Ion Beam Chemical Vapor Deposition Research Articles

Germanium carbon (Ge1-xCx)/diamond-like carbon (DLC) antireflective and protective coating on zinc sulfide window

The Ge1-xCx/DLC antireflective and protective coating was designed and deposited on the ZnS substrate to improve the long-wave infrared transmittance, the hardness and the environmental adaptability of the ZnS window. The Ge1-xCx film and DLC film were deposited by ion beam sputtering and chemical vapor deposition, respectively. The surface morphology, chemical bonds and hardness of the films were investigated. The optical constants of the films were determined from whole infrared optical spectrum. After depositing hard protective coating and antireflective coating on ZnS substrate, the transmittance of the ZnS is greatly improve in the range of 7.5μm–9.7 μm, and the average value of transmittance is 90%. The hardness of the protective coating is 16 GPa, which is much higher than that of the ZnS substrate. The hard protective coating also shows good environmental adaptability. These results suggest that the coating has the potential to be used as an antireflective and protective coating in long-wave infrared region of 7.5μm–9.7 μm.

Electron diffraction radial distribution function analysis of amorphous boron carbide synthesized by ion beam irradiation and chemical vapor deposition

Amorphous boron carbide (a-BxC) networks consist of light elements, and their low atomic scattering factors makes structural analysis by x-ray diffraction difficult. Electron diffraction has an advantage of detecting the light elements, because of the strong interaction between the matter and electrons. We prepared a-BxC by ion beam technologies and plasma-enhanced chemical vapor deposition, and characterized their structures via atomic pair-distribution functions derived from electron diffraction intensity profiles. It was found that a pentagonal pyramid is the most favorable cluster in a-B4C generated by ion irradiation, while CC homonuclear bonds were formed in the deposited a-BxC thin film. X-ray photoemission spectroscopy revealed that the a-BxC thin film possesses more carbon than B4C, which is responsible for the formation of the homonuclear bonds.

Shape Memory Alloy-Based Microscale Bending Actuator Fabricated by a Focused Ion Beam Chemical Vapor Deposition (FIB-CVD) Gap-Filling Process

Focused ion beam chemical vapor deposition (FIB-CVD) processes can be used to fabricate nano-/microstructures by enabling highly localized material deposition. Due to these advantages, the FIB-CVD process has been utilized extensively as a method for material analysis and device fabrication in the fields of nano-/microscale electronics, sensors, drivers, bio, and optics. In this study, we fabricated shape memory alloy (SMA) carbon composites using an FIB-CVD process and performed a micro-tensile test to evaluate the mechanical properties of the fabricated composites. According to the results of the tensile test, the fabricated composite structure had higher stiffness values and lower maximum tensile strength values than general SMA materials. Based on our experimental results, we fabricated an SMA microscale bending actuator by localized carbon block deposition and evaluated the bending characteristics of the microactuator.

Field emission and explosive electron emission process in focused ion beam fabricated platinum and tungsten three-dimensional overhanging nanostructure

Abstract Three-dimensional platinum and tungsten overhanging nanogap (∼70 nm) electrodes are fabricated on a glass substrate using focused ion beam milling and chemical vapour deposition processes. Current-voltage (I-V) characteristics of the devices measured at a pressure of ∼10−6 mbar shows space-charge emission followed by the Fowler-Nordheim (F-N) field emission. After the F-N emission, the system enters into an explosive emission process, at a higher voltage generating a huge current. We observe a sharp and abrupt rise in the emission current which marks the transition from the F-N emission to the explosive emission state. The explosive emission process is destructive in nature and yields micro-/nano-size spherical metal particles. The chemical compositions and the size-distribution of such particles are performed.

Approaching the resolution limit of W-C nano-gaps using focused ion beam chemical vapour deposition

Nano-gaps are fundamental building blocks for nanochannels, plasmonic nanostructures and superconducting Josephson junctions. We present a systematic study on the formation mechanism and resolution limit of W-C nano-gaps fabricated using focused-ion-beam chemical vapour deposition (FIB-CVD). First, the deposition size of the nanostructures is evaluated. The size averaged over 100 dots is 32nm at FWHM. Line and space are also fabricated with the smallest size, having a spacing of only 5nm at FWHM. Then, a model is developed to study the formation mechanism and provides the design basis for W-C nano-gaps. Both experimental and simulation results reveal that the shrinkage of W-C nano-gaps is accelerated as the Gaussian parts of the nano-wire profiles overlap. A Nano-gap with a length of 5nm and height difference as high as 42nm is synthesized. We believe that FIB-CVD opens avenues for novel functional nanodevices that can be potentially used for biosensing, photodetecting, or quantum computing.

Enhancing the oxidation resistance of graphite by applying an SiC coat with crack healing at an elevated temperature

The potential of reducing the oxidation of the supporting graphite components during normal and/or accident conditions in the Very High Temperature Reactor (VHTR) design has been studied. In this work efforts have been made to slow the oxidation process of the graphite with a thin SiC coating (∼10μm). Upon heating at≥1173K in air, the spallations and cracks were formed in the dense columnar structured SiC coating layer grown on the graphite with a functionally gradient electron beam physical vapor deposition (EB-PVD. In accordance with the formations of these defects, the sample was vigorously oxidized, leaving only the SiC coating layer. Then, efforts were made to heal the surface defects using additional EB-PVD with ion beam bombardment and chemical vapor deposition (CVD). The EB-PVD did not effectively heal the cracks. But, the CVD was more appropriate for crack healing, likely due to its excellent crack line filling capability with a high density and high aspect ratio. It took∼34min for the 20% weight loss of the CVD crack healed sample in the oxidation test with annealing at 1173K, while it took∼8min for the EB-PVD coated sample, which means it took ∼4 times longer at 1173K for the same weight reduction in this experimental set-up.

Synthesis of in-plane and stacked graphene/hexagonal boron nitride heterostructures by combining with ion beam sputtering deposition and chemical vapor deposition.

Graphene/hexagonal boron nitride (h-BN) heterostructures have attracted a great deal of attention in recent years due to their unique and complementary properties for use in a wide range of potential applications. However, it still remains a challenge to synthesize large-area high quality samples by a scalable growth method. In this work, we present the synthesis of both in-plane and stacked graphene/h-BN heterostructures on Cu foils by sequentially depositing h-BN via ion beam sputtering deposition (IBSD) and graphene with chemical vapor deposition (CVD). Due to a significant difference in the growth rate of graphene on h-BN and Cu, the in-plane graphene/h-BN heterostructures were rapidly formed on h-BN domain/Cu substrates. The large-area vertically stacked graphene/h-BN heterostructures were obtained by using the continuous h-BN film as a substrate. Furthermore, the well-designed sub-bilayered h-BN substrates provide direct evidence that the monolayered h-BN on Cu exhibits higher catalytic activity than the bilayered h-BN on Cu. The growth method applied here may have great potential in the scalable preparation of large-area high-quality graphene/h-BN heterostructures.

Three-dimensional printing of freeform helical microstructures: a review.

Three-dimensional (3D) printing is a fabrication method that enables creation of structures from digital models. Among the different structures fabricated by 3D printing methods, helical microstructures attracted the attention of the researchers due to their potential in different fields such as MEMS, lab-on-a-chip systems, microelectronics and telecommunications. Here we review different types of 3D printing methods capable of fabricating 3D freeform helical microstructures. The techniques including two more common microfabrication methods (i.e., focused ion beam chemical vapour deposition and microstereolithography) and also five methods based on computer-controlled robotic direct deposition of ink filament (i.e., fused deposition modeling, meniscus-confined electrodeposition, conformal printing on a rotating mandrel, UV-assisted and solvent-cast 3D printings) and their advantages and disadvantages regarding their utilization for the fabrication of helical microstructures are discussed. Focused ion beam chemical vapour deposition and microstereolithography techniques enable the fabrication of very precise shapes with a resolution down to ∼100 nm. However, these techniques may have material constraints (e.g., low viscosity) and/or may need special process conditions (e.g., vacuum chamber) and expensive equipment. The five other techniques based on robotic extrusion of materials through a nozzle are relatively cost-effective, however show lower resolution and less precise features. The popular fused deposition modeling method offers a wide variety of printable materials but the helical microstructures manufactured featured a less precise geometry compared to the other printing methods discussed in this review. The UV-assisted and the solvent-cast 3D printing methods both demonstrated high performance for the printing of 3D freeform structures such as the helix shape. However, the compatible materials used in these methods were limited to UV-curable polymers and polylactic acid (PLA), respectively. Meniscus-confined electrodeposition is a flexible, low cost technique that is capable of fabricating 3D structures both in nano- and microscales including freeform helical microstructures (down to few microns) under room conditions using metals. However, the metals suitable for this technique are limited to those that can be electrochemically deposited with the use of an electrolyte solution. The highest precision on the helix geometry was achieved using the conformal printing on a rotating mandrel. This method offers the lowest shape deformation after printing but requires more tools (e.g., mandrel, motor) and the printed structure must be separated from the mandrel. Helical microstructures made of multifunctional materials (e.g., carbon nanotube nanocomposites, metallic coated polymer template) were used in different technological applications such as strain/load sensors, cell separators and micro-antennas. These innovative 3D microsystems exploiting the unique helix shape demonstrated their potential for better performance and more compact microsystems.

Annealing Effect of W Incorporated Diamond-Like Carbon Fabricated by Ga Focused Ion Beam Chemical Vapor Deposition

The effects of thermal annealing of W incorporated diamond-like carbon (W-DLC) films fabricated with focused ion beam chemical vapor deposition (FIB-CVD) were investigated using X-ray absorption fine structure near the carbon K-edge (C-K NEXAFS) and the combination of Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA). W-DLC films were annealed for 32 h at temperatures, Ta, between 673 and 1073 K. Comparing the Ta dependences of Ga and H contents obtained from RBS-ERDA and the sp2/(sp2 + sp3) ratios from C-K NEXAFS, it was found that even a trace amount of W incorporation into DLC films fabricated by Ga+ FIB-CVD may cause a significant sp3 →sp2 structural change.

Annealing Effect of W Incorporated Diamond-Like Carbon Fabricated by Ga Focused Ion Beam Chemical Vapor Deposition

Annealing Effect of W Incorporated Diamond-Like Carbon Fabricated by Ga Focused Ion Beam Chemical Vapor Deposition

Influence of Processing Conditions on Mechanical and Structural Properties of DLC Produced by FIB-CVD Method

ABSTRACTInfluence of processing condition on mechanical and structural properties of diamond-like carbon (DLC) by focused ion-beam chemical vapor deposition (FIB-CVD) method was investigated. The DLC specimens were produced under conditions of varying supplied amount of material gas and probe current of FIB. Volume determination results of DLC structures indicated that a deposition rate was increased with both the amount of gas and the probe current. To evaluation of mechanical property, indentation hardness was measured by a nano-indentation tester. From evaluation of mechanical property, it was found that the indentation hardness was sensitive to the processing condition, showing in the range of 8-13 GPa. The hardness of DLC structures was seemed to be lower when etching process higher contributed for formation process. Crystallographic structure of DLC remained amorphous even though the mechanical properties varied widely. Results of hydrogen concentration measurement indicated that increase of hydrogen concentration might lead to decrease of hardness.

Comprehensive analysis of the deposition caused by scattered Ga ions during focused ion-beam-induced deposition

The authors report a detailed study on the deposition because of scattered Ga ions during the focused ion beam chemical vapour deposition (FIB-CVD). The scattered ions strike the surface of the substrate nearby the base of the structure being fabricated by the primary ions, and decompose the organometallic molecules adsorbed on it, leading to the broadening of the base. Such deposition is dominant up to several micron distances from the base of the nanostructures depending on the primary ion flux. During the FIB-CVD, similar deposition occurs on the surface of nearby pre-fabricated structures, situated up to a few micrometre distances from the nanostructure being fabricated. The scattered-ion-induced deposition complicates the fabrication of complex 3D structures. The authors present the parametric dependence of the deposition because of scattered Ga ions during FIB-CVD.

集束イオンビーム励起化学気相法によるマイクロ構造体の作製と機械的性質の評価

Three-dimensional micro structures fabricated by focused ion beam chemical vapor deposition (FIB-CVD) are expected to be used as structural materials for MEMS/NEMS. In this research, the square micro structures were fabricated by FIB-CVD using probe currents of 48, 200, 1300 and 5200 pA, and Vickers hardness tests of the micro structures were carried out. The Vickers tests revealed that the hardness of the micro structures depends on the probe current density. The cross-sectional TEM observations indicated that the micro structure has an amorphous phase. The results show that the consistent fabrication process of the micrometer-scale beam with both ends fixed by the FIB-CVD method was established. Mechanical properties of the micro structure with beam shape were investigated by three-point bending tests. Using a nano-indentation apparatus, the bending tests showed that Young's modulus of a beam-shaped structure was 20±2 GPa and the fracture stress was 2.2±0.1 GPa. Furthermore, SEM observation of the cleavage surface on a beam-shaped structure after failure showed brittle fracture. SEM-EDS images revealed that a homogeneous composition distribution of 94 at% carbon and 6 at% gallium over the entire micro structure.

Study of temperature rise during focused Ga ion beam irradiation using nanothermo-probe

Estimation of temperature rise during focused ion beam irradiation is of immense importance, since it affects various processes related to micro-machining and deposition. When ion beam impinges on a surface, it transfers its kinetic energy by way of electronic excitations and collisions, which eventually gets converted in the form of heat leading to rise in local temperature. This temperature rise affects and governs the properties of the machined region. The temperature rise can be calculated on the basis of energy deposition and heat transfer. However, there are very few reports on the measurement of such local temperature rise which lasts for very short time. We have designed and fabricated nanothermocouples of Pt–W to monitor local temperature rise (i) near a microheater and (ii) in the close proximity of an intense focused ion beam spot on a substrate. The junctions having size of 100 nm × 100 nm have been fabricated using focused ion beam chemical vapor deposition (FIB-CVD). The nanothermocouples have shown a fast response to the changes in temperature. These nanothermocouples can find useful applications in thermal characterization of nanomaterials and for understanding of temperature mediated phenomena in the samples treated under directed energy deposition processes, e.g. ion, laser and electron beam treatment.

The out of beam sight effects in focused ion beam processing

We report that during focused ion beam chemical vapor deposition (FIB-CVD) the effect ofdeposition is not limited to the area where the ion beam scanning takes placebut occurs on regions which are out of sight of the incident beam and extendsup to several micrometers away from the specified site. This phenomenon hasdeleterious effects, especially when the nanocontacts are fabricated for the electricalcharacterization of the nanodevices. The deposition occurs into the gap between thecontact pads and acts as a resistance in parallel with the resistance of the nanostructureto be measured. The extended deposition has been explained on the basis ofmolecular cracking of the precursor gas molecules induced by forward scatteredGa ions, and appropriate measures to remove the effect have been suggested.

Bimorph nano actuators synthesized by focused ion beam chemical vapor deposition

Bimorph nano actuators synthesized by a two-layer focused ion beam (FIB) chemical vapor deposition (CVD) process have been demonstrated. The core bimorph segment of the actuator is a column structure made of two 200-nm thick tungsten-based-conductor (TBC) and diamond-like-carbon (DLC) layers. Several segments can be connected together of different angles to construct actuators with various moving capabilities when joule heating is applied via silicon MEMS (Microelectromechanical System) heater as the actuation source. Experimentally, a prototype five-segment actuator has shown projection displacement of 600 ± 60 nm under an input power of 1.02 W (160 mA and 6.41 V). The actuator has been repeatedly operated for over 100 times without any indication of degradation. As such, this work represents a new class of nano actuators based on versatile and flexible FIB-CVD bimorph nanostructures.

Nanofabrication, Nanoinstrumentation and Nanoassembly by Nanorobotic Manipulation

A nanolaboratory is proposed to realize the capabilities of nanofabrication, nanoinstrumentation and nanoassembly to make three-dimensional structures, devices and systems in the nanoworld. A nanorobotic manipulation system is introduced to realize these capabilities inside a scanning electron microscope or a transmission electron microscope. Some precursors are introduced into the small working space in the nanoworld, so that cutting, bending, peeling and fixing operations in the nanoworld could be realized using nanomanipulators, electron-bean-induced deposition and other methodologies as in the macroworld. After making the three-dimensional structures, the nanodevices such as nanosensors and nanoactuators are fabricated using carbon nanotubes and a focused ion beam chemical vapor deposition process. Some nanodevices for bioapplications are also presented.

Evolution of surface morphology of nano and micro structures during focused ion beam induced growth

We report on the morphological studies of C, Pt and W nanopillars fabricated by focused ion beam chemical vapor deposition (FIB-CVD) process. The pillars have large base size as compared to the tip and they exhibit a rough morphology with whisker like structures protruding out of the surface. The whiskers have thickness of about 100nm and their length varies upto 1μm. The dimensions of these protrusions depend on the location of the protrusions on the pillar surface and show a systematic variation and saturation of growth as a function of ion flux. The growth of protrusions has been explained on the basis of formation of crystalline seeds on the surface due to ion beam induced temperature rise and cracking of the precursor gas in the vicinity of the seeds due to the secondary ion and electron impact. Pillars having smooth surfaces can be achieved by milling the edges of these structures.

Influence of compressive load on microstructure of micro-scaled DLC structures produced by FIB-CVD

Influence of compressive load on microstructure of micro-scaled diamond-like carbon (DLC) structures was investigated by high-resolution electron transmission microscopy (HRTEM) analyses. The micro-scaled structures were produced by the focused ion-beam chemical vapor deposition method. The compressive loads were applied by a dynamic ultra micro hardness tester equipped with a flat-tip diamond indenter. Microgrid images in HRTEM observation and selected area diffraction patterns were varied by the compressive loads. The variations revealed that constituent atoms arranged disorderly in DLC were clustered by compressive loads. Electron energy loss spectroscopy measurements indicated that sp3 fraction in DLC was decreased by the compressive load. Consequently, it was suggested that graphitic clusters were formed in the microstructure of DLC by the compressive loads.

Analysis on microstructure of interface layer in DLC/Si structures produced by FIB–CVD

To aid investigation of formation processes and/or adhesiveness properties, microstructures of the interface between diamond-like carbon (DLC) film produced by focused ion-beam chemical vapor deposition method and crystalline Si substrate were analyzed by high-resolution transmission electron microscopy (HRTEM) in detail. Bright field images showed that a transition layer existed at the DLC/Si interface. From EDS analysis, it was found that the transition layer consisted of both C and Si atoms and their concentrations varied continuously along growth direction over about 100 nm. In addition, HRTEM image and convergence beam electron diffraction pattern revealed that the transition layer was divided structurally into three layers, i.e., amorphous, clustered and crystalline Si–C layers.