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Thin films of Ga₂O₃ and ZnGa₂O₄ are of technological interest due to their applications in wide bandgap electronic and optoelectronic devices. In this study, we report on the deposition of amorphous and crystalline thin films (d ̅ = 260 nm) of Ga₂O₃ and ZnGa₂O₄ by reactive pulsed direct current magnetron sputtering from a liquid gallium target onto fused (f-) quartz and c plane (c-) sapphire substrates, where the temperature of the substrate is varied from room temperature (RT) to 800°C. Nonstoichiometric ZnGa₂O₄ thin films, covering a wide range of Ga:Zn atomic ratios (≈ 0.3 – 5.7), were deposited by co-sputtering solid Zn target next to liquid Ga target. The composition was controlled by varying the sputtering power of the Zn target and monitoring the process with plasma optical emission spectroscopy. Composition analysis shows no traces of impurities and a slight oxygen deficiency in the films. The static deposition rate of Ga₂O₃ (up to 37 nm/min at RT on f-quartz and 5 nm/min at 800 °C on c-sapphire) is two to five times higher than the rates reported in the literature for radio frequency sputtering. When deposited onto unheated substrates, the films are X-ray amorphous. Well-defined X-ray diffraction peaks of β-Ga₂O₃ begin to appear at a substrate temperature of 500°C, and ZnGa₂O₄ peaks at 300°C. Electron microscopy images reveal a dense and void-free microstructure. The thin films are highly transparent in the visible light range (≈ 84%) and the optical band-gap varies between approximately 3.9 eV and 5.1 eV, depending on the amount of Zn in the composition.

https://doi.org/10.14332/svc24.proc.0064

Bipolar pulsed sputter deposition provides a robust method for depositing insulating coatings like oxides and nitrides. For several years, both sine-wave and squarewave generators have been utilized for these processes. Different applications demand stringent and distinct coating requirements, and pulse mode provides an additional variable enabling a user to optimize film microstructure and thereby film properties. This presentation shows a comparative study of three types of bipolar pulsed modes: symmetric sinusoidal pulsing, symmetric square pulsing and the new asymmetric square pulsing mode called dynamic reverse pulsing. The three modes were tested on reactive sputter deposition of silicon nitride films in an industrial drum coater. The aim is to provide a comprehensive understanding of the different modes and their influence on the film properties in terms of deposition rate, heat load at the substrate, residual stress and optical properties. We show that the different pulse modes have inherent differences in plasma behavior and we outline their benefits.

https://doi.org/10.14332/svc24.proc.0024

Magnetron sputtering devices have a wide range of uses in the coatings industry, where they are used for optical coatings, metallization in integrated circuits, and coatings for wear resistance. Numerical simulations can aid in the design of such systems, as computation can allow one to predict the figures of merit, eliminating the need to test each conceived configuration on the path to the final design. Such figures of merit include the uniformity and extent of the distribution of sputtered material, the power consumption of the system, and the erosion of the cathode. Such computations must be self-consistent and kinetic, i.e., they must follow particle trajectories, since fluid approximations make simplifying assumptions that may not be valid (especially at low pressure) and only a kinetic approach can properly account for the critical physics, including the energy-angle distribution of the impacting sputterers and the resulting distribution. The Particle-In-Cell, Monte Carlo Collision (PIC-MCC method) is ideal for this, as it can properly account for the above physics as well as the physics involved in plasma creation, electron trapping by the magnetic field, and even dynamics that occurs in High Power Impulse Magnetron Sputtering (HIPIMS). Unfortunately, these calculations can take significant computing time, as the time scales for relaxation to steady-state are long compared with plasma processes. This talk presents computations using multiple techniques to speed up these calculations. The methods include using a circuit model that allows one to rapidly get to the final state, steady-state relaunch, where the results of one simulation that has reached steady-state are used to initialize another, and physics minimization, where initial analysis using a global model minimizes the number of included collisional processes. Results are compared with those available in the literature.

https://doi.org/10.14332/svc24.proc.0034

Austenitic steels are known for their high corrosion resistance but at the same time have low wear resistance and high interfacial contact resistance (ICR), which limits their application e. g. as bipolar plates in Proton Exchange Membrane Fuel Cells (PEMFC). Plasma diffusion treatment, especially the well-known plasma nitriding, improves the hardness and interfacial contact resistance but mostly worse the corrosion behavior in PEMFC environment. Aim of this study is to evaluate the less known plasma carburizing as a suitable process for functionalization austenitic stainless steels. For this purpose, a number of processes were executed under specific variation of temperature ranging from 360 °C to 450 °C and duration of 10 to 16 h. The samples were analyzed using x-ray diffractometer, x-ray photoelectron spectroscopy, SEM, Vickers micro-indentation, potentiodynamic polarization and ICR measurements. It could be shown that the corrosion current density (1.78 μA·cm^-2) of the treated samples are an order of magnitude lower than those of the reference (17.38 μA·cm^-2). The ICR was also reduced from > 1000 mΩ·cm^-2 down to 31 mΩ·cm^-2. After corrosion, even lower values around 15 mΩ·cm^-2 were achieved. The targets according to DOE ( < 1 μA·cm^-2 and < 10 mΩ·cm^-2) were almost achieved. A comparison to the plasma-nitrided samples was also performed and shows the high potential of plasma carburizing.

https://doi.org/10.14332/svc24.proc.0050

This article presents the integration of predictive maintenance strategies with vacuum transducers designed for measuring rough to ultra-high vacuum. Offering innovative solutions for various industrial sectors worldwide, the transducers combine digital precision with durability and intelligence, featuring modern combination sensors and interfaces like RS485, EtherCat, or PROFINET.
Predictive maintenance is crucial in industrial environments, aiming to prevent costly breakdowns, increase equipment longevity, boost performance, assure product quality, and maximize return on investment. Vacuum transducers can support predictive maintenance through continuous monitoring, analysis of sensor wear, and providing operating hour data. By leveraging these insights, industries can optimize maintenance schedules, reduce downtime, and enhance overall operational efficiency.
Furthermore, the transducers facilitate seamless integration into industry 4.0 environments, complying with OPC UA standards and enabling bidirectional data transfer. With the support of corresponding software and their PROFINET interface, the transducers contribute to efficient data management, downstream process optimization, and maintenance cycle enhancement.
In conclusion, the integration of predictive maintenance with vacuum transducers offers a proactive approach to optimize performance, reliability, and longevity of vacuum systems in industrial settings. Embracing predictive maintenance as a strategic priority empowers industries to stay competitive in today's dynamic business landscape.

https://doi.org/10.14332/svc24.proc.0040

Optical coatings for satellite communication (SatCom) applications using free-space optics (FSO) have demanding requirements for durability and spectral performance. Optical systems for SatCom require high transmission of telecommunication (telecom) bands while providing rejection of unwanted radiation from a wide band extending from UV to IR that correspond to both solar output and thermal energy from the Earth. It is critical that thermal energy from these sources entering the optical system be kept to a minimum in order to reduce the noise in both the data transmit and receive signals, as well as keep the sensitive piezo-driven mirrors within the system from experiencing thermally induced variability. Many systems utilizing polarization-multiplexing also require that optical coatings cause minimal phase retardance upon reflection or transmission. We demonstrate optical coating performance for dichroics and bandpasses used to separate telecom bands while maintaining low phase retardance over particular wavelengths. We will show spectral and phase performance for “solar filters” consisting of sputtered silver- or gold-based inducedtransmission type filters with over 90% transmission of the C-band and having high reflection of solar-Earth radiation over the full cone of angles. We will also show durability performance and discuss other applications for these coatings.

https://doi.org/10.14332/svc24.proc.0032

A collection of interesting vacuum-coating challenges will be presented, from uniformly coating small glass spheres to roll-to-roll coating paper, along with the solutions implemented.

https://doi.org/10.14332/svc24.proc.0026

processes. Ampres has developed a new generation of scalable closed drift gas ionizers. These sources provide an economical tool for the deposition of complex high quality multilayer thin film coatings. The gas ionizers provide very high ionization rates in a compact fully scalable design. They are used to supply ionized reactive gas for enhanced magnetron sputtering processes and for a unique hybrid PVD–PECVD process.
These sources are ideally suited to deliver ionized reactive gases like Oxygen, Nitrogen and Fluorine direct to the substrate surface to form metal oxide, metal nitride and other complex thin film coatings. They also can be used as standalone plasma sources for PECVD and plasma etching applications.

https://doi.org/10.14332/svc24.proc.0023

The average reflectance (Rave) of a coating over a bandwidth (B) depends on the overall thickness (C), the index of refraction of the last layer (L), and the difference in index between the high and low index materials used in the design (D). Composite experience from a myriad of designs over three decades has been empirically fit to an equation in Excel. The four factors can be entered into the program and the estimated Rave will be calculated along with the estimated minimum number of layers required for the design. This program makes it possible to know what Rave can reasonably be expected beforehand without spending time and effort designing the coating. This can avoid trying to design to an impossible specification and allows minimizing the number of layers in achievable designs. This also allows the designer to decide between a minimum overall thickness of the design versus adding up to three times that minimum thickness for some further reduction of the Rave. This Excel program is available on request from the author.

https://doi.org/10.14332/svc24.proc.0033

Normandale Community College offers a 2-year AAS degree and certificate programs in Vacuum and Thin Film Technology for technician education. Through a series of projects funded by the National Science Foundation Advanced Technological Education (NSF-ATE) program, Normandale’s Vacuum Technology faculty and staff have introduced, evaluated and adopted significant changes related to its vacuum and thin film technology program curriculum and the program’s delivery modes. These changes have enhanced the program’s ability to reach and engage new students. Many of these students are incumbent workers who are already working in the field using vacuum systems. In the current NSF funded project, Normandale faculty are developing a new curriculum that integrates instruction of foundational skills in automation with vacuum system operations. This curriculum will address skills development related to using documentation in support of maintenance and troubleshooting activities; setting up and testing the electrical interface between a controller, input and output (I/O) devices, and the system’s pumps, gauges, valves and other instrumentation; and creating a simple human machine interface (HMI) program that automates vacuum system functions. The course learning outcomes have been reviewed by the program’s advisory group participants and updated based on their feedback. This new curriculum which links automation skills with vacuum system operations is intended to support upskilling/reskilling incumbent workers.

https://doi.org/10.14332/svc24.proc.0039