40 Å Platinum-porous SiC gas sensor: Investigation sensing properties of H2 gas

The present paper reports on a new structure for H-2 gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 angstrom thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height (phi(Bp)) and series resistance (R-S) have been evaluated under different concentrations of H-2 gas. The experimental results show that upon exposure to H-2 gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H-2 concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity (Delta I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature. (C) 2012 Elsevier B.V. All rights reserved.