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37■SHS 2019 Moscow, Russia
MORPHOLOGICAL DIVERSITY OF METAL NITRIDES CRYSTALS: SYNTHESIS, CHARACTERIZATION AND THEORETICAL MODELING
H. H. Nersisyan*, W. B. Kim, and J. H. Lee
aRASOM, Chungnam National University, 99 Daehak-ro, Yuseong-gu,
Daejeon, 34134 Republic of Korea bGraduate School of Materials Science and Engineering, Chungnam National University, 99
Daehak-ro, Yuseong-gu, Daejeon, 34134 Republic of Korea
*e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10108
Among the nitrides, aluminum nitride (AlN), gallium nitride (GaN), and silicon nitride (Si3N4) have been identified as a key members of the group III-IV nitrides family. The most remarkable properties exhibited by metal nitrides are their high thermal conductivity (AlN: 150-200 Wm-1K-1; Si3N4: 10-43 Wm-1K-1; GaN: 130 Wm-1K-1), highest band gap (AlN: 6.2 eV; Si3N4: 5.0 eV; GaN: 3.4 eV), small electron affinity (AlN: 1.9; GaN: 4.1; &3N4: 0.9-3.2 eV), strong piezoelectricity (AlN: 4.81 pm/V; Si3N4: 3.1 pm/V; GaN: 15 pm/V), high surface acoustic wave (SAW) velocity (AlN: 5760 m/s; GaN: 3690 m/s), high chemical resistance, and high melting point (> 2500oC). They are ideal materials for applications in microelectrochemical systems (MEMS), surface acoustic waves (SAWs), optoelectronic devices such as light emitting diodes (LED), field emitters, flexible pulse-wave sensors, and ultraviolet nanolasers. The metal nitrides exist in various morphological forms such as nanoparticles, nanowires, nanotubes, nanorods, nanobelts, nanosheets, thin films, and dendritic structures such as sectored plates, stellar, and fern-like dendrites, six and multifold symmetry crystals, and this make nitride materials unique for a broad application. Four main topics are covered in this keynote lecture: (1) general synthesis, fabrication and classification as zero-dimensional (0D), one dimensional (1D), two-dimensional (2D) and three-dimensional (3D) nano- and microstructures of metal nitrides; (2) nucleation and growth of nitride crystals; (3) computer simulation of growth processes based on density functional theory (DFT) and phase field (PF) modeling approaches; (4) metal nitride application and micro-devices. Our lecture also provides a perspective on future research relevant to metal nitride micro- and nanostructures. In the beginning of the lecture, we will address to the morphological diversity of metal nitride nano- and microstructures and the synthesis of these materials through various chemical and physical methods. We will place a particular focus on the various synthesis approaches, involving direct nitridation, combustion synthesis (SHS), chemical vapour deposition (CVD), physical vapor deposition (PVD), and reactive sputtering. The structural development of micro- and nanostructures upon the process temperature, reaction mixture composition, type of additives, presence of a catalyst, and the type of substrate will be highlighted. For illustration, the several morphological fragments of AlN, Si3N4, and GaN crystals fabricated by different synthesis methods are shown in Fig. 1a. Figure 1a (1-3) demonstrate 6-fold symmetry dendritic crystals of AlN prepared by SHS technique [1, 2]. Figure 1a (4-6) shows combustion synthesized-Si3N4 branched structures consisted of some long and slender prisms. These structures have a central junction from which the columnar crystals radiate in c-axis direction forming branched microstructures. Figure 1a (7-9) shows GaN columnar crystals grown by metal organic vapour phase epitaxy (MOVPE) [3, 4]. The growth mechanism of metal nitride micro- and nanostructures will be discussed based on synthesis methods and the vapor-solid (VS) and vapor-liquid-solid (VLS) growth mechanisms. Moreover, the preferable crystallographic directions in which the crystals grow will be highlighted.
XV International Symposium on Self-Propagating High-Temperature Synthesis
Fig. 1. (a) SEM morphology of AlN (1-3), Si3N (4-6), and GaN (7-9) structures. (b) AlN crystals: phase-field, DFT calculations and experiments.
The growth mechanism of metal nitride micro- and nanostructures will be discussed based on synthesis methods and the vapor-solid (VS) and vapor-liquid-solid (VLS) growth mechanisms. Moreover, the preferable crystallographic directions in which the crystals grow will be highlighted.
We will also discuss the growth process of nitride structures based on two well-known computational models: quantum-mechanical calculations based on density-functional theory (DFT) and Wulff constructions, used for the prediction of equilibrium shapes of metal nanostructures, and (2) phase-field models for solving interface problems and predicting the solidification dynamics. Figure 1b shows the shape of 6-fold symmetry crystals of AlN obtained by the experiments and validated by phase field and DFT simulations. All results are well-agreed with each other's.
Finally, we will briefly discuss the application and microelectronic devices based of metal nitride micro- and nanostructures. Lastly but not least, some issues that need to be clarified in the near future will be also discussed.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B03936187).
1. H.H. Nersisyan, J.H. Lee, J.R. Ding, K.S. Kim, K.V. Manukyan, A.S. Mukasyan, Combustion synthesis of zero-, one-, two- and three-dimensional nanostructures: Current trends and future perspectives, Prog. Energy Combust. Sci., 2017, vol. 63, pp. 79-118.
2. H.H. Nersisyan, S.H. Lee, J.H. Choi, B.U. Yoo, J.H. Lee, Single-step combustion process for the synthesis of 1-D, 2-D, and 3-D hierarchically grown AlN structures, Combust. Flame, 2017, vol. 185, pp. 210-219.
3. M. Nami, I.E. Stricklin, K.M. DaVico, et. al., Carrier dynamics and electro optical characterization of high performance GaN/InGaN core-shell nanowire light-emitting diodes, Sci. Rep., 2018, vol. 8, pp. 501-507.
4. T. Kente, S.D. Mhlanga, Gallium nitride nanostructures: Synthesis, characterization and applications, J. Cryst. Growth., 2016. vol. 444. pp. 55-72.
