The effect of ultra-thin Al2O3 layers on the dielectric properties of LaAlO3 thin film on silicon

HHigh-k LaAlO3 (LAO) thin films with and without Al2O3 buffer layers were deposited on n-type silicon substrates using a pulsed laser deposition method. The dielectric constant of the LAO thin film increased from 5.2 to 23.1 as its thickness increased from 20 to 500 Å. The effective dielectric constants of the LAO (120 Å)/Si and LAO(105 Å)/Al2O3(15 Å)/Si were 12.5 and 23.2, respectively. The flatband voltage of the LAO(105 Å)/ Al2O3(15 Å)/Si sample decreased from 2.0 V to 1.2 V after the sample was annealed for 5 min at 850 ◦C in air atmosphere, while the dielectric constant value of the annealed sample did not changed. It was found that a 15 Å thick Al2O3 buffer layer could enhance the dielectric properties of the LAO thin film, making it one of the good candidates for high-k materials.