Transfer of Thin Silicon Films from SiO _2 and HfO _2 to C-Sapphire: Effect of Substrate Thickness on Ferroelectric Properties of Hafnium Dioxide

Silicon-on-sapphire (SOS) substrates with nanolayers of silicon and hafnium dioxide are studied structurally, electrophysically, and optically depending on the thickness of the substrate. It is shown that the biaxial tensile stress in the HfO _2 intermediate layer induced as a result of heat treatment of such structures stimulates the current hysteresis in the channel of the SOS pseudo-MOS transistor due to the large difference in the coefficients of thermal expansion between the silicon layer, sapphire layer, and hafnium dioxide layer. It is found that a decrease in mechanical stress in hafnium dioxide leads to an increase in the coercive field and ferroelectric switching at low fields in hafnium dioxide nanolayers.