Optimization of SnO2-Based CMOS-Integrated Gas Sensors by Mono-, Bi- and Trimetallic Nanoparticles

In this paper, we report on the optimization of SnO2-based thin film gas sensor devices by mono-, bi- and trimetallic nanoparticles. Ag, AgRu, and AgRuPd nanoparticles are sputter deposited on CMOS-integrated SnO2-thin film gas sensor devices. The CMOS device is a worldwide unique chip containing an array of eight microhotplates. The response towards the target gas CO was dramatically increased from 10% to more than 70% by using trimetallic AgRuPd nanoparticles

Transfer Printing Technology for Fabricating Chemical Sensors Based on Tin Dioxide Nanowires

Multi-nanowire based chemical gas sensors were produced employing a fast and simple transfer printing technology. SnO2 nanowires (NWs) were grown by a specific two-step technology including spray pyrolysis deposition and a thermal annealing process in presence of a Cu-catalyst. Subsequently the SnO2 NWs were print transferred by a polydimethylsiloxane (PDMS) stamp on Si-substrates with gold inter-digital electrode structures (IDES) creating a multi-NW chemical sensing device. The print-transfer technology enables a fast, easy and cheap fabrication of NW-based sensor devices with a good reproducibility. High sensitivity to H2S has been achieved, the performance results are presented in this work

Optimization of SnO₂-Based CMOS-Integrated Gas Sensors by Mono-, Bi- and Trimetallic Nanoparticles

In this paper, we report on the optimization of SnO2-based thin film gas sensor devices by mono-, bi- and trimetallic nanoparticles. Ag, AgRu, and AgRuPd nanoparticles are sputter deposited on CMOS-integrated SnO2-thin film gas sensor devices. The CMOS device is a worldwide unique chip containing an array of eight microhotplates. The response towards the target gas CO was dramatically increased from 10% to more than 70% by using trimetallic AgRuPd nanoparticles

In-Situ Temperature Measurement on CMOS Integrated Micro-Hotplates for Gas Sensing Devices

Metal oxide gas sensors generally need to be operated at elevated temperatures, up to and above 400 °C. Following the need for miniaturization of gas sensors and implementation into smart devices such as smartphones or wireless sensor nodes, recently complementary metal-oxide-semiconductor (CMOS) process-based micro electromechanical system (MEMS) platforms (micro-hotplates, µhps) have been developed to provide Joule heating of metal oxide sensing structures on the microscale. Heating precision and possible spatial temperature distributions over the µhp are key issues potentially affecting the performance of the overall gas sensor device. In this work, we use Raman spectroscopy to directly (in-situ and in-operando) measure the temperature of CMOS-based µhps during the application of electric current for Joule heating. By monitoring the position of the Raman mode of silicon and applying the theoretical framework of anharmonic phonon softening, we demonstrate that state-of-the-art µhps are able to reach the set temperature with an error below 10%, albeit with significant spatial temperature variations on the hotplate. This work demonstrates the potential of Raman spectroscopy for in-situ and in-operando temperature measurements on Si-based devices, an aspect of high relevance for micro- and nano-electronic device producers, opening new possibilities in process and device control

Exploring Temperature-Modulated Operation Mode of Metal Oxide Gas Sensors for Robust Signal Processing

Metal oxide (MOx) gas sensor signals are mainly governed by adsorption and desorption processes of oxygen and its reaction with surrounding gas molecules. Different target gases exhibit different reaction rates leading to characteristic sensor responses for specific gas species and their concentrations. In this work, we compare temperature-modulated sensor operation (TMO) with sensor operation at a single temperature. Further, we explore if under specific TMO regimes, a simple signal processing allows for quantification of gas concentrations. We specifically investigate, if the relevant information can be captured in selected discrete wavelet coefficients. In addition, we compare the results received from this wavelet features to reaction rate evaluation features

SPM—SEM Investigations of Semiconductor Nanowires for Integrated Metal Oxide Gas Sensors

Integration of metal oxide nanowires in metal oxide gas sensors enables a new generation of gas sensor devices, with increased sensitivity and selectivity. For reproducible and stable performance of next generation sensors, the electric properties of integrated nanowires have to be well understood, since the detection principle of metal oxide gas sensors is based on the change in electrical conductivity during gas exposure. We study two different types of nanowires that show promising properties for gas sensor applications with a Scanning Probe Microscope—Scanning Electron Microscope combination. Electron Beam Induced Current and Kelvin Probe Force Microscopy measurements with a lateral resolution in the nanometer regime are performed. Our work offers new insights into the dependence of the nanowire work function on its composition and size, and into the local interaction between electron beam and semiconductor nanowires

CuO Thin Films Functionalized with Gold Nanoparticles for Conductometric Carbon Dioxide Gas Sensing

Metal oxides (MOx) are a well-established material for gas sensing. MOx-based gas sensors are sensitive to a wide variety of gases. Furthermore, these materials can be applied for the fabrication of low-cost and -power consumption devices in mass production. The market of carbon dioxide (CO 2 ) gas sensors is mainly dominated by infra-red (IR)-based gas sensors. Only a few MOx materials show a sensitivity to CO 2 and so far, none of these materials have been integrated on CMOS platforms suitable for mass production. In this work, we report a cupric oxide (CuO) thin film-based gas sensor functionalized with gold (Au) nanoparticles, which exhibits exceptional sensitivity to CO 2 . The CuO-based gas sensors are fabricated by electron beam lithography, thermal evaporation and lift-off process to form patterned copper (Cu) structures. These structures are thermally oxidized to form a continuous CuO film. Gold nanoparticles are drop-coated on the CuO thin films to enhance their sensitivity towards CO 2 . The CuO thin films fabricated by this method are already sensitive to CO 2 ; however, the functionalization of the CuO film strongly increases the sensitivity of the base material. Compared to the pristine CuO thin film the Au functionalized CuO film shows at equal operation temperatures (300 ∘ C) an increase of sensitivity towards the same gas concentration (e.g., 2000 ppm CO 2 ) by a factor of 13. The process flow used to fabricate Au functionalized CuO gas sensors can be applied on CMOS platforms in specific post processing steps

3D-integrated multi-sensor demonstrator system for environmental monitoring

This paper summarizes the outcome of the EC FP7 project MSP - Multi Sensor Platform for Smart Building Management (Grant Agreement No. 611887). The MSP consortium comprising 17 partners from 6 European countries developed a full manufacturing chain for 3D system integration, which has never been realized before. It enables 3D-integration of highly sophisticated components and sensor devices on a CMOS electronic platform chip. The final multi-sensor system comprises a variety of gas sensors as well as optical sensors for ultraviolet, visible and infrared light. The MSP demonstrator system implemented in a wearable wristband device integrates a total of 57 sensors - this is a worldwide unique sensor system

3D-integrated multi-sensor demonstrator system for environmental monitoring

\u3cp\u3eThis paper summarizes the outcome of the EC FP7 project MSP - Multi Sensor Platform for Smart Building Management (Grant Agreement No. 611887). The MSP consortium comprising 17 partners from 6 European countries developed a full manufacturing chain for 3D system integration, which has never been realized before. It enables 3D-integration of highly sophisticated components and sensor devices on a CMOS electronic platform chip. The final multi-sensor system comprises a variety of gas sensors as well as optical sensors for ultraviolet, visible and infrared light. The MSP demonstrator system implemented in a wearable wristband device integrates a total of 57 sensors - this is a worldwide unique sensor system.\u3c/p\u3