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

该项目是由Lisa Porter/Carnegie Mellon University(CMU)教授和瑞典林科平大学S传感器技术中心的Anita Lloyd Spetz教授共同合作完成的。其目的是通过联合的协作专业知识来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的选择性催化还原和发电厂的废气。该方法是开发和表征碳化硅化学传感器的欧姆接触和绝缘体，这些接触和绝缘体在高温(例如300-800摄氏度)下的长期稳定性显著改善，这是最佳检测某些气体物种(例如碳氢化合物或NH3)所需的。具体地说，测试设备(电容器和肖特基二极管)将基于CMU集团开发的接触和绝缘材料以及相关的工艺条件来制造。然后，这些设备将在S-Sense进行测试，以确定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(例如，TaC和PtSI)、栅金属(例如，Pt3Si)和栅绝缘体(例如，SiO_2或AlN)的材料选择，然后是器件制造。这些设备将由用于接触电阻测量的TLM图案、管理信息系统电容器和肖特基二极管组成。然后将使用电流-电压(I-V)和/或电容-电压(C-V)测量作为退火温度和测量温度的函数来测量这些器件的稳定性。选定的样品将被送往或带到S学院进行气体响应测量。这将通过将每个样品安装在陶瓷加热器上来实现，陶瓷加热器连接到16针支架上。在将特定气体引入组件后，传感器的响应将以0.1或1 mA的恒流电压进行测量。MISiCFET器件将采用有前途的材料结构。这项研究的一个重要部分将包括对传感器的形态和界面化学及其与电学性能的关系的研究。使用扫描电子显微镜对接触膜的形貌进行表征。采用俄歇电子能谱(AES)、透射电子能谱(TEM)、X射线衍射谱(XRD)和SIMS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将研究和教育相结合，并开展国际合作，提供科学和教育方面的好处。在独特的技术、文化和专业背景下对本科生和研究生进行教育，体现了与该项目相关的更广泛的影响。该方法包括：1)通过访问瑞典和从瑞典交流研究生，2)监督与化学传感器有关的本科生研究项目，3)推出午餐/演讲系列，旨在激励和留住材料科学方面的女研究生和博士后。该NSF项目是NSF和欧洲在材料研究方面的合作活动(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).