Digital Library

Modern society runs on seamless mobile connectivity. Yet, the wide commercial adoption of low-emissivity (low-E) windows introduces significant problems in the transmission of mobile signals, which is further exacerbated by the global adoption of 5G networks, particularly mid to high-band 5G frequencies. This presentation introduces a production-line integrated and cost-competitive low-E manufacturing technology enabling mobile signal penetration of low-E windows while maintaining optical and thermal performance. Core technology leverages lithography and is fully compatible with the throughput of existing Low-E production lines. Final low-E products enable 5G transmission across low and high frequency bands while maintaining superior visual aesthetics with invisible pattern lines under any angle and any lighting conditions. Furthermore, the technology meets low-E’s durability criteria, including mechanical alcohol wiping durability and thermal tempering tests. Supported by NSF funding, this project aims to commercialize next-generation mobile signal penetrating Low-E products at scale and cost competitively for global adoption in architectural applications to enhance indoor connectivity in the 5G era.

https://doi.org/10.14332/svc24.proc.0021

The advent of the extensive use of Zoom and similar meeting venues has made the reflection from eyeglasses more apparent and distracting. Eyeglass lenses which have not been antireflection (AR) coated typically reflect more than 4% of light from each lens surface or more than 8% per lens. Lenses with the common 4-layer AR coating still reflect more than 0.5% of greenish or bluish light per surface. When we observe the reflection of a bright computer screen or other illumination sources in someone’s glasses while they are communicating with a video image, it is particularly distracting if they have uncoated lenses, but it still can be distracting even with the common 4-layer AR coatings. The currently available technology will allow the reduction of these reflections by an order of magnitude so that we can “look someone in the eye” when we talk with them via video conferencing. The new coatings would probably use 6-10 layers, which is not many layers as compared to more sophisticated applications where over 100 layers are now used. The common production issues limiting performance now are inadequate reproducibility of factors like pressure, rate, uniformity, temperature, etc. Tighter process control would tend to make these coatings somewhat more expensive than the present 4-layer coatings, but discerning users would probably be willing to pay a premium for their improved appearance when being viewed by video.

https://doi.org/10.14332/svc24.proc.0030

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

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

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

Over the past years, increased understanding of arc behaviour during thin film deposition processes has led to improvements in plasma power supply design. This has helped significantly minimize negative effects related to arcing. In this contribution, we demonstrate the effect of different arc handling parameters available at the power supplies that can be used to tailor arcing characteristics during sputtering of insulating films. We show the effect of arc management parameters on arc energies, backed by experimental studies on silicon oxide and aluminium oxide processes performed in an industrial drum coater.
To deposit these insulating materials, different power delivery modes are available to a user such as dual magnetron bipolar mode (BP) and dynamic reverse pulsing mode (DRP). We discuss the differences between these two modes, provide an in-depth statistical study to showcase the effect of pulsing frequency on these modes, and compare them in terms of arc rates and energies.

https://doi.org/10.14332/svc24.proc.0020

Gravitational-wave detectors (GWD) are ultra-sensitive, large-scale facilities whose successful operation depends critically -among various factors- on the performance of high-reflective mirrors. These consist of doublets of high- and low-refractive-index amorphous oxide coatings deposited by ion beam sputtering (IBS). Their performance, defined in terms of high reflectivity, low optical absorption and low thermal noise, can be enhanced by optimizing the constituent materials, the deposition and post-deposition processes such as the thermal annealing. In this contribution, an implementation of real-time spectroscopic ellipsometry is proposed as a convenient tool to understand the evolution of coatings properties during the post-deposition thermal annealing. The amorphous titania-tantala coating and the annealing protocol considered here match those currently used in mirrors for GWD. In-situ analysis shows the evolution of the coating refractive index and thickness throughout the annealing, including the heating and cooling ramps. Results indicate that the current annealing protocol leaves room for further possible modifications in the coatings properties and suggest ways to optimize it. The in-situ analysis discussed here can be beneficial to screen and validate other coating materials as well as to test new annealing protocols to enhance the properties of mirror coatings for GWD applications.

https://doi.org/10.14332/svc24.proc.0029

The Vera C. Rubin Observatory construction is poised to be completed, finishing the Integration phase and starting the Commissioning phase. The Coating Plant is delivering the coated main science mirrors to the project. The M2 mirror was coated with protected Silver in 2019 and the M1M3 mirror coated in 2024 with protected Silver as well, both coatings achieving the main project requirements. This paper describes the main project milestones in terms of construction, assembly and integration, the coating results on both mirrors. This paper also describes a characterization of the Coating Plant and its ancillary equipment, a characterization of the coating delivered by us, the coating tests that we made prior of the final coating recipe decision, and the final coating results over the main telescope mirrors, finishing with the future projects related to this Coating System.

https://doi.org/10.14332/svc24.proc.0025

Atomic Layer Deposition (ALD) is now a well-established process broadly used in the manufacture of leading-edge semiconductor chips. ALD is required for this application due to its high level of precision and ability for conformal deposition of pinhole-free coatings on complex surfaces. These same coating attributes are highly desirable in other applications, such as thin film encapsulation, on the large area substrates used in the display and photovoltaic industries. But to date, scaling of ALD processes to such large substrates, with sufficient throughput and at the low cost required for these applications, has been elusive. In this work, a novel Spatial Plasma Enabled ALD (S-PEALD) process is demonstrated that offers the economic scalability of ALD to these large area substrates. The use of a simple DC plasma source, enabled by the use of spatial processing, allows plasma generation over the multi-meter distances required for these substrate sizes. Meanwhile, a novel method for spatial precursor separation provides the means to utilize a simple, compact, and rapidly moving coating head for executing the ALD cycle. In combination with a mixed oxide barrier material, a process is demonstrated that provides a path to the in-line deposition of OLED-quality barrier coatings on multi-meter substrates, with a takt time of less than one minute.

https://doi.org/10.14332/svc24.proc.0022

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