  This work reports the first study of periodically poled piezoelectric film
(P3F) lithium niobate (LiNbO3) resonators at cryogenic temperatures. We
experimentally investigate the temperature dependency of resonant frequencies
and quality factor (Q) of higher-order Lamb modes up to 20 GHz between
80{\deg}K and 297{\deg}K, using a tri-layer P3F LiNbO3 resonators as the
experimental platform. The supported thickness-shear Lamb modes between
second-order symmetric (S2) and eleventh-order antisymmetric (A11) modes show
temperature coefficients of frequency (TCF) averaging -68.8 ppm/K. Higher Q and
more pronounced spurious modes are observed at lower temperatures for many
modes. Upon further study, the cryogenic study will be crucial for identifying
dominant loss mechanisms and origins of spurious modes in higher-order Lamb
wave devices for millimeter-wave applications.
