Platinum Thin Films Research Articles

Exploring Platinum Thin Films as Electrodes for High‐Temperature and ‐Pressure Electrochemical Studies in Aqueous Systems

ABSTRACTThis work reports a methodology for the fabrication of Pt thin‐film electrodes for electrochemical studies in hydrothermal systems. The research process was meticulous, with particular attention paid to the multilayer Ti/Pt/Ti/Al2O3 film structure and annealing conditions that are expected to impact the morphology of the films, surface composition and electrochemical response. The findings of this study are significant, as they provide valuable insights into the behaviour of Pt thin‐film electrodes in various media and conditions. Two different approaches were adopted for the preparation of the electrodes: in one case, the Ti/Pt/Ti/Al2O3 films deposited on sapphire wafers were exposed to rapid thermal annealing at 900°C under argon for 5 min, followed by argon ion milling to etch the final electrode pattern (Pt‐RA(900)), while in the other case, uncapped Pt films were annealed, after etching, in a tubular oven under argon at specific temperatures between 200°C and 900°C (Pt‐TO). Rapid annealing at 900°C on capped films resulted in the formation of a Pt3Ti intermetallic alloy with remarkable mechanical and chemical stability even after 10 h of immersion in deionised water, acid (0.1 M H2SO4) and alkaline media (0.1 M KOH) conditions at temperatures up to 150°C, despite the dissolution of the Al2O3 top layer at 150°C and long immersion times (> 10 h). In the case of uncapped Pt films, diffusion and oxidation of Ti through the Pt film at high temperature resulted in the formation of TiO2 on the surface of Pt. The results were confirmed by using a comprehensive suite of ex‐situ characterisation techniques to follow changes in the Pt electrode surface morphology and composition before and after immersion in H2O, 0.1 M H2SO4 and 0.1 M KOH solutions under argon. Ex‐situ electrochemical characterisation studies were also conducted to correlate the changes in the electrode surface properties, including the electrochemical surface area, with different annealing conditions and after various hydrothermal treatments in neutral, alkaline and acidic media.

Grain rotation mechanisms in nanocrystalline materials: Multiscale observations in Pt thin films.

Near-rigid-body grain rotation is commonly observed during grain growth, recrystallization, and plastic deformation in nanocrystalline materials. Despite decades of research, the dominant mechanisms underlying grain rotation remain enigmatic. We present direct evidence that grain rotation occurs through the motion of disconnections (line defects with step and dislocation character) along grain boundaries in platinum thin films. State-of-the-art in situ four-dimensional scanning transmission electron microscopy (4D-STEM) observations reveal the statistical correlation between grain rotation and grain growth or shrinkage. This correlation arises from shear-coupled grain boundary migration, which occurs through the motion of disconnections, as demonstrated by in situ high-angle annular dark-field STEM observations and the atomistic simulation-aided analysis. These findings provide quantitative insights into the structural dynamics of nanocrystalline materials.

Proximity-induced ferromagnetism of platinum thin film on magnetic insulating CrI3 nanoflakes

The induced magnetization of Pt holds significant promise for the development of spintronic devices. In this study, we constructed a two-dimensional heterostructure consisting of a ferromagnetic insulating CrI3 nanoflake and metallic Pt thin films. The observation of anomalous Hall effect suggests the emergence of a ferromagnetic long-range order in the Pt thin film induced by the magnetic proximity effect. Density functional theory calculations were performed to investigate the underlying mechanisms. We propose that the spontaneous magnetization of Pt in Pt/CrI3 stems from an intensified exchange interaction between Pt 5d and Cr 3d electrons, which is facilitated by the interface coupling and the formation of interfacial hybrid orbitals. These results contribute to a deeper understanding of spin-based phenomena and have potential implications for advancements in the field of spintronics.

A 0.00179 mm2/Ch Chopper-Stabilized TDMA Neural Recording System With Dynamic EOV Cancellation and Predictive Mixed-Signal Impedance Boosting.

This article presents a digitally-assisted multi-channel neural recording system. The system uses a 16-channel chopper-stabilized Time Division Multiple Access (TDMA) scheme to record multiplexed neural signals into a single shared analog front end (AFE). The choppers reduce the total integrated noise across the modulated spectrum by 2.4 × and 4.3 × in Local Field Potential (LFP) and Action Potential (AP) bands, respectively. In addition, a novel impedance booster based on Sign-Sign least mean squares (LMS) adaptive filter (AF) predicts the input signal and pre-charges the AC-coupling capacitors. The impedance booster module increases the AFE input impedance by a factor of 39 × with a 7.1% increase in area. The proposed system obviates the need for on-chip digital demodulation, filtering, and remodulation normally required to extract Electrode Offset Voltages (EOV) from multiplexed neural signals, thereby achieving 3.6 × and 2.8 × savings in both area and power, respectively, in the EOV filter module. The Sign-Sign LMS AF is reused to determine the system loop gain, which relaxes the feedback DAC accuracy requirements and saves 10.1 × in power compared to conventional oversampled DAC truncation-error ΔΣ-modulator. The proposed SoC is designed and fabricated in 65 nm CMOS, and each channel occupies 0.00179 mm2 of active area. Each channel consumes 5.11 μW of power while achieving 2.19 μVrms and 2.4 μVrms of input referred noise (IRN) over AP and LFP bands. The resulting AP band noise efficiency factor (NEF) is 1.8. The proposed system is verified with acute in-vivo recordings in a Sprague-Dawley rat using parylene C based thin-film platinum nanorod microelectrodes.

Sensitivity enhancement of thermal acoustic particle velocity sensor based on metal film optimization

Thermal acoustic particle velocity sensors find widespread application in sound field measurements and sound source localization, owing to their capacity to capture vectorial information. This paper focuses on enhancing the sensitivity of detecting weaker signals by elevating the temperature coefficient of resistance (TCR) in the platinum thin film on the sensor's sensing wires. The study delves into the impact of annealing on the TCR of Pt thin films applied to small-sized elongated wires for thermal acoustic particle velocity sensors. The augmented effects of annealing Pt thin films with three adhesion layer metals—Chromium (Cr) and Titanium (Ti), previously commonplace in this sensor, and the newly introduced Tantalum (Ta) are scrutinized. Additionally, the influence of the deposition of Au electrodes, employed for wire bonding, both before and after annealing, on the annealing effect is also explored. In conclusion, a Pt thin film annealing process tailored for thermal acoustic particle velocity sensors is proposed, along with the recommendation of the optimal adhesion layer metal. This approach results in a substantial 20 % improvement in the TCR of the Pt thin film on the sensing wires, coupled with a corresponding 2.2 dB increase in sensor sensitivity.

Small-size temperature/high-pressure integrated sensor via flip-chip method

Hydraulic technology with smaller sizes and higher reliability trends, including fault prediction and intelligent control, requires high-performance temperature and pressure-integrated sensors. Current designs rely on planar wafer- or chip-level integration, which is limited by pressure range, chip size, and low reliability. We propose a small-size temperature/high-pressure integrated sensor via the flip-chip technique. The pressure and temperature units are arranged vertically, and the sensing signals of the two units are integrated into one plane through silicon vias and gold–gold bonding, reducing the lateral size and improving the efficiency of signal transmission. The flip-chip technique ensures a reliable electrical connection. A square diaphragm with rounded corners is designed and optimised with simulation to sense high pressure based on the piezoresistive effect. The temperature sensing unit with a thin-film platinum resistor measures temperature and provides back-end high-precision compensation, which will improve the precision of the pressure unit. The integrated chip is fabricated by MEMS technology and packaged to fabricate the extremely small integrated sensor. The integrated sensor is characterised, and the pressure sensor exhibits a sensitivity and sensitivity drift of 7.97 mV/MPa and −0.19% FS in the range of 0–20 MPa and −40 to 120 °C. The linearity, hysteresis, repeatability, accuracy, basic error, and zero-time drift are 0.16% FS, 0.04% FS, 0.06% FS, 0.18% FS, ±0.23% FS and 0.04% FS, respectively. The measurement error of the temperature sensor and temperature coefficient of resistance is less than ±1 °C and 3142.997 ppm/°C, respectively. The integrated sensor has broad applicability in fault diagnosis and safety monitoring of high-end equipment such as automobile detection, industrial equipment, and oil drilling platforms.

Stability Enhancement of the Platinum Thin-Film Temperature Detector up to 1400 °C by Printing Al₂O₃ Protective Layer

Stability Enhancement of the Platinum Thin-Film Temperature Detector up to 1400 °C by Printing Al₂O₃ Protective Layer

Dung Beetle Optimized Fuzzy PID Algorithm Applied in Four-Bar Target Temperature Control System

With the widespread application of infrared thermal imagers in various fields, the demand for thermal imagers and their performance parameter testing equipment has increased significantly. There are particularly high demands on the detection accuracy of minimum resolvable temperature difference (MRTD) testers. Traditional MRTD testers have an issue with the four-bar target temperatures being easily affected by the external environment, resulting in non-uniform temperatures and imprecise detection results. This paper proposes an improvement to the four-bar targets by making them temperature-controllable. Temperature is controlled by installing thermoelectric coolers (TECs) and thin-film platinum resistors at the center and periphery of the four-bar targets with different spatial frequencies. The dung beetle algorithm is used to optimize fuzzy PID parameters to regulate the TEC’s heating and cooling, improving the overall temperature uniformity of the four-bar targets. Temperature simulations of the four-bar targets were conducted on the COMSOL platform, with the control part simulated on the Simulink platform. The simulation results show that, compared to traditional PID, the fuzzy PID controller reduces overshoot by approximately 3.6%, although the system still exhibits mild oscillations. The fuzzy PID controller optimized by the dung beetle optimization (DBO) algorithm, in comparison to standard fuzzy PID, reduces the settling time by about 40 s and lowers overshoot by around 7%, with oscillations in the system nearly disappearing. Comparing the fuzzy PID optimized by the particle swarm optimization (PSO) algorithm with the fuzzy PID optimized by the DBO algorithm, the DBO-based controller shows shorter rise and settling times, further illustrating the superiority of the fuzzy PID control optimized by the dung beetle algorithm. This provides a theoretical foundation for improving the accuracy of MRTD detector measurements. Finally, experimental verification was carried out. The experimental results indicate that DBO (drosophila-based optimization) has significant advantages, and its optimized results are closer to the actual values.

Temperature coefficient of resistance and thermal boundary conductance determination of ruthenium thin films by micro four-point probe

Accurate characterization of the temperature coefficient of resistance (α TCR) of electrically conductive materials is pertinent for reducing self-heating in electronic devices. In-situ non-destructive measurements of α TCR using the micro four-point probe (M4PP) technique have previously been demonstrated on platinum (Pt) thin films deposited on fused silica, assuming the thermal conductivity of the substrate as known. In this study, we expand the M4PP method to obtain the α TCR on industrially relevant stacks, comprising ruthenium (Ru) thin films (3.3 nm and 5.2 nm thick) deposited on bulk silicon (Si), separated by a 90 nm SiO2 spacer. The new M4PP methodology allows simultaneous determination of both α TCR and the total thermal boundary conductance (G TBC) between the metallic film and its substrate. We measured the α TCR and the G TBC to be 542 ± 18 ppm K−1 and 15.6 ± 1.3 MW m−2K−1 for 3.3 nm Ru, and 982 ± 46 ppm K−1 and 19.3 ± 2.3 MW m−2K−1 for 5.2 nm Ru. This is in good agreement with independent measurements of α TCR. Our methodology demonstrates the potential of M4PP to characterize thermal properties of metallic thin films used in semiconductor technology.

Fourier Transform Thermoreflectance Method Under Front-Heat Front-Detect Configuration

The thermoreflectance method, which can measure thermal diffusivity in the cross-plane direction of thin films, mainly has two possible configurations; rear-heat front-detect (RF) and front-heat front-detect (FF) configuration. FF configuration is applicable to a wide variety of thin films including thin films deposited on opaque substrates, but this configuration has some problems in determination of the thermal diffusivity. One of the main problems is the effect of the penetration of pump beam and probe beam in thin film, which affects the initial temperature distribution near the sample’s surface after pulse heating. Several studies have tried to analyze the effect but there have been no practical analytical solutions which can solve this problem in FF configuration. In this paper, we propose a new analytical solution which considers the penetration of pump beam and probe beam into thin film, and by applying Fourier expansion analysis which we developed in a previous study to thermoreflectance signals, we have determined the thermal diffusivity of thin film in the thermoreflectance method under FF configuration. We measured platinum thin films with different thickness under both FF and RF configuration and obtained consistent thermal diffusivity values from both configurations.

Artificial Hair Cell Sensor Based on Nanofiber-Reinforced Thin Metal Films.

Engineering artificial mechanosensory hair cells offers a promising avenue for developing diverse biosensors spanning applications from biomedicine to underwater sensing. Unfortunately, current artificial sensory hair cells do not have the ability to simultaneously achieve ultrahigh sensitivity with low-frequency threshold detection (e.g., 0.1 Hz). This work aimed to solve this gap by developing an artificial sensory hair cell inspired by the vestibular sensory apparatus, which has such functional capabilities. For device characterization and response testing, the sensory unit was inserted in a 3D printed lateral semicircular canal (LSCC) mimicking the environment of the labyrinth. The sensor was fabricated based on platinum (Pt) thin film which was reinforced by carbon nanofibers (CNFs). A Pi-shaped hair cell sensor was created as the sensing element which was tested under various conditions of simulated head motion. Results reveal the hair cell sensor displayed markedly higher sensitivity compared to other reported artificial hair cell sensors (e.g., 21.47 mV Hz-1 at 60°) and low frequency detection capability, 0.1 Hz < f < 1.5 Hz. Moreover, like the LSCC hair cells in biology, the fabricated sensor was most sensitive in a given plane of rotational motion, demonstrating features of directional sensitivity.

Ultrasmooth Epitaxial Pt Thin Films Grown by Pulsed Laser Deposition.

Platinum (Pt) thin films are useful in applications requiring high-conductivity electrodes with excellent thermal and chemical stability. Ultrasmooth and epitaxial Pt thin films with single-crystalline domains have the added benefit of providing ideal templates for the subsequent growth of heteroepitaxial structures. Here, we grow epitaxial Pt (111) electrodes (ca. 30 nm thick) on sapphire (α-Al2O3 (0001)) substrates with pulsed laser deposition. This versatile technique allows control of the growth process and fabrication of films with carefully tailored parameters. X-ray scattering, atomic-force microscopy, and electron microscopy provide structural characterization of the films. Various gaseous atmospheres and temperatures were explored to achieve epitaxial growth of films with low roughness. A two-step (500 °C/300 °C) growth process was developed, yielding films with improved epitaxy without compromising roughness. The resulting films possess ultrasmooth interfaces (<3 Å) and high electrical conductivity (6.9 × 106 S/m). Finally, Pt films were used as current collectors and templates to grow lithium manganese oxide (LiMn2O4 (111)) epitaxial thin films, a cathode material used in Li-ion batteries. Using a solid-state ionogel electrolyte, the films were highly stable when electrochemically cycled in the 3.5-4.3 V vs Li/Li+ range.

Electrochemical cycling durability of platinum overlayers formed by self-terminating electrodeposition

Platinum thin films comprising nominally 1 to 20 atomic overlayers were formed on a gold-coated substrate using the self-terminating electrodeposition (STED) method. The platinum overlayer loading and morphology were characterized using X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FESEM), Cyclic Voltammetry (CV) and Chronoamperometry (CA). The durability of these platinum overlayer samples was estimated by subjecting the samples to ex-situ electrochemical potential cycling. The extent of platinum overlayer growth is lower than expected till four STED cycles and then increases non-linearly, leading to increased roughness. The shifts of platinum redox peaks in CVs and Pt4f signals in XPS spectra indicate surface-alloying of gold and platinum. After the durability test, the morphological evolution of platinum overlayers conforms with the extent of platinum dissolution estimated from CVs. Our results reveal that more than four STED cycles are needed to form platinum overlayers that meet the US Department of Energy (DOE) criteria for durability.

Titanium–Platinum Thin Films as a Tool for the Electrooxidation of Cyanide

This paper presents a detailed study of a titanium–platinum thin film-based electrode preparation and its practical application in the electrooxidation of cyanides to help protect our environment. The novel electrochemical deposition process of Pt on nearly atomically smooth magnetron-sputtered Ti film has been used to prepare a highly effective glass|Ti|Pt composite electrode with high catalytic activity for the electrooxidation of cyanide ions. The composite electrode exhibits over a 90% electrical current efficiency in the cyanide electrooxidation process and can be used for the decontamination of highly concentrated KCN solutions (up to 0.1 M) without any chemical additives. A high current efficiency (70%) of Pt thin film deposition on a glass|Ti electrode was achieved using a potentiostatic double-pulse method. Fast Fourier transform electrochemical impedance spectroscopy revealed the oxidation kinetics for cyanide ions at the electrode. The glass|Ti electrode was prepared using the magnetron sputtering technique, which allows us to fabricate electrodes of any shape suitable for any electrochemical cell or electroplating bath. Meanwhile, electrochemical deposition of Pt on the glass|Ti electrode is an efficient and environmentally friendly method, since various salts of Pt and/or Pt-containing wastes can be used for electrodeposition instead of pure Pt, which is more expensive.

Thermal and optical characterization of a resistance-temperature detector based on platinum thin film: Design and fabrication

In this research, it is presented an easy-to-implement method, utilizing spin coating-sputtering technique, for the production of cost-effective resistance temperature detectors (RTDs) based on platinum (Pt). By employing physical patterning mask techniques such as lithography, the shape of RTDs can be readily customized to meet specific requirements. Furthermore, the developed Pt-based RTDs exhibit a higher sensitivity, with a temperature coefficient of resistance (α) approximately at 3.87 × 10−3 ◦C−1, compared to RTDs based on Au, Ag, and Cu. The sensitivity of these Pt-based RTDs is comparable to that of commercially available Pt-based sensors. Moreover, these RTDs demonstrate exceptional repeatability, maintaining consistent performance within a temperature range of up to 200 ◦C. According to interesting nonlinear optical findings, Pt-based RTD sensor showed the nonlinear optical responses in the 532 nm wavelength because of two photon absorption phenomena in nonlinear absorption coefficient (NLA) and self-focusing effect in addition to their excellent temperature sensing capabilities, the Pt-based RTDs exhibit notable nonlinear optical refractive index (NLR) and nonlinear absorption (NLA) properties. The NLR index of the RTDs is on the order of 10−8 cm2/W, while the NLA index is on the order of 10−3 cm/W. This implies that these RTDs possess significant nonlinear optical response characteristics. Moreover, the Pt-based RTDs demonstrate rapid response times to changes in temperature, making them suitable for applications in nonlinear optical equipment such as optoelectronics and photonics.

Study on High-Temperature Oxidation Behavior of Platinum-Clad Nickel Composite Wire

Platinum-clad nickel composite wires with platinum layer thicknesses of 5 μm and 8 μm were prepared by a cladding drawing process. Oxidation experiments were performed using a muffle furnace at temperatures of 500 °C, 600 °C, 700 °C, and 800 °C for 1 h, 2 h, and 3 h. The oxidized samples were examined for high-temperature oxidation behavior using scanning electron microscopy (SEM) with an energy-dispersive X-ray (EDX) spectrometer attached. The results showed that the interface bond between the platinum cladding and the nickel core wire was serrated and that the thickness of the platinum cladding was not uniform. At low temperatures (500 °C and 600 °C), the diffusion rate of the nickel was low. The composite wire could be used for a short time below 600 °C. When the temperature reached 700 °C and above, the nickel diffused to the surface of the composite wire and was selectively oxidized to form a nickel oxide layer. The research results provide a theoretical reference for the selection of a service temperature for platinum-clad nickel composite wires used as the lead material for thin-film platinum resistance temperature sensors.

Velocity-selected spatial map ion imaging spectrometer for direct imaging of near-surface catalytic activity

We propose and demonstrate an approach permitting direct imaging of the spatial distribution of gas-surface reaction products with &amp;lt;60 μm lateral spatial resolution using a velocity filtered ion imaging technique. We demonstrate direct imaging of the density of hydrogen deuteride (HD) molecules desorbed from a patterned platinum (Pt) thin film exposed to molecular beams of hydrogen (H2) and deuterium (D2). Resonance enhanced multiphoton absorption was performed with a 2 + 1 scheme through the E,F state using a nanosecond UV laser at ∼201 nm. The generated cations of HD, D2, and H2 were velocity filtered and accelerated with ion imaging optics toward a multichannel plate and phosphor screen. To reduce the significant image blur caused by the translational energy of the parent molecules, a grounded pinhole with 50 μm diameter is placed at the velocity-mapped imaging plane of the ion optics, which velocity-filters the ions that form the image of the near-surface origination plane, improving the ion imaging resolution by a factor of ∼10. The instrument demonstrates the capability to directly image catalytic output in the gas phase in the near-surface region with tens of micrometers of spatial resolution simultaneously with mass and molecular velocity resolution.

Reliability estimation of thin film platinum resistance MEMS thermal mass flowmeter by step-stress accelerated life testing

Assuring reliability is a key aspect of sensor quality. In this article, we introduce the reliability test results of thin film platinum resistance (TFPR) MEMS thermal mass flowmeter based on accelerated life testing (ALT). The influences of temperature stress (Ts) and temperature-voltage double-stress ((T + V)s) on sensor reliability are assessed through ageing experiments using a climatic chamber. According to the performance in ageing test, we chose output voltage as a characteristic parameter. We analyze the causes for degradation of the characteristic parameter. In addition, based on Arrhenius model and Weibull distribution (WD), we predict the lifetime and estimate the reliability of the TFPR MEMS thermal mass flowmeter. The average lifetime of Ts group is 1.826 × 104 h (2.085 years) in 85 °C test conditions; and the (T + V)s group is 1.003 × 104 h (1.145 years). The reliability of Ts group is 87 %, and the (T + V)s group is 80 %, in the first working year. The results reveal the temperature and voltage stress influences on lifetime. This research provides a good way for reliability analysis of thermal mass flowmeter units.

PEM Electrochemical Hydrogen Compression with Sputtered Pt Catalysts.

This work presents research on thin magnetron-sputtered platinum (Pt) films deposited over commercial gas diffusion electrodes and applied to convert and pressurize hydrogen in an electrochemical hydrogen pump. The electrodes were integrated into a membrane electrode assembly with a proton conductive membrane. Their electrocatalytic efficiency toward hydrogen oxidation and hydrogen evolution reactions was studied in a self-made laboratory test cell by means of steady-state polarization curves and cell voltage measurements (U/j and U/pdiff characteristics). The achieved current density at a cell voltage of 0.5 V, the atmospheric pressure of the input hydrogen, and a temperature of 60 °C was more than 1.3 A cm-2. The registered increase in the cell voltage with the increasing pressure was only 0.05 mV bar-1. Comparative data with commercial E-TEK electrodes reveal the superior catalyst performance and essential cost reduction of the electrochemical hydrogen conversion on the sputtered Pt films.

Interfacial Connections between Organic Perovskite/n+ Silicon/Catalyst that Allow Integration of Solar Cell and Catalyst for Hydrogen Evolution from Water

AbstractThe rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin‐film semiconductors has triggered interest in their use for direct solar‐driven water splitting to produce hydrogen. However, application of these low‐cost, electronic‐structure‐tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic‐catalyst‐electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high‐temperature annealing of the catalyst/TiO2‐protected‐n+silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA1‐xCsx)PbI3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro‐OMeTAD‐hole‐transport‐layer (HTL)‐based HOIP/n+Si solar cell, and a high photocurrent density of −15.9 mA cm−2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n+Si/Pt photocathode in 1 m NaOH under simulated 1‐sun illumination. While this thin‐film design creates stable interfaces, the intrinsic photo‐ and electro‐degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices.