Adsorption and Reaction of Water on the AlN(0001) Surface from First Principles

Abstract

Aluminum nitride (AlN) with a combination of very high thermal conductivity and excellent electrical insulation properties exhibits wide applications. However, it is quite sensitive to a moist environment and hydrolyzes slowly in water. In this work, density functional theory was adopted to examine the atomistic reaction mechanism on the wurtzite AlN( 0001) surface. The results indicate that water molecules are preferentially adsorbed at the top site of the AlN(0001) surface. The decomposition of adsorbed H 2 O into OH and H on the AlN(0001) surface occurs spontaneously without any energy barrier. However, a further dissociation reaction of OH into O and H has an energy barrier of 22.046 kcal/ mol. The dissociation of H 2 O is strongly dependent on the H 2 O coverage when more water molecules are adsorbed. Ammonia (NH 3 ) is determined as the dominant gas product at 4/9 monolayer H 2 O coverage, which will induce N vacancy (V N ) formation in AlN ceramic. The V N will be occupied by O 2− after geometry optimization and plays an acceleration role in the degradation of AlN by water. H 2 O adsorption and the formation of NH 3 occur alternately with the H 2 O coverage increasing. An OH−Al−O layer is formed as a precursor of AlOOH after the first AlN bilayer is fully degraded. This work can guide the manufacture and application of AlN from the theoretical viewpoint.

Study on Tungsten Metallization and Interfacial Bonding of Silicon Nitride High-Temperature Co-Fired Ceramic Substrates

“…Metallization based on AlN was carried out in the early 21st century, and now it has been applied in the military and other industries [ 7 , 8 , 9 ]. The major drawback of AlN is its low mechanical properties and chemical stability [ 10 ]. On the other hand, silicon nitride (Si 3 N 4 ) possesses high strength [ 11 ], toughness [ 12 ], heat shock resistance [ 13 ], a high dielectric constant [ 14 ] and other characteristics, making it a suitable substrate material for high-power and high-density electronic devices [ 15 , 16 ].…”

The Interplay Between Ferroelectricity and Electrochemical Reactivity on the Surface of Binary Ferroelectric AlxB1‐xN

“…[17] However, ferroelectricity in the wurtzite compounds shows multiple unique behaviors that are uncommon in classical ferroelectrics. These include effects such as wake up, i.e., emergence of the ferroelectric response after multiple cycles, [17,18] the possible absence of a paraelectric phase, [19][20][21] the coupling between polarization and surface chemistry, [22][23][24] retention of ferroelectricity down to small thicknesses (≈10 nm) [25,26] and the ability to observe square ferroelectric hysteresis loops even in materials that are structurally disordered.…”

Highly Homogeneous Current Transport in Ultra-Thin Aluminum Nitride (AlN) Epitaxial Films on Gallium Nitride (GaN) Deposited by Plasma Enhanced Atomic Layer Deposition

“…However, the measured sheet electron density values are typically lower than in MBE-grown AlN with equivalent thickness and were found to depend on the deposition conditions [19] as well as on the deposited AlN thickness [21]. Moreover, significant oxygen incorporation is commonly observed in ALD grown AlN films, with the highest concentration at the film surface, probably due to exposure to the atmosphere after the deposition process [22][23][24]. The oxygen interdiffusion through the AlN layer occurs for few nanometers, but in the ultrathin layers the oxygen incorporation can reach also the interface region.…”