| AVS 66th International Symposium & Exhibition | |
| Vacuum Technology Division | Tuesday Sessions |
| Session VT-TuP |
| Session: | Vacuum Technology Poster Session |
| Presenter: | Taku Suzuki, National Institute for Materials Science (NIMS), Japan |
| Authors: | T. Suzuki, National Institute for Materials Science (NIMS), Japan Y. Adachi, National Institute for Materials Science (NIMS), Japan I. Sakaguchi, National Institute for Materials Science (NIMS), Japan |
| Correspondent: | Click to Email |
One of the biggest problems in surface analysis of gas sensors is the pressure gap; a conventional surface analytical tool needs high vacuum (10-4 Pa), while gas sensors are usually employed in atmospheric pressure (105 Pa).This problem has been partially overcome by recent operando techniques for surface characterization. In such a operando measurements, either effective differential pumping or a pressure separation technique, which is often called a high pressure cell, are typically utilized. With those techniques, surface analytical tool can be operated in (ultra-) high vacuum while keeping the pressure in the vicinity of a sample (near) atmospheric pressure. Those techniques are obviously useful to analyze gas sensing mechanism on surfaces. However, a high-speed evacuation system is expensive and a membrane for separating pressure limits applicable analytical techniques.
Besides above-mentioned operando measurements, a dynamic high pressure (DHP) technique has been proposed to analyze a device surface in operating condition. Briefly, it is a technique of pulsed-gas injection to a sample surface. The technique seems attractive considering economical cost and possible wide range of applicability. However, the number of reports concerning DHP is quite limited, and thus, it is not clear whether DHP is useful for surface analysis of gas sensors.
In the present study, we have developed a pulsed gas injection system of pure air combined with an ultra-high vacuum chamber and a fast pressure transducer. The pressure at the sample position reached at about 103 Pa and 104 Pa with pulse width of 10 ms and 100 ms, respectively, with the inlet pressure of 1 MPa. The background pressure was below 10-2 Pa with pulse width of 10 ms except for the duration of 1 s after the gas injection. We further developed a gas sensor measurement system combined with the pulsed gas injection system. In our preliminary experiment using a W-ZnO thin film gas sensor, we successfully observed substantial change of electric resistance with introducing the pulsed pure air by using a lock-in technique.