First-Principles Investigation of the Structure, Energetics, and Electronic Properties of Ru/HfO₂ Interfaces

Abstract

The electronic properties of metal oxide semiconductor gate electrodes are strong functions of the structure of the metal−dielectric interface. We use density functional theory to investigate the structures, energetics, and electronic properties of Ru/HfO2 interfaces. We find that atom-by-atom deposited Ru films have significantly different interfacial structures from epitaxially connected Ru films on the m-HfO2(001) surface. Atom-by-atom deposited films are rougher than epitaxially connected films, even when forced to form two-dimensional films. These interfacial structural differences lead to differences in the electronic properties of the films and therefore affect electrical properties, such as the work function of the gate electrode. We found that for both types of films the partial densities of states of interfacial layers are significantly different from that of the bulk region. Each shows charge transfer from the interfacial Ru layer to the interfacial dielectric layer, although the magnitude of charge transfer varies. Thus both films exhibit metal induced gap states in the band gap region of the interface localized on atoms of the HfO2 interfacial layer.

Growth of Pt Particles on the Anatase TiO2(101) Surface

“…The above results demonstrate that Pt growth thermodynamically favors 3-D structures, as expected given the high cohesive energy of Pt and the observed tendency of Pt to not wet many substrates . This agrees with our previous results for Ru, another high cohesive energy metal, on HfO 2 . The high cohesive energy is thus responsible for the island growth observed in Pt ALD.…”

“…49 This agrees with our previous results for Ru, another high cohesive energy metal, on HfO 2 . 50 The high cohesive energy is thus responsible for the island growth observed in Pt ALD. Therefore, despite the layerby-layer nature of ALD, deposited Pt atoms configure themselves into 3-D structures as predicted by DFT calculations and experimentally demonstrated by TEM images of Pt/TiO 2 particles after 1 and 20 cycles of Pt ALD, as shown in Figure 4.…”

The synergistic effect of Hf-O-Ru bonds and oxygen vacancies in Ru/HfO2 for enhanced hydrogen evolution

“…Consequently, correlative theoretical models including Ru (001), HfO 2 (001), Ru 3 , Ru 6 , Ru 10 , and Ru 13 clusters, and supported Ru clusters denoted as Ru 3 / HfO 2 , V O -Ru 3 /HfO 2 , Ru 6 /HfO 2 , Ru 10 /HfO 2 , and Ru 13 /HfO 2 were constructed, as shown in Supplementary Figs. 22, 23. Previous ab initio thermodynamic phase diagrams show that the (001) face is indeed a thermodynamically stable face of HfO 2 38 . The O-terminated (001) surface is the most stable surface for HfO 2 , as revealed by total energy-based DFT calculations (Supplementary Fig.…”

Impact of Interfacial Oxygen Content on Bonding, Stability, Band Offsets, and Interface States of GaAs:HfO2 Interfaces

“…It should be noted that DFT is a well-established method to address the structural and electronic properties of metal/insulator, semiconductor/semiconductor, semiconductor/insulator, and insulator/insulator interfaces. 18,19 To build a model interface, we consider the interface between cubic HfO 2 and GaAs. Although HfO 2 exists in cubic, tetragonal, and monoclinic phases, they all have very similar local ionic bonding, and the atomic structures are closely related.…”