Electrochemical deposition and characterization of Cu2O nanowires

Cu₂O nanowires were successfully synthesized by an electrochemical method using an alumina membrane as template through precise control of the pH value of the electrolyte. The deposition process was monitored by the time–current curve. Characterization was performed by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The growth directions of the Cu₂O nanowires were determined and the possible growth mechanism is discussed. PACS 68.37.Lp; 81.07.-b; 81.16.Be     

Materials characterization of n - ZnO / p - GaN : Mg / c - Al2O3 UV LEDs grown by pulsed laser deposition and metal–organic chemical vapor deposition

n-ZnO/p-GaN:Mg hybrid heterojunctions grown on c-Al₂O₃ substrates showed 375 nm room temperature electroluminescence. It was suggested that the high materials and interface quality obtained using pulsed laser deposition for the n-ZnO growth and metal–organic chemical vapor deposition for the p-GaN:Mg were key factors enabling the injection of holes and the radiative near band edge recombination in the ZnO. In this paper we present the materials characterization of this structure using x-ray diffraction, scanning electron microscopy and atomic force microscopy.     

Axial distribution of plasma fluctuations,plasma parameters,deposition rate and grain size during copper deposition

Floating potential fluctuations, plasma parameters and deposition rate have been investigated as a function of axial distance during deposition of copper in direct current (DC) magnetron sputtering system. Fluctuations were analyzed using phase space, power spectra and amplitude bifurcation plots. It has been observed that the fluctuations are modified from chaotic to ordered state with increase in the axial distance from cathode. Plasma parameters such as electron density (n_e), electron temperature (T_e) and deposition rate (D_r) were measured and correlated with plasma fluctuations. It was found that more the deposition rate, greater the grain size, higher the electron density, higher the electron temperature and more chaotic the oscillations near the cathode. This observation could be helpful to the thin film technology industry to optimize the required film.     

Controllable synthesis of highly ordered Ag nanorod arrays by chemical deposition method

Highly ordered Ag nanorod arrays were successfully fabricated using a simple chemical deposition method with the assistance of porous alumina membrane (PAM) template. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ag⁺ ions in the PAM nanochannels were reduced by acetaldehyde reagent and resulting in the formation of rod array structures. It is found that the diameter of the Ag nanorods is determined by the PAM template, and the length of the Ag nanorods is depended on the reaction temperature. The growth mechanism of the Ag nanorod arrays is investigated in the study.     

Focused electron beam induced deposition as a tool to create electron vortices

Focused electron beam induced deposition (FEBID) is a microscopic technique that allows geometrically controlled material deposition with very high spatial resolution. This technique was used to create a spiral aperture capable of generating electron vortex beams in a transmission electron microscope (TEM). The vortex was then fully characterized using different TEM techniques, estimating the average orbital angular momentum to be ∼0.8ℏ per electron with almost 60% of the beam ending up in the ℓ = 1 state.     

Micropatterned ZnO rod arrays prepared by Au‐catalyzed electroless deposition

Micropatterned ZnO was synthesized by an electroless deposition process using Au stripes as catalytic surfaces. The Au‐patterned electrodes were prepared on SiO₂/Si wafers using photolithography. The site‐selective deposition of patterned ZnO hexagonal rod arrays is confirmed by scanning electron microscopy. The ZnO micropatterned surface revealed a conversion of wettability from hydrophilic to superhydrophobic depending on the deposition reaction param‐ eters. The electrical measurements carried out at room temperature before and after exposure to ammonia vapors of the patterned ZnO arrays show a resistance variation with exposure time. Highly reproducible, easy scalable and low‐cost, photolithography and electroless deposition techniques could provide a facile approach to fabricate functionalized micropatterns, for a wide range of applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pulsed laser deposition of nanostructured Ag films

Ultra-thin (0.5-5 nm) films of Ag have been prepared by pulsed laser deposition in vacuum using a 26 ns KrF excimer laser at 1 J cm⁻². The deposition was controlled using a Langmuir ion probe and a quartz crystal thickness monitor. Transmission electron microscopy showed that the films are not continuous, but are structured on nanometer size scales. Optical absorption spectra showed the expected surface plasmon resonance feature, which shifted to longer wavelength and increased in strength as the equivalent film thickness was increased. It is shown that Maxwell Garnett effective medium theory can be used to calculate the main features of optical absorption spectra.     

Characterization of polymer thin films obtained by pulsed laser deposition

The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate).The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry.It was found that for laser fluences up to 1.5 J/cm² the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm² the polyepichlorohydrin films present deviations from the bulk polymer.Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm²).The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material.The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.     

Rugate filters prepared by rapidly alternating deposition

A methodology for the fabrication of composite (Nb₂O₅)_1-x(SiO₂)_x thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technology. The optical properties of the composite films varying with the composition of the material are studied in detail. Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a reflection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra are in good agreement with each other. The causes of the slight differences between them are also analysed.     

Nanoscale electron beam-induced deposition and purification of ruthenium for extreme ultraviolet lithography mask repair

One critical area for the adoption of extreme ultraviolet (EUV) lithography is the development of appropriate mask repair strategies. To this end, we have explored focused electron beam-induced deposition of the ruthenium capping or protective layer. Electron beam-induced deposition (EBID) was used to deposit a ruthenium capping/protective film using the liquid bis(ethylcyclopentyldienyl)ruthenium(II) precursor. The carbon to ruthenium atomic ratio in the as-deposited material was estimated to be ~9/1. Subsequent to deposition, we demonstrate an electron stimulated purification process to remove carbon by-products from the deposit. Results indicate that high-fidelity nanoscale ruthenium repairs can be realized.     

Combining wire and coaxial powder feeding in laser direct metal deposition for rapid prototyping

Powder and wire deposition have been used separately in many laser-cladding, rapid prototyping and other additive manufacturing applications. In this paper, a new approach is investigated by simultaneously feeding powder from a coaxial nozzle and wire from an off-axis nozzle into the deposition melt pool. Multilayer parts are built from 316L steel using a 1.5 kW diode laser and different configurations of the powder and wire nozzles are compared in terms of surface roughness, deposition rate, porosity and microstructure. The parts are analysed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy techniques. Results show that deposition efficiency increased and surface roughness decreased with the combined process; some porosity was present in samples produced by this method, but it was 20-30% less than in samples produced by powder alone. Wire injection angles into the melt pool in both horizontal and vertical planes were found to be significant for attaining high deposition efficiency and good surface quality. Reasons for the final sample characteristics and differences between the combined process and the separate powder and wire feeding techniques are discussed.     

Effect of deposition power and pressure on rate deposition and resistivity of titanium thin films grown by DC magnetron sputtering

ABSTRACT

Based on magnetron sputtering deposition technology, titanium (Ti) thin films are deposited on silicon (Si) substrate using different preparation conditions such as sputtering power and pressure. The influence of altering these conditions on deposition rate and microstructure is studied. The results show that sputtering power significantly affects the rate of deposition and the resistivity. The deposition rate of the Ti thin film increases when the resistivity decreases under sputtering powers of 150–225?W with a pressure of 0.8?Pa and Argon (Ar) flux of 80 sccm. As sputtering power was increased further (from 225 to 250?W), the deposition rate reduced and the resistivity augmented. Pressure also has influence on the deposition rate and resistivity – when pressure increases from 0.6 to 0.8?Pa, the deposition rate escalates while the resistivity reduces; when the pressure is raised from 0.8 to 1.0?Pa with Ar flux of 100 sccm, the deposition rate decreases and resistivity increases. The surface chemical compositions and the structures of the Ti film were studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). Observing the cross-section of the thin-film samples produced by scanning electron microscope (SEM) reveals the influence of the preparation conditions used on the microstructure and confirms the influence of sputtering power and pressure on the resistivity.     

Pulsed laser deposition of hard magnetic films

Pulsed laser deposition from elemental targets was used to prepare highly textured hard magnetic Nd–Fe–B and Fe–Pt films with coercivities of 2 T and 5.2 T, respectively. In situ methods such as reflection high energy electron diffraction and Auger electron spectroscopy were applied to analyse film composition and structure during growth. Optimisation of the hard magnetic properties is discussed together with the specific advantages of pulsed laser deposition. PACS 81.15.Fg; 75.50.Ww; 75.50.Vv     

Evolution of the deposition rate during pulsed laser deposition of hydroxyapatite coatings and its relation with target morphology

The evolution of the deposition rate during pulsed laser deposition of hydroxyapatite coatings with a KrF excimer laser was studied. This evolution was related to the changes produced on the target morphology during laser irradiation. Laser fluences in the 1.0–5.2 J/cm² range, typical for the deposition of hydroxyapatite coatings, were investigated. Deposition rates were measured through a quartz-crystal microbalance, and the target surface was observed by scanning electron microscopy. At the lowest fluences, the deposition rate decreases as the number of pulses increases. At the same time, a cone structure is developed on the target surface. At the highest fluences, the deposition rate increases with the number of pulses. In this case, the target surface becomes rough but cones are not formed. In all cases, an enlargement of the effective irradiated area results. This enlargement produces the effect of fluence dilution and also an increase of the emitting area. These opposite effects could account for the different evolutions found for the deposition rate. At low fluences the effect of fluence dilution would predominate over the increase of the emitting area, and at high fluences the second effect would predominate over the first. Received: 28 September 2000 / Accepted: 4 October 2000 / Published online: 10 January 2001     

电子束在相对论返波管振荡器收集极上的能量沉积

在圆周对称的磁场作用下,环形电子束以一定角度轰击在圆柱面的相对论返波管振荡器(RBWO)收集极上并将能量沉积其中,采用蒙特卡罗程序FLUKA,建立了电子的能量沉积分布计算模型,研究了电子能量沉积分布规律;建立了背散射电子的运动模型,模拟了磁场作用下背散射电子的运动轨迹;研究了圆周对称径向磁场的近似方法。研究结果表明:随着磁场强度的增大,最大能量沉积密度增大,背散射电子在更靠近电子束入射区域的位置再次入射并沉积能量,且可能形成一个新的能量沉积峰值。在磁场强度较大时,采用单向的径向磁场即可较好地计算圆周对称径向磁场下背散射电子的能量沉积分布。     

A new fabrication technique for photonic crystals: Nanolithography combined with alternating-layer deposition

We propose two photonic crystal structures that can be created by combining nanolithography with alternating-layer deposition. Photonic band calculations suggest that a drilled alternating-layer photonic crystal combining two-dimensional (2D) alternating multilayers and an array of vertically drilled holes may achieve a full photonic bandgap. In addition, a 3D/2D/3D cross-dimensional photonic crystal, which sandwiches a 2D photonic crystal slab between three-dimensional (3D) alternating-layer photonic crystals, should provide better vertical confinement of light than a conventional index guiding slab. Fabrication techniques based on existing technologies (electron beam lithography, bias sputtering, and low-pressure ECR etching) require very few process steps. Our preliminary fabrication suggests that, by refining these technologies, we will be able to realize photonic crystals.     

Single-crystalline AlN growth on sapphire using physical vapor deposition

A novel technique for growing single crystalline aluminum nitride (AlN) films is presented. The novelty of the technique, specifically, comes from the use of an innovative physical vapor deposition magnetron sputtering tool, which embeds magnets into the target material. A relatively high deposition rates is achieved (∼0.2 μm/min), at temperatures between 860 and 940 °C. The AlN, grown onto sapphire, is single-crystalline as evidenced by observation using transmission electron microscopy. Tool configuration and growth conditions are discussed, as well as a first set of other analytical results, namely, x-ray diffraction and ultraviolet-visible transmission spectrophotometry.     

Synthesis and characterization of silica nanosprings by a low temperature chemical vapor deposition

Silica nanosprings were synthesized using a simple, low temperature, chemical vapor deposition method via a vapor–liquid–solid mechanism. Nanosprings with excellent uniformity and helicity in high and repeatable yields have been observed. The morphology and crystal structure of the nanosprings were characterized by scanning electron microscopy and transmission electron microscopy. The chemical composition of the nanosprings was determined using the energy-filtered transmission electron microscopic method. The as-grown nanomaterials were confirmed to be amorphous silica with irregularly shaped Au catalytic particles located at the tips. In addition, we propose a spontaneous spinning growth model to explain the formation of such helical nanostructures.     

Paschen curve approach to investigate electron density and deposition rate of Cu in magnetron sputtering system

In this work, Paschen curve for argon gas was obtained during copper deposition using a DC magnetron sputtering system. Five process parameters of Paschen curve were used to obtain the electron density and deposition rate of the deposited nanostructured thin films. Plasma parameter such as electron density was correlated with the deposition rate. It is observed that a minimum deposition rate was obtained for the plasma process parameter corresponding to the Paschen minimum. This investigation helps to understand and optimize the quality of nanostructured thin films depending on the process parameters.     

Pulsed electron beam deposition of highly oriented thin films of polytetrafluoroethylene

Thin films of polytetrafluoroethylene (PTFE) were deposited by pulsed electron deposition (PED) technique. The transmission electron microscopy (TEM) image of the RT fabricated (20 Å thick) film on carbon coated copper grid shows crystalline nature. Infrared spectra show one to one correspondence between PED ablated film and the PTFE bulk target. The asymmetrical and symmetrical -CF₂- stretching modes were observed at 1220 and 1156 cm⁻¹, respectively. The -CF₂- wagging and bending modes occur at 644 and 512 cm⁻¹, respectively. X-ray diffraction patterns of the film deposited at room temperature (RT) show oriented film along (1 0 0) plane of hexagonal structure and the crystalline nature is retained up to 300 °C on vacuum annealing. The room temperature fabricated film shows smooth and pin hole free surface whereas post-annealing brings discontinuity, roughness and pin holes.