Enhanced Adhesion Energy at Oxide/Ag Interfaces for Low-Emissivity Glasses: Theoretical Insight into Doping and Vacancy Effects

Abstract

Low-emissivity glasses rely on multistacked architectures with a thin silver layer sandwiched between oxide layers. The mechanical stability of the silver/oxide interfaces is a critical parameter that must be maximized. Here, we demonstrate by means of quantum-chemical calculations that a low work of adhesion at interfaces can be significantly increased via doping and by introducing vacancies in the oxide layer. For the sake of illustration, we focus on the ZrO2(111)/Ag­(111) interface exhibiting a poor adhesion in the pristine state and quantify the impact of introducing n-type dopants or p-type dopants in ZrO2 and vacancies in oxygen atoms (nVO; with n = 1, 2, 4, 8, 10, 16), zirconium atoms (mVZr; with m = 1, 2, 4, 8), or both (nVO + mVZr; with m/n = 1:2, 1:4, 2:2, 2:4). In the case of doping, interfacial electron transfer promotes an increase in the work of adhesion, from initially 0.16 to ∼0.8 J m–2 (n-type) and ∼2.0 J m–2 (p-type) at 10% doping. A similar increase in the work of adhesion is obtained by introducing vacancies, e.g., VO [VZr] in the oxide layer yields a work of adhesion of ∼1.5–2.0 J m–2 at 10% vacancies. An increase is also observed when mixing VO and VZr vacancies in a nonstoichiometric ratio (nVO + mVZr; with 2n ≠ m), while a stoichiometric ratio of VO and VZr has no impact on the interfacial properties.

Adhesion Microscopy as a Nanoscale Probe for Oxidation and Charge Generation at Metal-Oxide Interfaces

“…Image charge forces have been known for some time to enhance adhesion at metal-oxide interfaces, ,, and our results provide further evidence for this phenomenon at the nanoscale. Our assertion that charged V O defects are the major contribution to the observed image force is supported by many previous studies which highlight that introducing charged V O defects in an oxide can greatly increase the metal-oxide interfacial adhesion, e.g., in MgO, , ZrO 2 , and TiO 2 …”

“…Here, we are concerned with the change in adhesion after SBD rather than the fundamental adhesion of the initial surface contact, with the observed increase in adhesion after SBD (excluding the first adhesion measurement at positive bias) being the result of the generation of fixed oxygen vacancy charge (negative V O – ) at the SBD location inducing an image charge force on the AFM tip. Image charge forces have been known for some time to enhance adhesion at metal-oxide interfaces, ,, and our results provide further evidence for this phenomenon at the nanoscale. Our assertion that charged V O defects are the major contribution to the observed image force is supported by many previous studies which highlight that introducing charged V O defects in an oxide can greatly increase the metal-oxide interfacial adhesion, e.g., in MgO, , ZrO 2 , and TiO 2 …”

“…Chemical Bonding-Enhanced Adhesion of the First Force Curve at Positive Bias. Adhesion is correlated to the formation of bonds at the interface, 50 and in oxides, strong polar or covalent bond formation often arises from charge transfer and the resultant chemical reactions at the metal-oxide interface. Fu and Wagner 49 identify four general reaction mechanisms at metal-oxide interfaces, namely, redox reactions, alloy formation, encapsulation of nanoparticles (NP), and interdiffusion of metal, all of which have been observed in the SiO 2 -metal systems.…”

Nanostructure, Plastic Deformation, and Influence of Strain Rate Concerning Ni/Al2O3 Interface System Using a Molecular Dynamic Study (LAMMPS)

“…As the interface is separated to form two new free surfaces, the adhesive energy increases. The work of adhesion was defined as the energy required to break down the interfacial bonds and separate the interface into two free surfaces [ 56 ]. In Figure 2 a, corresponds to the well depth of the adhesive energy curves.…”

High-Throughput First-Principles Prediction of Interfacial Adhesion Energies in Metal-on-Metal Contacts

“…However, within a given contact area, the main driving forces that determine the strength of adhesion originate from the specific chemistry of the interface, namely the reactivity and willingness in bonding of the nanoasperity contacts. Indeed, adhesion energy is directly controlled by the atomistic structure of the interface and, as such, can be influenced by microscopic details such as crystal orientation and stacking, presence of adsorbates, impurities, defects, and segregates. − Hypothetically, the knowledge and control of these nanoscale contacts could allow the understanding, anticipation, and optimization of the mechanical behavior of interfaces. However, such knowledge and control are extremely difficult to gain from an experimental point of view.…”