In situ chemoresistive sensing in the environmental TEM: probing functional devices and their nanoscale morphology

In situ transmission electron microscopy provides exciting opportunities to address fundamental questions and technological aspects related to functional nanomaterials, including the structure-property relationships of miniaturized electronic devices. Herein, we report the in situ chemoresistive sensing in the environmental transmission electron microscope (TEM) with a single SnO2 nanowire device, studying the impact of surface functionalization with heterogeneous nanocatalysts. By detecting toxic carbon monoxide (CO) gas at ppm-level concentrations inside the microscope column, the sensing properties of a single SnO2 nanowire were characterized before and after decoration with hybrid Fe-Pd nanocubes. The structural changes of the supported nanoparticles induced by sensor operation were revealed, enabling direct correlation with CO sensing properties. Our novel approach is applicable for a broad range of functional nanomaterials and paves the way for future studies on the relationship between chemoresistive properties and nanoscale morphology

Integrating LCA in process development

The development of environmentally friendly processes & products is becoming increasingly important to meet global challenges, but how can we prove that our development is really more sustainable than existing systems? Or how can we find out for different process variants on which substances we should focus in terms of sustainability? One of the preeminent tools for quantifying environmental sustainability is the life cycle assessment (LCA). It aims to quantify the environmental impacts by capturing relevant environmental flows across a product’s life cycle (from raw material extraction and manufacturing, through distribution, use and disposal), assigns these flows relevant impact categories and converts those within an impact category into common units such as litres of water withdrawal or kg CO2 equivalents/unit[1]. Life cycle analyses have been trying to make these effects measurable since the 70s and are often used with objectives such as product optimisation or product comparison [2]. Mostly, however, the focus here was on already existing products with established processes, so that working with processes in development places new demands on the methodology. The political support for a change towards a more sustainable way of doing business is also driving the need to assess products for ecological compatibility from the very beginning in the field of technology development and therefore enables companies and researchers to reduce cost consuming exploration of process ways, who will have little chance of standing stricter environmental legislation. However, since LCAs are more and more often prescribed in projects and scientists should be able to use the results for their own work in order to further develop processes, an introduction to this matter is given here, introducing the current PhD-work and outlining LCA-types that might be encountered at low Technology Rediness Levels (TRL).MoP3-(03) page 1MoP3-(03) page 4

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

Size-Dependent Thresholds in CuO Nanowires: Investigation of Growth from Microstructured Thin Films for Gas Sensing

An experimental characterization of cupric oxide nanowire (CuO NW) growth from thermally oxidized, microstructured Cu thin films is performed. We have systematically studied the influence of the thickness and dimension of Cu layers on the synthesis of CuO NW. The objective was to determine the optimum Cu geometries for increased CuO NWs growth to bridge the gap between adjacent Cu structures directly on the chip for gas sensing applications. Thresholds for CuO-NW growth regarding film thickness and lateral dimensions are identified based on SEM images. For a film thickness of 560 nm, NWs with lengths > 500 nm start to grow from the edges of Cu structures with an area ≥ 4 µm2. NWs growing from the upper surface were observed for an area ≥ 16 µm2. NW growth between adjacent thermally oxidized thin films was analyzed. The study provides information on the most relevant parameters of CuO NWs growth, which is mandatory for integrating CuO NWs as gas sensor components directly on microchips. Based on this result, the gap size of the structure was varied to find the optimum value of 3 µm

A Novel Device for Functional Evaluation of Gas Sensing Layers

Chemical gas sensors are operated at elevated temperatures and the actual temperature has a tremendous influence on sensitivity and selectivity. From that perspective, precise temperature control over the chip is an absolute requirement. Next to a stable heating system, a controlled gas flow in the test box is required. The test gases should not cool down the sensor surface too much and not be heated up by the heater. To make the material integration easy and reduce the costs for sensor platforms, often rather large sensor devices are fabricated. We demonstrate that a combined approach of thermal analysis and computational fluid dynamics enables the co-design of gas flow path and heater to archive precise temperature conditions at the sensor material and in the surrounding test gas atmosphere

3D-Integrated Multi-Sensor Demonstrator System for Environmental Monitoring

his 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

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