Temperature behavior of solid polymer film coated quartz crystal microbalance for sensor applications

Abstract

Experimental data on the temperature behavior of quartz crystal microbalances (QCMs) rigidly coated with solid polymer films of hexamethyldissiloxane (HMDSO) for gas and liquid-phase sensor applications are provided. 16MHz AT-cut quartz resonators used as QCMs are coated at seven different HMDSO thicknesses in the 70–400nm range by using a RF-plasma polymerization process. Their quasi cubic temperature frequency characteristics (TFCs) are measured over a temperature of −50°C to 90°C for each film thickness. A cubic spline approximation of the experimental data reveals a periodic oscillating behavior of the temperature coefficients of the TFC, while its inflection point oscillates between 24°C and 28°C in the above thickness range. Devices coated at 150, 260 and 380nm, i.e. at a thickness period of 110–120nm, were found to have identical thermal stability and TFC behavior. A simple practical method for correcting the sensor readings for thermally induced frequency shifts, based on an additional temperature measurement at each sensor reading, is suggested and verified experimentally.