Agarwal Pankaj B, Sharma Rishi, Mishra Dharmesh, Thakur Navneet Kumar, Agarwal Ajay, Ajayaghosh Ayyappanpillai
Nano Biosensors Group, Smart Sensors Area, CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI), Pilani 333031, India.
Academy for Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
ACS Appl Mater Interfaces. 2020 Sep 9;12(36):40901-40909. doi: 10.1021/acsami.0c10189. Epub 2020 Aug 26.
Single-walled carbon nanotubes (SWNTs) are incorporated in different device configurations such as chemiresistors and field-effect transistors (FETs) as a sensing element for the fabrication of highly sensitive and specific biochemical sensors. For this purpose, sorting and aligning of semiconducting SWNTs between the electrodes is advantageous. In this work, a silicon shadow mask fabricated using conventional semiconductor processes and silicon bulk micromachining was used to make metal contacts over SWNTs with a minimum feature of 1 μm gap between the electrodes. The developed silicon shadow mask-based metal contact patterning process is cost-effective and free from photoresist (PR) chemical coatings and thermal processing. After a detailed investigation, sodium dodecyl sulfate (SDS), an anionic surfactant, along with ultrasonication process, was found to be effective for the removal of unclamped and metallic SWNTs, resulting in aligned and clamped semiconducting SWNTs between the electrodes. The presence of aligned semiconducting SWNTs was confirmed using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy techniques. The fabricated devices were tested for nitrogen dioxide (NO) gas sensing as a test case. The sensitivity enhancement of ∼21 to 76% in the 20-80 ppm NO concentration range has been observed in the case of aligned semiconducting SWNT devices compared to the random network SWNT-based sensors.
单壁碳纳米管（SWNTs）被纳入不同的器件配置中，如化学电阻器和场效应晶体管（FET），作为传感元件用于制造高灵敏度和特异性的生化传感器。为此，在电极之间对半导体单壁碳纳米管进行分类和排列是有利的。在这项工作中，使用传统半导体工艺和硅体微加工制造的硅掩膜用于在单壁碳纳米管上制作金属接触，电极之间的最小特征间隙为1μm。所开发的基于硅掩膜的金属接触图案化工艺具有成本效益，且无需光刻胶（PR）化学涂层和热处理。经过详细研究，发现阴离子表面活性剂十二烷基硫酸钠（SDS）与超声处理一起，对于去除未夹紧和金属性的单壁碳纳米管是有效的，从而在电极之间形成排列整齐且夹紧的半导体单壁碳纳米管。使用原子力显微镜（AFM）、场发射扫描电子显微镜（FESEM）和拉曼光谱技术确认了排列整齐的半导体单壁碳纳米管的存在。作为测试案例，对制造的器件进行了二氧化氮（NO）气体传感测试。与基于随机网络单壁碳纳米管的传感器相比，在排列整齐的半导体单壁碳纳米管器件中，在20 - 80 ppm NO浓度范围内观察到灵敏度提高了约21%至76%。
