We discuss the possibility of determining shear moduli for thin polyme
ric films coated on quartz resonators by analysing the variation of no
rmalized frequency shift delta f/f with different harmonics. For suffi
ciently thick films, the elastic compliance can be deduced from the in
crease in delta f/f with overtone order. However, a correction must be
applied to account for a frequency dependence of the Sauerbrey factor
relating frequency shift to film mass. Since the elastic effect scale
s with the square of the film mass, the correction is most important f
or thin films. Possible sources of frequency dependence of the Sauerbr
ey factor are the finite thickness of the electrodes, lateral stress c
omponents, and insufficient control of the electrical boundary conditi
ons. In order to obtain the shear compliance, the frequency dependence
of the Sauerbrey factor was measured and subtracted from the data on
polymeric thin films. The correction procedure can be avoided by using
electrodeless quartzes and exciting the vibration with external elect
rodes across an air gap. Since, in this case, the Sauerbrey factor is
approximately constant, the shear compliance can be obtained directly
from the variation of delta f/f with overtone order.