Advances In Thin Film Technology Research Articles

A Self-Assembled Multiphasic Thin Film as an Oxygen Electrode for Enhanced Durability in Reversible Solid Oxide Cells.

The implementation of nanocomposite materials as electrode layers represents a potential turning point for next-generation of solid oxide cells in order to reduce the use of critical raw materials. However, the substitution of bulk electrode materials by thin films is still under debate especially due to the uncertainty about their performance and stability under operando conditions, which restricts their use in real applications. In this work, we propose a multiphase nanocomposite characterized by a highly disordered microstructure and high cationic intermixing as a result from thin-film self-assembly of a perovskite-based mixed ionic-electronic conductor (lanthanum strontium cobaltite) and a fluorite-based pure ionic conductor (samarium-doped ceria) as an oxygen electrode for reversible solid oxide cells. Electrochemical characterization shows remarkable oxygen reduction reaction (fuel cell mode) and oxygen evolution activity (electrolysis mode) in comparison with state-of-the-art bulk electrodes, combined with outstanding long-term stability at operational temperatures of 700 °C. The disordered nanostructure was implemented as a standalone oxygen electrode on commercial anode-supported cells, resulting in high electrical output in fuel cell and electrolysis mode for active layer thicknesses of only 200 nm (>95% decrease in critical raw materials with respect to conventional cathodes). The cell was operated for over 300 h in fuel cell mode displaying excellent stability. Our findings unlock the hidden potential of advanced thin-film technologies for obtaining high-performance disordered electrodes based on nanocomposite self-assembly combining long durability and minimized use of critical raw materials.

Low temperature (Ts/Tm < 0.1) epitaxial growth of HfN/MgO(001) via reactive HiPIMS with metal-ion synchronized substrate bias

Low-temperature epitaxial growth of refractory transition-metal nitride thin films by means of physical vapor deposition has been a recurring theme in advanced thin-film technology for several years. In the present study, 150-nm-thick epitaxial HfN layers are grown on MgO(001) by reactive high-power impulse magnetron sputtering (HiPIMS) with no external substrate heating. Maximum film-growth temperatures Ts due to plasma heating range from 70 to 150 °C, corresponding to Ts/Tm = 0.10–0.12 (in which Tm is the HfN melting point in K). During HiPIMS, gas and sputtered metal-ion fluxes incident at the growing film surface are separated in time due to strong gas rarefaction and the transition to a metal-ion-dominated plasma. In the present experiments, a negative bias of 100 V is applied to the substrate, either continuously during the entire deposition or synchronized with the metal-rich portion of the ion flux. Two different sputtering-gas mixtures, Ar/N2 and Kr/N2, are employed in order to probe effects associated with the noble-gas mass and ionization potential. The combination of x-ray diffraction, high-resolution reciprocal-lattice maps, and high-resolution cross-sectional transmission electron microscopy analyses establishes that all HfN films have a cube-on-cube orientational relationship with the substrate, i.e., [001]HfN||[001]MgO and (100)HfN||(100)MgO. Layers grown with a continuous substrate bias, in either Ar/N2 or Kr/N2, exhibit a relatively high mosaicity and a high concentration of trapped inert gas. In distinct contrast, layers grown in Kr/N2 with the substrate bias synchronized to the metal-ion-rich portion of HiPIMS pulses have much lower mosaicity, no measurable inert-gas incorporation, and a hardness of 25.7 GPa, in good agreement with the results for epitaxial HfN(001) layers grown at Ts = 650 °C (Ts/Tm = 0.26). The room-temperature film resistivity is 70 μΩ cm, which is 3.2–10 times lower than reported values for polycrystalline-HfN layers grown at Ts = 400 °C.

Two‐Dimensional Mott Insulators in SrVO3 Ultrathin Films

Strongly correlated oxides that undergo a metal‐insulator transition (MIT) are a subject of great current interest for their potential application to future electronics as switches and sensors. Recent advances in thin film technology have opened up new avenues to tailor MIT for novel devices beyond conventional CMOS scaling. Here, dimensional‐crossover‐driven MITs are demonstrated in high‐quality epitaxial SrVO3 (SVO) thin films grown by a pulsed electron‐beam deposition technique. Thick SVO films (∼25 nm) exhibit metallic behavior with the electrical resistivity following the T2 law corresponding to a Fermi liquid system. A temperature driven MIT is induced in SVO ultrathin films with thicknesses below 6.5 nm. The transition temperature TMIT is at 50 K for the 6.5 nm film, 120 K for the 5.7 nm film and 205 K for the 3 nm film. The emergence of the observed MIT can be attributed to the dimensional crossover from a three‐dimensional metal to a two‐dimensional Mott insulator, as the resulting reduction in the effective bandwidth W opens a band gap at the Fermi level. The magneto‐transport study of the SVO ultrathin films also confirm the observed MIT is due to the electron‐electron interactions other than disorder‐induced localization.

Hematite-based Photo-oxidation of Water Using Transparent Distributed Current Collectors

High specific surface area transparent and conducting frameworks, fabricated by atomic layer deposition (ALD), were used as scaffolds for fabrication of equally high area, ALD-formed hematite structures for photo-oxidation of water to dioxygen. The frameworks offer high transparency to visible light and robust conductivity under harsh annealing and oxidizing conditions. Furthermore, they also make possible the spatially distributed collection of photocurrent from ultrathin coatings of hematite layers, enabling the formation of photoanodes featuring both large optical extinction and a hematite layer thickness nearly commensurate with the hole-collection distance. The distributed-current-collection approach increases the efficiency of water oxidation with hematite (by about a factor of 3 compared with an optimized flat electrode), is highly adaptable to future advances in thin film technology, and is further applicable to a multitude of nanostructures and optoelectronic applications that require ultrathin films without sacrificing optical thickness.

V-Band Beam-Steering ASK Transmitter and Receiver Using BCB-Based System-on-Package Technology on Silicon Mother Board

We report V-band fully integrated planar beam-steering Amplitude-Shift-Keying (ASK) transmitter (Tx) and receiver (Rx) system using advanced thin-film technology on a silicon (Si) mother board. BCB-on-Si System-on-Package (SOP) technology allows Rotman lens, patch antennas, and other passive elements to be integrated on a Si substrate together with active circuits. All MMIC chipsets are flip-chipped on a BCB substrate. Tx beam-steering is achieved by a combination of a SP3T switch and a Rotman lens terminated with the embedded resistors. The measured Tx antenna gain is 17.5 dBi and the effective isotropic radiated power is 26 dBm. The Tx module can steer the beam to three different directions of 0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and ±12 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> in the H-plane. A wireless link was successfully demonstrated at a data rate of 2 Gb/s with less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> bit error rate.

Advances in Thin Film Technology through the Application of Modulated Pulse Power Sputtering

High power pulsed magnetron sputtering (HPPMS) is an emerging thin film deposition technology that generate high ionization plasma by applying a very large amount of peak power to a sputtering target for a short period of time. HPPMS is also known as High Power Impulse Magnetron Sputtering (HiPIMS). However, HPPMS/HiPIMS exhibits decreased deposition rate as compared to continuous dc magnetron sputtering. Modulated pulse power (MPP) magnetron sputtering is an alternative HPPIMS deposition technique that overcomes the rate loss problem while still achieving a high degree of ionization of the sputtered material. In the present work, the principles and some important characteristics of MPP technology were presented. Technical examples of CrN coatings were deposited using MPP and continuous dc sources. The positive ion mass distributions were characterized using an electrostatic quadrupole plasma mass spectrometer. The structure and properties of MPP and dc CrN coatings were characterized using x-ray diffraction, scanning electron microscopy, nanoindentation tests, and ball-on-disc wear test. It was found that the MPP CrN coating exhibits denser microstructure and improved mechanical and tribological properties as compared to the dc CrN coating.

Advanced thin film technology for ultrahigh resolution X-ray microscopy

Further progress in the spatial resolution of X-ray microscopes is currently impaired by fundamental limitations in the production of X-ray diffractive lenses. Here, we demonstrate how advanced thin film technologies can be applied to boost the fabrication and characterization of ultrahigh resolution X-ray optics. Specifically, Fresnel zone plates were fabricated by combining electron-beam lithography with atomic layer deposition and focused ion beam induced deposition. They were tested in a scanning transmission X-ray microscope at 1.2 keV photon energy using line pair structures of a sample prepared by metalorganic vapor phase epitaxy. For the first time in X-ray microscopy, features below 10 nm in width were resolved.

A V-Band Beam-Steering Antenna on a Thin-Film Substrate With a Flip-Chip Interconnection

We propose a planar V-band beam-steering antenna based on a millimeter-wave (mm-wave) system-on-package technology using advanced thin-film technology on a silicon mother board. The thin-film substrate has the capability of integrated passive elements and flip-chip interconnection. Space-consuming components such as a microstrip Rotman lens and patch antennas are implemented on a low-loss, low-cost, and low-dielectric-constant material, benzocyclobutane. V-band monolithic microwave integrated circuits, a power amplifier, and a SP4T switch, are flip-chipped on the thin-film substrate while minimizing parasitic effects. The fabricated antenna module shows if-plane beam steering at four angles, plusmn6deg and plusmn20deg. The measured effective isotropic radiated power is in the range of 17.3-18 dBm. To our knowledge, this is the first demonstration of a planar mm-wave beam-steering antenna module on a thin-film substrate incorporating integrated terminating loads and flip-chip interconnections.

Silicon-integrated uncooled infrared detectors: Perspectives on thin films and microstructures

Uncooled infrared (IR) photodetectors for telecommunications, optical processor interconnects, and focal plane arrays are advantageously integrated into systems that are silicon based through advanced thin-film technologies. This paper reviews challenges of materials, microstructures, interfaces, and reactions of thin-film materials and technologies posed by such applications.

Effects of the Multilayer Structure on the Responsivity of Pyroelectric Thin Film Detectors

AbstractPyroelectric thin film detectors have advantages of wavelength independent sensitivity, room temperature operation and direct incorporation with integrated circuit amplifiers. Pyroelectric thin films with good quality have be prepared by many advanced thin film technologies [1-2]. The responsivity of pyroelectric thin film detectors is dependent on the thermal properties of the substrate, on which pyroelectric thin film detectors are prepared. The heat conduction in the detectors was investigated using the one-dimensional heat flow equation and the expressions describing the detectors performance were derived for pyroelectric thin films detectors with multilayer structure. The numerical simulation showed that the pyroelectric thin film detectors need effective heat isolation. If the air gap could be the heat isolation layer, which is between the bottom electrode and substrate, the iesponsivity of detectors would be higher than that of detectors which have no heat isolation in certain modulation frequency range.

Magnetic thin films for data storage

Applications of magnetic thin films in data storage technology and areas for future research on thin films are discussed. Recent work at various laboratories indicates that magnetic recording densities of at least two orders of magnitude greater than those of today will be achieved. Among the advances in thin film technology which are needed to make this possible are the following: improved wear resistant overcoats for magnetic media; higher coercivity thin film media with isolated grain structure and multilayers to achieve low noise; high magnetization, high permeability multilayer thin film materials for advanced recording heads; giant magnetoresistive materials for advanced read heads. Although magnetic recording is expected to continue to dominate the data storage industry for the next two decades, magnetic-optic recording is likely to play an increasingly large role as a removable storage medium for large files of data involving images and multimedia. For increased storage density in magneto-optic recording, new magneto-optic thin film materials which are sensitive in the blue (or shorter) wavelength spectrum are needed. These films must not only provide large magneto-optic coefficients, but must also have the proper microstructure so that noise is low during readback. In order for these advances to be possible, new materials, new processing techniques, improved models and improved resolution imaging systems for studying both the magnetic and physical microstructure of thin films are needed.

Electrochemical biosensors on thin-film metals and conducting polymers

Electrochemical biosensors using advanced thin-film technology employing 1,4-arenequinones substituted with at least two halogens in para positions as new agents for the immobilization of enzymes are described. For special applications, thin-film electrodes were combined with permeation-selective polypyrrole layers as sensory modifying devices.