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Humidity sensing properties of vacuum deposited thin polyimide layers

B. GEORGIEVA1,* , I. PODOLESHEVA1, I. ZHIVKOV1, V. STRIJKOVA1, V. PLATIKANOVA1

Affiliation

  1. Central Laboratory of Photoprocesses “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Acad. G. Bonchev St., bl. 109, 1113 Sofia, Bulgaria

Abstract

The aim of this investigation is to study the humidity sensing properties of thin polyimide layers at room temperature. The layers are prepared by two different techniques – simultaneous deposition of the precursors on planetary rotating substrates and evaporation on linearly moving substrates (layer-by-layer). The influence of the layer thickness on the sensitivity to water vapour is also followed. As a measure of the sensitivity, the change in the electrical resistance as a function of the relative humidity in air is used. The resistance changes linearly in its semi-logarithmic graph, spanning over 4 decades. For studying the sensor response kinetics, the relative humidity is changed in a steplike manner, and the electrical resistance is monitored as a function of time. The fast response of the sensor could be related to dominant physical adsorption. The recovery process requires more time because it is not forced by heating or air flow through the vessel..

Keywords

Polyimide, Vacuum evaporation, Humidity sensors, Resistive sensors.

Submitted at: Nov. 1, 2006
Accepted at: Feb. 15, 2007

Citation

B. GEORGIEVA, I. PODOLESHEVA, I. ZHIVKOV, V. STRIJKOVA, V. PLATIKANOVA, Humidity sensing properties of vacuum deposited thin polyimide layers, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 2, pp. 498-500 (2007)