Dopant effects on the response of gas-sensitive resistors utilising semiconducting oxides
Dopant effects on the response of gas-sensitive resistors utilising semiconducting oxides
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DOI：
10.1039/jm9910100809
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发表时间：
1991
影响因子：
--
通讯作者：
David E. Williams;P. Moseley
中科院分区：
文献类型：
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作者：
David E. Williams;P. Moseley
在半导体氧化物中诱导的电导率变化的结果，在空气中的反应性气体的存在下的小浓度（ppm水平）被推定为引起的电离氧物种（表面受体状态）的表面覆盖的非平衡变化。不同氧化物材料的多孔颗粒对空气中低浓度的不同还原气体的响应通常可以分为p型（电阻增加）或n型（电阻降低）。然而，一些材料对某些还原性气体显示出n型响应，而对其他还原性气体显示出p型响应，并且一些材料可以随着还原性气体浓度的增加而显示出响应符号的变化;这种效应可以通过系统地取代到复合氧化物的晶格中来实现。本文阐述了这些影响，并开发了一个简单的模型，其主要特点是，体施主密度足够低，平均晶粒尺寸足够小，表面受主态密度足够高，晶粒是完全耗尽的传导电子。结果表明，随着受体态表面密度的增加，电导率经历一个最小值。由于受体态的表面密度是由于与还原气体的相互作用而变化的，因此观察结果是可以解释的。
Conductivity changes induced in semiconducting oxides as a consequence of the presence of small concentrations (ppm level) of reactive gases in air are presumed to be caused by non-equilibrium changes in surface coverage of ionised oxygen species (surface acceptor states). Responses of porous pellets of different oxide materials to small concentrations of different reducing gases in the air can usually be classified as either p-type (resistance increases) or n-type (resistance decreases). However, some materials show n-type responses to some reducing gases and p-type to others, and some materials can show a change in sign of the response with increasing concentration of the reducing gas; such effects can be brought about by systematic substitution into the lattice of complex oxides. This paper illustrates these effects and develops a simple model, the principal features of which are that the bulk donor density is low enough, the average grain size small enough and the surface acceptor state density high enough that the grains are fully depleted of conduction electrons. It is then shown that the conductivity goes through a minimum with increasing surface density of acceptor states. Since it is the surface density of acceptor states which is varied as a consequence of interaction with the reducing gas, the observations are thereby accounted for.