Sputtering System Research Articles

High-Performance SAW-Based Microfluidic Actuators Composed of Sputtered Al–Cu IDT Electrodes

To realize highly sensitive SAW devices, novel Al–Cu thin films were developed using a combinatorial sputtering system. The Al–Cu sample library exhibited a wide range of chemical compositions and electrical resistivities, providing valuable insights for selecting optimal materials for SAW devices. Considering the significant influence of electrode resistivity and density on acoustic wave propagation, an Al–Cu film with 65 at% Al was selected as the IDT electrode material. The selected Al–Cu film demonstrated a resistivity of 6.0 × 10−5 Ω-cm and a density of 4.4 g/cm3, making it suitable for SAW-based microfluidic actuator applications. XRD analysis revealed that the Al–Cu film consisted of a physical mixture of Al and Cu without the formation of Al–Cu alloy phases. The film exhibited a fine-grained microstructure with an average crystallite size of 7.5 nm and surface roughness of approximately 6 nm. The SAW device fabricated with Al–Cu IDT electrodes exhibited excellent acoustic performance, resonating at 143 MHz without frequency shift and achieving an insertion loss of −13.68 dB and a FWHM of 0.41 dB. In contrast, the Au electrode-based SAW device showed significantly degraded acoustic characteristics. Moreover, the SAW-based microfluidic module equipped with optimized Al–Cu IDT electrodes successfully separated 5 μm polystyrene (PS) particles even at high flow rates, outperforming devices with Au IDT electrodes. This enhanced performance can be attributed to the improved resonance characteristics of the SAW device, which resulted in a stronger acoustic radiation force exerted on the PS particles.

Effects of anode geometry on DC magnetron sputtering of copper oxide films deposition

Abstract Effects of anode shape are examined in a custom-made DC magnetron sputtering system. Polycrystalline copper-oxide (CuO) films are deposited using wedge, ring and disc shaped anodes. Current–voltage (I-V) characteristics of the discharge were fitted with models of plasma discharge. Above 700 V a notable rise in average plasma impedance, from approximately 2kΩ to 7kΩ was observed. Scanning electron microscope (SEM) images reveal uniform and porous film growth. The deposition increased significantly with increasing the anode surface area due to decrease in gas density in cathode sheath. For all the anode shapes tested, the deposition rates were higher in magnetron sputtering compared to DC sputtering mode. X-ray diffraction (XRD) of the films deposited with the disk anode revealed polycrystalline films with predominant CuO phase. With increasing sputtering power, average crystallite size vary from 11 nm to 21 nm, dislocation density vary from approximately 8.4×〖10〗^(-3) nm-2 to 2.3×〖10〗^(-3) nm-2 and micro strain from approximately 3.3×〖10〗^(-3) to 1.7×〖10〗^(-3). This indicate that higher sputtering at higher powers produce higher quality films. Atomic force microscopy revealed that the rms roughness of the samples is about 4 nm.

Effect of substrate rotation on the growth behavior and topography of the [formula omitted] film deposited over a large area using DC magnetron sputtering with a rectangular target: Simulation approach and experiment

It is often challenging to achieve a uniform film with the necessary surface properties when using deposition techniques. If the film is not uniformly deposited or lacks suitable surface roughness, it may not meet performance standards. To understand and control the factors controlling the deposition process, this paper presents a simulation approach to predict the growth behavior of a Ti-film deposited on substrates during the bombardment of the target with argon ions at low pressure. The simulation of the deposition process consists of several Monte Carlo simulations, which include predicting the source of the atoms flow from the target surface and tracing its trajectories through the vacuum chamber until it falls or reaches the surface of the substrates, then predicting the thickness distribution and topography of film. After conducting a comparison between simulation predictions and experimental data, it was found that the measurements obtained using the Profilometer, Scanning Electron Microscope, and Atomic Force Microscopy were relatively close. The results indicate that substrate rotation during deposition leads to a thinner film that is more uniform and less rough, it was also found that the coefficient of variation in the film thickness distribution was improved from 3.96% in the case of a non-rotating substrate to 0.33% in the case of a rotating substrate. The proposed approach can be used to improve the design of magnetron sputtering systems and to provide theoretical guidance for optimizing the thickness distribution and topographical characteristics of the performance specifications of high-quality film without economic constraints.

Semiconductor WO3 thin films deposited by pulsed reactive magnetron sputtering

A pulsed reactive magnetron sputtering system with a tungsten target and a gas mixture of argon and oxygen was investigated as a source for the deposition of semiconductor WO3 thin films on soda lime glass substrates and on the glass with transparent conductive SnO2:F (FTO) electrode. The reactive sputtering process was performed in HiPIMS mode with low pulse repetition frequency fp ≈ 50–100 Hz and short pulse duration in HiPIMS discharge Ton = 100 μs. The second mode investigated was the mid-frequency (MF) magnetron discharge with pulse frequency fp = 40 kHz and pulse length Ton = 15 μs. The plasma parameters were investigated for both HiPIMS and MF modes using the planar RF probe operating at the frequency fprobe = 350 kHz and the grid QCM with biased collector electrode. Ion density ni and tail electron temperature (Te) were determined in both pulsed reactive magnetron sputtering discharge modes with time resolution. The maximum value ni ≈ 5 · 1017 m−3 was found in the reactive HiPIMS mode, and the maximum value ni ≈ 7 · 1016 m−3 was found in the reactive MF (40 kHz) mode. The degree of ionization of sputtered particles in reactive HiPIMS was determined for different values of (QO2) and was found to be in the range of ri ≈ 0.1–0.3. The deposition rate determined by QCM in reactive HiPIMS was practically independent on (QO2), but in the case of reactive MF, the measured deposition rate decreased significantly with increasing (QO2). The WO3 films deposited in both modes have a predominantly monoclinic crystal structure. The light and dark conductivity and the light/dark conductivity ratio (Ld) were measured under dark conditions and UV light illumination. At higher (QO2), the maximum value of Ld ≈ 300 was found for MF deposited WO3 and the maximum value of Ld ≈ 30 was found for HiPIMS deposited WO3. The photoelectrochemical measurement of WO3 deposited on FTO electrodes confirmed the n-type conductivity, and these films functioned as photoanodes in photoelectrochemical cells. MF deposited WO3 films systematically exhibited slightly higher photocurrents than HiPIMS deposited WO3. It was shown that these optimum photocurrents for HiPIMS and MF were found at QO2 ≈ 80 sccm and could not be improved by further increasing of (QO2).

Mechanical properties and biocompatibility evaluation of TiZrNbTaFe high entropy alloy films deposited using a hybrid HiPIMS and RF sputtering system

Given the well-documented low biocompatibility issues associated with conventional metallic biomaterials, there is an urgent need to develop new biomaterials. Biological high entropy alloys (HEAs), designed with non-toxic elements for biomedical applications, represent a significant advancement in metal biomedical materials due to their tunable mechanical properties and excellent biological safety. This study employed a hybrid system that combined a high power impulse magnetron sputtering (HiPIMS) power with a radio frequency (RF) power to synthesize a series of amorphous TiZrNbTaFe HEA coatings, in which the Ti content was varied by changing the RF power applied to the Ti target. One exemplary TiZrNbTaFe film, deposited with a Ti target RF power of 75 W, was thoroughly examined. This film demonstrated several highly promising attributes as a novel metallic biomaterial, including a dense and fine microstructure, good adhesion quality, superior corrosion resistance, and exceptional biocompatibility both in vitro and in vivo. These findings could provide new insights for innovative biomaterials development and help address long-term implantation and implant failure issues.

Orientation-dependent structural properties during growth and growth mechanism of CoO films

The orientation-dependent local structural properties of CoO films on sapphire substrates during growth were investigated through linearly-polarized extended X-ray absorption fine structure (EXAFS) measurements. Specifically, CoO(111) and (100) crystals with a rock-salt structure (Fm3m) were epitaxially grown on α-Al2O3(0001) and (101¯2) substrates, respectively, at 700℃ using a radio-frequency sputtering system. The local structural properties of CoO films in the in-plane and out-of-plane orientations were quantitatively determined using linearly-polarized EXAFS at the Co K-edge during growth. The EXAFS analysis revealed that during the initial stages of growth, the local structural properties exhibit significant differences compared to thick films, with short atomic distances and large (small) Debye-Waller factors observed in the out-of-plane (in-plane) orientations. The local structural strain mostly diminished when approximately 20 CoO layers accumulated on the substrate. Density functional theory (DFT) calculations further supported these findings by confirming that cobalt atoms initially form stable bonds with the sapphire surface, leading to the simultaneous growth of oxygen and cobalt layers in a coordinated manner through layer-by-layer growth.

Role of growth temperature on microstructural and electronic properties of rapid thermally grown MoTe2 thin film for infrared detection

In the field of electronic and optoelectronic applications, two-dimensional materials are found to be promising candidates for futuristic devices. For the detection of infrared (IR) light, MoTe2possesses an appropriate bandgap for which p-MoTe2/n-Si heterojunctions are well suited for photodetectors. In this study, a rapid thermal technique is used to grow MoTe2thin films on silicon (Si) substrates. Molybdenum (Mo) thin films are deposited using a sputtering system on the Si substrate and tellurium (Te) film is deposited on the Mo film by a thermal evaporation technique. The substrates with Mo/Te thin films are kept in a face-to-face manner inside the rapid thermal-processing furnace. The growth is carried out at a base pressure of 2 torr with a flow of 160 sccm of argon gas at different temperatures ranging from 400 °C to 700 °C. The x-ray diffraction peaks appear around 2θ= 12.8°, 25.5°, 39.2°, and 53.2° corresponding to (002), (004), (006), and (008) orientation of a hexagonal 2H-MoTe2structure. The characteristic Raman peaks of MoTe2, observed at ∼119 cm-1and ∼172 cm-1, correspond to the in-plane E1gand out-of-plane A1gmodes of MoTe2, whereas the prominent peaks of the in-plane E12gmode at ∼234 cm-1and the out-of-plane B12gmode at ∼289 cm-1are also observed. Root mean square (RMS) roughness is found to increase with increasing growth temperature. The bandgap of MoTe2is calculated using a Tauc plot and is found to be 0.90 eV. Electrical characterizations are carried out using current-voltage and current-time measurement, where the maximum responsivity and detectivity are found to be 127.37 mA W-1and 85.21 × 107Jones for a growth temperature of 600 °C and an IR wavelength illumination of 1060 nm.

Inverse-proximity effect and 2D superconductivity of Ta/Au bilayer thin films

This study investigated the inverse-proximity effect (IPE) and two-dimensional (2D) superconductivity in α-phase Ta films and Ta/Au bilayers. These bilayers were deposited onto silicon substrates using a direct current (DC) sputtering system. The findings reveal that higher substrate temperatures and increased film thickness facilitate the formation of α-Ta up to a temperature limit of 300°C, resulting in higher Tc around 3.5–3.7 K. The fundamental superconductivity of α-Ta thin films is similar to that of a conventional s-wave BCS superconductor. The IPE in the Ta/Au bilayer films was observed, where the Tc increases and decreases with the Au overlayer thickness. This behavior was quantitatively described by considering a model accounting for the reduced superconducting fluctuations induced by the highly conductive Au layer. Furthermore, the presence of 2D superconductivity in the Ta film and Ta/Au bilayer was examined through critical field analysis, vortex motions, and Berezinskii-Kosterlitz-Thouless (BKT) transition detection. Finally, the results were summarized in an H-T phase diagram illustrating the presence of IPE and 2D superconductivity in a Ta/Au bilayer. This study provides additional insights into 2D superconductivity within normal/superconductor (N/S) bilayers, laying the groundwork for future research to optimize film properties to align more closely with theoretical expectations.

Laered composite hydrogenated films of zirconium and niobium: method of production and control of properties by thermopower method

In this work, to obtain layered materials with the inclusion of hydrogen, Nb/Zr films with different numbers of layers from 50 to 100 were used. The films were sputtered onto a silicon substrate using the vacuum-magnetron method in a specialized installation. The film thickness was varied from 10 to 50 nm. The resulting material was hydrogenated with protons on a TPU electrostatic generator with an energy of up to 1,2 MeV. The optimal modes for deposition of nano-sized metal multilayer Zr/Nb systems have been determined: for a Zr target, the specific power of the sputtering system is 37,9 W/cm2, for a Nb target — 26,4 W/cm2. A coating with clear boundaries between the individual layers of zirconium and niobium was obtained. It is shown that the optimal modes for studying nano-sized Zr/Nb layers are pressure 700 Pa, power 40 W, frequency 2 kHz, plasma fill factor 12,5 % for coatings with a thickness of individual layers of 100 nm. For coatings with individual layer thicknesses from 10 to 50 nm, the optimal pressure is 650 Pa, power 40 W, frequency 1 kHz. To control properties, the thermopower method is used. It was revealed that after proton irradiation there is an intensive accumulation of hydrogen atoms near the interfaces, which entails a change in the thermopower up to an inversion of its sign. The hydrogen distribution is predominantly bimodal, with local maxima in hydrogen concentration observed at the Nb/Zr interface, and the accumulation at the Zr/Nb interface is significantly lower. Hydrogen localization near the interfaces occurs predominantly in the vicinity of zirconium.

Improvement of titanium film uniformity by magnetron sputtering with electromagnetic coil design

A novel magnetron assembly based on a combination of permanent magnet and adjustable electromagnetic coil is proposed for improved uniformity of the magnetron sputtering deposition process. The design of the magnetron sputtering system containing a rotating substrate and an off-axis arranged magnetron. A numerical framework has been developed to describe the evolution of the plasma density and distribution of sputtered particles. Specifically, the finite element method (FEM) was used to calculate the magnetic field and to model the magnetron sputtering discharge, and binary-collision Monte Carlo method was used to determine the transport of sputtered atoms to the substrate. Through parametric analyses, it was found that increasing the substrate-to-target distance, gas pressure, and coil current intensity benefits the uniform distribution of particles. The condition where the off-axis displacement of the magnetron effectively enhances uniformity. A strategy for optimizing deposition uniformity by combining adjustable current with an off-axis magnetron arrangement was proposed, which reduce the non-uniformity of film thickness by 77.6 % compared to the traditional fixed magnetic field model.

Studies on the Morphological and Mechanical Properties of TiZrHfNiCuCo Metallic Coatings Deposited by DC Magnetron Sputtering

This research aimed to investigate the effects of input power and gas flow rate on the composition, microstructure, and mechanical properties of TiZrHfNiCuCo metallic coatings. These metallic coatings were deposited on a p-type Si wafer using a direct current magnetron sputtering system with varying input powers (100–300 W) and Ar flow rates (5–20 sccm). It was observed that increasing input power and decreasing Ar flow rate led to TiZrHfNiCuCo metallic coatings with higher hardness and smoother surfaces. The experiment resulted in the formation of a metallic amorphous coating. This study describes the mechanism by which the mechanical properties of the TiZrHfNiCuCo coating change according to sputtering parameters. Based on these results, the effects of sputter variables, such as input power and gas flow rate properties, on the properties of coatings are discussed.

Enhanced UV photodetector performance using sputtered Mg-doped ZnO thin film

In this article, we demonstrate UV photodetector synthesized using Mg-doped ZnO thin film (TF) (10 % Mg) grown on a p-Si substrate using the radio frequency (RF) magnetron sputtering system. The fabricated MgZnO TF was annealed at 500 °C in air resulting in notable changes in morphology, optical band gap and crystallinity that significantly improved the UV light sensitivity. The annealed device (MgZnO TF/p-Si) exhibited a remarkable 155-fold increase in photocurrent density compared to the as-deposited device at + 2 V bias. Also, at the same bias the annealed device (500 °C) exhibited high photosensitivity (up to 1262 times), responsivity (20.32 A/W), specific detectivity (1.82 × 1013 Jones) and external quantum efficiency (EQE) (7745 %) in comparison to the as-deposited device. Additionally, the 500 °C device achieved a low noise equivalent power (NEP) of 0.07 × 10−12 W which is about 262 times lower than that of the as-deposited device (18.4 × 10−12 W). Furthermore, on UV illumination (λ = 325 nm) the MgZnO TF/p-Si (500 °C) detector showed fast device response with rise time/fall time values of 0.26 s/0.25 s respectively at + 2 V applied bias.

Mechanical properties and tribological behavior of hard phase doped Pb/MoS2 composite films

MoS2 is commonly used as a lubricant in spacecraft applications, and it is necessary to improve the vacuum tribological properties of MoS2 films. Thus, in the current study, hard phase (Ta, Ti, and TiN) and soft metal (Pb) double-doped MoS2 composite films were designed and prepared using an unbalanced magnetron sputtering system. The microstructures and mechanical and tribological properties of the hard-soft phase doped Pb/MoS2 composite films were systematically investigated. The results showed that the synergistic effect of the hard and soft metals gave a denser MoS2 structure denser. In addition, an amorphous structure was generated along with fine crystals, leading to a structure typical of nanocrystals embedded in an amorphous phase. Furthermore, compared with the Ti-doped Pb/MoS2 film, the doped alternative hard phase (i.e. Ta and TiN) improves the mechanical properties, among which the adhesion strength of Ta-Pb/MoS2 film is the highest, and the hardness of TiN-Pb/MoS2 film is the highest. Importantly, the soft metal Pb and its sulfide are excellent lubricants, while the hard phase ensures the long-term reliability of the films. Overall, these soft-hard bimetallic-doped MoS2 films exhibit superior tribological properties to their un-doped equivalents.

Influence of deposition pressure on microstructure, mechanical and electrical properties of niobium thin films

Niobium (Nb) thin films were deposited on a Si substrate using magnetron sputtering system by varying the deposition pressure. The effect of deposition pressure on the microstructure, residual stresses, and electrical properties was investigated by systematically varying the deposition pressure from 0.15 to 0.60 Pa. The Nb thin films were characterized using hard x-ray reflectivity, grazing incidence x-ray diffraction, four point probe method, and atomic force microscopy. The films grown at lower deposition pressures had smooth surfaces and more compact structures, which are advantageous for lowering electrical resistance but had higher compressive stress. On the other hand, the films grown at higher deposition pressures had columnar type growth with less dense structures, which leads to increase in electrical resistance. However the nature of stresses transform from compressive to tensile. Hard X-ray reflectivity performed on Nb films provides direct insight into the growth and the microstructure which were correlated with the mechanical and electrical properties.

Precision depth-controlled isolated silver nanoparticle-doped diamond-like carbon coatings with enhanced ion release, biocompatibility, and mechanical performance

Silver doped diamond-like carbon (Ag/DLC) coatings are in high demand for biomedical applications such as artificial implants, surgical instruments, and medical devices. However, recent reports indicate that the excess Ag concentration required in typically made Ag/DLC coatings significantly reduces their mechanical performance and biocompatibility. Here, we propose a novel single-step approach to precisely dope small quantities of Ag in the form of isolated nanoparticles embedded at defined depths in a DLC matrix. This new Ag/DLC coating architecture is designed to release controlled Ag ion levels to fight infection in the early post-surgery stages, while a confined Ag amount maintains the excellent mechanical and biocompatibility performance of the underlying DLC coating when compared to typically made Ag/DLC coating designs. Coatings of pure DLC, typically made Ag/DLC with Ag doped throughout the carbon matrix and the new Ag/DLC design with precise Ag doping, are made using a modified magnetron sputtering system. The coatings are characterised for structural, mechanical, ion leaching, and biocompatibility profiles against L929 fibroblast cells. Results indicate that the new Ag/DLC coating requires only 2 at.% Ag to release a similar level of Ag ions (∼0.6 ppm) to a typical Ag/DLC coating with a much higher Ag content of 17 at.%. The new Ag/DLC coating design also outperforms the typical design with a 63 % increase in hardness, 100 % higher Young's modulus, and 21 % higher biocompatibility. The enhanced biomechanical performance of the proposed new Ag/DLC architecture could have significant potential for coating of future medical devices.

Nano-multilayered ZrN-Ag/Mo-S-N film design for stable anti-frictional performance at a wide range of temperatures

A multilayer film, composed by ZrN-Ag (20 nm) and Mo-S-N (10 nm) layers, combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system, to promote lubrication in a wide-range of temperatures. The results showed that the ZrN-Ag/Mo-S-N multilayer film exhibited a sharp interface between the different layers. A face-centered cubic (fcc) dual-phases of ZrN and Ag co-existed in the ZrN-Ag layers, whilst the Mo-S-N layers displayed a mixture of hexagonal close-packed MoS2 (hcp-MoS2) nano-particles and an amorphous phase. The multilayer film exhibited excellent room temperature (RT) triblogical behavior, as compared to the individual monolayer film, due to the combination of a relative high hardness with the low friction properties of both layers. The reorientation of MoS2 parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT. At 400 °C, the reorientation of MoS2 as well as the formation of MoO3 phase were responsible for the lubrication, whilst the hard t-ZrO2 phase promoted abrasion and, consequently, led to increasing wear rate. At 600 °C, the Ag2MoO4 double-metal oxide was the responsible for the low friction and wear-resistance; furthermore, the observed transformation from t-ZrO2 to m-ZrO2, could also have contributed to the better tribological performance.

Commissioning of a modulated pulse-power magnetron sputtering system for depositing niobium thin films

A modulated pulse-power magnetron sputtering system (MPPMS) was commissioned and used to deposit niobium on copper. MPPMS utilizes a modulated pulse train with high peak-to-average energy ratios, thereby increasing the energy density leading to the production of the energetic ions. The MPPMS modulator was designed and constructed based on large voltage/current IGBT modules, which can be externally modulated, produce bi-polar waveforms, and are readily available. A high voltage power supply provides moderate current to the IGBT module to create the precise pulse structure. The MPPMS system was used to deposit ∼1 μm thick, niobium film on a copper substrate held at ∼77 K to minimize Nb atom surface diffusion and maximize intrinsic film energy. The Nb film had an average grain size of ∼8 nm.

Compositional Analysis of Pt1-XCox Thin Film with Single Deposition, Combinatorial Co-Sputter Technique

Applications of thin-film magnetic materials often have narrow windows that the magnetic characteristics (i.e., remnant magnetization and coercive field) must meet – for instance magneto-optical devices [1] with latching operations [2] or amplitude- [3] or phase-control [4] of superconducting-ferromagnetic hybrid systems for next-generation computing memory. As systems become more complex, manipulating magnetic layers without affecting the rest of the device becomes increasingly challenging. Alloys of magnetic materials can alleviate this but determining viability – whether an alloy has any composition that can meet design needs – requires fabricating and analyzing samples that span the compositional space.Despite the community utilizing high-throughput methods for decades, including for thin-film materials [5], most exploratory research is still conducted by creating one composition per run, varying relative power or time during a deposition, for example. Obtaining a library of samples that vary in subtle but non-trivial ways becomes time-intensive, often prohibitive, and the resulting data set is prone to systematic errors that result from run-to-run variations. High-throughput methods, especially those that can produce a breadth of variation in a single fabrication or synthesis run, can expedite the discovery phase and reduce errors that complicate comparative analysis.One method that can provide, in a single run, a broad range of compositions for a material system is combinatorial fabrication using oblique angle co-deposition [6]. Using this method, we co-sputtered samples using targets of elemental Pt and Co to obtain PtCo thin film (Figure 1a). During deposition, the wafer is not rotated, relying instead on the target and sample geometry in the chamber to provide compositional variation across the wafer. After unloading and dicing our test wafer into 4mm-by-4mm samples, we ran XRD of multiple samples to determine thickness and composition of the thin film alloys as a function of position (Figure 1b).Across an 8” wafer, this technique yielded Pt1-xCox thin film between 5% and 83% atomic composition Co. A subset of samples (68 nm < t < 117 nm, where t is the PtCo thickness) were measured with VSM up to 1 T applied field to obtain B-H curves (Figure 1c), from which the remnant magnetization and coercive field characteristics relative to composition were extracted (Figure 1d). We find that remnant magnetization varies from 0 T to about 0.6 T, mostly increasing as %Co increases. Coercivities vary between 0 Oe and 1800 Oe, maximized at about 50% Co. Because the samples were fabricated in the same run, all samples are free from run-to-run variations and differences in processing, and thus they can be compared directly. Utilizing this technique, we were able to determine the viability window of Pt1-xCox films for nearly all compositions (5%-83% Co) in a single run.Figure 1 a) Sputtering system running combinatorial Co-Pt growth. b) Thickness and atomic%-composition of Co relative to sample location. c) J-H curve for 66at% Co. d) Remnant magnetization (JR) and coercive field (H0) for Pt1-xCox , 0.05 < x < 0.83. Acknowledgement: This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This written work is authored by an employee of NTESS. The employee, not NTESS, owns the right, title and interest in and to the written work and is responsible for its contents. Any subjective views or opinions that might be expressed in the written work do not necessarily represent the views of the U.S. Government. The publisher acknowledges that the U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this written work or allow others to do so, for U.S. Government purposes. The DOE will provide public access to results of federally sponsored research in accordance with the DOE Public Access Plan. Figure 1

Lithography-Free Metaplasmonic Sensors Developed by TWD/GLAD Technique

Nowadays, plasmonic sensors are the most widely used and commercialized label-free optical biosensors and have become a widespread tool for studying chemical/biochemical interactions. Label-free, real-time, and direct measurements are the major benefits of the plasmonic sensors, including high-throughput surface bio-functionalization strategies without amplification or pretreatment of the sample [1]. The working principle of plasmonic sensing has been extensively described and reviewed over the decades [2], however, the possibility to develop cheap, effective, and clinically-accepted biosensors has recently become available due to the development of nanotechnology. Briefly, these nanostructures can be localized or can be arranged on 2D arrays of plasmonic metasurfaces, and can be fabricated by single-layer metallic films and a combination of metallic and dielectric films. The most popular plasmonic metals are gold and silver due to their high conductivity and low dielectric losses. Generally, top-down nanofabrication methods based on laser/e-beam lithography have been used, including nanostencil lithography based on shadow-masked nano-pattering and nanoimprint lithography [3]. Although such technologies have a high potential to achieve scalable and cost-effective nanofabrication at the wafer scale, these processes maintain the following main challenge: a master nano-mold/pattern is required to transfer metasurfaces with an associated high cost. Therefore, other technologies are the subject of research that overcomes this limitation and still offer an outstanding quality of metallic films, such as TDW (thermal dewetting) and GLAD (glancing angle deposition) (Fig.1). These techniques do not require master nano-mold/patterns; consequently, they can achieve lithography-free large-scale plasmonic metasurfaces [4]. TDW and GLAD usually generate quasi-ordered plasmonic metasurfaces compared to conventional lithographic methods.In this paper, the experimental results of the optical sensing properties of the sensors developed by the utilization of the combination of these two technologies in a single system are presented. The TWD/GLAD magnetron sputtering system has been designed and manufactured based on the Kurt J. Lesker MAG-Torus magnetrons, supplied with DC/RF power sources and an ECR manipulator that enables deposition at various angles with maximal 20 rpm rotation speed and heating option up to 850oC. The system is controlled by the software that enables deposition of the samples with the same parameters which pave the way for fabrication of the sensors on the industrial scale. The optical-sensing system was built based on an ST-VIS-50 spectrometer (Ocean Optics) and Tungsten Halogen Source (360-2000 nm, 2800 K, Ocean Optics) and optical table from Thorlabs. The obtained reflectance measurement has shown that the utilization of the GLAD technique decreases the reflectance peak in comparison with samples deposited without GLAD (flat samples). At the same time, angles in the range of 82-86oC seem to be preferable for nanostructure fabrication.Additionally, the utilization of the TWD technique, i.e. deposition at lower temperatures in the range of 60-100oC (depending on the substrate) and then annealed at higher temperatures such as 250oC and 300oC in a vacuum and under argon flow in the deposition chamber led to increased normalized response. However, the experiments have shown that the optimal annealing time is between 30-45 min depending on the SPR multi-structure, for example for Ag (6nm), Ti (2nm), and Au (2nm) the 30min at 250oC seems to be the best set. For such compositions, the surface sensitivity (nm/nm) and bulk sensitivity (nm/RIU) are more or less the same - 0.9 and 300, respectively. The obtained results are very promising for developing cheap, rapid, and very effective biosensors for various applications. Therefore, the obtained results seem to be very interesting for the ECS conference audience, for example, the developed Ag/Ti/Au multi-structures can be applied in novel organ-on-a-chip platforms for LADMET (liberations, absorption, distribution, metabolism, excretion, and toxicology) analysis [5].Fig. 1. Schematic diagram representation of lithography free methods for developing quasi-ordered metamaterials from left to right: Thermal dewetting and glancing angle deposition. The insert shows the chiral plasmonic nanospirals fabrication by glanced angle deposition [4].

(Dielectric Science & Technology Thomas Callinan Award) Rare-Earth Luminescence in Silicon-Based Thin Film Structures

For Si-based materials to be used in solid-state lighting and silicon photonics schemes it is necessary to have precise control of the optical emission from these materials. This can be accomplished using rare earth dopants such as Ce, Tb, and Eu to obtain blue, green, and red emissions, respectively. In this talk, we first will provide a review of our work in this field and then focus on Eu-doped films, which are particularly attractive for silicon photonic applications due to their intense emission in the visible spectral region [1]. We will also discuss the benefits of introducing a novel hybrid radio frequency (RF) magnetron sputtering source in the electron cyclotron resonance (ECR) plasma enhanced chemical vapour deposition (PECVD) reactor chamber [2], using the example of Tb-doped SiON films [3]. This approach contrasts with traditional doping methods which use metal-organic precursors or ion implantation to introduce rare-earth dopant species into the host matrix.[1] F. Azmi et al., “Tunable Emission from Eu:SiOxNy Thin Films Prepared by Integrated Magnetron Sputtering and Plasma Enhanced Chemical Vapor Deposition”, J. Vac. Sci. Technol. A 40, 043402 (2022); DOI: 10.1116/6.0001761[2] J.W. Miller et al., “Integrated ECR-PECVD and Magnetron Sputtering System for Rare-Earth-Doped Si-Based Materials”, Surface and Coatings Technology 336, 99 (2018); DOI: 10.1016/j.surfcoat.2017.08.051[3] Z. Khatami et al., "A comprehensive calibration of integrated magnetron sputtering and plasma enhanced chemical vapor deposition for rare-earth doped thin films", J. Mater. Res. (2023); DOI: 10.1557/s43578-023-01207-2