Novel resistive readout CO2 sensor based on receptor -transducer work function coupling and electron affinity - band bending compensation

该项目旨在展示一种通过使用基于半导体金属氧化物的接收器和换能器材料的组合来检测二氧化碳的新方法。我们的主要目标是将受体功函数的变化--由二氧化碳吸附决定--转化为电耦合换能器层中可测量的电导变化。这是一个至关重要的事实，因为测量电阻很简单。二氧化碳是气相中的一种惰性分子，它的吸附可以发生在特定金属氧化物表面(受体)的碱性位置上，在某些情况下(表面位置和二氧化碳分子之间的电荷重新分配)决定了电子亲和力Δχ的变化。这种效应很难监测，因为局域化学吸附过程引起的变化不会影响电阻，因为它们不会影响自由电荷载流子的浓度；要检测这种影响，需要进行功函数测量。我们计划将受体材料电耦合到另一种材料(换能器)上，这种材料对二氧化碳的反应性应该很小或没有反应，并以这种方式使受体功函数的变化-由二氧化碳吸附引起-转化为换能器的电阻变化。这应该通过由受体的费米能级(受体和换能器的费米能级耦合)钉扎/控制其费米能级来控制换能器的电子性质来确定。

The project aims to demonstrate a new approach for CO2 detection by using a combination of receptor and transducer materials based on semiconducting metal oxides. Our main objective is the translation of the changes in the work function of a receptor - determined by CO2 adsorption - into measurable conductance changes in an electrically coupled transducer layer. This is a crucial fact because measuring resistances is straightforward. Adsorption of CO2, an inert molecule in the gas phase, can take place on basic sites on specific metal oxide surfaces (receptors) and in some cases (redistribution of electrical charge between the surface site and the CO2 molecule) determines changes in the electron affinity Δχ. Such effects are difficult to monitor for the changes induced by localised chemisorption processes are not influencing the electrical resistance because they are not affecting the concentration of free charge carriers; to sense such effects one needs work function measurements. We plan to electrically couple the receptor material to another one (transducer) – that should have little or no reactivity towards CO2– and make it possible in this way for the receptor’s changes of the work function - induced by CO2 adsorption - to be translated into resistance changes of the transducer. This should be determined by the control of the electronic properties of the transducer by the pinning/control of its Fermi level by the Fermi level of the receptor (Fermi level coupling of receptor and transducer).