Abstract:Aluminum nitride (AlN) is a popular buffer layer and interlayer. The understanding of how AlN serves as a wetting and fracturemitigating layer relies on molecular pictures of the AlN layer and the interfaces. However, molecular dynamics (MD) simulation studies on AlN system, particularly on its wurtzite phase, have been limited. This is because most existing interatomic force fields of AlN target the less common zinc blende phase. Here, we report a new Tersoff-based AlN force field for its wurtzite structure. … Show more
“…All MD simulations are carried out by using the LAMMPS software package and adopting the Tersoff potential (all the potential parameters are given in Table S1) to model Al–N bonding interactions. After energy minimization with stress relaxation, the h -AlN model (see Figure a) is equilibrated for 1 ns under the NPT ensemble − under in-plane ( x - and y -axis) pressures of 1 bar and at 300 K with a coupling time constant of 20 ps.…”
Discovery of graphene
and its astonishing properties have drawn
great interest in new two-dimensional (2D) materials for practical
applications in micro- and nanodevices. 2D hexagonal aluminum nitride
monolayer (h-AlN), a III–V group wide-bandgap
semiconductor, has promising applications in optoelectronics and energy
conversion. Unfortunately, their high temperature thermodynamic stability
and thermal transport properties have not been reported. Here we investigate
these properties, for the first time, of monolayer h-AlN using both equilibrium and nonequilibrium molecular dynamics
simulations. We find that h-AlN has a very high melting
point in the range of 3500–4000 K due to the strong Al–N
covalent bonding. On the basis of the kinetic theory of thermal transport
and quantum corrections, the intrinsic in-plane thermal conductivity
of ∼264.1 W m–1 K–1 and
phonon mean free path of ∼154 nm of h-AlN
are estimated at quantum-corrected room temperature. The analysis
of phonon transport properties demonstrates that there is a notable
frequency gap between acoustic and some optical modes. Moreover, we
find that the low elastic stiffness (phonon group velocity) and missing
phonon modes in such gap attribute to the lower thermal conductivity
of h-AlN than that of its 2D III–V group counterpart, h-BN. Our computational work not only characterizes the
thermal transport behavior of h-AlN for practical
applications in electronics, but also inspires optimal selections
of other 2D III–V group materials as more efficient high-temperature
heat conductors.
“…All MD simulations are carried out by using the LAMMPS software package and adopting the Tersoff potential (all the potential parameters are given in Table S1) to model Al–N bonding interactions. After energy minimization with stress relaxation, the h -AlN model (see Figure a) is equilibrated for 1 ns under the NPT ensemble − under in-plane ( x - and y -axis) pressures of 1 bar and at 300 K with a coupling time constant of 20 ps.…”
Discovery of graphene
and its astonishing properties have drawn
great interest in new two-dimensional (2D) materials for practical
applications in micro- and nanodevices. 2D hexagonal aluminum nitride
monolayer (h-AlN), a III–V group wide-bandgap
semiconductor, has promising applications in optoelectronics and energy
conversion. Unfortunately, their high temperature thermodynamic stability
and thermal transport properties have not been reported. Here we investigate
these properties, for the first time, of monolayer h-AlN using both equilibrium and nonequilibrium molecular dynamics
simulations. We find that h-AlN has a very high melting
point in the range of 3500–4000 K due to the strong Al–N
covalent bonding. On the basis of the kinetic theory of thermal transport
and quantum corrections, the intrinsic in-plane thermal conductivity
of ∼264.1 W m–1 K–1 and
phonon mean free path of ∼154 nm of h-AlN
are estimated at quantum-corrected room temperature. The analysis
of phonon transport properties demonstrates that there is a notable
frequency gap between acoustic and some optical modes. Moreover, we
find that the low elastic stiffness (phonon group velocity) and missing
phonon modes in such gap attribute to the lower thermal conductivity
of h-AlN than that of its 2D III–V group counterpart, h-BN. Our computational work not only characterizes the
thermal transport behavior of h-AlN for practical
applications in electronics, but also inspires optimal selections
of other 2D III–V group materials as more efficient high-temperature
heat conductors.
“…Such thermalized fluxes are analogous to those of a molecular beam epitaxy or a high pressure sputtering process. The three-body Tersoff potential is applied to describe the atomic interactions between atoms, and its reliability and application have already been proved [ 25 , 27 , 29 ]. Figure 1.…”
Section: Model and Methodsmentioning
confidence: 99%
“…In this paper, the growth of AlN on c-plane AlN is studied by the large-scale atomic/molecular massively parallel simulator [ 26 ] with the Tersoff potential [ 27 ]. At an N : Al flux ratio of 2.0, the growth temperature is varied from 1000 K to 2000 K with an increment of 200 K. Then the N : Al flux ratio is varied from 0.8 to 2.8 with an increment of 0.4 at 1800 K. The growth rate, crystallinity and stoichiometry under different conditions are discussed in detail.…”
Heteroepitaxial growth of aluminum nitride (AIN) has been explored by experiments, but the corresponding growth mechanism is still unrevealed. Here, we use molecular dynamics simulations to study effects of temperature and N : Al flux ratio on deposited AlN. When the temperature increases from 1000 K to 2000 K with an N : Al flux ratio of 2.0, the growth rate of the AlN film decreases. The crystallinity of the deposited AlN is distinctly improved as the temperature increases from 1000 K to 1800 K and it becomes saturated between 1800 K and 2000 K. The crystallinity of the deposited film at 1800 K increases with an increase in the N : Al flux ratio from 0.8 to 2.4, and this degraded a little at an N : Al flux ratio of 2.8. In addition, stoichiometry is closely related to crystallinity of deposited films. Film with good crystallinity is connected with a near 50% N fraction. Furthermore, the average mean biaxial stress and mean normal stress at 1800 K with N : Al flux ratios of 2.0, 2.4 and 2.8 are calculated, indicating that the deposited film with lowest stress has the best crystal quality and the defects appear where stresses occur.
“…The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [24] with SW potential [25,26] has been adopted. So far, there have been many potentials developed for GaN [27][28][29] and AlN [30,31], but few potentials describe the interatomic potentials of Al-Ga-N. In this work, the SW potential is chosen to describe the interatomic interaction in Al-Ga-N.…”
The growth of AlGaN has been extensively studied, but corresponding research related to the effect of AlN substrate surface has rarely been reported in literature. In this article, the effects of AlN substrate surface on deposition of AlGaN films were investigated by molecular dynamics (MD) simulations. (0001) Al-terminated and 0001 N-terminated AlN were considered as substrates. The quality of surface morphology and atomic scale structure of deposited AlGaN film are discussed in detail. The results show that the surface morphology and crystal quality of AlGaN film grown on (0001) Al-terminated AlN surface are better than for that grown on 0001 N-terminated AlN surface under various growing temperatures and Al/Ga injection ratios between Al and Ga. This can be attributed to the higher mobility of Al and Ga adatoms on the (0001) Al-terminated AlN surface. These findings can provide guidance for the preparation of high-quality AlGaN thin films on AlN substrate.
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