title: Optimization of a PVC Membrane for Reference Field Effect Transistors.
abstract: For the miniaturization of ISFET sensing systems, the concept of a REFET with low ion sensitivity is proposed to replace the conventional reference electrodes through the arrangement of a quasi reference electrode and a differential readout circuit. In this study, an ion-unblocking membrane was used as the top layer of a REFET. To optimize the REFET performance, the influences of the silylating process, different plasticizers, and the composition of the PVC cocktails were investigated. A low sensitivity (10.4 ± 2.2 mV/pH) and high linearity (99.7 ± 0.3 %) in the range from pH 2.2 to pH 11.6 was obtained for the REFET with a 60 wt.% DNP/(DNP + PVC) membrane. To evaluate the long term stability, the drift coefficient was estimated, and for the best REFET, it was -0.74 mV/h. Two criteria for assessing the lifetime of REFETs were used, namely the increase in pH sensitivity to a value higher than 15 mV/pH and the degradation of linearity below 99 %. For the best REFET, it was approximately 15 days.
authors.affiliation: Department of Electronic Engineering in Chang Gung University. / 259 Wen-Hwa 1  Road, Kwei-Shan, Tao-Yuan, R.O.C., Taiwan, 333.
authors.forename: Chao-Sung
authors.initials: CS
authors.lastname: Lai
authors.forename: Cheng-En
authors.initials: CE
authors.lastname: Lue
authors.forename: Chia-Ming
authors.initials: CM
authors.lastname: Yang
authors.forename: Marek
authors.initials: M
authors.lastname: Dawgul
authors.forename: Dorota G
authors.initials: DG
authors.lastname: Pijanowska