Abstract
Ultrathin (~10 nm) InN ion sensitive field effect transistors (ISFETs) with gate region modified with 3-mercaptopropyltrimethoxysilane (MPTMS) by molecular vapor deposition (MVD) are used to detect hybridization of deoxyribonucleic acid (DNA). The ultrathin InN ISFETs have a high sensitivity and short response time for anion detection, showing a great potential for chemical and biological sensing applications. Vapor-phase silanization of MPTMS using MVD substantially shortens the response time for surface modification compared to the conventional self-assembled monolayer (SAM) techniques. The change of contact angle of water on InN surface was observed from 0o, indicating the O2 plasma cleaning, to 68o after 1.5 h vapor deposition. MPTMS with -SH terminal functional groups was used to immobilize probe DNA with acrylic phosphoramidite modification at 5'-end. After immersed in 10 uM DNA probes solution for 12 h, the functionalized InN ISFET was used to perform the hybridization with complementary single stranded (ss) DNA 5'-ATTGTTATTAGG-3'. A drain-source current decrease (~6 uA) was observed when a complementary DNA was introduced to the gate region of ISFETs. The current decrease is attributed to the attachment of negatively charged DNA. For a 12-mer oligonucleotide probe, the detection of 1 nM target DNA was accomplished, while the noncomplementary DNA with one base mismatch did not show any obvious current variation.