This work documents the first example of deposition of high-quality Gd(2)O(3) thin films in a surface-controlled, self-limiting manner by a water-based atomic layer deposition (ALD) process using the engineered homoleptic gadolinium guanidinate precursor [Gd(DPDMG)(3)]. The potential of this class of compound is demonstrated in terms of a true ALD process, exhibiting pronounced growth rates, a high-quality interface between the film and the substrate without the need for any additional surface treatment prior to the film deposition, and most importantly, encouraging electrical properties.
For the first time, the combination of the homoleptic erbium tris-guanidinate metalorganic complex ([Er(NMe 2 -Guan) 3 ]) simply with water yielded high quality Er 2 O 3 thin films on Si(100) substrates employing the atomic layer deposition (ALD) process. The process optimization to grow good quality Er 2 O 3 layers was performed by varying the Er precursor pulse time, water pulse time and purge time.The high reactivity of the Er compound towards water and good thermal stability in the temperature range of 150-275 C (ALD window) resulted in homogeneous, stoichiometric Er 2 O 3 layers with high growth rates (1.1 Å per cycle) and the as-deposited films crystallized in the cubic phase. The saturation behavior at different temperatures in the ALD window and the linear dependence of film thickness as a function of precursor pulse time confirmed the true ALD process. The potential of Er 2 O 3 thin films as gate dielectrics was verified by performing capacitance-voltage (C-V) and current-voltage (I-V) measurements. Dielectric constants estimated from the accumulation capacitance were found to be in the range of 10-13 for layers of different thicknesses (15-30 nm).
In this work, Gd 2 O 3 thin films grown by molecular beam epitaxy on Si(1 1 1) substrates were investigated by various diffraction methods. The Gd 2 O 3 layers exhibit a highly perfect cubic bixbyite structure with a single domain orientation, low lattice mismatch with Si and good crystallinity. Threefold in-plane symmetry and bright streaky patterns were observed during the oxide growth by in situ high-energy electron diffraction. X-ray diffraction results demonstrate that Gd 2 O 3 on Si(1 1 1) is fully epitaxial with a single domain orientation with a [
Thin epitaxial rare earth oxide layers on Si exhibit K values that are much larger than the known bulk values. We investigate the thickness dependence of that enhancement effect for epitaxial Gd2O3 on Si(111). Controlling the oxide composition in ternary (Gd1-xNdx)2O3 thin films enables us to tune the lattice mismatch to silicon and thus the K values of the dielectric layer from 13 (close to the bulk value) up to 20. We show that simple tetragonal distortion of the cubic lattice is not sufficient to explain the enhancement in K. Therefore, we propose more severe strain induced structural phase deformations.
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