High tunability (Ba,Sr)TiO_(3) thin films grown on atomic layer deposited TiO_(2) and Ta_(2)O_(5) buffer layers

摘要

In this letter, we report on increased tunability of Ba_(0.6)Sr_(0.4)TiO_(3) (BST) thin films by use of Ta_(2)O_(5) and TiO_(2) films as buffer layers between BST and Si substrates. Ta_(2)O_(5) and TiO_(2) buffer layers were grown by atomic layer deposition (ALD) onto Si substrates followed by pulsed laser deposition of Ba_(0.6)Sr_(0.4)TiO_(3) thin films onto the buffer layers. The randomly oriented BST films deposited on TiO_(2)/Si substrates exhibited a broader grain size distribution than the (110) textured BST films grown on Ta_(2)O_(5)/Si substrates. At an applied voltage of 10 V, the BST films grown on Ta_(2)O_(5)/Si and TiO_(2)/Si substrates showed much enhanced tunability values of 53.1% and 72.9%, respectively, as compared to the 20.7% value obtained with BST films grown on MgO single crystal substrates. Successful integration of BST low voltage microwave tunable devices onto Si substrates thus appears possible with the aid of ALD grown Ta_(2)O_(5) or TiO_(2) buffer layers.