Hydroxylation of SiO2 surface and Threshold Voltage Shift of Organic Field Effect Transistors

Publication Issue: 
Volume 37, Issue 1, 2016
Page No: 
Date Received: 
Monday, August 1, 2016
Authors' Name: 
Chong Lim Chua
Kai Lin Woon
Authors' Affiliation and Address: 
Low Dimensional Materials Research Center, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
Two methods of SiO2 substrate cleaning are compared. One method, the SiO2 surface are intentionally hydroxylated with a mixture of hydrochloric acid and hydrogen peroxide during cleaning, while the other method uses acetone, isopropyl alcohol (IPA) and water to clean the surface sequentially with the aid of ultrasonic agitation. A super-hydrophilic surface with contact angle less than 10o is obtained by intentionally hydroxylating the surface. The contact angles for both surfaces after the phenyltrichlorosilane (PTCS) treatment increased significantly to more than 75o . The hole mobility of these devices are 3 x 10-3 cm2/Vs. However, the transfer characteristics of the organic field effect transistor (OFET) over time are drastically different. Intentionally hydroxylating the SiO2 surface yields very little shift of threshold voltages (less than 5 V) over 4 weeks. The OFET characteristics for the organic solvent cleaned SiO2 surface disappeared after a week. It seems that hydroxylating the SiO2 surface before application of PTCS significantly prolongs the lifetime of the OFET devices.