가스 감응용 3차원 구조체 TiO2 박막 성장기구
Growth mechanism of three dimensionally structuredTiO2 thin film for gas sensors
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초록
Polystyrene (PS) microspheres were used to good advantage as a template material to prepare macroporous TiO2 thin films. This is enabled to run the thermal decomposition of the PS without the collapsing of the 3-D macroporous framework during the calcination step. TiO2 thin films were deposited onto the colloidal templated substrates at room temperature by RF sputtering, and then samples were thermally treated at 450℃ for 40 ﾠmin in air to remove the organic colloidal template and induce crystallization of the TiO2 film. The macroporous TiO2 thin film exhibited a quasi-ordered partially hexagonal close-packed structure. Burst holes, estimated to be formed during PS thermal decomposition, are seen as the hemisphere walls. the inner as well as the outer surfaces of the hollow hemispheres formed by the method of thermal decomposition can be easily accessed by the diffusing gas species. As a consequence, the active surface area interacting with the gas species is expected to be enlarged about by a factor of fourth as large as compared to that of a planar films. Also the thickness at neighboring hemisphere could be controlled a few nm thickness. If the acceptor density becomes as large that depletion width reaches those thickness, the device is in the pinch off-situation and a strong resistance change should be observed.
Abstract
Polystyrene (PS) microspheres were used to good advantage as a template material to prepare macroporous TiO2 thin films. This is enabled to run the thermal decomposition of the PS without the collapsing of the 3-D macroporous framework during the calcination step. TiO2 thin films were deposited onto the colloidal templated substrates at room temperature by RF sputtering, and then samples were thermally treated at 450℃ for 40 ﾠmin in air to remove the organic colloidal template and induce crystallization of the TiO2 film. The macroporous TiO2 thin film exhibited a quasi-ordered partially hexagonal close-packed structure. Burst holes, estimated to be formed during PS thermal decomposition, are seen as the hemisphere walls. the inner as well as the outer surfaces of the hollow hemispheres formed by the method of thermal decomposition can be easily accessed by the diffusing gas species. As a consequence, the active surface area interacting with the gas species is expected to be enlarged about by a factor of fourth as large as compared to that of a planar films. Also the thickness at neighboring hemisphere could be controlled a few nm thickness. If the acceptor density becomes as large that depletion width reaches those thickness, the device is in the pinch off-situation and a strong resistance change should be observed.
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