Hydrogen ion sensors based on indium tin oxide thin film using radio frequency sputtering system

• Published in: Thin solid films Vol. 517; no. 17; pp. 4805 - 4809
• Main Authors: Chiang, Jung-Lung, Jhan, Syun-Sheng, Hsieh, Shu-Chen, Huang, An-Li
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2009; Elsevier
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; EGFET; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; ITO; pH sensitivity; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Sputtering system; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Transistors; Sputtering system; ITO; pH sensitivity; EGFET; Grain size; Chemical sensors; MOSFET; pH value; Semiconductor materials; Electrical properties; Field effect transistors; Indium oxide; Sputtering; Thin films; pH metering; Silicon oxides; Tin oxide; Silicon; Gas sensors; IV characteristic; Gates; Radiofrequency sputtering
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2009.03.050

Indium tin oxide (ITO) thin films were deposited onto Si and SiO 2/Si substrates using a radio frequency sputtering system with a grain size of 30–50 nm and thickness of 270–280 nm. ITO/Si and ITO/SiO 2/Si sensing structures were achieved and connected to a standard metal-oxide-semiconductor field-effect transistor (MOSFET) as an ITO pH extended-gate field-effect transistor (ITO pH-EGFET). The semiconductor parameter analysis measurement (Keithley 4200) was utilized to measure the current–voltage ( I– V) characteristics curves and study the sensing properties of the ITO pH-EGFET. The linear pH voltage sensitivities were about 41.43 and 43.04 mV/pH for the ITO/Si and ITO/SiO 2/Si sensing structures, respectively. At the same time, both pH current sensitivities were about 49.86 and 51.73 µA/pH, respectively. Consequently, both sensing structures can be applied as extended-gate sensing heads. The separative structure is suitable for application as a disposable pH sensor.