Development of new type sensor structures using epitaxial-thin-film growth technology

市场上有两种类型的气体传感器。一种是吸附式气体传感器，它是由气敏半导体氧化物烧结的细小颗粒组成的多孔结构。另一种是由烧结氧化物固体电解质组成的扩散型气体传感器。我们将外延薄膜生长技术应用到新型气敏结构中。对于气体吸附型传感器，将外延薄膜应用于气体传感器结构中，在较低的目标气体浓度下具有良好的传感能力，提高了响应时间。采用脉冲激光沉积(PLD)技术，通过引入锌铁氧体(ZFO)同质外延缓冲层，在Y_2O_3掺杂的氧化锆衬底上制备了掺钛锌铁氧体(ZFTO)外延膜。同向外延的ZFTO/ZFO/YSZ薄膜比异质外延的ZFTO/YSZ薄膜具有更高的电导率。同质外延ZFTO薄膜的电阻率随N22气体浓度的变化而变化。ZFTO薄膜的灵敏度随薄膜厚度和NO气体浓度的变化而变化。当ZFTO薄膜厚度为3 nm时，灵敏度达到最大。在SrTiO单晶衬底上制备的掺铬SrTiO23外延薄膜在10-23atm的氧分压下仍表现出较高的灵敏度。在扩散型气敏元件中，掺Y的ZrO_(232)薄膜在2.5 nm处获得了最大的灵敏度。在(100)Si衬底上制备了(YSZ)外延薄膜。该膜不含干扰氧离子扩散的晶界。与烧结体相比，薄膜厚度较薄，降低了内阻。利用多孔铂电极在硅上生长YSZ外延膜，在350℃下得到了电动势的计算值。交流阻抗测量表明，在150La0.6Sr0.4Co0.98Ni0.02O(LSCNO)电极上，YSZ薄膜中的氧离子扩散到YSZ外延膜中，降低了180℃的工作温度

There are commercially available two types of gas sensors. One is the adsorption type gas sensor that isporous structure with sintered fine particles of gas sensitive semiconductor oxide. The other is thediffusion type gas sensor that is composed of the sintered oxide solid electrolyte. We apply epitaxialthin film growth technology into the new type gas sensor structures. In case of gas adsorption type sensor, applying the epitaxial thin film to the gas sensor structure bringsthe excellent sensing ability at lower concentration of the target gas and improved the response time. Tidoped Zn ferrite (ZFTO) epitaxial films were deposited on Y2O3 doped ZrO substrate by introducing Znferrite (ZFO) homo-epitaxial buffer layer using pulsed laser deposition (PLD). Homo-epitaxialZFTO/ZFO/YSZ films showed higher conductivity then hetero-epitaxial ZFTO/YSZ films. Resistivityof the homo-epitaxial ZFTO films changed with NO22 gas concentration. Sensitivity of the ZFTO filmswere changed with film thickness and NO gas concentration. The maximum sensitivity was obtained atthe 3 nm of ZFTO film thickness. The Cr doped SrTiO23 epitaxial thin film deposited on the SrTiOsingle crystal substrate showed high sensitivity even at 10-23 atm of O partial pressure. The maximumsensitivity was obtained at the 2.5 nm of Cr doped SrTiOIn case of gas diffusion type gas sensor, Y doped ZrO232 film thickness. (YSZ) epitaxial thin film was deposited on (100)Si substrate. This film did not contain the grain boundary which disturbs the oxide ion diffusion. Thethinner film thickness compared with sintered body reduced the internal resistivity. The calculated EMFvalue was obtained at 350oC using YSZ epitaxial film on Si with porous Pt electrode. AC impedancemeasurement revealed the oxide ion in the YSZ thin film diffused at 150La0.6Sr0.4Co0.98Ni0.02 O (LSCNO) electrode to YSZ epitaxial film reduces the working temperature at180℃