Fabrication and practical application of metallo-phthalocyanine thin film-based NO_2 gas sensor

在150 ℃的NO_2气氛中，经HF处理的200 nm厚酞菁铜薄膜具有良好的气敏特性。然而，从实际应用的角度来看，仍然存在一些问题。制备超薄薄膜是解决这些问题的方法之一。膜厚度的减小预期导致更快的气体响应和改进的恢复特性。同时，可能导致气体灵敏度的降低。氟铝酞菁（AlFPc）分子具有线性骨架（Al-F）_x，周围有一系列平面的酞菁环，可以形成高导电性的超薄薄膜，采用真空升华法在未经处理的玻璃基片上沉积了厚度为10 ~ 20 nm的AlFPc薄膜<-4>。该薄膜具有良好的导电性能，可用于实际的气敏元件 ...更多信息 .对1ppmNO_2气体的掺杂和脱掺杂循环的气敏特性也表明，即使在80 ℃的工作温度下，它也具有较高的气敏度、较快的响应速度和良好的恢复特性。这一结果可以用AlFPc分子在薄膜中的特殊排列和NO_2气体分子向薄膜中扩散的减少来解释。为了制备具有更高取向性的AlFPc超薄膜，合成了四叔丁基氟铝酞菁（AlFPc（C_4/H_9）_4）和八甲基氟铝酞菁（AlFPc（CH_3）_8）。由于这两种分子都被不对称基团取代，它们可能在真空升华薄膜中形成更特异的阵列。此外，取代基可以改善气体响应特性，由于它们对AlFPc大环的给电子效应。事实上，基于两种取代的AlPcF分子的真空升华非常薄的薄膜显示出改善的NO_2气体响应特性。实验结果还表明，AlFPc分子的替代是实现薄膜型NO_2气敏元件实用化的另一途径。少

Copper phthalocyanine thin films with the thickness of 200 nm have shown good gas response characteristics in the NO_2 ambience at the operation temperature of 150 ℃, after the HF treatment of glass substrates. However, there are still some problems from the viewpoint of practical uses. Fabrication of very thin film is one of the methods to solve them. Reduction in the thickness of film is expected to lead a faster gas response and improved recovery characteristics. At the same time, reduction in the gas sensitivity may be caused. Fluoroaluminum phthalocyanine (AlFPc) molecules have a linear backbone (Al-F)_x surrounded by a stack of planar Pc rings, which may result in a high conductive very thin film.The AlFPc films with the thickness of 10 to 20 nm have been deposited on the non-treated glass substrate by using a vacuum sublimation method in the vacuum of 10^<-4> Pa range. The films have revealed an enough electric conductivity for the use of practical gas sensor element as expected … More . The gas response characteristics for the cycle of doping and dedoping of 1 ppm NO_2 gas have also showed the high gas sensitivity, the faster response rate and the good recovery characteristics even at the operation temperature of 80 ℃. These results can be interpreted by the specific array of the AlFPc molecules in the film and the decrease in diffusion of NO_2 gas molecules into the film. As a result, the very thin film based on AlFPc molecules is a promising material for the practical application to thin film-based NO_2 gas element.In order to fabricate a more highly oriented very thin film, substituted AlFPc molecules, fluoroaluminum tetra-t-butyl-phthalocyanine (AlFPc(C_4/H_9)_4) and fluoroaluminum octa-methyl-phthalocyanine (AlFPc(CH_3)_8) have been synthesized. Since both molecules have been substituted by the asymmetric groups, they may cause more specific arrays in the vacuum sublimed thin films. Furthermore, the substituted groups may improve the gas response characteristics due to their electron-donating effect on the AlFPc macrocycles. Indeed, the vacuum sublimed very thin films based on both substituted AlPcF molecules have shown the improved NO_2 gas response characteristics. The results also suggest that the substitution of AlFPc molecules is another approach to realize the practical thin film-based NO_2 gas sensors. Less