The effect on the ion energy distribution function (IEDF) of plasma produced during a high-power impulse magnetron sputtering (HiPIMS) discharge as the pulse conditions are varied is reported. Pressure was varied from 0.67–2.00 Pa (5–15 mTorr), positive kick pulses up to 200 V tested with a constant 4 μ s delay between negative and positive cycles. The results demonstrate that the resulting plasma during the positive cathode voltage reversal is the result of expansion through the largely neutral gas species between the end of the magnetic trap of the target and the workpiece. The plasma potential rises on similar time scale with the evolution of a narrow peak in the IEDF close to the applied bias. The peak of the distribution function remains narrow close to the applied bias irrespective of pulse length, and with only slight pressure dependence. One exception discovered is that the IEDF contains a broad high energy tail early in the kick pulse due to acceleration of ions present beyond the trap from the main pulse separate from the ionization front that follows.

The time-dependent plasma properties of a high-power impulse magnetron sputtering plasma are investigated which include a positive ‘kick’ pulse on the sputtering target 2 μ s after the main negative pulse, this reversing the voltage on the cathode. At a substrate 15 cm distant from the magnetron, the time-dependent electron energy distribution function (EEDF), plasma potential, potential commute time and plasma diffusion properties are measured using a single Langmuir probe. Results show that the positive pulse on the target expels plasma and raises the plasma potential across the chamber on the order of 1 to 2 μ s, which is the time scale of the electron diffusion. The EEDF at the substrate fits a Druyvesteyn distribution during the main negative pulse rising slightly in average energy over time. The distribution is still Druyvesteyn and at the very start of the positive pulse, but then loses the higher energy electrons and drops in average electron energy as the positive pulse progresses. A Boltzmann equation solver, BOLSIG+, was used to predict the EEDF at the substrate during the positive pulse and it agrees best with the measurements assuming a value of 0.2 Td for the E / N (electric field/gas number density).

The program goal was the development and demonstration of a novel material coating system using an innovative atmospheric cold microwave plasma jet to enable surface functionalization for corrosion protection, wear resistance and improved bonding strength. The technical approach was directed towards proof-of-concept demonstration of advanced point-of-manufacturing material bonding to improve adhesive joint performance subject to harsh environmental exposure. The assembled team, consisting of the researchers at the University of Illinois, end-users at General Motors and small business manufacturer Starfire Industries, successfully demonstrated a single, cost-effective, high-volume production process that meets the requirements of multi-material combinations relevant to the energy-intensive transportation industry (e.g. Al-steel, Mg-steel, Al-Mg and Al-CFRP joints for body-in-white structures) while eliminating offline pretreatment for Al and Mg alloy substrates that are energy intensive, have chemical waste disposal issues, and add cost. Technical demonstration of dissimilar material joining while maintaining bonding strength and cohesion after long-duration environmental exposure was accomplished for all materials of interest. This novel approach has broad applicability for manufacturing in automotive, aerospace, marine, railcar, and specialty consumer goods, etc.

This work aims to demonstrate the barrier coating, and adhesion promoting properties of silica-based coatings deposited using an atmospheric pressure plasma torch (APPT). This is achieved by applying an industrial grade adhesive to silica thin films deposited, on the surfaces to be joined, using atmospheric pressure plasma chemical vapor deposition (APP-CVD), to make single joint lap shear samples of different metal combinations commonly found in lightweight manufacturing, such as aluminum and magnesium as well as steel. To deposit these thin films, two separate silicon based organic precursors, hexamethyldisiloxane (HMDSO), and tetraehylorthosilicate (TEOS), are used. Samples are bonded using DuPont Betamate 1486 adhesive, and the lap shear results for these films are compared to the lap shear results of a chemically cleaned control using the same adhesive. The APPT uses a microwave power supply and gas mixtures of N2 and Ar. The adhesion of the films are tested using lap shear, and elevated temperature water soaks are conducted on the joints as well to simulate environmental exposure. Lap shear results, from samples with silica thin films, have an increase of max shear stress of 25%-115% compared to control samples depending on material. After exposure to water soak the max shear strength of the joints decreased by less than 15%, which demonstrates the films capabilities as a water barrier. Film morphology is examined using Scanning Electron Microscopy (SEM), and the film's composition and approximate thickness are obtained using Rutherford Backscattering Spectroscopy (RBS).

An Associated Particle Imaging (API) system consists of a high vacuum chamber where deuterium ions are accelerated on a tritium-loaded target, resulting in alpha particles and neutrons emitted back-to-back, the latter escaping the chamber and used, for example, for tomography of a high-Z sample. An accurate determination of the alpha position is crucial to determine the trajectory of the neutron. Existing API systems have several limitations which a semiconductor-based API detector placed inside the vacuum chamber should not present. The semiconductor material can be either silicon or diamond. In particular, large and fast signals are generated by the alpha interactions in these materials. A pixelated API detector will measure the time and hit position of the alphas produced in the reaction. However, during the lifetime of the generator, the semiconductor detector will be exposed to an intense flux of alpha particles that will degrade its performance over time. To assess the radiation hardness of silicon and diamond against the alpha particles, we exposed single diodes made of either of the two materials to a 5 MeV alpha flux generated by an 241Am radioactive source. During irradiation, the diodes were biased and mounted on current-sensitive preamplifier boards. We have therefore been able to measure insitu the evolution of the waveforms as the damage was accumulating in their substrates.

Bipolar pulse High Power Impulse Magnetron Sputtering (HiPIMS) based on conventional HiPIMS is put forward to deposit Cu films on silicon wafers. Positive kick pulses with different pulse width and magnitude are applied after the initial negative pulse to drive Cu ions to the substrate, improving the properties of Cu films. Compared to films deposited by conventional HiPIMS, the Cu films prepared by modified HiPIMS exhibit a higher deposition rate. And the increase in voltage and pulse width of kick pulse results in a reduction of tensile stress of the Cu films. The bipolar pulse HiPIMS has potential applications in Cu metallization for semiconductor processing and other applications.

A 900 MHz surface wave antenna was used for plasma-enhanced chemical vapor deposition (PECVD) of silicon thin films in an H2 + SiH4 discharge, with an emphasis on photovoltaic applications. Gas mixtures of 0.7–10% SiH4 at medium pressure (~ 100 mTorr) were tested with an optimal substrate temperature of 285 ± 15 °C, producing nanocrystalline hydrogenated silicon (nc-Si:H) at rates up to 3 nm/s, while amorphous films were grown in excess of 10 nm/s. A sharp transition from crystalline to amorphous growth was seen as SiH4 flowrate increased, as is characteristic of silane PECVD. Increasing both substrate temperature and source power served to move this transition to higher flowrates, and by extension, higher deposition rates for the crystalline phase. Grain size also increased with substrate temperature, ranging from 10 ± 2 nm at 200 °C up to 15 ± 3 nm at 400 °C. Electron spin resonance showed that a-Si:H films grown via SWP were of acceptable defect density (~ 1016 cm− 3) and conductivity (~ 10− 8 S/cm). Conversely, nc-Si:H films were poor quality (~ 1018 cm− 3 defect density, 10− 3–10− 2 S/cm conductivity) due to low hydrogenation and small grain size.

The objective of this project is to advance the state-of-the-art and to develop an integrity inspection system capable of detecting physical flaws in the wellbore structure of conventional and unconventional hydrocarbon producing wells. Measuring the integrity of multiple wellbore casings and cement annuli for onshore and offshore wells remains a challenging task. We propose a multi-modality inspection system composed of neutron and X(gamma)-ray imaging modalities (nXis) to address the above challenge. The functional principle of this wellbore integrity inspection system is the combination of high-energy modalities, such as X(gamma)-ray and neutron backscatter imaging, with conventional low-energy modalities, such as electromagnetic or ultrasound imaging techniques. By combining multiple sensing modalities into one sensing system and by fusing data between modalities, one can gather more information about the integrity of the wellbore structure compared to simply using multiple sensors individually. Imaging prototypes for gamma, neutron, and electromagnetics were designed, manufactured, and tested at GE Global Research and Starfire Industries. Wellbore phantoms with engineered defects were manufactured and the performance of the developed wellbore integrity inspection tool prototypes was evaluated in a test pit test at an industrial GE Oil & Gas facility. Data analysis and fusion between various inspection techniques show enhanced defect detectability. These exciting results were presented at various technical conferences and discussed with operators in the oil & gas industry. Great interest from oil operators lead to discussions about joint industrial partnerships to move the developed technology from the prototype phase to the product phase.

High power pulsed magnetron sputtering is a promising physical vapor deposition technique with two minor challenges that obstruct its broader implementation in industry and its use by researchers. The first challenge is the availability of low cost HPPMS power supplies with output power under 2kW. Such power supplies are suited for circular planar magnetrons with target diameters between 50mm to 150mm. The second challenge is the overall lower deposition rates of HPPMS when compared with direct current magnetron discharges. The “ε” magnet pack designed for a 100mm sputter magnetron which was developed by the Center for Plasma Material Interactions at the University of Illinois at Urbana Champaign in collaboration with Kurt J. Lesker Company was capable of producing twice higher deposition rates in HPPMS compared to a conventional magnet pack. The cylindrically symmetric “TriPack” magnet pack presented here was developed based on magnetic field design solutions from the “ε” magnet pack in order to keep the high deposition rates, but improve deposition uniformity, without the need for substrate rotation. The new cylindrically symmetric magnet pack for 100mm diameter targets, along with a specially designed cooling well provides stable operation at 2kW average power, even with low-temperature melting-point target materials. The deposition rates from the TriPack magnet pack is compared with a commercial conventional magnet pack for DC and HPPMS power supplies.

High-power impulse magnetron sputtering (HIPIMS) is an ionized physical vapor deposition (iPVD) technique that utilizes high-power pulses applied to the sputtering target at low-duty cycles. Because of the high peak power densities in HIPIMS discharges, a larger fraction of sputtered material is ionized when compared with direct current magnetron sputtering (DCMS), producing depositions of higher quality but suffering from intrinsically low deposition rates when compared with DCMS, due to the "return effect." These low deposition rates hinder the ability to implement HIPIMS on an industrial scale. A new magnetic field configuration, "Tripack" magnet pack, which provides a higher deposition rate in a HIPIMS discharge for circular sputtering magnetrons, has been developed. The Tripack yielded deposition rates in HIPIMS comparable to or greater than standard magnet pack DCMS deposition rates for titanium. Also, the Tripack showed equivalent deposition rates for carbon at 500 W average power. To become industrially relevant, HIPIMS must produce higher deposition rates for linear cathodes, which can be scaled to any desirable size. This work shows the modeling and design of a linear cathode-driven Tripack that can be a simple upgrade to existing commercially available magnetrons.