Modification of Dielectric Layers with Diamond‐Like Carbon for Biosensor Applications
H. Long, Y. Zhang, D. Zhulai, N. Boichuk, D. Pustovyi, S. Zain, V. Chekubasheva, M. Petrychuk, B. Klingebiel, V. Weihnacht, S. VitusevichABSTRACT
Liquid‐gated transistor biosensors, fabricated using complementary metal‐oxide‐semiconductor (CMOS)‐compatible technology, face significant challenges relating to their long‐term stability when utilized in complex bio‐liquid environments. In this study, we use diamond‐like carbon (DLC) layers of nanometer‐scale thicknesses, ranging from 1 to 14 nm, to modify the surface properties of a low‐defect‐density SiO 2 layer. By analyzing the capacitance–voltage characteristics and stability time traces of DLC‐covered silicon‐based structures, we registered three well‐separated regions of the flat‐band voltage values. The DLC layers demonstrate advanced properties: enhanced stability compared to the bare SiO 2 layer and good sensitivity. X‐ray photoemission and Raman spectroscopy results enable an analysis of DLC material and the estimation of sp 2 graphitic and sp 3 diamond components. Measurements of different pH and biological C‐reactive protein solutions show that DLC‐modified structures, including nanowire field‐effect transistors (FET), have great potential for bio‐signal monitoring. The mechanism of long‐term stability is established using impedance spectroscopy and modeling data analysis. This study opens up prospects for the design of dielectric layer‐covered structures and their surface modification at the liquid–solid interface of biosensors, providing valuable insights into DLC interface engineering for the development of highly sensitive and reliable FET biosensors.