Pd/Ta2O5/SiC Schottky-diode hydrogen sensors formed by using rapid thermal oxidation of Ta thin films

• Published in: Journal of the Korean Physical Society 2013, 63(9), , pp.1794-1798
• Main Authors: Joo, Sung-Jae, Choi, Je Hoon, Kim, Seong Jeen, Kim, Sang-Cheol
• Format: Article
• Language: English
• Subjects: Mathematical and Computational Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Theoretical; 물리학
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.63.1794

Pd/Ta 2 O 5 /SiC Schottky-diode hydrogen sensors were fabricated, and their hydrogen gas sensing performance was investigated at 573 K and 773 K. Interfacial Ta 2 O 5 films of 120 nm in thickness were formed by using rapid thermal oxidation (RTO) of the sputtered Ta films on SiC. The crystallinity of the Ta and the Ta 2 O 5 films were characterized by using X-ray diffraction (XRD). As-sputtered Ta films on 4H-SiC are composed of α -Ta (body-centered-cubic) and β -Ta (tetragonal), and α -Ta (110) is the dominant orientation. After RTO at 573 K, the Ta films are converted to β -Ta 2 O 5 (orthorhombic). The diode sensors show high sensitivity to H 2 even at the low H 2 concentration of 500 ppm, and the voltage change of the sensor upon H 2 exposure is proportional to the H 2 concentration in the range of 500 ∼ 2000 ppm at 573 K. The response voltage ΔV is shown to arise mostly from the change in the series resistance component of the sensor upon H 2 exposure; the main origin of that change is believed to be the Ta 2 O 5 interfacial layer. The response time t 90 of the sensor at 573 K was estimated to be approximately 8 s.