Computational materials science research group

2024

  
  

            

 

Density Functional Theory and its application to the computational simulation and modeling of optical, vibrational, electronic and thermoelasic properties of materials.

 

   

Research Areas

 

1.     Rahul Trivedi, Po-Liang Liu, Radek Roucka, John Tolle, A.V.G. Chizmeshya, I. S. T. Tsong and J. Kouvetakis*, ”Mismatched Heteroepitaxy of Tetrahedral Semiconductors with Si via ZrB2 Templates”, Chemistry of Materials, Vol. 17, No.18, pp.4647-4652, 2005.

Comparison of the observed (a) and simulated (b) XTEM micrographs of the SiC-ZrB2 interface microstructure. The simulated XTEM pattern (b) was obtained from the ab initio interface structure corresponding to the lowest energy model A. This comparison suggests that the transition layer (X), above, consists of silicon atoms bonded to adjacent Zr and C atomic rows as shown in model structure c. Yellow, black, blue and pink spheres represent the atoms Si, C, Zr and B, respectively.

 

 

2.     Po-Liang Liu, A. V. G. Chizmeshya, John Kouvetakis, and Ignatius S. T. Tsong*, “First-Principles Studies of GaN(0001) Heteroepitaxy on ZrB2(0001)”, Physical Review B, Vol. 72, pp.245335, 2005.

Atomistic representations of the six GaN(0001)/ZrB2(0001) relaxed interface models fixed at the sto- ichiometry of Ga6N6Zr6B12. The atoms are represented by spheres: Ga  brown, large , N  dark blue, small , Zr  light blue, large , and B  pink, small . Models 1, 4, and 6 have N-polar GaN surfaces, while models 2, 3, and 5 have Ga-polar GaN surfaces.

 

 

3. T. Wang, Y. Yamada-Takamura, Y. Fujikawa, T. Sakurai, Q. K. Xue, J. Tolle, P.-L. Liu, A. V. G. Chizmeshya, J. Kouvetakis, and I.S.T. Tsong*, “Surface and interface studies of GaN epitaxy on Si(111) via ZrB2 buffer layers”, Physical Review Letters, Vol. 95, pp.266105, 2005.

Atomistic representations of the six GaN(0001)/ZrB2(0001) interface models. The atoms are repre- sented by spheres: Ga (brown), N (dark blue), Zr (light blue), and B (pink). Models 1, 4, and 6 are N-polar, while models 2, 3, and 5 are Ga-polar.


 

4.     Po-Liang Liu, A. V. G. Chizmeshya*, and John Kouvetakis, “Structural, Electronic and Energetic Properties of SiC[111]/ZrB2[0001] Heterojunctions: A First Principles DFT Study”, Physical Review B, Vol. 77, pp.035326, 2008.

Ball and stick structural representations of the six interface configuration models considered in this study.

 

 

5.     Po-Liang Liu*, “Highly Strained Metastable Heterojunction between Wurtzite GaN(0001) and Cubic CrN(111)”, Journal of The Electrochemical Society, Vol. 157, pp. D577-D581, 2010.

(a) Atomic structure of the interface in model 1 showing the detailed Ga–Cr bonding arrangements consisting of sixfold-coordinated Ga with three Ga–N and three Ga–Cr bonds, and (b) bulklike Cr2GaN is identical in crystalline structure (hexagonal) and atomic coordination (sixfold-coordinated Ga) to those of the interface of model 1 (brown, orange, and blue spheres are Ga, Cr, and N atoms, respectively) .

 

6.     Po-Liang Liu* and Yu-Jin Siao, “Ab initio study on preferred growth of ZnO”, Scripta Materialia, Vol. 64, pp. 483-485, 2011.

Atomistic representations of the five ZnO surface models. The atoms are represented by spheres: O, red; Zn, light gray.

 

 

7.     Po-Liang Liu*, Yu-Jin Siao, Yen-Ting Wu, Chih-Hao Wang and Chien-Shun Chen, “Structural, electronic and energetic properties of GaN[0001]/Ga2O3[100] heterojunctions: A first-principles density functional theory study”, Scripta Materialia, Vol. 65, pp. 465-468, 2011.

An orthorhombic b-Ga2O3 lattice representation comprising 16 Ga and 24 O atoms constructed from a center of a 3 X 3 X 3 repeat of the basic monoclinic b-Ga2O3 unit cell (green rectangle). Ga and O atoms are represented by brown and red spheres, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

 

 

8.     Yu-Jin Siao, Po-Liang Liu*, and Yen-Ting Wu, “Ab initio Study of Atomic Hydrogen on ZnO Surfaces”, Applied Physics Express, Vol. 4, pp. 125601, 2011.

The most favorable surface configuration models for (a) the Zn-terminated ZnO(0001) surface with zinc cluster and O–H bonds, (b) the O-terminated ZnO(0001) surface with H2O molecules, (c) the ZnO(10-10) surface with O–H bonds, and (d) the ZnO(2-1-10) surface with O–H and Zn–H bonds. The atoms are represented by spheres: Zn (gray, large), O (red, middle), and H (white, small).

 

9.     Po-Liang Liu* and Kuo-Cheng Liao, “Accommodation at the interface of highly dissimilar GaN(0001)/Sc2O3(111) heteroepitaxial systems”, Scripta Materialia, Vol. 68, pp. 211-214, 2013.

Schematic illustration showing the simulated HRTEM micrographs (a) obtained from the ab initio interface structure (b) of the lowest energy model. Comparison of the graphitic-like GaN nanofilms derived from the optimized model (c) and graphitic structure (d), which indicates similar microstructures. The atoms are represented by spheres: Ga (brown), N (blue), Sc (gray) and O (red). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

 

10.  Po-Liang Liu*, Yen-Ting Chou, and Jia-Yang Hong, “Valence-Band Offset of m-Plane GaN(1100) Films Grown on LiAlO2(100) Substrates”, Applied Physics Express, Vol. 6, pp. 071001, 2013.

Valence charge density maps corresponding to (a) I-type and (b) II-type interface structural models, respectively. The contours are plotted in the range from 0.018 to 0.288 electrons/A3 in 16 steps. The arrows indicate the position of the interface.

 

 

11.  Yen-Wei Chen, Po-Liang Liu*, and Chun-Hsiang Chan, “First-Principles Studies of Er2O3(110) Heteroepitaxy on Si(001)”, International Journal of Applied Physics and Mathematics, Vol. 4, pp. 108–112, 2014.

Ball and stick structural representations of (a) Er–Si–Er, (b) O–Si–O, and (c) Er–Si–O bonding environments on Er2O3/Si interfaces considered in this study. The dashed line is the interface. The atoms are represented by spheres: Er (green, large), O (red, small), and Si (yellow, medium).

 

12.  Cheng-Lun Hsin, Hsu-Shen Teng, Hsiang-Yuan Lin, Tzu-Hsuan Cheng, Chao- Chia Cheng, and Po-Liang Liu, ”Electronic structure and infrared light emission in dislocation-engineered silicon”, IEEE Transactions on Nanotechnology, Vol. 14, pp. 399-403, 2015.

Top panel: schematic illustration of the twist–bonded interfacial concept for Si (gold spheres) alloys. The Stwist slab has been rotated via the twist slab angle θ with respect to the Sfixed slab. Bottom panel: HOMO and LUMO slab isosurfaces of Models 1 and 2 arranged by energy and denoted by the shade of blue.

 

 

13.  Kuo-Cheng Liao, Yu-Hsien Wang, Po-Liang Liu*, and Huan-Chen Wang, “Fundamental properties of GaN(0001) films grown directly on Gd2O3(0001) platforms: ab initio structural simulations”, Optical and Quantum Electronics, Vol. 48, pp.198, 2016.

Schematic illustration showing the valence charge density map in a range from 0.04 to 0.62 electrons/A ̊3 in 15 steps (a) obtained from the ab initio interface structure (b) of the lowest energy model. The dashed lines indicate the midpoint positions within each interface. Comparison of the graphiticlike GaN nanofilms derived from the optimized model (c) and graphitic structure (d) which indicates similar microstructures. The atoms are represented by spheres: Ga (brown), N (blue), Gd (green), and O (red). (Color figure online)

 

 

14.  Ray-Hua Horng*, Chiung-Yi Huang, Sin-Liang Ou, Tzu-Kuang Juang, and Po-Liang Liu, “ Epitaxial Growth of ZnGa2O4: A New Deep Ultraviolet Semiconductor Candidate”, Crystal Growth & Design , Vol. 17, pp. 6071-6078, 2017

Bulk energies per unit cell of Ga8O12(2̅01) and Zn8Ga16O32(111) as a function of interplanar spacings. The shade region indicates the tensile region leads to more unfavorable Ga8O12 and more favorable Zn8Ga16O32 structures. The atoms are represented by spheres: Ga (brown, large), Zn (purple, middle), and O (red, small).

 

 

15.  Li-Chung Cheng, Min-Ru Wu, Chiung-Yi Huang, Tzu-Kuang Juang, Po-Liang Liu, and Ray-Hua Horng*, “ Effect of Defects on the Properties of ZnGa2O4 Thin-Film Transistors”, ACS Applied Electronic Materials, Vol. 1, pp. 253-259, 2019

Representative interfaces of the optimized structural ZnGa2O4 grown on (0001) sapphire substrates, corresponding to an (a) in-plane view of model 1, (b) six O−Al bonds in model 1, (c) six Ga−Al bonds in model 2, (d) six Zn−Al bonds in model 3, (e) four Ga−Al and two Zn− Al bonds in model 4, (f) six Ga−O bonds in model 5, (g) six Zn−O bonds in model 6, and (h) three Ga−O and Zn−O bonds in model 7 interfaces indicated by the dashed lines. The atoms are represented by spheres: Zn (purple, medium), Ga (brown, large), O (red, small), and Al (pink, medium).

 

 

16.  Ming-Chun Tseng, Dong-Sing Wuu, Chi-Lu Chen, Hsin-Ying Lee, Cheng-Yu Chien, Po-Liang Liu, and Ray-Hua Horng*, “Characteristics of atomic layer deposition–grown zinc oxide thin film with and without aluminum”, Applied Surface Science, Vol. 491, pp. 535–543, 2019.

Illustration of the ZnO/AZO interface re- sulting in a small lattice mismatch of 0.5% de- termined using relaxed optimized Zn32O32 and Zn30Al2O32 structures. Atoms are represented by spheres: O (red, small), Zn (gray, medium), and Al (pink, large). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)