ion beam and plasma based sputtering processes are presented in this paper. Films were deposited on silicon (1 0 0) wafers not only by ion beam assisted sputtering deposition, in which the sputtered Ti and Cu and/or Si were deposited with simultaneous bombardment of nitrogen ions with different ion density, but also by d.c. magnetron co-sputtering of two pure elemental targets, where the substrate was negatively or positively biased. From TEM and XRD analyses it was verified that in both cases of nanocomposite formation TiN was composed of nanocrystallite of approximately 20–30 nm. The maximum hardness reached a value higher than 40 GPa in both cases. Hardness enhancement was observed in these TiN/Cu films with pronounced TiN (1 1 1) orientation and without diffraction peaks of crystal Cu in their X-ray diffractograms. However, the hardest TiN/Si film revealed randomly oriented TiN crystallites. The XPS spectra of Si 2p indicate that the Si atoms are mainly in Si 3N 4 form.

Characterization of calcium phosphate bioceramic films using ion beam analysis techniques

The analytical techniques using ion beams are powerful tools for surface analysis of solid materials. Constituent elements are important in determining the biocompatibility and corrosion resistance of a biomaterial implant. The focus of this article is on the application of ion beam analysis towards quantifying the composition of calcium phosphate based biomaterials. Thin films of calcium phosphate bioceramics were prepared on Si and Ti substrates using ion beam sputter deposition (IBSD) and ion beam assisted sputter deposition (IBASD) methods. Precise amounts of calcium, phosphorus, oxygen and hydrogen in these thin films are determined by combining four ion beam analysis techniques. The simultaneous application of proton induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) were utilized to quantify composition and amounts of elements heavier than helium. Elastic recoil detection analysis (ERDA) was used to determine hydrogen content while resonance-enhanced RBS (RE-RBS) was utilized to measure oxygen concentration. The amount of assisting ion beam current density during deposition affected the concentration ratios of Ca, O and H to P. Combination of different ion beam analysis methods is useful in characterizing the elemental composition and distribution of composite biomaterials.

Improved anti-wear performance of nanostructured titanium boron nitride coatings

Titanium boron nitride coatings were synthesized by ion beam assisted sputter deposition. Structural analysis showed that the coatings had a composite structure comprising nanosized TiB 2/TiN crystallites and a thin layer matrix of hexagonal BN. Although, the hardness of these Ti–B–N coatings was generally lower than that of pure TiB 2, improved anti-wear performance was observed. This improvement is explained by the beneficial configuration of hard nanoparticles embedded in a soft lubricating matrix, which increases the coating’s capability to dissipate stress without brittle fracture. Effects of process parameters, such as bombarding energy and nitrogen flow rate were also thoroughly studied.

Structure refinement and hardness enhancement of titanium nitride films by addition of copper

Titanium nitride films with a low added copper content were synthesized by ion beam-assisted sputtering deposition. The role of copper was examined with regard to the structure, hardness and elastic/plastic deformation capacity of the composite films produced. It was found that copper had significant modifying effects on the structure and property of titanium nitride films. When a very low content of Cu (<2 at.%) was added, the film showed apparent hardness enhancement. Films with low content of Cu also displayed highly elastic characteristics (91% elastic recovery under nanoindentation). On the contrary, films with >2 at.% copper were comparatively soft, up to 53% of the deformation under indentation could be plastic in this case. In addition, copper additions could also be used to tune the grain size of TiN in the range of 25–5 nm, at the same time causing a transition from a strong (111) preferred orientation to random polycrystalline morphology.

Structural response and stress release of hexagonal and cubic boron nitride films due to the bombardment with 170-MeV iodine ions

Abstract To investigate the stability of the cubic (c-) and the hexagonal (h-) phase of boron nitride (BN) against radiation damage induced predominantly by electronic energy loss processes of high energy density (typical value 25 keV nm−1), thin films prepared by ion-beam-assisted sputter deposition (IBAD) were irradiated at room temperature with 170-MeV iodine ions. Though the average sample stoichiometry, as continuously monitored during the irradiation by elastic recoil detection (ERD), remains unchanged in both cases, Fourier transform infra-red (FTIR) spectra as well as reflection electron energy loss spectra (REELS) taken before and after each irradiation step clearly demonstrate that c-BN is converted to h-BN, even by small ion fluences, while h-BN remains stable. Additionally, interferometric measurements indicate a dramatic stress release for both, h-BN and c-BN starting structures. In all cases, a pronounced volume expansion of the samples perpendicular to the beam direction is observed maintaining a constant mass area density as again monitored by ERD. Atomic force microscopy (AFM) on bombarded samples reveals characteristic surface features on different length scales, which can be interpreted as being due to stress release and ion track formation. These results are consistent with h-BN being the stable high-temperature phase under relaxed pressure conditions.

Electron energy loss spectroscopy—An additional tool to characterize thin films of cubic boron nitride

Applying Reflection Electron Energy Loss Spectroscopy (REELS) to boron nitride (BN) films in principle should allow us to distinguish between different crystal structures, i.e. between the cubic (c-) and the hexagonal (h-) phase, respectively. This possibility results from the fact that the two phases exhibit well separated plasmon loss lines. In practice, however, largely varying line positions are reported in the literature for these plasmon losses leading to contradictory conclusions on the reliability of the REELS method. It is the aim of the present contribution to resolve the above inconsistencies and to demonstrate that REELS can reliably be used to characterize c-BN films if the sampling depth of the spectroscopy is properly adjusted via the energy of the primary electron beam. For this purpose, BN films with various contents of the cubic phase (0–95%) as determined by infra-red (IR)-spectroscopy have been prepared by ion beam assisted sputter deposition onto Si (100) substrates. The as-prepared films were analyzed in situ by REELS followed by ion irradiation (3 keV Ar + ) to investigate the influence of the sputter cleaning process frequently applied to ex situ prepared samples prior to spectroscopic measurements. As the main result, an h-BN-like surface layer on top of the c-BN phase can clearly be identified for the as-prepared samples, yielding a thickness of this top layer of approx. 0.5 nm. In addition, it will be shown that the plasmon loss line of c-BN is continuously shifted towards the corresponding line of h-BN by introducing lattice defects as produced by, e.g. Ar + ion bombardment, offering a simple explanation for the variety of spectroscopic results found for sputter-cleaned ex situ prepared specimens.

Phase stability and stress relaxation effects of cubic boron nitride thin films under 350 keV ion irradiation

Abstract To investigate the effect of radiation damage on the stability and the compressive stress of cubic boron nitride (c-BN) films, samples either prepared by r.f. magnetron sputtering or ion beam-assisted sputter deposition (IBAD) were irradiated at room temperature with 350 keV inert ions (Kr + ). FTIR spectra taken before and after each irradiation step clearly demonstrate that c-BN is stable under this medium energy bombardment. Furthermore, additional AES measurements show that the average film stoichiometry is not affected by the ion fluences used in the present experiments. While the observed broadening of the different lines in the IR spectra with increasing ion fluences points to a build-up of disorder and/or a decreasing average grain size due to the bombardment, the additionally found significant shift of the line related to the c-BN TO-mode towards smaller wave numbers, indicates a strong relief of the compressive stress present in the as-prepared films. This irradiation-induced stress relief could be independently confirmed by profilometer measurements yielding post-bombardment values of 5.1 GPa as compared to 20.5 GPa before irradiation.

Bone apposition along thin Ca-P composite films prepared by the ion-beam assisted sputter deposition method

Bone apposition along thin Ca-P composite films prepared by the ion-beam assisted sputter deposition method

Growth and characterization of Ta 2O 5 thin films on Si by ion beam sputter deposition

The original chemical state of Ta 2O 5 thin films grown by reactive ion-beam-sputter deposition (RSD) and ion-beam-assisted sputter deposition (IBAD) was XPS-sputter-depth profiled using a 3 keV oxygen ion beam of 30° incidence angle. The metallic Ta component found at the Ta 2O 5/Si interface of the film grown using the RSD method was not found at the interface of the film grown using the IBAD method. The same results were observed using the in situ XPS analysis for the initial stage of the thin film growth. The difference in the chemical state and the thickness of the interfacial SiO 2 layer of the thin films grown by the 2 processes could be related to the reactivity of the silicon surface. In the case of the IBAD process, the silicon surface was depassivated in the initial film growth stage by oxygen-ion-beam sputtering of hydrogen atoms.

Characterization of thin films for biomaterial applications using PIXE and RBS

In this paper, the results of applying Proton Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectroscopy (RBS) in order to determine the compositions of TiO 2 thin films prepared by Ion Beam Assisted Sputter Deposition (IBASD), are presented. The PIXE analysis of the oxide films determined, with high precision, the incorporation of impurities and the variation of the ratio of the constituent elements, possible as a result of preferential sputtering, due to ion beam irradiation. The results of the present investigation showed that the PIXE analysis combined with RBS can be effectively used for qualitative and quantitative analysis of thin film on the surface and in the film-substrate interface.

The Deposition of Cubic Boron Nitride Fillms by Ion Beam Assisted Sputter Deposition

Abstract The relationship between film properties and assisting ion beam parameters such as the ion-to-atom arrival ratio, the mean energy transfer or the mean momentum transfer to a depositing atom has been established with a new method. We have made use of a focused assisting ion beam which generates zones of locally varying current densities on the film surface. By mapping these and the deposition rate, and measuring film properties as function of surface coordinates, we can determine their relationship from few samples. The: advantage is that the number of deposition runs can considerably be reduced, and errors can be avoided which may originate from slightly different deposition conditions (pressure, temperature, gas flow etc.) in different deposition runs. This method has been applied to establish the relationship between the cubic phase formation of a boron nitride film and various assisting beam parameters. The BN films were characterized by transmission FTIR spectroscopy. The spectra were evaluat...

Hardness and elasticity of diamond-like carbon films prepared by ion-beam assisted sputter deposition

Hardness H and Young's modulus Y of non-hydrogenated amorphous carbon (a-C) films have been determined by an ultra-low-load depth-sensing nanoindenter to examine their dependence on the energy and momentum transferred to a depositing carbon atom by an assisting argon-ion beam. The results indicate that the film formation process is momentum-transfer controlled. Amorphous carbon films were prepared and analyzed by a new procedure: the ion-beam sputter-deposited film was asisted by a focused argon-ion beam. This method produces a film with a high central zone and progressively decreasing zones of energy and momentum transfer. By measuring H and Y in these different regions, a large data set was obtained from just one film. From the analysis of two films which were prepared at different assisting ion-beam voltages of 100 and 300 V, it was found that H and Y display a uniform functional dependence only if plotted vs. momentum transfer.