Hybrid graphene/h-BN model is studied via molecular dynamics simulation to observe the evolution of graphene layer upon heating. Model containing 20,064 atoms is heated up from 50 to 8000 K via Tersoff and Lennard–Jones potentials. Various thermodynamic quantities, structural characteristics, and the occurrence of liquid-like atoms are studied. The Lindemann criterion for 2D case is calculated and used to observe the appearance of liquid-like atoms. The atomic mechanism of structural evolution upon heating is analyzed on the basis of the occurrence/growth of liquid-like atoms, the formation of clusters, the coordination number, and the ring statistics. The liquid-like atoms tend to form clusters and the largest cluster increases slightly in order to form a single largest cluster of liquid-like atoms. The other models such as free-standing graphene, zigzag GNR, and armchair GNR are also presented to have an entire picture about the evolution of graphene upon heating in different models. Note that the largest clusters of free-standing graphene as well as zigzag GNR, and armchair GNR tend to decrease to form a ring-like 2D liquid carbon.

Aluminum nitride (AlN) has versatile and intriguing properties, such as wide direct bandgap, high thermal conductivity, good thermal and chemical stability, and various functionalities. Due to these properties, AlN thin films have been applied in various fields. However, AlN thin films are usually deposited by high temperature processes like chemical vapor deposition. To further enlarge the application of AlN films, atomic layer deposition (ALD) has been studied as a method of AlN thin film deposition at low temperature. In this mini review paper, we summarize the results of recent studies on AlN film grown by thermal and plasma enhanced ALD in terms of processing temperature, precursor type, reactant gas, and plasma source. Thermal ALD can grow AlN thin films at a wafer temperature of 150~550 oC with alkyl/amine or chloride precursors. Due to the low reactivity with NH3 reactant gas, relatively high growth temperature and narrow window are reported. On the other hand, PEALD has an advantage of low temperature process, while crystallinity and defect level in the film are dependent on the plasma source. Lastly, we also introduce examples of application of ALD-grown AlN films in electronics.

Recently, the use of an aluminum nitride(AlN) buffer layer has been actively studied for fabricating a high quality gallium nitride(GaN) template for high efficiency Light Emitting Diode(LED) production. We confirmed that AlN deposition after N2 plasma treatment of the substrate has a positive influence on GaN epitaxial growth. In this study, N2 plasma treatment was performed on a commercial patterned sapphire substrate by RF magnetron sputtering equipment. GaN was grown by metal organic chemical vapor deposition(MOCVD). The surface treated with N2 plasma was analyzed by x-ray photoelectron spectroscopy(XPS) to determine the binding energy. The XPS results indicated the surface was changed from Al2O3 to AlN and AlON, and we confirmed that the thickness of the pretreated layer was about 1 nm using high resolution transmission electron microscopy(HR-TEM). The AlN buffer layer deposited on the grown pretreated layer had lower crystallinity than the as-treated PSS. Therefore, the surface N2 plasma treatment on PSS resulted in a reduction in the crystallinity of the AlN buffer layer, which can improve the epitaxial growth quality of the GaN template.