Two types of carbon nanotubes [single walled nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs)] are deposited on porous silicon by the drop casting technique. Upon exposure to test gas mixing ratio 3% NO 2 , the sensitivity response results show that the SWCNTs' sensitivity reaches to 79.8%, where MWCNTs' is 59.6%. The study shows that sensitivity response of the films increases with an increase in the operating temperature up to 200• C and 150℃ for MWCNTs and SWCNTs. The response and recovery time is about 19 s and 54 s at 200℃ for MWCNTs, respectively, and 20 s and 56 s at 150℃ for SWCNTs.

Two t ypes of carbon nanot u bes ( M W C N Ts and SW C N Ts) fi l ms were u sed t o fabri cat e hyd rogen gas sensors. C N Ts fi l ms were d eposi t ed on porou s si l i con su bst rat e by t he d rop cast i ng met hod .The t wo sensors showed hi gh sensi t i vi t y t o hyd rogen gas at d i fferent concent rat i ons.E x peri ment alresu l t s i nd i cat ed t hat t he SW C N Ts have abet t erperformance t han M W C N Ts.The SW C N Ts gas sensorshows hi gh sensi t i vi t y at150 o C wi t h 29sec response t i me,whereas M W C N Ts gas sensor shows bestsensi t i vi t y at200 o C wi t h24sec response t i me.