Ion Beam Sputtering Deposition Technique Research Articles

Application the Ion Beam Sputtering Deposition Technique for the Development of Spin-Wave Structures on Ferroelectric Substrates

The microwave properties of structures in the form of the 2 μm iron-yttrium garnet (YIG) films, grown by the ion beam sputtering deposition method on epitaxially mismatched substrates of ferroelectric ceramics based on lead zirconate titanate (PZT, PbZr0.45Ti0.55O3), are discussed. The obtained structures were formed and pre-smoothed by the ion beam planarization substrates with the use of an anti-diffusion layer of titanium dioxide TiO2. The atomic force microscopy showed that the planarization of the substrates allows for reaching a nanoscale level of roughness (up to 10 nm). The presence of smooth plane–parallel interfaces of YIG/TiO2 and TiO2/PZT is evidenced by scanning electron microscopy performed in focused gallium ion beams. Ferromagnetic resonance spectroscopy revealed a broadening in the absorption line of the ferrite garnet layers in the resonance ≈ 100 Oe. This broadening is associated with the presence of defects caused by the of the ceramic substrate non-ideality. The estimated damping coefficient of spin waves turned out to be ~10−3, which is two orders of magnitude higher than in an ideal YIG single crystal. The YIG/TiO2/PZT structures obtained can be used for the study of spin waves.

Effect of Silver Clusters Deposition on Wettability and Optical Properties of Diamond-like Carbon Films

In this study, the effect of silver clusters deposition was investigated on optical, wettability and surface properties of diamond-like carbon (DLC) films. Silver clusters and DLC films were deposited on Ni-Cu (70.4-29.6;W/W) alloy substrates by ion beam sputtering deposition (IBSD) technique. Optical and structural properties were measured using UV-visible spectroscopy and Raman spectroscopy, respectively. The wettability and surface free energy of films were determined by the contact angle (CA) measurements. Raman spectra of DLC thin film with 121±6nm thickness without accumulated Ag showed that the size of the graphite crystallites with sp 2 bands (La) was 3.36A by the ID/IG ratio equal to 0.062 with large optical band gap equal 3eV extracted from Tauc relation. The results of the deposition Ag in the various ion beam energy between 0.6 to 2keV showed the Ag clusters were accumulated uniformity on the surface of DLC films at 0.9keV. The volume percentage of silver clusters was varied from 5.0±2.01 to 16.3±1.4. The variation was caused by controlling the screen voltage and the deposition time. The CA of the deposited films increases from 79°±2 to 95°±2 as well as the reflection values in the visible and near-infrared region due to the increase in the Ag concentration in the surface of DLC films; while the surface free energy decrease from 86±1 to 66±2mJ/m2 and the optical transmittance is almost constant. Our results demonstrate that the deposition of silver particles on DLC films is potentially useful for biomedical applications having good hydrophobic characteristics without causing a destructive effect on the optical properties of DLC films.

Optimization of dielectric films with dual ion beam sputtering deposition for high reflectivity mirrors

Abstract Dielectric thin films deposited by Ion beam sputtering deposition technique have superior properties of good adhesion and customized optical properties suits to many optical filters for electro-optical sensors. In the present work Tantalum Pentoxide (Tantala) and Silicon Dioxide (Silica) thin films are fabricated with dual ion beam sputtering deposition process. The process parameters are optimized to achieve better surface quality and optical constants. The effect of the assist ion beam on the film properties is evaluated. Multi-layer dielectric mirrors realized with 1000 ppm loss on optimization of single-layer Silica and Tantala films, which will be suitable for linear and Ring Laser Resonators. The films are characterized by ellipsometer, non-contact optical profiler, spectrophotometer, and cavity ring-down loss meter. The multi-layer mirrors were subjected to vacuum annealing and the effect of annealing on film reflectivity is evaluated. The work emphasizes the process requirements of Ion Beam Sputtering to realize high reflectivity and low loss mirrors of Tantala and Silica films from Ta2O5 and SiO2 target materials. It gives an insight into the process deficiencies in matching the theoretical design of multi-layer mirrors from the practical aspects of coatings.

Magnetic behaviour of $$^{57}$$Fe/Co/Al multilayers deposited on a glass substrate

Multilayers of \(^{57}\hbox {Fe/Co/Al}\) 20 and 40 trilayers (TLs) prepared on a glass substrate using ion beam sputtering deposition techniques have been studied. Magnetization curves obtained at different angles show the anisotropic nature of both the samples. Both samples show strong in-plane uniaxial anisotropy. Negative \(\delta m\) values suggest that dipolar type interactions between grains contribute to the in-plane uniaxial anisotropy. Angular dependence of coercivity indicates that the magnetization reversal mechanism is different for both samples. The variation in coercivity with azimuthal angle is well reproduced in the 20 TL sample using the modified Kondorsky model and by the Stoner–Wohlfarth model in the 40 TL sample.

Highly tunable doping in Ge quantum dots/graphene composite with distinct quantum dot growth evolution

Quantum dots/graphene (QDs/Gr) composites have become the research hotspot recently due to their unique synergistic effect as optical absorption material for next-generation electronic and optoelectronic devices. In this work, Ge QDs/Gr composite is prepared by a simple and effective ion-beam sputtering deposition technique. The intact growth evolution process is detailly investigated by means of the effect of Ge deposition amount, which will induce the enhanced crystallinity in QDs and the reduced defects in graphene. Moreover, a feasible and inspiring strategy to effectively tune doping in graphene by artificial control through changing the deposition amount of Ge atoms on graphene is demonstrated. In addition, charge transfer and interaction strength at the interface of Ge QD and graphene is influenced via the oxygen defect in the QD surface, which is consistent with field-effect transistor test and first-principle calculations. The p-doping characteristics of graphene decorated by Ge QDs may have significant application prospects in energy band engineering of graphene-based building blocks for graphene-based composite development and near-infrared detector applications.

Thermal effect on microstructure vibration of SiO2 thin films

The microstructure of amorphous SiO2 thin film is a random network structure in which a large amount of [SiO4] is interconnected with a specific SiOSi bond angle. The SiO2 thin films used in this paper were prepared by ion beam sputtering and electron beam evaporation deposition techniques. Two-dimensional correlation spectroscopy analysis techniques were used in this study. By measuring the infrared temperature spectrum, we obtained the two-dimensional correlation synchronous spectrum and asynchronous spectrum, and decomposed the in-phase and out-phase asymmetric stretching vibration characteristics of SiOSi. As the temperature increases, the spectral transmittance of the vibrating peak decreases, and the relative change of in-phase asymmetric stretching vibration absorption peak is higher than that of the out-phase asymmetric stretching vibration absorption peak.

Study on SiO2 thin film modified by post hot isostatic pressing

SiO2 thin film is one of the important low refractive index films commonly used in the field of optical thin films. In this paper, the Hot Isostatic Pressing (HIP) technique is applied to the post-treatment of SiO2 thin film materials for the first time. The thin film samples were prepared by ion beam sputtering deposition technique. The samples were heated at 300 °C for 50 MPa under vacuum argon atmosphere for 24 h. The samples were analyzed by the spectra in the visible and infrared bands and surface deformation. The effects of HIP treatment on the refractive index, physical thickness, stress, Si-O-Si bond angle and relative density of films were obtained. The results show that the refractive index decreases from 1.4685 to 1.4591, the physical thickness increases 0.6%, the stress changes from −493 MPa to −226 MPa, and the Si-O-Si bond angle increases from 129.85° to 131.32°. The fundamental physical mechanism of the change for all the characteristics is the film stress. The release of film stress leads to the decrease of the density of the film, and the variation of the thin film density is proved by the change of asymmetric stretching vibration frequency of SiO2 thin film. In addition, the HIP treatment can reduce the OH-group chemical defects in the SiO2 thin film.

Ion beam energy dependence of surface and structural properties of amorphous carbon films deposited by IBSD method on Ni–Cu alloy

Abstract

Room temperature blue LED based on p-ZnO/(CdZnO/ZnO) MQWs/ n-ZnO

Blue multiple quantum well light-emitting diodes comprising of p-ZnO/(Cd0.12Zn0.88O/ZnO) multiple quantum wells/n-ZnO were grown on n-Si substrates using dual ion-beam sputtering deposition technique. X-ray diffraction of individual thin films revealed growth preferentially in c-axis direction perpendicular to the substrate. Photoluminescence studies indicated blue emission ~ 440nm from CdZnO and UV emission ~384nm arising from ZnO thin films. The LED showed a rectifying current–voltage behavior with a turn-on voltage of ~4.69V at room temperature. It emanated a room-temperature electroluminescence peak centered at 442nm, along with shoulder peak at 380nm in ultra-violet region associated with the recombination in ZnO layers of structure. It was found that with the increase in injection current the blue EL intensity increased and UV emission decreased, leading to improvement in successful radiative recombination in quantum wells. The results indicate prospects of fabrication of ZnO-based blue multiple quantum well LEDs.

Direct growth of Ge quantum dots on a graphene/SiO2/Si structure using ion beam sputtering deposition

The growth of Ge quantum dots (QDs) using the ion beam sputtering deposition technique has been successfully conducted directly on single-layer graphene supported by SiO2/Si substrate. The results show that the morphology and size of Ge QDs on graphene can be modulated by tuning the Ge coverage. Charge transfer behavior, i.e. doping effect in graphene has been demonstrated at the interface of Ge/graphene. Compared with that of traditional Ge dots grown on Si substrate, the positions of both corresponding photoluminescence (PL) peaks of Ge QDs/graphene hybrid structure undergo a large red-shift, which can probably be attributed to the lack of atomic intermixing and the existence of surface states in this hybrid material. According to first-principles calculations, the Ge growth on the graphene should follow the so-called Volmer–Weber mode instead of the Stranski–Krastanow one which is observed generally in the traditional Ge QDs/Si system. The calculations also suggest that the interaction between Ge and graphene layer can be enhanced with the decrease of the Ge coverage. Our results may supply a prototype for fabricating novel optoelectronic devices based on a QDs/graphene hybrid nanostructure.

Enhanced resistive switching and multilevel behavior in bilayered HfAlO/HfAlOx structures for non-volatile memory applications

In this work, hafnium aluminum oxide (HfAlO) thin films were deposited by ion beam sputtering deposition technique on Si substrate. The presence of oxygen vacancies in the HfAlOx layer deposited in oxygen deficient environment is evidenced from the photoluminescence spectra. Furthermore, HfAlO(oxygen rich)/HfAlOx(oxygen poor) bilayer structures exhibit multilevel resistive switching (RS), and the switching ratio becomes more prominent with increasing the HfAlO layer thickness. The bilayer structure with HfAlO/HfAlOx thickness of 30/40 nm displays the enhanced multilevel resistive switching characteristics, where the high resistance state/intermediate resistance state (IRS) and IRS/low resistance state resistance ratios are ≈102 and ≈5 × 105, respectively. The switching mechanisms in the bilayer structures were investigated by the temperature dependence of the three resistance states. This study revealed that the multilevel RS is attributed to the coupling of ionic conduction and the metallic conduction, being the first associated to the formation and rupture of conductive filaments related to oxygen vacancies and the second with the formation of a metallic filament. Moreover, the bilayer structures exhibit good endurance and stability in time.

Correlation study of structural, optical and electrical properties of amorphous carbon thin films prepared by ion beam sputtering deposition technique

The correlation of structural, optical and electrical properties of amorphous carbon thin films deposited by ion beam sputtering technique on the glass substrate was investigated. The film thickness varied over a wide range from 57 to 408nm by controlling the deposition time. Raman spectra and X-ray photoelectron spectroscopy showed that the size of the graphite crystallites with sp2 bonds (La) and the sp3/sp2 fraction are smaller than 1.5nm and 1.4, respectively. The values of ID/IG ratio, the ‘G’ peak position, and surface roughness depend on the film thickness; all of them increased by increasing film thickness up to 360nm, and then decreased by increasing time and thickness. Furthermore, the resistivity followed similar trends of these structural properties. According to Tauc equation the optical band gap of these films was in the range of 3.2–3.9eV. A broad emission peak at around 2.94eV was observed on a photoluminescence spectrum of amorphous carbon film with highest resistivity.

Effect of Annealing Temperature and Oxygen Flow in the Properties of Ion Beam Sputtered SnO-₂x Thin Films.

Tin oxide (SnO2−x) thin films were prepared under various flow ratios of O2/(O2 + Ar) on unheated glass substrate using the ion beam sputtering (IBS) deposition technique. This work studied the effects of the flow ratio of O2/(O2 + Ar), chamber pressures and post-annealing treatment on the physical properties of SnO2 thin films. It was found that annealing affects the crystal quality of the films as seen from both X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. In addition, the surface RMS roughness was measured with atomic force microscopy (AFM). Auger electron spectroscopy (AES) analysis was used to obtain the changes of elemental distribution between tin and oxygen atomic concentration. The electrical property is discussed with attention to the structure factor.

Electronic properties of single Ge/Si quantum dot grown by ion beam sputtering deposition

The dependence of the electronic properties of a single Ge/Si quantum dot (QD) grown by the ion-beam sputtering deposition technique on growth temperature and QD diameter is investigated by conductive atomic force microscopy (CAFM). The Si–Ge intermixing effect is demonstrated to be important for the current distribution of single QDs. The current staircase induced by the Coulomb blockade effect is observed at higher growth temperatures (>700 °C) due to the formation of an additional barrier between dislocated QDs and Si substrate for the resonant tunneling of holes. According to the proposed single-hole-tunneling model, the fact that the intermixing effect is observed to increase as the incoherent QD size decreases may explain the increase in the starting voltage of the current staircase and the decrease in the current step width.

Influence of ion-beam sputtering deposition parameters on highly photosensitive and transparent CdZnO thin films

CdZnO thin films with a nominal thickness of ~200 nm were grown on c-plane sapphire substrates by dual ion-beam sputtering deposition technique. The effect of substrate temperature (300–600 °C) and gas ambience on structural, morphological, compositional and opto-electronic properties was studied. X-ray diffraction patterns confirmed that all the films were polycrystalline in nature and were preferentially oriented along the c-axis. It was revealed that the films grown at Ar/O2 ratio of 4:1 were structurally more ordered and the film quality was found to be the best at 500 °C. The compositional studies specify that approximately 11.8 at.% of cadmium were present in the film deposited at 300 °C in Ar–O2 mixture. Investigations on optical properties by photoluminescence and absorption studies indicate band gap shrinkage with the increase in argon partial pressure and substrate temperature. It was found that photosensitivity of the deposited films was highly dependent on growth conditions. The photosensitivity was found to be 5000-fold higher for CdZnO film grown at 600 °C in Ar–O2 ambience compared to the best reported result, and this was promising to realize high-performance opto-electronic devices on such CdZnO films.

Study of Sb/SnO2 bi-layer films prepared by ion beam sputtering deposition technique

In the present work, bi-layer thin films of Sb/SnO2 were produced on unheated glass substrates using ion beam sputtering (IBS) technique without post annealing treatment. The thickness of Sb layers was varied from 2 to 10nm and the Sb layers were deposited on SnO2 layers having thicknesses of 40nm to 115nm. The effect of thickness was studied on the morphological, electrical and optical properties. The Sb/SnO2 bi-layer resulted in lowering the electrical resistivity as well as reducing the optical transmittance. However, the optical and electrical properties of the bi-layer films were mainly influenced by the thickness of Sb layers due to progressive transfer in structures from aggregate to continuous films. The bi-layer films show the electrical resistivity of 1.4×10−3Ωcm and an optical transmittance of 26% for Sb film having 10nm thickness.

Structural, magnetic and magnetoelectric studies of BaTiO3:Co nanocomposite films formed by ion-beam methods

Thin-film samples of ferroelectric barium titanate (BaTiO3) with cobalt nanoparticles were obtained by using either ion implantation or ion beam sputtering deposition (IBSD) techniques. The samples were characterized using X-ray diffraction, transmission electron microscopy, magnetometry and ferromagnetic resonance to investigate the efficiency of above ion-beam methods in the synthesis of magnetoelectric nanocomposite materials. Our structural studies show that high-fluence implantation with Co+ ions results in the formation of cobalt nanoparticles with mean size of 5nm in thin surface layer of monocrystalline plate of BaTiO3. On the other hand, larger nanoparticles of cobalt with sizes from 5 up to 40nm are formed in polycrystalline BaTiO3 matrix only after high-temperature annealing of BaTiO3:Co composite film prepared by IBSD method. Both types of thin-film nanocomposite samples have similar magnetic hysteresis curves in the sample plane. However Co-implanted BaTiO3 reveals strong uniaxial magnetic anisotropy for out-of-plane orientation, while BaTiO3:Co nanocomposite film demonstrates almost isotropic magnetic response. Strong magnetoelectric effect are observed in Co-implanted BaTiO3, and no magnetoelectric coupling are detected in BaTiO3:Co nanocomposite film formed by IBSD with subsequent high-temperature annealing.

Assessment of effective-medium theories of ion-beam sputtered Nb<sub>2</sub>O<sub>5</sub>–SiO<sub>2</sub> and ZrO<sub>2</sub>–SiO<sub>2</sub> mixtures

Single-layer mixture coatings of ZrO2–SiO2 and Nb2O5–SiO2 produced by the ion beam sputtering (IBS) deposition technique were investigated in detail. Effective medium approximation (EMA) models and two non-optical methods, namely Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) were applied for characterization of elemental composition of these films. The comparison of obtained results indicates discrepancies in atomic material concentrations. The reasons and potential sources of such discrepancies are discussed qualitatively and indicate limitations of optical models.

Assessment of effective-medium theories of ion-beam sputtered Nb<sub>2</sub>O<sub>5</sub>–SiO<sub>2</sub> and ZrO<sub>2</sub>–SiO<sub>2</sub> mixtures

Single-layer mixture coatings of ZrO2–SiO2 and Nb2O5–SiO2 produced by the ion beam sputtering (IBS) deposition technique were investigated in detail. Effective medium approximation (EMA) models and two non-optical methods, namely Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) were applied for characterization of elemental composition of these films. The comparison of obtained results indicates discrepancies in atomic material concentrations. The reasons and potential sources of such discrepancies are discussed qualitatively and indicate limitations of optical models.

Study of surfactant mediated growth of Ni/V superlattices

The Ni/V multilayers are useful as soft x-ray mirrors, polarizers, and phase retarders. For these applications, it is necessary that the interfaces roughness and interdiffusion must be as small as possible. The V-on-Ni and Ni-on-V interfaces are asymmetric due to the difference in the surface free energy of Ni and V. In this work, we report Ag surfactant mediated growth of Ni/V superlattices prepared using ion beam sputter deposition technique. These superlattices were studied using x-ray and neutron scattering techniques. It was found that when added in an optimum amount, Ag surfactant results in reduced interface roughness and interdiffusion across the interfaces. Obtained results can be understood with the surfactant floating-off mechanism leading to a balance in the surface free energy of Ni and V.