Deposition Facility Research Articles

Fluorocarbon film as cathode protective coating in organic light-emitting devices

The present work demonstrates the use of fluorocarbon (CFx) film as a cathode protective layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with the CFx cathode protective layer showed a threefold increase in operational lifetime, about 10000h, comparing to those without the CFx layer. Growth of dark spots was significantly suppressed. The superior moisture-resistant capability of the CFx is attributed to its hydrophobic nature and low moisture permeation. As most OLED production lines are already equipped with CFx deposition facilities, the present cathode protective coating can be easily adopted for further stability enhancement without additional capital investment.

Metal spray deposition of cylindrical preforms

A number of deposition experiments were carried out in a metal spray deposition facility for cylindrical preforms, at Sandvik Steel AB. Thick layers of modified Inconel 625 were sprayed over steel bars 170 mm in diameter and 8 m long. The rods were at room temperature during the deposition process. The effect of rotational velocity and fraction solidified in the spray was studied. Measurements of grain length intercept and porosity content were performed, as well as estimations of the shape of the actual deposition profile. Microprobe analysis was accomplished in different locations on the samples. A computational fluid dynamic model is implemented together with a continuum heat transfer model in order to facilitate the analysis. The range of the rotational velocity studied did not show any large effect on the formation of the base porosity. Three main zones were identified in the microstructure, i.e. porous-dendritic, transition and equiaxed. The segregation patterns suggested that a chemical homogenization occurred during the process. This was supported by the results of the numerical calculations.

The corrosion properties of Al/Al 2O 3 multilayered coatings on CK45 steel deposited by IBAD

For the purpose of providing corrosion protection, multilayered Al/Al 2O 3 coatings were deposited on CK45 steel by an Ion Beam Assisted Deposition (IBAD) facility. Five kinds of multilayered coatings with overall thickness of 3 μm were made in the experiment, and 0.1 μm graded Al 2O x ( x<3) layers were formed between the Al and Al 2O 3 layers instead of sharp Al/Al 2O 3 interface. The coating structure and composition were examined with RBS and AES measurement; and the corrosion behavior was determined by potentiodynamically controlled current–potential measurements under conditions of uniform corrosion and pitting corrosion attack. The results show that these multilayered coatings can give good protection to the steel substrate, the corrosion current density decreases three to four orders. Also, the protection ability depends on the coating structure and composition when the overall thickness was fixed.

Simulated Land-Based Turbine Deposits Generated in an Accelerated Deposition Facility

This report presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. This facility was designed to produce turbine deposits in a 4-h test that would simulate 10000h of turbine operation. This is accomplished by matching the net foreign particulate throughput of an actual gas turbine. Flow Mach number, temperature and particulate impingement angle are also matched. Validation tests were conducted to model the ingestion of foreign particulate typically found in the urban environment. The majority of this particulate is ceramic in nature and smaller than 10microns in size, but varies up to 80microns. Deposits were formed for flow Mach number and temperature of 0.34 and 1150°C, respectively, using MCrAlY coated coupons donated from industry. Investigations over a range of impingement angles yielded samples with deposit thicknesses from 10to50microns in 4h, accelerated-service simulations. Deposit thickness increased substantially with temperature and was roughly constant with impingement angle when the deposit thickness was measured in the direction of the impinging flow. Test validation was achieved using direct comparison with deposits from service hardware. Deposit characteristics affecting blade heat transfer via convection and conduction were assessed. Surface topography analysis indicated that the surface structure of the generated deposits were similar to those found on actual turbine blades. Scanning electron microscope (SEM) and x-ray spectroscopy analyses indicated that the deposit microstructures and chemical compositions were comparable to turbine blade deposit samples obtained from industry.

Nitrogen beam RBS for concentration uniformity measurements of SiO 2:Au thin layer co-depositions

Co-depositions of gold and silica (amorphous silicon dioxide) on silica substrates using the ion beam assisted deposition (IBAD) facility at the Center for Irradiation of Materials at Alabama A&M University (CIM-AAMU) were analyzed for Au concentration, distribution and uniformity within the layer deposited. High resolution RBS using 4 MeV nitrogen ions combined with RUMP simulations accurately provided useful feedback to the fabrication process.

1-D nanochannels fabricated in polyimide.

A simple method using spin-deposition and sacrificial layer etching is used to fabricate all-polyimide nanochannels (100 and 500 nm channel height). Channels are characterized using spontaneous capillary filling with water, ethanol and isopropanol, and with electroosmotic flow. The channels can be produced with simple cleanroom equipment, namely spinning and metal deposition facilities. Polyimide is an excellent material for micro- and nanofluidic channels due to its favourable electrical and mechanical properties and its biocompatibility.

In situ plasma diagnostics study by means of optical emission spectroscopy for diamond chemical vapor deposition under high gravity conditions

A complete optical spectroscopy apparatus has been developed on board of a high gravity chemical vapor deposition facility. The article describes in detail the experimental apparatus and its main features. Preliminary results concern in situ plasma diagnostics under various gravity conditions up to 75g. The developed diagnostic apparatus is found to be a convenient tool for systematic in situ investigation of the influence of high gravity on the plasma composition. Thus, it is an effective means to clarify the most relevant active species playing a role during diamond film growth under high gravity conditions.

Fabrication of 100 A class, 1 m long coated conductor tapes by metal organic chemical vapor deposition and pulsed laser deposition

SuperPower has been scaling up YBa 2Cu 3O x -based second-generation superconducting tapes by techniques such as pulsed laser deposition (PLD) using industrial laser and metal organic chemical vapor deposition (MOCVD). Both techniques offer advantage of high deposition rates, which is important for high throughput. Using highly-polished substrates produced in a reel-to-reel polishing facility and buffer layers deposited in a pilot ion beam assisted deposition facility, meter-long second-generation high temperature superconductor tapes have been produced. 100 A class, meter-long coated conductor tapes have been reproducibly demonstrated in this work by both MOCVD and PLD. The best results to date are 148 A over 1.06 m by MOCVD and 135 A over 1.1 m by PLD using industrial laser.

Scale up of high-performance Y-Ba-Cu-O coated conductors

YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) coated conductors have been produced in meter lengths in pilot scale facilities established at IGC-SuperPower. Highly-smooth nickel alloy substrates have been polished in reel-to-reel polishing facility, with a uniform roughness of 2 nm. A pilot-scale ion beam assisted deposition (IBAD) facility has been used to produce 1 to 5 m lengths of buffered tapes with a uniform in-plane texture of 11 degrees and a surface roughness of 12 nm. YBCO has been deposited on meter-lengths of substrates by both pulsed laser deposition (PLD), and metal organic chemical-vapor deposition (MOCVD). End-to-end critical current of 43 A has been achieved in meter-long PLD-based YBCO. Meter-long YBCO tapes with a critical current of 90 A have been produced in MOCVD facility.

Performance of a double-multilayer monochromator at Beamline 2-BM at the Advanced Photon Source

We describe the performance of the double-multilayer monochromator that is installed at bending magnet beamline 2-BM at the Advanced Photon Source. In order to achieve continuous operation over energies from 3.2 to 10.9 keV, four different multilayer stripes were deposited onto Si substrates using the in-house sputtering deposition facility at the APS. The optical performance of the four stripes depends on their operating energy ranges, and produces 45%–75% peak reflectivity at first-order reflection with a 1%–6% bandwidth and a total flux increase of 20–40 compared to the Si(111) double-crystal monochromator.

Status of Cat-CVD (Hot-Wire CVD) research in Europe

In Europe, an increasing number of groups are commencing and expanding research on the Hot Wire CVD process, and on the unique materials and optoelectronic devices that can be obtained with this process. There are at least seven laboratories that are intensively studying and utilizing the Hot Wire CVD process, while other groups who do not presently have such deposition facilities, have developed an interest in the characterization of the unique properties of Hot Wire deposited materials. Even now, the number of groups that are actively engaged in processing of the thin films is still growing. Silicon thin films with amorphous, microcrystalline, and polycrystalline character have been made. Doped layers, both p- and n-type, and dielectric layers with device-quality properties are available. There are numerous applications, of which solar cells and thin film transistors are the most intensively studied. This paper describes the ongoing investigations and results obtained in Europe. It is not meant to be an exhaustive review, but rather a snapshot of the current highlights.

Redeposition Effects During the FIB Milling of Silicon

The technique for the preparation of specimens for transmission electron microscopy (TEM) using the focused ion beam (FIB) miller typically consists of a series of milling steps performed over both sides of an area of interest until an electron transparent membrane is achieved [1]. This process is often accompanied by the formation of damage layers on the surfaces of the specimen. The origins of any damage layer are still not clear. On one hand the process of amorphisation of the target material by the highly energetic ion beam is well known. Alternatively, other workers have reported that this damage layer can be connected with redeposition of milled material. [2,3]. in this paper we have studied redeposition effects during FIB milling of silicon TEM specimens.A FEI xP200 FIB system with a Ga+ ion source operating at 30 kV was used in this work. to study redeposition effects a row of trenches on a silicon specimen was milled under different beam currents ranging from 1000 to 6600 pA. The size of such trenches was 15x10 μm wide and 1 μm deep. The specimen was then removed from the FIB and sputter coated with a ∼50-100 nm thick Au film to preserve the trench surfaces from further damage during subsequent milling. The specimen was then placed back in the FIB system and a second set of trenches 5×8 μm wide and 0.6 μm deep was milled on the bottom of first set of trenches (Fig. 1a). The specimens were sputter coated with Au again and were placed back in the FIB system and the trenches were then covered with 1 μ thick Pt strips using the metal deposition facility of the FIB. The presence of these protection layers (Au and Pt) ensures that the final TEM specimen have unmodified original damage layers resulting from the initial milling steps. Cross-sectional TEM specimens of the trench walls were then prepared using normal FIB procedures (Fig. 1b) [2].

Effect of thermal conditions on microstructural features during spray forming

The evolution of fine-grained microstructure, during spray forming is a noteworthy feature and it is achieved by properly designed parameters. These parameters include the thermodynamic properties of the gas and the material and the important process variables like superheat temperature, gas pressure, metal flow rate and flight distance. In the present investigation, fundamental characteristics of droplet dynamics and heat flow pattern have been analysed during the process. It has been indicated that the heat transfer coefficient at the droplet–gas interface is strongly influenced by the size of the droplets and their relative velocity with the gas stream. The droplet dynamics and the thermal state during deposition accordingly govern the microstructure evolution in the deposit. The solidification structure along peripheral to central regions of spray deposits, obtained using a spray atomization and deposition facility available at NPL in conical and flat disc shapes, has been evaluated. On the basis of preliminary observations, the analysis of process parameters during atomization and deposition and their consequences on the scale of microstructure in atomized droplets and spray deposits has been compared and discussed.

Feasibility study of chemical liquid deposition based solid freeform fabrication

The Chemical Vapor Deposition (CVD) process has been used in Solid Freeform Fabrication (SFF) for several years, and it has faced some critical problems in deposition rate, product accuracy and facility cost. To overcome these shortcomings and explore new chemical deposition methods and materials, a new rapid tooling and SFF technique named Chemical Liquid Deposition based Solid Freeform Fabrication (CLD-SFF) is proposed. CLD-SFF can further be sub-divided as Thermochemical Liquid Deposition Based SFF (TCLD-SFF) and Electrochemical Liquid Deposition Based SFF (ECLD-SFF). TCLD-SFF is based on the following experimental fact: when cold (room temperature) liquid reactants are sprayed from a nozzle and come in contact with a hot substrate, the reactants can decompose or react with one another, and then the solid products are deposited on the substrate. By controlling the motion of the nozzle and the spray time, a desired three-dimensional shape of deposited material can be formed through layer-by-layer scanning. In ECLD-SFF a special anode was designed to deposit metallic materials among powder particles on a plate cathode. By controlling the motion of the anode and the current and voltage of the electrical field, a desired three-dimensional part made of connected powder particles can be formed through layer-by-layer scanning. According to our initial experimental results, the feasibility of CLD-SFF is discussed and demonstrated.

Interconnected UHV facilities for materials preparation and analysis

A UHV system for in-situ preparation and analysis of ultra thin films has been built. The system includes a rapid thermal processing furnace which allows production of samples over a wide range of temperatures and pressures using isotopically enriched gases. XPS, AES , and LEED analyses provide information on the surface structure and composition. With a transportable UHV chamber, the samples can be transferred to a 4π γ-ray spectrometer facility (in UHV), where analytical ion beam methods can be used to determine isotopic depth profiles and total amounts of isotopes in the films. Furthermore, an ion beam deposition facility (in UHV) can produce isotopically enriched silicon films on Si substrates for in situ isotopic tracing.

Spin-polarized quantum well states

Abstract Highly-quality Cu/Co/Cu(100) quantum wells are grown in a newly-constructed growth chamber that contains RHEED, LEED, SMOKE, MBE, and sputter deposition facilities. The low defect density of the fcc Co(100) layers is evidenced by a record low coercivity of 0.7 Oe, which indicates minimal pinning of the domains. Spin-polarized, angle-resolved photoemission spectra are obtained using synchrotron radiation from an undulator. They exhibit quantum well states of minority spin character which are derived from states at the neck of the Cu Fermi surface. Such states have been predicted to dominate the magnetic coupling in multilayers. They have been difficult to observe because their short wavelength requires atomically-sharp interfaces. The key to obtaining high quality films with sharp interfaces is deposition at low temperature (≈175 K) and annealing to room temperature.

Large area and high sensitivity a-Si:H/a-SiC:H based detectors for visible and ultraviolet light

In this article we discuss the fabrication and performance of a-Si:H/a-SiC:H based ultraviolet sensitive devices. They were deposited over a large area (10 cm×10 cm) in p-i-n configuration using a new, multichamber, ultrahigh vacuum plasma enhanced chemical vapor deposition facility. The intrinsic layer thickness was 10–100 nm. The devices were characterized in the spectral range 365–660 nm and showed good sensitivity in the UV (365 nm). A good rejection of visible light was also measured. Responsivity as high as 0.30 A/W was measured at 365 nm for samples where the p layer and i layer were 5 and 10 nm thick, respectively. The linearity of the photogenerated current as a function of photon flux was measured. It was found that over an area of 25 cm2 the uniformity was within 15%. Using a laser (200 mW at 351 and 363 nm) the aging characteristics were measured and showed a 25% decrease in responsivity after the absorption of 105 J cm−2 under operating conditions.

Hot rolling and superplastic forming response of net shape processed Ti-6AI-4V produced by centrifugal spray deposition

The hot rolling and superplastic forming response of Ti-6Al-4 V deposits, produced using a unique low pressure centrifugal spray deposition (LPCSD) facility, have been examined. Fundamental information has been generated relating to the parameters which govern microstructural development (porosity distribution, grain size, and α/β phase volume fraction) both during the deposition process and following post-spray thermomechanical processing. As sprayed deposits were characterised by relatively coarse transformed β microstructures, with α lath and prior β grain sizes varying from about 0.6 to 1.1 μm and from 70 to 400 μm respectively, depending on the spray forming environment (Ar or vacuum) and the position within the preform. Despite these coarse microstructural features, and relatively high levels of porosity, single and multipass hot rolling reductions of up to 80% were successfully achieved, yielding microstructures and strain rate sensitivity factors (m values) compatible with superplasticforming grade sheet specifications.

Hot rolling and superplastic forming response of net shape processed Ti-6AI-4V produced by centrifugal spray deposition

The hot rolling and superplastic forming response of Ti-6Al-4 V deposits, produced using a unique low pressure centrifugal spray deposition (LPCSD) facility, have been examined. Fundamental information has been generated relating to the parameters which govern microstructural development (porosity distribution, grain size, and α/β phase volume fraction) both during the deposition process and following post-spray thermomechanical processing. As sprayed deposits were characterised by relatively coarse transformed β microstructures, with α lath and prior β grain sizes varying from about 0.6 to 1.1 μm and from 70 to 400 μm respectively, depending on the spray forming environment (Ar or vacuum) and the position within the preform. Despite these coarse microstructural features, and relatively high levels of porosity, single and multipass hot rolling reductions of up to 80% were successfully achieved, yielding microstructures and strain rate sensitivity factors (m values) compatible with superplasticforming grade sheet specifications.

Properties of IBAD alumina coatings of different thicknesses

Alumina coatings of different thicknesses were deposited on CK45 steel substrate under the bombardment of 10 keV Ar + with an incidence angle of 45° by using an ion beam assisted deposition (IBAD) facility. The composition and structure of these coatings was analyzed by RBS, AES and XRD methods. The adhesion between the coatings and the substrates was measured by pull-off tests, and the microhardness was also measured using a Vickers' indentor. Corrosion protection ability to the steel substrate, both in Cl −-containing and non-Cl −-containing buffered acetic solutions was evaluated by electrochemistry method. Experimental results show that a stoichiometric, amorphous Al 2O 3 coating with excellent adhesion to CK45 steel substrate can be obtained by using the IBAD technique. Microhardness and corrosion resistance can be improved significantly by the use of alumina coating, and the amount of improvement depends greatly on the coating thickness.