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Porous platinum is a frequently used catalyst material in electrosynthesis and a robust broadband absorber in thermoelectrics. Pore size distribution and localization determine its properties by a large extent. However, the pore formation mechanism during the growth of the material remains unclear. In this work we elucidate the mechanism underlying electrochemical growth of nanoporous platinum layers and its control by ionic concentration and current density during electrolysis. The electrode kinetics and reduction steps of PtCl4 on platinum electrodes are investigated by cyclic voltammetry and impedance measurements. Cyclic voltammograms show three reduction steps: two steps relate to the platinum cation reduction, and one step relates to the hydrogen reduction. Hydrogen is not involved in the reduction of PtCl4, however it enables the formation of nanopores in the layers. These findings contribute to the understanding of electrochemical growth of nanoporous platinum layers in isopropanol with thickness of 100 nm to 500 nm. Porous platinum is a frequently used electrocatalyst and thermoelectric material, but the growth mechanism of nanopores in platinum layers is still not fully understood. Here, the authors show that hydrogen is not involved in the reduction process of PtCl4, however it enables the formation of nanopores.

In microstructural corrosion studies, knowledge on the initiation of corrosion on an nm-scale is lacking. In situ transmission electron microscope (TEM) studies can elucidate where/how the corrosion starts, provided that the proper corrosive conditions are present during the investigation. In wet corrosion studies with liquid cell nanoreactors (NRs), the liquid along the electron beam direction leads to strong scattering and therefore image blurring. Thus, a quick liquid removal or thickness control of the liquid layer is preferred. This can be done by the use of a Peltier element embedded in an NR. As a prelude to such in situ work, we demonstrate the local wetting of a TEM sample, by creating a temperature decrease of 10 ± 2°C on the membrane of an NR with planar Sb/BiSb thermoelectric materials for the Peltier element. TEM samples were prepared and loaded in an NR using a dual-beam focused ion beam scanning electron microscope. A mixture of water vapor and carrier gas was passed through a chamber, which holds the micro-electromechanical system Peltier device and resulted in quick formation of a water layer/droplets on the sample. The TEM analysis after repeated corrosion of the same sample (ex situ studies) shows the onset and progression of O2 and H2S corrosion of the AA2024-T3 alloy and cold-rolled HCT980X steel lamellae.

The sensitivity of planar multijunction thermal converters was significantly increased by filling the housing with noble gasses, preferably xenon or krypton. The performance was observed for almost two years, and no degradation of the sensitivity was found. Also, the frequency response of the ac–dc transfer difference remains unchanged at high frequencies and even improves below 40 Hz. Using the lowest at present manufacturable heater resistance of 90 $\Omega $ with the noble gas filling, ac–dc transfer at voltages down to almost 70 mV compared to about 100 mV in air becomes possible.

In microstructural corrosion studies, knowledge on the initiation of corrosion on an nm-scale is lacking. In situ transmission electron microscope (TEM) studies can elucidate where/how the corrosion starts, provided that the proper corrosive conditions are present during the investigation. In wet corrosion studies with liquid cell nanoreactors (NRs), the liquid along the electron beam direction leads to strong scattering and therefore image blurring. Thus, a quick liquid removal or thickness control of the liquid layer is preferred. This can be done by the use of a Peltier element embedded in an NR. As a prelude to such in situ work, we demonstrate the local wetting of a TEM sample, by creating a temperature decrease of 10 ± 2°C on the membrane of an NR with planar Sb/BiSb thermoelectric materials for the Peltier element. TEM samples were prepared and loaded in an NR using a dual-beam focused ion beam scanning electron microscope. A mixture of water vapor and carrier gas was passed through a chamber, which holds the micro-electromechanical system Peltier device and resulted in quick formation of a water layer/droplets on the sample. The TEM analysis after repeated corrosion of the same sample (ex situ studies) shows the onset and progression of O2 and H2S corrosion of the AA2024-T3 alloy and cold-rolled HCT980X steel lamellae.

Tailoring the physicochemical properties of the metallic multijunction nanolayers is a prerequisite for the development of microelectronics. From this perspective, a desired lower reflectance of infrared radiation was achieved by an electrochemical deposition of porous platinum in nonaqueous media on silver mirror supported nickel-chrome and nickel-titanium metallic films with incremental decreasing thicknesses from 80-10 nm. The electro-assembled architectures were examined by means of scanning electron microscopy and Fourier transform infrared spectroscopy and it was observed that the layer and sublayer thicknesses and resistivities have a substantial effect upon the porous platinum morphology and its optical properties. It is here reported that the augmentation of the metallic layer electrical conductivity determines the electroformation of more compact platinum nanolayers. Moreover, the platinum black coating of metallic nanolayers causes a considerable decrease of the reflectance in the region from 1000-8000 cm-1.

The development of new application fields of microelectromechanical systems (MEMS) devices often implies a high degree of complexity and the integration of several functionalities within these devices. In this paper, thermoelectric planar thin-film microcoolers become more and more important due to their cooling and temperature stabilization ability, respectively, in MEMS devices. This paper reports on the investigation of the design, manufacturing, and characterization of a membrane-integrated thin-film thermoelectric cooling arrangement for active temperature control and precise local cooling of the sensitive region in a thin-film dew-point sensor. The sensor concept is based on the combination of a thermal sensor heater and a planar thin-film Peltier cooler, which are all arranged on a freestanding and thermally insulated membrane. To obtain a high performance concerning the maximum temperature decrease of the active-cooled membrane, a highly efficient thermoelectric materials combination of Sb and Bi0.87Sb0.13 was used for the fabrication of the in-plane Peltier configuration. For the first sensor setup, a temperature decrease of 10.6 K was achieved under atmospheric conditions at 293 K. In combination with an externally assembled two-stage Peltier cooler dew-point, temperature measurements down to 213 K (−60 °C) were performed in a climatic exposure test cabinet. [2014-0132]

Aluminum nitride (AlN) thin films with thicknesses from 20 to 100 nm were deposited on silicon, amorphous silica, silicon nitride, and vitreous carbon by plasma enhanced atomic layer deposition (PE-ALD). Trimethylaluminum (TMA) and a H2/N2 plasma mixture were used as precursors. We investigated the influence of deposition temperature and plasma parameters on the growth characteristics and the film properties of AlN. Stable PE-ALD growth conditions were obtained from 150 °C to the highest tested temperature of 300 °C. The growth rate, refractive index, and thickness homogeneity on 4″ wafers were determined by spectroscopic ellipsometry. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectrometry (RBS) were carried out to analyze crystallinity and composition of the films. Furthermore, the thermal conductivity and the film stress were determined. The stress was sufficiently low to fabricate mechanically stable free-standing AlN membranes with lateral dimensions of up to 2.2 × 2.2 mm2. The membranes were patterned with focused ion beam etching. Thus, these AlN membranes qualify as dielectric support material for a variety of potential applications.

Zusammenfassung Eine Luftbrückenstruktur wurde entwickelt, auf der ein Dünnschicht-Thermoelement angeordnet ist. Dieses Thermoelement dient als Abschlusswiderstand einer Antenne und gleichzeitig als Temperatursensor [1]. Die Brückenstruktur wurde mittels Oberflächenmikromechanik hergestellt. Die thermischen Eigenschaften der Luftbrückenstruktur wurden durch Computersimulationen untersucht, und basierend auf diesen Ergebnissen wurde eine geeignete Technologie entwickelt, um eine hochleistungsfähige thermoelektrische Terahertz-Sensorstruktur herzustellen. Die Messung der elektrischen Empfindlichkeit dieser Thermoelement-Luftbrückenstruktur ergab eine NEP von 18 pW/Hz1/2 unter Vakuumbedingungen und von 67 pW/Hz1/2 an Luft.

We present a newly designed high-detectivity thermoelectric linear array, based on an organic membrane for use in the room temperature range. The sensor array has 64 individual readable channels and was designed and developed for IR spectroscopy. This detector may be used to infer the condition of lubricants and coolants within a mechanical system, so that they can be replaced when needs be, e.g. determining the age of technical oils of wind power plants in real time. Thus valuable resources can be saved and costly damage to equipment avoided. In order to achieve a D* greater than 2 × 109 cmHz1/2/W, the sensor was designed and optimized to be operated under vacuum conditions. To minimize the thermal cross talk between individual pixels, the pixels are separated from each other by a 50 μm slit in the self-supporting organic membrane made of SU-8.

Graphical abstractDisplay Omitted Highlights? We investigated a high performance THz sensing structure for room temperature operations. ? We combined a highly effective thermocouple materials combination with a freestanding air-bridge. ? The fabrication was accomplished by using surface micromachining. ? Simulated results were confirmed by measurements. Antenna-coupled sensing elements, microbolometers as well as thermocouples, are potential solutions in focal plane arrays (FPA). The applications for these lightweight and low-cost sensors are specified in the field of infrared and millimeter wave imaging and sensing. Typically, these detectors can be operated uncooled in various frequency ranges. The purpose of this work is the fabrication of THz sensing structures with a low noise equivalent power (NEP) based on antenna-coupled thermocouples, which are arranged on air-bridges. For the first configuration level, a 2D thermoelectric array consisting of 2i?4 pixels was investigated. Thereby, each pixel comprises eight thermocouples, which are connected in series to increase the responsivity. A highly effective Bi0.87Sb0.13/Sb thermocouple materials combination was used. The thermoelectric structure was matched to the impedance (200?) of the planar dipole antenna. To improve the responsivity of the sensor elements the substrate thickness was adapted to an operation frequency of 812GHz and acts as an optical resonator in combination with a backside gold reflector and a tuned antenna geometry. The fabrication of the 30µm long and 3µm wide air-bridges was realized by surface micromachining with a polyimide sacrificial layer. Thermoelectric layers as well as antenna structure and diffusion layer were patterned almost exclusively by lift-off technique in order to obtain very small structure dimensions with high reliability. In first functional tests the NEP of so manufactured THz sensing structures with eight thermocouples was determined to be 51pW/Hz1/2 by an AC-DC-measurement at room temperature operation and under vacuum conditions.

Thermopile detectors are particularly well suited for spectral imaging, space science applications, track recording, presence detection and applications with low energy consumption. The purpose of this work is the fabrication of a surface-micromachined 2-D high detectivity thermopile array using a highly effective BiSb/Sb thermocouple materials combination. The thermoelectric array is built on 8x8 pixels with an active area of [email protected] in square, which are wired directly. Thermopile structure and absorber area are manufactured upon a sacrificial layer based on polyimide, which is removed at the end of the manufacturing process. Thermoelectric layers as well as wiring layers has been patterned almost exclusively by lift-off technique in order to obtain very small structure dimension with high reliability as well as high integration level. The active area of detectors can be equipped with two absorber types for different application, a broadband colloidal silver black layer as well as a quarter wavelength arrangement for the MIR wavelength range from 8 to [email protected] The detectivity of so manufactured FPAs is about 1x10^9 Jones exceeding most of the state-of-the-art thermopile detectors.

This paper reports on a method for hermetic sensor housing including lateral feedthroughs and room-temperature anodic bonding. The planarisation of the lateral feedthroughs, essential for the purpose of hermetic sealing, is realised by means of an etch-back process of (PE)CVD silicon dioxide combined with an additional spin-on glass (SOG) layer. The quality of the planarisation technique with regard to the main process variables is evaluated by FIB and tactile measurements. It is proven that 3D surfaces, represented here by the wiring and feedthrough layer, can be planarised almost completely. The applied bonding process features thin-films of a highly ionic conductive glass, enabling anodic bonding at unique conditions (room temperature and low applied voltages in order of 100 V). The general applicability of the packaging method is demonstrated with a setup of encapsulated, commercially available thermoelectric radiation sensors, which are used for the verification of the hermeticity of the setup as well.

As manmade space debris in the low earth orbit becomes an increasing risk to space missions, which could even result in total mission loss, it has become even more critical to have detailed knowledge of the properties of these particles like the mass, the velocity and the trajectory. In this paper, we present a newly designed, highly sensitive impact detector array with 16 pixels for space debris analysis. The thermopile sensor array, which was developed in the project, consists of 16 miniaturized multi-junction thermopile sensors made by modern thin-film technology on Si wafers. Each thermopile sensor consists of 100 radially arranged junction pairs formed from evaporated antimony and bismuth thin films. The centrally located active (hot) junctions comprise the active area of 1 mm². The output e.m.f. of the sensor is proportional to the temperature difference between the active and the reference junctions. The thermopile requires no cooling and no bias voltage or current for operation. It generates no 1/f noise but only the thermal resistance (Nyquist) noise. The sensor can be used for DC and low frequency AC measurements. The impact energy of micro sized particles is measured by a calorimetric principle. This means that the kinetic energy of the particle is converted into heat by hitting the absorbing foil, which is glued on the surface of the membrane area. This setup in combination with a preceded velocity detector allows the measurement of the most interesting particle quantities mass, velocity and trajectory.

We present a newly designed thermoelectric detector chip of high detectivity for the space mission BepiColombo to Mercury. The sensor is part of the MERTIS radiometer, which enables radiometric measurements in the spectral range from 7-40 micron to study the thermo-physical properties of the planet's surface material. In collaboration with the DLR Institute of Planetary Research, the Institute of Photonic Technology has developed a sensor array with a specific detectivity D* of 1.3 x 10 9 Jones in vacuum environment and 2 x 15 individual readable channels. In addition, it has an optical slit in the middle, which serves as the entrance slit of a spectrometer downstream. The sensor area is coated with an absorbing layer, in this case silver black having an absorption coefficient of nearly 100 percent in a wavelength range from 0.4 up to 20 micron. To minimize the thermal cross talk between the individual pixels, each pixel is separated by a 50 micron slit in the self-supporting silicon nitride membrane. For good mechanical stability of the pixels, the pixel membrane is tensioned by 10 micron bridges like braces. The sensor is electrically contacted with a star-flex PCB by direct wire bonding and both are mounted on milled aluminum housing. At the Institute of Photonic Technology (IPHT), high detectivity radiation sensors are developed and based on the thermoelectric principle. The thermoelectric materials used are the highly effective combination of n-bismuth(87%)- antimony(13%) / p-antimony. The sensors are designed, in the main, as miniaturized multi-junction thermocouples and made by state of the art thin film technologies allowing for achievable and reproducible detectivities D* in the range of 10 8 up to 2 x 10 9 Jones.

We report on uncooled antenna-coupled thermoelements with a fast response time operating at 0.812 THz. Each sensor pixel consists of 8 thermocouples in series. As thermoelectric structure, a BiSb/Sb freestanding air-bridge is used, fabricated by micromachining. A thermal time constant as low as 22 µs and a NEP of 130 pW/Hz0.5 at 1 kHz modulation frequency is measured in air at room temperature. The integration capability of the thermocouple sensors enables cost-efficient large-scale detector arrays.

A newly designed highly detective intra-slit thermoelectric room-temperature linear array is presented. The thermoelectric sensor array ZS-64-2 with 64 individually readable channels was designed and developed for IR spectroscopy. It is suitable for analytical measurement technology, for example, in determining the age of technical oils in real time. For this, the selected absorption bands of the oil are analyzed and evaluated. This allows conclusions be drawn about the condition of lubricants and coolants, so that they can be replaced when it is needed. This method helps to save valuable resources and it helps to avoid costly damages. In order to achieve the high detectivity of D* = 1.8 x 109 Jones the sensor was designed and optimized to be operated under vacuum conditions. For minimizing the thermal cross talk between the individual pixels, they are separated from each other by a 50 micron slit in the self-supporting silicon nitride membrane, which has a thickness of nearly 1 micron.

An experimental setup is presented to measure and interpret the solid phase crystallization of amorphous silicon thin films on glass at very high temperatures of about 800 °C. Molybdenum-SiO(2)-silicon film stacks were irradiated by a diode laser with a well-shaped top hat profile. From the relevant thermal and optical parameters of the system the temperature evolution can be calculated accurately. A time evolution of the laser power was applied which leads to a temperature constant in time in the center of the sample. Such a process will allow the observation and interpretation of solid phase crystallization in terms of nucleation and growth in further work.

We report on fast terahertz detectors based on antenna-coupled BiSb/Sb thermoelements operating at room temperature. A response time of the thermocouples as low as 22 μs and a noise equivalent power of 170 pW/Hz at 1 kHz modulation frequency is measured in air at room temperature. The integration capability of these mass producible devices enables large-scale detector arrays for real-time terahertz imaging applications. Due to the fast response time, multiplexing of the detectors can be used to reduce the required readout circuits.