Electron Beam Evaporation Method Research Articles

A Fractal Analysis of the Nucleation Transition in Annealed La2O3 Thin Films

A La2O3 thin film of 57 nm thickness was deposited by the electron beam evaporation method. To investigate the effect of annealing temperature on crystalline structure of La2O3 thin film, surface morphologies and crystalline states of annealed La2O3 thin films were characterized. It was found that fractal patterns presented on the surfaces of crystallized films with cubic phase. The connections between the annealing temperature and the surface morphology were disclosed by fractal analysis. Fractal dimension and multifractal spectra were calculated. It showed that the annealing temperature apparently affected the width of spectrum $$ \Delta a $$ and the range of probability $$ \Delta f $$ . Combining fractal characteristics with x-ray diffraction (XRD) results, it was found that there was a critical annealing temperature in the range of 850–900°C, above which a transition happened from the dominant hexagonal phase nucleation to the prevailing cubic phase nucleation.

On the interrelationship of porosity and structural defects in amorphous-crystalline nanopowders SiO2-doped Gd2O3 with their magnetic and luminescent properties

The pulsed electron beam evaporation method (PEBE) was used to obtain mesoporous amorphous-crystalline pure and SiO2-doped Gd2O3 nanopowders (NPs). An HRTEM phase analysis showed the existence in nanopowder Gd2O3 of an amorphous, as well as three crystalline phases. The influence of silicon oxide doping on the textural, magnetic and luminescent properties of NPs Gd2O3@SiO2 was studied. The size and volume of the interparticle pores of NPs Gd2O3@SiO2 was dependant on the concentration of a dopant. The doping supported an increase in amorphicity and the growth of a concentration of different structural defects in NPs. Two different processes – annealing and doping, led to crystallinity degradation of the Gd2O3 matrix. The correlation of porosity concentration dependences, paramagnetic response, and the intensity of pulsed cathodoluminescence spectra in NPs Gd2O3@SiO2 was revealed. The dependence of the paramagnetic response Gd2O3 on the volume of interparticle mesopores in nonporous nanoparticles expands our understanding of the nature of diluted magnetic semiconductors.

Shape controlled synthesis of Cu3BiS3 nano- and microstructures by PEG assisted solvothermal method and functional properties

One-dimensional Cu3BiS3 nano-and microstructures were synthesized by solvothermal route using structural directing agent polyethylene glycol (PEG) as soft template. The effects of thiourea concentration on the morphological, structural and optical properties of Cu3BiS3 nano- and microstructures were investigated. X-ray diffraction study revealed that the synthesized Cu3BiS3 belongs to orthorhombic structure. Raman spectrum of the Cu3BiS3 exhibited its functional groups. The chemical bonding of the ions was examined by X-ray photoelectron spectroscopy. Field emission scanning electron microscope and transmission electron microscope analyses evidently showed that thiourea concentration acts as a crucial factor in tuning the morphology of Cu3BiS3 nano- and microstructures. The presence of Cu3BiS3 was confirmed by Energy Dispersive X-ray Analysis and elemental mapping. The growth mechanism of Cu3BiS3 nanostructures has been discussed. Conductivity of Cu3BiS3 measured by I-V characteristics of the nano- and microstructured film of ~ 2.5 µm thickness deposited on FTO substrate using electron beam evaporation method showed linear curve. The Hall measurements of the Cu3BiS3 films deposited on glass substrate were determined.

Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO2 nanorod arrays

Rutile TiO2 nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermal methods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO2 nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on the growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as substrates. We document the structural properties of the TiO2 seed layers and describe the relationship between the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO2 nanorods are compared depending on whether they are grown on polycrystalline TiO2 or FTO seed layers. In both cases, a homogenous TiO2 bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybrid solar cells. Detached NRAs illustrate the effect of rutile FTO and TiO2 on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seed layers fabricated by electron-beam lithography.

Twisted nanocolumns for LIBs via phi-sweep method in ion assisted e–beam deposition

In this work, twisted nanostructured silicon-copper (with 19%at. copper) thin film is fabricated by glancing angle deposition phi-sweep process of ion beam assisted electron beam evaporation method. The thin film delivers 977 mAh g−1 after 100 cycles, when cycled with 100 mA g−1 rate and performs 280 mAh g−1 at 2.5 A g−1 rate. The morphological and the compositional particularities of the electrode might govern this noticeable cycle performance: Gaps among the nanostructures accommodate large volume changes and provide easy access to lithium ions for reacting with silicon to deliver high capacity. Plus, the direct connection of nanostructures to the current collector displays short lithium travelling distance promoting lithiation kinetic. Moreover, small intermetallics creating electronic conductive pathways enhance the reversibility. And finally, 5 min ion assisted deposition increases the adhesion of the film while avoiding possible delamination, hence quick failure of the electrode in the early stages of cycling.

Preparation and Investigation of the Properties of W/CeB6/W Heterostructure as a Sensitive Element of Single-Photon Thermoelectric Detector

The possibility of W/CeB6/W heterostructure preparation on Al2O3, AlN, Si, and W substrates by electron-beam evaporation method was investigated. The conditions for preparation of W thin films on dielectric substrates and CeB6 films, as well as of stoichiometric CeB6 films on W films, dielectric and tungsten substrates are determined. The reflection spectra of W films, the results of X-ray diffractometry, X-ray microanalysis, and electron microscopy of W and CeB6 films are presented. W/CeB6/W heterostructures of various configurations and sizes are produced. It was shown by means of computer simulation that at the detection of 6–50 eV photons, a detector with W/CeB6/W heterostructure-based sensitive element may provide microvolt level signal at terahertz count rate. The obtained results serve as the basis for creation of a prototype of a sensitive element of single-photon thermoelectric detector.

Nucleate Pool Boiling Heat Transfer of Hydro-Fluorocarbon Refrigerant R134a on TiO2 Nanoparticle Coated Copper Heating Surfaces

ABSTRACTPool boiling heat transfer performance of hydro-fluorocarbon refrigerant R-134a on titanium dioxide (TiO2) nanoparticle coated surface is experimentally studied in the article. The test surfaces, viz, 100 nm, 200 nm and 300 nm thick TiO2 nanoparticle coated surfaces over 100 nm thin film surface are used in this experimentation. The surfaces are synthesized and fabricated by simple and cost-effective electron beam evaporation method. The test surfaces were characterized by scanning electron microscope and atomic force microscope to uncover the formation of crystalline structure on coated surfaces. These surfaces are utilized in pool boiling test rig using refrigerant R134a at 10°C saturation temperatures. The result indicated that a maximum of 87.5% augmentation in the boiling heat transfer has been achieved by higher thickness of TiO2 coated surface than the bare copper surface. In addition, the incipience wall superheat is reduced for higher thickness coated surface. The augmentation of heat transfer coefficient might be the reason for increase in micro/nano-porosity, active nucleation site density and surface area of the heating surface. It is observed that with the increase of sub-cooling temperature of liquid, the bubble departure diameter was reduced while the heat transfer coefficient has been increased.

Xenon-ion irradiation of Co/Si bilayers: Magnetic and structural properties

Evolution of the structure of cobalt-silicon films during Xe ions irradiation has been studied and the same is correlated with magnetic properties. The polycrystalline cobalt films were deposited by electron beam evaporation method to a thickness of 50 nm on crystalline silicon (c-Si) and silicon with pre-amorphized surface (a-Si). After deposition the layers were irradiated with 400 keV Xe ions to the fluences in the range of 2–30 × 1015 ions/cm2. Structural analysis was done by means of transmission electron microscopy, atomic force microscopy (AFM) and X-ray diffraction (XRD), while the magnetic properties were analyzed by using magneto-optical Kerr effect (MOKE) technique. For the both types of substrate the AFM and XRD results show that after Xe ions irradiation the layers become more rough and the grain size of the crystallites increases; the effects being more evidenced for all fluences for the layers deposited on pre-amorphized Si. The MOKE measurements provided the in-plane azimuthal angular dependence of the hysteresis loops and the change of magnetization with the structural parameters. Although the coercive field is influenced by the surface roughness, in the case of c-Si substrate we found it is much more determined by the size of the crystallites. Additionally, independently on the substrate used the magnetic anisotropy in the Co films disappeared as the Xe ion fluence increased, indicating that the changes of magnetization in both systems occur for similar reasons.

Effect of Growth Parameters on SnO2 Nanowires Growth by Electron Beam Evaporation Method

Tin oxide (SnO2) nanowires were synthesized via catalyst assisted VLS growth mechanism by the electron beam evaporation method at a growth temperature of 450 °C. The effects of growth parameters such as evaporation rate of Tin, catalyst film thickness, and different types of substrates on the growth of SnO2 nanowires were studied. Nanowires (NWs) growth was completely seized at higher tin evaporation rates due to the inability of the catalyst particle to initiate the NWs growth. Nanowires diameters were able to tune with catalyst film thickness. Nanowires growth was completely absent at higher catalyst film thickness due to agglomeration of the catalyst film. Optimum growth parameters for SnO2 NWs were presented. Nanocomposites such as Zinc oxide - SnO2, Graphene oxide sheets- SnO2 and Graphene nanosheets-SnO2 were able to synthesize at a lower substrate temperature of 450 °C. These nanocompsoites will be useful in enhancing the capacity of Li-ion batteries, the gas sensing response and also useful in increasing the photo catalytic activity.

Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

A mid-infrared (mid-IR) semiconductor saturable absorber mirror (SESAM) based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

Oxygen Electroreduction in Alkaline Solution on Pd Coatings Prepared by Galvanic Exchange of Copper

Thin Pd coatings were obtained on glassy carbon electrodes by galvanically replacing the electron beam-deposited copper layers with palladium. The prepared electrodes were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The electrodes were electrochemically tested for oxygen reduction reaction (ORR) employing the rotating disc electrode (RDE) method in alkaline solution. The remaining copper was detected for two of the thickest (5 and 10 nm) sacrificial Cu layers using energy-dispersive X-ray spectroscopy (EDX). SEM images of thin Pd films showed some larger particle growth for all the studied film thicknesses, but spherical particles such as those achieved for example by the electron beam evaporation method were not visible. Specific activity of the electrodes for O2 reduction did not depend on the thickness of the sacrificial copper layer. The O2 reduction reaction followed a four-electron pathway with a mechanism similar to that of commercial Pd/C, where the first electron transfer to the O2 molecule is the rate-determining step.

Investigation of growth parameters influence on Au-catalyzed ITO nanowires by electron beam evaporation method

Indium tin oxide (ITO) nanowires (NWs) were synthesized via Gold (Au) catalyst assisted Vapor–Liquid–Solid (VLS) growth mechanism by electron beam evaporation method (EBE). Effects of growth parameters such as evaporation rate of ITO, oxygen partial pressure, and different types of substrates on the growth of ITO NWs were studied. Experimental investigations show that the Au-catalyzed VLS growth mechanism was dominating over self-catalytic VLS growth mechanism at lower evaporation rates of ITO. Self-catalytic VLS growth was dominating over Au-catalyzed VLS growth at the higher ITO evaporation rates of 6 Å/sec and above. Furthermore, change of growth mechanism was explained by considering incubation time and diameter of the catalyst particles. It was observed that the NWs growth enhanced at lower oxygen partial pressures and completely seized at higher oxygen partial pressure of 6×10−4 mbar and above. The complete absence of NWs growth at higher oxygen partial was explained by considering the growth rates of VLS and VS deposition. It was found that, the ITO NWs growth is independent of type of the substrate used. Understanding the growth mechanism transition and growth behaviour with deposition parameters are novel findings for the present report. In addition to the above, optical and electrical properties of ITO NW films were also studied. These ITO NWs films will be useful in antireflection, transparent conducting oxide coating applications. Moreover, these ITO NWs films may improve the performance of the various optoelectronic devices.

Demonstration of Large Flatband Voltage Shift by Designing Al2O3/SiO2 Laminated Structures with Multiple Interface Dipole Layers

The presence of the dipole layer often results in a flatband voltage (VFB) shift in metal/high-k/SiO2/Si gate stacks typically in the order of a few hundreds of mV [1]. Enlargement of the attainable range of VFB shift caused by those interface dipole layers would be advantageous in some applications including power MOSFETs, which need high VTH for the stable operation of the devices. However, the amount of positive VFB shift attainable by a single interface dipole layer formation is limited within ~0.6 V using Al2O3-on-SiO2 stacks. One of the simple solutions to overcome this limitation would be adding up the VFB shifts induced by multiple interface dipole layers in a laminated dielectric stack. In this study we investigated the VFB shifts of MOS capacitors employing laminated stacks with Al2O3 and SiO2 layers ((Al2O3/SiO2)n) as the gate dielectric [2], to demonstrate a possible design of a stack with a large positive shift of VFB (>1 V).Silicon wafers with a resistivity of 1-5 Ωcm were thermally oxidized to grow 5 nm-thick-SiO2 followed by the fabrication of three kinds of samples (i)-(iii). The sample (i) is Au/Al2O3(2-8 nm)/SiO2/Si stack obtained by Al2O3 deposition by rf-sputtering on thermally grown oxide. The sample (ii) is Au/SiO2(2-7 nm)/Al2O3(3.0 nm)/SiO2/Si stacks, prepared by a SiO2 growth by the oxidation of metallic-Si with different thicknesses on the identical structure with the sample (i), to investigate the effects of the dipole layer formation by the deposition of top-SiO2. The metallic-Si was deposited by electron beam evaporation method followed by the oxidation conducted at 800°C in O2 ambient. The sample (iii) is Au/Al2O3(2-6 nm)/SiO2(3.0 nm)/Al2O3(3.0 nm)/SiO2/Si stack fabricated by the deposition of Al2O3 on the identical structure with the sample (ii), to evaluate the effects of dipole layer formation at top-Al2O3-on-SiO2 interface. The VFB shift caused by each dipole layer was determined from capacitance-voltage characteristics by excluding the effect of fixed charges. From the first-Al2O3 thickness-dependence of VFB for Al2O3/SiO2/Si structure of sample (i), it was found that a dipole layer inducing +0.47±0.05 V VFB shift was formed. For SiO2/Al2O3/SiO2/Si structure of sample (ii), one might expect a formation of the dipole layer at the top SiO2-on-Al2O3 interface should induce VFB shift with the same magnitude but the opposite direction to the one observed for the sample (i), because both are the interfaces between Al2O3 and SiO2 but with the opposite stacking sequences. However, the experimentally observed VFB shift due to dipole layer at the top SiO2-on-Al2O3 was determined to be only 0~+0.2V in our experimental condition. We speculate that the dipole effects for this interface would be suppressed because the thermal oxidation process of metallic-Si on Al2O3 results in a reduction of the stress at this interface, taking account of the model [1] that the dipole layer would be triggered by structural relaxation by an adjustment of oxygen density at the interface. For Al2O3/SiO2/Al2O3/SiO2/Si structure of sample (iii), the VFB shift caused by the dipole layer at the top Al2O3-on-SiO2 interface was estimated as approximately +0.8±0.2 V to the positive direction. As a result, a large VFB shift ~+1.2 V in total was demonstrated for this stack due to the additivity of multiple dipole layers in the laminated stack [2], thanks to the selective formation of dipole layers at Al2O3-on-SiO2 interfaces and the effective suppression of those at SiO2-on-Al2O3 interfaces. From these results we can conclude that by designing the number of laminated layers and tuning the stacking conditions, a very large VFB shift (>1V) is attainable with ((Al2O3/SiO2)n) laminated dielectric layers.[1] K. Kita and A. Toriumi, Appl. Phys. Lett. 94, 132902 (2009).[2] H. Kamata and K. Kita, Appl. Phys. Lett. 110, 102106 (2017).

Performance of hydrogenated diamond MISFET using Zr-Si-N as the dielectric layer

ABSTRACTTo better stabilize the hydrogen-terminated surface, a diamond based metal-insulator-semiconductor field-effect transistor with Zr-Si-N dielectric layer has been investigated. On the diamond epitaxial layer grown by microwave plasma chemical vapor deposition system, Pd films were patterned as the source and drain electrodes by photolithography and electron beam evaporation methods. Then, a Zr-Si-N dielectric layer and W metal film were fabricated as the gate structure by radio frequency magnetron sputtering technique. The device illustrates p-type depletion mode, in which the threshold voltage, maximum transconductance, drain current maximum, capacitance and dielectric constant were calculated to be 3.0V, 1.27mS/mm, -5.16 mA/mm, 0.275μF/cm2 and 7.8, respectively. The result suggest that Zr-Si-N dielectric layer is shown to have the ability to protect the two-dimensional hole gas.

The high capacity and cycle stability of NiFe2O4 thin film prepared by E-beam evaporation method for lithium ion batteries

NiFe2O4 thin film has been prepared by electron beam evaporation method and has been investigated as anode materials providing large reversible Li+ capacity with high cycling performance for lithium ion batteries. The NiFe2O4 thin film crystallized with annealing process after NiFe2O4 thin film deposition. In electrochemical measurements, the first discharge and charge capacity of NiFe2O4 thin film were found to be 1693 mAh g−1 and 1108 mAh g−1, which is above its theoretical capacity (915 mAh g−1). In addition, the cycle performance test of NiFe2O4 thin film also showed steady charge-discharge capacity at 0.1 C during 100 cycles compared to other NiFe2O4 materials, indicating that the empty space or porous surface of electrode was beneficial for accessibility of electrolyte and served as buffer to alleviate stress.

Modeling of the Structural State of Amorphous Phases of the Nano-Sized Al2O3 Produced by Different Synthesis Methods

The paper examines the structural state of the Al2O3 alloy nanopowders synthesized by different methods: electron beam evaporation, hydrolysis, and plasma-chemical method. X-ray structural analysis demonstrated that Al2O3 nanopowders synthesized by different methods are in X-ray amorphous and semi-amorphous states. These synthesis methods stimulate the creation of amorphous structures with different specific surfaces. The structural state of the Al2O3 alloy was studied by methods of X-ray structural analysis and simulation modeling. In order to identify the internal structure, modeling of the amorphous state of the elementary cell of the Al2O3 phase was performed within molecular dynamics. As a result of full-profile refinement of parameters of the model phases of Al2O3 nanopowders, complete structural information was identified for the synthesized Al2O3 alloys. It was shown from first principles that the cells of X-ray amorphous Al2O3 turned out to be highly stable. Researchers identified the parameters of elementary cells, spatial distribution of atoms, and node occupancy. It was shown that specific surface increases in the Al2O3 alloy nanopowders with the increase in bond energy of atoms in the cell.

Electrochromic behavior of NiO film prepared by e-beam evaporation

Abstract The NiO thin films were prepared by the electron beam evaporation method using synthesized sintered targets. As-prepared films were characterized using X-ray diffraction, scanning electron microscopy, UV–VIS spectroscopy and cyclic voltammetry. The thicker films were found to exhibit a well-defined structure and a well-developed crystallite size with greater transmittance modulation and durability. The as-deposited thinner films of 170 nm showed a faster response time during electrochromic cycles with a coloration efficiency of 53.1 C/cm 2 than the thicker ones. However, the thicker films showed no enhanced electrochromic properties such as a larger intercalated charge than the thinner ones. The electrochromic properties of the thinner films became deteriorated after 800 cycling tests.

High-speed vacuum evaporation of large-area targets by a focused electron beam

A method of electron-beam evaporation of a target in a vacuum of ~10–2 Pa is considered. Initially, a focused electron beam spot moves at the periphery of the target in a circular path with an angular velocity of 8–80 rad/s by means of a ring sweep in the frequency range of 50–500 Hz. Then, by radial displacement with a linear velocity of 10–100 mm/s, the spot is guided over a spiral path from the edge of the target to its center. Due to spiral scanning, the spot runs across the entire target surface with a much larger area in 0.1–1.0 s and rapidly vaporizes the target.

Influence of substrate temperature on the structural, morphological, optical and electrical properties of copper telluride thin films prepared by electron beam evaporation method

Copper telluride thin films were deposited on the glass substrates at different substrate temperatures viz., Room Temperature, 200, 300, 400 and 500°C employing electron beam evaporation method. The effect of substrate temperature on the physical properties of copper telluride films was investigated. The X-ray diffraction pattern revealed that the films deposited at 300, 400 and 500°C are polycrystalline in nature. The crystallite size, dislocation density and microstrain of these films were evaluated. Scanning electron microscopy images showed that the surface morphology of the films is modified by the variation in the substrate temperature. Further variation in the shape, size and distribution of the agglomerated crystallites formed on the surface of the copper telluride films and the roughness of the films were studied as a function of deposition temperature using atomic force microscopy. The direct optical band gap value of copper telluride films varies from 2.45 to 2.93eV with variation in the substrate temperature. Positive sign of the Hall coefficient showed p-type conductivity. The copper telluride film deposited at 500°C showed relatively low resistivity of 1.36×10−3Ωcm.

Fabrication of carbon sandwiched thin targets of 138Ba by evaporation technique

138Ba enriched isotopic targets, of thickness ranging from 200 μg/cm2 - 240 μg/cm2, with carbon sandwich have been fabricated from barium metal, by high vacuum evaporation technique at Inter-University Accelerator Centre (IUAC), New Delhi. Resistive heating and electron beam evaporation methods were used for the deposition of barium and carbon respectively. 138Ba being a highly reactive metal, target foils with carbon sandwich is fabricated in a continuous process without breaking the vacuum. The eight targets so prepared were further subjected to RBS analysis to check their purity. The thicknesses of these targets were verified by alpha energy loss method and DektakXT surface profilometer.