Deposition Rate Stability Research Articles

Fabrication of Plasmonic Indium Tin Oxide Nanoparticles by Means of a Gas Aggregation Cluster Source.

In this work, we demonstrate, for the first time, the possibility to fabricate indium tin oxide nanoparticles (ITO NPs) using a gas aggregation cluster source. A stable and reproducible deposition rate of ITO NPs has been achieved using magnetron sputtering of an In2O3/SnO2 target (90/10 wt %) at an elevated pressure of argon. Remarkably, most of the generated NPs possess a crystalline structure identical to the original target material, which, in combination with their average size of 17 nm, resulted in a localized surface plasmon resonance peak at 1580 nm in the near-infrared region.

High Sensitivity SERS Substrate of a Few Nanometers Single-Layer Silver Thickness Fabricated by DC Magnetron Sputtering Technology.

Surface-enhanced Raman spectroscopy (SERS) is commonly used for super-selective analysis through nanostructured silver layers in the environment, food quality, biomedicine, and materials science. To fabricate a high-sensitivity but a more accessible device of SERS, DC magnetron sputtering technology was used to realize high sensitivity, low cost, a stable deposition rate, and rapid mass production. This study investigated various thicknesses of a silver film ranging from 3.0 to 12.1 nm by field emission scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. In the rhodamine 6G (R6G) testing irradiated by a He-Ne laser beam, the analytical enhancement factor (AEF) of 9.35 × 108, the limit of detection (LOD) of 10−8 M, and the relative standard deviation (RSD) of 1.61% were better than the other SERS substrates fabricated by the same DC sputtering process because the results showed that the 6 nm thickness silver layer had the highest sensitivity, stability, and lifetime. The paraquat and acetylcholine analytes were further investigated and high sensitivity was also achievable. The proposed SERS samples were evaluated and stored in a low humidity environment for up to forty weeks, and no spectrum attenuation could be detected. Soon, the proposed technology to fabricate high sensitivity, repeatability, and robust SERS substrate will be an optimized process technology in multiple applications.

Highly precise multi-cathode pulsed-DC sputtering employing digital processing–application to layer–by–layer synthesis of cubic (Er0.1Y0.9)2Zr2O7 thin film

A digitally processed DC reactive sputtering (DPDRS) system employing field-programmable gate-array has been developed. In this report, atomically precise pulsed-DC sputtering of a metal oxide compound, cubic (Er0.1Y0.9)2Zr2O7 (c-EYZO), is demonstrated by using DPDRS. An alternating process of pulsed metal sputtering and reactive gas pulsing was applied in order to realize layer-by-layer reactive sputtering. The pulsed metal sputtering separated from the oxidation process results in a stable and high deposition rate of c-EYZO at 1.9 μm h−1, which corresponds to 1.56 nm/cycle. By adjusting the deposition rate to the d-spacing of 0.26 nm corresponding to the (200) diffraction, layer-by-layer synthesis of a highly oriented c-EYZO thin film showing the d-spacing was achieved. X-ray diffraction and photoluminescence measurements indicate drastic improvement of the crystalline properties and the emission properties due to the layer-by-layer synthesis. It is expected that DPDRS enables arbitrarily designed atomically precise deposition of the metal oxide compound synthesis.

Wire arc additive manufacturing Ti6Al4V aeronautical parts using plasma arc welding: Analysis of heat-treatment processes in different atmospheres

PAW (Plasma Arc Welding), a WAAM (Wire Arc Additive Manufacturing) technology with high deposition rates, can produce metallic components, layer by layer, of varied sizes, from different alloys, yielding high mechanical performance. Two Ti6Al4V walls are manufactured in an inert argon atmosphere using WAAM-PAW to analyze the deposition process in terms of growth in height per layer, deposition process temperature, and cooling times. The properties of the walls are compared with the values obtained from a thermo-mechanical simulation and both the microstructural and mechanical properties of the annealed WAAM-PAW wall are studied. Moreover, the effect of the media on the oxidation layer and on the mechanical properties are also analyzed throughout the heat treatment process, as well as the microstructure of Ti6Al4V. Stable deposition rates were achieved for a high deposition ratio of Ti6Al4V at 2 kg/h, restricting the oxygen levels to under 100 ppm. No significant differences were found in either the microstructural or the mechanical properties following heat treatments in a vacuum, in air or in argon. All the heat-treated samples met the AMS4928 standard for Yield Strength (YS) and Ultimate Tensile Strength (UTS).

Process stabilization during reactive high power impulse magnetron sputtering of Ce/Gd target

In this study, a simple approach to stabilize reactive high power impulse magnetron sputtering process in the transition zone between the metallic and oxide modes was investigated. The method is based on the use of peak current value as feedback and control signal. It was shown that the change in the state of the target surface causes almost instantaneous change in the amplitude and shape of the current pulses. To stabilize the deposition process, the pulse frequency was regulated to maintain a constant maximum discharge current. The hysteresis behavior and the variations of the pulse current waveforms over a wide range of O2 flow rates and pulse frequencies during a reactive HiPIMS deposition of gadolinia-doped ceria (GDC) thin films in an Ar-O2 atmosphere were examined. Stable process conditions were maintained at the O2 flow from 0.9 to 3.9 sccm by adjustment of the pulse frequency from 1.45 to 2.9 kHz. GDC films deposited using peak current regulation exhibited a stable stoichiometry and high deposition rate in comparison with films obtained without process stabilization.

Effects of precursors on silica particle generation in CVD synthesis for fused silica glass

High purity fused silica glass can be synthesized by CVD process in which silica particles are generated by precursors reacted in H2/O2 flame and deposited on the substrate. Selection of precursors has significant influence on silica particle generation, and further affects particle transport and deposited glass quality. This paper aims to reveal the underlying mechanisms that make silica particles generation different when using the precursors of SiCl4 and OMCTS. Comparative investigations were conducted using the computational fluid dynamics method. When using OMCTS as the precursor, the main reactions of precursor in the H2/O2 flame are exothermic. The rapid heat release from the precursor near the burner exit can promote SiO2 generation from endothermic reactions at the center of the jet close to the inlet. When using SiCl4 as the precursor, the main reactions of SiCl4 in the H2/O2 flame are endothermic. In this case, the precursor will diffuse further to high temperature H2/O2 flame to make SiO2 generation reactions happen. Thus the generated SiO2 will be away from the burner exit. The production efficiency of SiO2 by OMCTS is almost 3 times of that by SiCl4. To achieve a stable and high deposition rate, an oxygen-enriched atmosphere is preferable for both precursors. More fuel is needed for the fused silica glass process using SiCl4 than OMCTS as the precursor.

Reliability and characteristics of magnetron sputter deposited tantalum nitride for thin film resistors

Tantalum nitride (TaN) films were deposited onto SiO2/Si and multilayer ceramic (MLC) substrates with a reactive direct current magnetron sputtering method. After they were kept at different N2 partial pressures and substrate temperatures, these were characterized for their electrical, structural, and mechanical properties for use as thin film resistors (TFRs). Results of X-ray diffraction analysis, observation of microstructure, sheet resistance measurement, and accelerated degradation tests highly indicated that TaN films with high crystalline phases, good surface roughness, stable deposition rates, appropriate sheet resistances, and high reliabilities could be obtained if N2 partial pressure was maintained at around 20%. Adhesive strengths of TaN films grown on MLC substrates were increased with increasing substrate temperature up to 300 °C. A low resistance change was confirmed by temperature coefficient of resistance variation as a function of temperature, implying high reliability and durability. Results of this study suggest that TFRs described in this study are suitable for embedded passive resistors with practical applications, including controlled resistances for fabricated TaN based TFRs with different widths.

Photon Absorption Enhancement of TiO2 Nanotube Arrays Decorated with Aluminum Nanoparticles

Highly ordered TiO2 nanotube (NT) arrays fabricated by electrochemical anodization have shown promising potential for photocatalystic applications [1]. Loading metallic nanoparticles has been introduced to enhance photocatalytic activity of the TiO2 nanotubes. However, the applications are primarily focused on silver or gold due to their strong plasmonic behaviors at visible wavelength [2]. As a low cost alternative, nanoparticles Al exhibit strong plasmon resonances spanning much of visible region of the spectrum as well. In this paper, we fabricated nanoparticles Al on the wall of TiO2nanotube arrays by magnetron sputtering technique and investigated their optical characteristics. A representative SEM (Scanning Electron Microscope) image of TiO2 nanotube structure is shown Fig.1. [3] The nanoparticles Al were deposited on TiO2 nanotubes by a radio frequency (RF) reactive magnetron sputtering system (Sputter AJA 4050). The deposition parameters were kept at pressure (4.2 mTorr), power (120 W), gas (10 sccm), stable deposition rate (0.4Å/S). The nanoparticle thin films Al have been calibrated on glass substrates and TiO2 with thickness from 0 to 20 nm, which can be well-controlled by the sputtering time, the photographs of various nanoparticles Al on glass (22 mm × 22 mm) and TiO2 (10 mm × 20 mm) are shown in the Fig. 2. Compared with pure TiO2 nanotubes, the absorbance spectra (400 - 850 nm) confirms that the absorption intensity of Al/TiO2 NTs increases with increasing the thickness of Al NPs. The 10 nm Al/TiO2 NTs sample exhibits a broad absorption peak centered close to 550 nm in the visible light region. The enhanced visible light absorption peak is ascribed to the enhancement of localized surface plasmon resonance of nanoparticle Al. These results indicate that the photo-response of TiO2 NTs could be easily extended to the visible-light region through the aid of nanoparticles Al (Fig. 3). In summary, well-dispersed distribution of nanoparticles Al have been assembled on the TiO2 NTs by RF magnetron sputtering technique. The nanoparticles Al are readily controlled with thickness from 5 to 20 nm. The visible light absorption have been systematically studied. The optimized thickness is ~10 nm, which efficiently absorb light over a broad range of wavelength.

Effect of discharge power on target poisoning and coating properties in reactive magnetron sputter deposition of TiN

Reactive magnetron sputtering is a well-established technique for the deposition of high quality functional compound coatings. However, avoiding the undesired hysteresis effect that occurs when the metal target becomes covered by a compound layer at a certain reactive gas flow or partial pressure, typically referred to as target poisoning, is still an intense field of research. In the current work, the effect of the discharge power on target poisoning and coating structure and properties was assessed by determining the hysteresis and by characterizing the sputter-deposited TiNx coatings, where x ≤ 1. With increasing discharge power, the hysteresis was shifted to higher N2 gas flow values. In metallic mode, the increase in discharge power enabled therefore the incorporation of high nitrogen fractions in the TiNx coatings at stable discharge conditions and high deposition rates. In poisoned mode, all coatings were stoichiometric, but the deposition rates were lower by a factor of 1/3. Regardless of the deposition mode, grain refinement and high stresses generated due to the increase in the deposition rate at elevated deposition power increased the hardness and elastic modulus of the deposited TiNx coatings. At a power density of 34 W/cm2, the hysteresis was largely eliminated and a deposition rate of 0.15 μm/min for stoichiometric TiNx with high hardness of up to ∼30 GPa could be achieved. The results presented in this paper demonstrate that increasing the discharge power density facilitates the deposition of stoichiometric TiN by operating in the metal/transition mode.

Design calculations and characterization of C/Cr multilayer mirrors in the 6 nm BEUV

This paper focuses on the design, fabrication and characterization of the reflectivity and bandwidth of C/Cr multilayer mirrors of variable layer numbers (N=30, 40, 100, 150 and 200) in order to exploit them as efficiently as possible at a wavelength of 6nm. Magnetron sputtering technique was used with high base vacuum and high purity working gas (Argon 99.99%) together with a stable deposition rate during the fabrication process. The multilayers were probed using a hard X-ray diffraction method (Cu Kα radiation, λ=0.154nm) to characterize their reflectivity, bi-layers structure and surface roughness. An atomic force microscope was used to determine the surface topography and to analyze the surface structure imperfections such as roughness and stress induced damage. These were believed to occur during the preparation of the substrate or fabrication process. Various imperfections may also have developed due to oxidization after post production exposure to air. The surface roughness values obtained using X-ray scattering and atomic force microscopy were found to be in good agreement with each other.

Role of oxygen admixture in stabilizing TiO x nanoparticle deposition from a gas aggregation source

For the use of a gas aggregation cluster source a high and stable deposition rate is desired. For many metals, nanoparticle formation is enhanced by admixture of reactive gases. Here, the role of reactive gas admixtures on the nanoparticle deposition rates is investigated for the case of reactive direct current magnetron sputtering of Ti in a gas aggregation chamber. The results show that, at low working gas (argon) pressures, stable cluster deposition at high rates can only be achieved for admixtures with a very narrow oxygen flow range. At higher pressures, stable deposition can be observed only after an intermediate maximum rate has been crossed or a stable deposition rate is not reached at all. For the different sputtering conditions, the partial pressure of oxygen was monitored with a mass spectrometer. The results are explained in terms of the competing roles of oxygen in cluster nucleation as well as in target poisoning. The cluster size distributions for different conditions were characterized by scanning electron microscopy.

Combination of a Knudsen effusion cell with a quartz crystal microbalance: In situ measurement of molecular evaporation rates with a fully functional deposition source

We describe a straightforward, reliable, and inexpensive design of a Knudsen type molecular effusion cell capable of measuring molecular evaporation rates in situ. This is accomplished by means of a quartz crystal microbalance integrated into the shutter of the effusion cell. The presented layout facilitates both the measurement of effusion rates under ultrahigh vacuum conditions without the need for a separate experimental setup and the growth of surface supported molecular layers and nanostructures. As an important prerequisite for reproducible deposition of molecular films with defined coverages ranging from submonolayers up to multilayers, the Knudsen cell features a stable deposition rate for crucible temperatures between 50 and 500 degrees C. Experimental determination of deposition rates for different crucible temperatures allows to approximate sublimation enthalpies of the evaporant based on the Clausius-Clapeyron equation.

Long-term atmospheric bulk deposition of polycyclic aromatic hydrocarbons (PAHs) in rural areas of Southern Germany

A novel passive sampling technique using a funnel–adsorber–cartridge device was adopted and validated in the field during a long-term monitoring program on the atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) in three rural regions of southern Germany. Apart from seasonal variations, fairly stable annual deposition rates around 200 μg m −2 yr −1 for the sum of PAHs were obtained. The time-integrating passive samplers showed that spatial variability due to topography was negligible and differences between open-field and forest deposition were within a factor of 2. Based on correlations with ambient temperature, advection was identified as the most important factor that controls the atmospheric deposition of PAHs. Gas-adsorption contributes significantly to the deposition of the semivolatile compounds in forests, but particle deposition seems to be the major pathway for all PAHs.

30.4: Vertical Inline Deposition Technology for Full-Color OLED Production

Linear evaporation sources for substrates of up to 400 × 470 mm2 have been developed. The thermal load on the substrate during deposition has been reduced and the influence of different grain sizes has been analyzed. Automatic rate control gave stable deposition rate over three days. For full-color OLED production a mask alignment system for the vertical inline deposition technology has been developed. The system handles substrate sizes of 370×470 mm2 and achieves a precision of better than +/− 5 μm. Mask cleaning is carried out in vacuum for long mask life and process stability.

Flexible microprocessor-based evaporation controller

Electron beam evaporation sources require two power supplies, one each for the filament current and the electron acceleration. To obtain a stable deposition rate, the emission current between filament and target must remain constant. During film deposition, slight geometry changes in the evaporator cause significant rate variations, making constant readjustment of the emission current necessary. While in commercial solutions, analog feedback regulators are often used to perform this task, these controllers cannot easily be adapted to home-built evaporation sources. The microcontrolled feedback controller presented here is more flexible and versatile than the commercial solutions. The controller can be easily modified to work with different external power supplies and allows the easy upgrade of most existing electron beam evaporation setups. A serial-port computer interface completely integrates the controller into the automated laboratory environment.

Versatile UHV compatible Knudsen type effusion cell

A versatile Knudsen type effusion cell has been fabricated for growing nanostructures and epitaxial layers of metals and semiconductors. The cell provides excellent vacuum compatibility (10−10 mbar range during operation), efficient water cooling, uniform heating, and moderate input power consumption (100 W at 1000 °C). The thermal properties of the cell have been determined. The performance of the cell has been assessed by x-ray photoemission spectroscopy (XPS) for Mn adlayer growth on Al(111). We find that this Knudsen cell has a stable deposition rate of 0.17 monolayer per minute at 550 °C. From the XPS spectra, we show that the Mn adlayers are completely clean, i.e., devoid of any surface contamination.

50.4: First Hybrid OLED by Organic Vapor Phase Deposition and Its Advantages in Deposition Rate Control for OLED Manufacturing

AbstractWe are discussing the latest results in the field of Organic Vapor Phase Deposition (OVPD) on basis of our experimental data. In particular the use of carrier gas and its controlled mass flow are adding an additional parameter to control deposition rates in OLED manufacturing by OVPD. Many advantages offered by this key parameter in this technology like stable deposition rates, wide range of adjustable deposition rates and doping concentrations are discussed.A small molecule hybrid OLED (SM‐HLED) consisting of a polymer layer of PEDT:PSS and two small molecule layers of α‐NPD and Alq3 was fabricated by OVPD. For this 3‐layer device we observed a turn on voltage of 2.5 V, a luminance brightness of 100 cd/m2 at 5.2 V and 300 cd/m2 at 6.5 V. Furthermore a passive matrix OLED‐display (PMOLED‐display) was demonstrated by OVPD. The display had a turn‐on voltage of about 3.0 V and showed a very homogeneous light emission.These device characteristics confirm that OVPD is close to be comparable to Vacuum Thermal Evaporation (VTE).

Optical investigations in a PEM controlled reactive magnetron sputter process for aluminium doped zinc oxide layers using metallic alloy targets

The use of aluminium doped zinc oxide (ZAO) as transparent conductive layer (TCO) has growing importance especially for production of solar modules. A significant cost reduction of TCO thin film production is expected by use of much less expensive metallic alloy targets. ZAO films with good TCO properties can be achieved only in the transition mode of the reactive sputter process. To stabilize the discharge for long stretched magnetron sputter sources on the working point needed a process control system is required. The intensity of zinc emission lines is used as control parameter. The control is performed by adding varying amounts of oxygen gas to the discharge region using the Plasma Emission Monitor PEM ®05. This allows a combination of reproducible TCO film properties with stable high deposition rates. By use of an optical emission spectrometer AOS-4 it was investigated in situ, which emission lines are best suited for the process control. Herefore the chronogram mode of the spectrometer is used, which allows spectral lines to be monitored with a time resolution of a few milliseconds. Furthermore, other spectral line intensities are investigated for use as regulation parameter. A concept for regulating a reactive sputter process by use of several emission lines is discussed. The concept was applied for DC discharge and MF discharge as well. A time-resolved investigation of the interesting spectral lines in MF discharge is carried out with microsecond resolution.

Tribological and optical properties of crystalline and amorphous alumina thin films grown by low-temperature reactive magnetron sputter-deposition

Amorphous and crystalline alumina thin films were grown by reactive magnetron sputtering. A pulsed d.c. bias was applied to both the aluminum target and the substrate to maintain a stable deposition process and high deposition rate. An external solenoid coil was placed underneath the substrate to form a magnetic trap between the substrate and the target, thus enhancing ion bombardment of the growing film. Effects of substrate bias and magnetic trap on film properties were investigated. Under optimum conditions, crystalline alumina films were obtained at substrate temperatures of ∼340°C, with hardness ∼25 GPa and refractive index 1.65–1.85 in the visible region. Friction and wear properties of crystalline and amorphous alumina thin films were compared.

Low-temperature magnetron sputter-deposition, hardness, and electrical resistivity of amorphous and crystalline alumina thin films

Aluminum oxide films were grown by reactive magnetron sputtering. In order to maintain a stable deposition process and high deposition rate, a pulsed direct current bias was applied to the aluminum target and the substrate. An external solenoid was used to form a magnetic trap between the target and the substrate. The influence of substrate temperature, substrate bias, and the magnetic trap on film growth and properties was studied by different surface and thin-film analysis techniques and electrical measurements. Normally, amorphous alumina films were produced. However, under optimum process conditions, crystalline alumina films can be obtained at temperatures as low as 250 °C, with a hardness ∼20 GPa and excellent electrical insulating properties.