NSF-Europe: Development and Characterization of Electrically-Active Interfaces for Chemical Sensors

该项目是卡内基梅隆大学（CMU）丽莎波特教授和瑞典林雪平大学S-SENCE（传感器技术中心）的Anita Lloyd Spetz教授的联合合作。其目的是通过联合协作专业知识，推动材料科学的理解和高温传感器的后续开发，并了解限制其性能的机制。这些传感器的应用实例包括监测汽车内燃机中的选择性催化还原和发电厂的烟道气。该方法是开发和表征用于SiC基化学传感器的欧姆接触和绝缘体，其在高温下的长期稳定性（例如，300-800 ℃），以最佳地检测某些气体种类（例如，烃或NH3）。具体而言，测试器件（电容器和肖特基二极管）将根据CMU小组开发的接触和绝缘体材料以及相关工艺条件制造。然后，这些设备将在S-SENCE测试其在高温下的气体传感器响应。卡内基梅隆大学的初步研究将包括欧姆接触的材料选择（例如，TaC和PtSi）、栅极金属（例如，Pt 3Si）和栅极绝缘体（例如，SiO2或AlN），然后进行器件制造。这些器件将包括用于接触电阻测量的TLM图案、MIS电容器和肖特基二极管。然后将使用电流-电压（I-V）和/或电容-电压（C-V）测量来测量这些器件的稳定性，作为退火温度和测量温度两者的函数。选定的样品将被送到或带到S-SENCE，以测量其气体响应。这将通过将每个样品安装到陶瓷加热器上来实现，陶瓷加热器连接到16针保持器。在将特定气体引入组件后，传感器响应将被测量为0.1或1 mA恒定电流下的电压。有前途的材料结构将被纳入MISiCFET设备。这项研究的一个重要部分将包括形态和界面化学及其与传感器的电性能的关系的调查。接触膜的形态将使用扫描电子显微镜进行表征。利用俄歇电子能谱（AES）、透射电镜（TEM）、X射线衍射（XRD）和二次离子质谱（西姆斯）对金属-绝缘体、绝缘体-半导体和金属-半导体的界面化学进行了表征。该项目解决了与具有技术相关性的电子材料相关的基础研究问题。该项目的一个重要特点是研究和教育的一体化，以及提供科学和教育效益的国际合作。与该项目相关的更广泛的影响体现在本科生和研究生在独特的技术，文化和专业背景下的教育。该方法包括：1）通过访问和来自瑞典的研究生交流，2）有关化学传感器的本科生研究项目的监督，和3）旨在激励和留住女性研究生和博士后材料科学的午餐/演讲系列介绍。该项目是美国国家科学基金会和欧洲之间的材料研究合作活动（NSF 02-135）。

This project is a joint collaboration between Prof. Lisa Porter/Carnegie Mellon University (CMU) and Prof. Anita Lloyd Spetz from S-SENCE (Center for Sensor Technology) at Linkoping University, Linkoping, Sweden. The aim is through the combined collaborative expertise to push forward materials science understanding and subsequent development of high-temperature sensors, and to understand mechanisms that limit their performance. Examples of applications for these sensors include monitoring of selective catalytic reduction in automobile combustion engines and of flue gases from power plants. The approach is to develop and characterize ohmic contacts and insulators for SiC based chemical sensors that demonstrate substantial improvements in long-term stability at high temperatures (e.g., 300-800 C) required for optimum detection of certain gas species (e.g., hydrocarbons or NH3). Specifically, test devices (capacitors and Schottky diodes) will be fabricated based on contact and insulator materials, as well as associated processing conditions, developed by the CMU group. The devices will then be tested at S-SENCE for their gas sensor response at high temperatures. Initial research at Carnegie Mellon will consist of materials selection for ohmic contacts (e.g., TaC and PtSi), gate metals (e.g., Pt3Si) and gate insulator (e.g., SiO2 or AlN) followed by device fabrication. The devices will consist of TLM patterns for contact resistance measurements, MIS capacitors and Schottky diodes. The stability of these devices will then be measured using current-voltage (I-V) and/or capacitance-voltage (C-V) measurements as a function of both annealing temperature and measurement temperature. Selected samples will be sent, or brought, to S-SENCE for measurements of their gas response. This will be accomplished by mounting each sample onto a ceramic heater, which is attached to a 16-pin holder. After introducing specified gases into the assembly, the sensor response will be measured as the voltage at a constant current of 0.1 or 1 mA. Promising materials structures will be incorporated in MISiCFET devices. An important part of this research will include investigations of the morphology and interfacial chemistry and their relationship to the electrical properties of the sensors. The morphologies of the contact films will be characterized using scanning electron microscopy. The interfacial chemistry of the metal-insulator, insulator-semiconductor and metal-semiconductor will be characterized by Auger electron spectroscopy (AES), TEM, XRD and SIMS. %%% The project addresses fundamental research issues associated with electronic materials having technological relevance. An important feature of the project is the integration of research and education, and an international collaboration providing both scientific and educational benefits. Broader impacts associated with the project are exemplified by the education of undergraduate and graduate students in a unique technical, cultural and professional context. The approach includes: 1) graduate student exchange through visits to and from Sweden, 2) supervision of an undergraduate research project pertaining to chemical sensors, and 3) introduction of a lunch/speaker series designed to inspire and retain women graduate students and post-docs in materials science. This NSF project is a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135).