Research

Overview of research

I am a theoretical/computational condensed matter physicist by training. The general theme of my professional work is fundamental theoretical physics research in areas of high practical interest and relevance to experiments. My research specialization is in the simulation of classical and quantum-mechanical electronic and thermal transport in low-dimensional nanostructures, such as carbon nanotubes and graphene, using classical and quantum mechanical methods. I am also interested in the development of new simulation methods as well as the general theory of nanoscale energy and charge transport. More recently, I have developed a keen interest in the phenomenon of wave scattering in random media and from irregular boundaries.

Potential research collaboration opportunities and ideas

In recent years, I developed a frequency-domain technique for the direct and efficient calculation of mode-resolved phonon transmission/reflection coefficients and scattering amplitudes based on the Atomistic Green’s Function (AGF) method (see https://aip.scitation.org/doi/abs/10.1063/1.5048234 and https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.195301). This technique has proved to be very useful for  understanding phonon scattering in different systems, such as the reflection of phonons by rough edges and the transmission/reflection of phonons at grain boundaries.  

Given the potential and versatility of this AGF-based numerical techniques that I developed for the calculation of scattering amplitudes, I am interested in generalizing and extending it to elastodynamic, photonic, geophysical and acoustic problems. Currently, I am seeking collaborators who are keen on working on wave scattering problems for fundamental scientific or industrially relevant applied research. If this is something that interests you, please get in touch with me via email!

Keywords: phonons; nanoscale themal and charge transport; wave scattering; numerical methods; Atomistic Green’s Function; phononics

I am also open to collaboration in the topics listed in Current research interests and projects and General research interests.

Current research interests and projects

1. Wave scattering in random media and from irregular boundaries

2. Development of an efficient atomistic method for calculating phonon transmission probabilities across interfaces

3. Theory and simulation of phonon transmission in one-dimensional structures with correlated disorder

4. Topological acoustic metamaterials

5. Theory of scattering specularity from rough boundaries

6. Modeling of low-field electron mobility in semiconducting transition metal dichalcogenides such as MoS2 and WS2

General research interests

1. Interfacial thermal and charge transport

2. Thermal conductivity of low-dimensional nanostructures

3. Development of new computational techniques for simulating thermal and charge transport

4. Substrate-limited carrier mobility in 2D crystals (graphene, MoS2)

5. Stochastic processes and methods in transport simulations

6. Electron and phonon transport in low-dimensional nanostructures with disorder

7. Anderson localization and percolation theory

8. Wave scattering theory and simulation methodology

9. Wave specularity in scattering from nonideal boundaries

Significant research achievements

• 2018: Atomistic S-matrix method for phonon transmission and reflection coefficients

• 2016: Formulation of theory of cross-plane substrate-directed heat dissipation for 2D materials (e.g. graphene and MoS2), in very good agreement with experimental data

• 2015: Reformulation of the Atomistic Green's Function (AGF) method for calculating the transmission coefficient of individual phonon modes

• 2014: Observation that the short-range correlated disorder can enhance high-frequency phonon transmission but also degrade low-frequency phonon transport

• 2013: First paper to suggest that the mobility temperature dependence measured in monolayer MoS2 is due charged impurity scattering rather than electron-phonon interaction

• 2012: Demonstration of how graphene plasmon coupling to surface optical phonons in dielectrics leads to the screening of remote phonon scattering

• 2010: Derivation of the Green-Kubo form of the Kapitza conductance for molecular dynamics simulation

Peer-reviewed journal publications

1. H. Khodavirdi, Z.-Y. Ong, and A. Srivastava, "The Atomistic Green’s Function method for acoustic and elastic wave-scattering problems," Int. J. Mech. Sci. 275,  109263 (2024). [Link]

2. Z.-Y. Ong, "Effect of boundary roughness on the attenuation of specular phonon reflection in graphene," Phys. Rev. B 109, 184207 (2024). [Link]

3. Z.-Y. Ong, "Control of wave scattering for robust coherent transmission in a disordered medium," Phys. Rev. A 108, 033523 (2023). [Link]

4. H. Zhou, Z.-Y. Ong, G. Zhang, and Y.-W. Zhang, "Computational predictions of quantum thermal transport across nanoscale interfaces," Nanoscale 14,  9209-9217 (2022). [Link]

5. Z.-Y. Ong, G. Zhang, and Y.-W. Zhang, "The role of flexural coupling in heat dissipation from a two-dimensional layered material to its hexagonal boron nitride substrate,"  2D Mater. 8, 035032 (2021). [Link]

6. Z.-Y. Ong, "Specular transmission and diffuse reflection in phonon scattering at grain boundary," Europhysics Letters 133, 66002 (2021). [Link]

7. C. K. Gan and Z.-Y. Ong, "Complementary local-global approach for phonon mode connectivities," J. Phys. Commun.  5, 015010 (2021). [Link]

8. Z.-Y. Ong, Y. Cai, G. Zhang, and Y.-W. Zhang, "Theoretical analysis of thermal boundary conductance of MoS2-SiO2 and WS2-SiO2 interface," Nanotechnology 32, 135402 (2021). [Link]

9. Z.-Y. Ong, G. Zhang, Y.-W. Zhang, and Linyou Cao, "Gate-tunable cross-plane heat dissipation in single-layer transition metal dichalcogenides," Phys. Rev. Research 2, 033470 (2020). [Link]

10. Z.-Y. Ong, G. Schusteritsch, and C. J. Pickard, "Structure-specific mode-resolved phonon coherence and specularity at graphene grain boundaries," Phys. Rev. B 101, 195410 (2020). [Link]

11. Z.-Y. Ong and M.-H. Bae, "Energy dissipation in van der Waals two-dimensional devices," 2D Mater. 6, 3 (2019). [Link]

12. M. Lawson, I. Williamson, Z.-Y. Ong, and L. Li, "First-principles analysis of structural stability, electronic and phonon transport properties of lateral MoS2-WX2 heterostructures," Computational Condensed Matter 19, e00389 (2019). [Link]

13. Z.-Y. Ong, "Atomistic S-matrix method for numerical simulation of phonon reflection, transmission and boundary scattering," Phys. Rev. B 98, 195301 (2018). [Link]

14. Z.-Y. Ong, "Tutorial: Concepts and numerical techniques for modeling individual phonon transmission at interfaces," J. Appl. Phys. 124, 151101 (2018). [Link]

15. Z.-Y. Ong, Q. Bo, S. Xu, X. Ruan, and E. Pop, "Flexural resonance mechanism of thermal transport across graphene-SiO2 interfaces," J. Appl. Phys. 123, 115107 (2018). [Link] [PDF]

16. Z. Yu, Z.-Y. Ong, S. Li, J.-B. Xu, G. Zhang, Y.-W. Zhang, Y. Shi, and X. Wang, "Analyzing the carrier mobility in transition-metal dichalcogenide MoS2 field-effect transistors," Adv. Funct. Mater. 27, 1604093 (2017). [Link] [PDF]

17. Z.-Y. Ong, "Thickness-dependent Kapitza resistance in multilayered graphene and other two-dimensional crystals," Phys. Rev. B 95, 155309 (2017). [Link] [PDF]

18. Y. Liu, Z.-Y. Ong, J. Wu, Y. Zhao, K. Watanabe, T. Taniguchi, D. Chi, G. Zhang, J. TL Thong, C.-W. Qiu, and K. Hippalgaonkar, "Thermal conductance of the 2D MoS2/h-BN and graphene/h-BN interfaces," Sci. Rep. 7, 43886 (2017). [Link] [PDF]

19. V. Sorkin, Y. Cai, Z.-Y. Ong, G. Zhang, and Y.-W. Zhang, "Recent advances in the study of phosphorene and its nanostructures," Crit. Rev. Solid State Mater. Sci. 42, 1 (2017). [Link] [PDF]

20. Z.-Y. Ong, Y. Cai, and G. Zhang, "Theory of substrate-directed heat dissipation for single-layer graphene and other two-dimensional crystals," Phys. Rev. B94, 165427 (2016). [Link] [PDF]

21. Z.-Y. Ong and C. H. Lee, "Transport and localization in a topological phononic lattice with correlated disorder," Phys. Rev. B 94, 134203 (2016). [Link] [PDF]

22. Z.-Y. Ong, G. Zhang, and Y.-W. Zhang, "Controlling the thermal conductance of the graphene/h-BN lateral interface with strain and structure engineering," Phys. Rev. B 93, 075406 (2016). [Link] [PDF]

23. Z. Yu, Z.-Y. Ong, Y. Pan, Y. Cui, R. Xin, Y. Shi, B. Wang, Y.-W. Zhang, G. Zhang, and X. Wang, "Realization of room-temperature phonon-limited carrier transport in monolayer MoS2 by dielectric and carrier screening," Adv. Mater. 28, 547 (2016). [Link] [PDF] [Supplement]

24. Y. Cui, R. Xin, Z. Yu, Y. Pan, Z.-Y. Ong, X. Wei, J. Wang, Y. Shi, B. Wang, Y.-W. Zhang, G. Zhang, and X. Wang, "High-performance monolayer WS2 field-effect transistors on high-k dielectrics," Adv. Mater. 27, 5230 (2015). [Link] [PDF] [Supplement]

25. Z.-Y. Ong and G. Zhang, "Efficient approach for modeling phonon transmission probability in nanoscale interfacial thermal transport," Phys. Rev. B 91, 174302 (2015). [Link] [PDF]; Z.-Y. Ong and G. Zhang, "Erratum: Efficient approach for modeling phonon transmission robability in nanoscale interfacial thermal transport," Phys. Rev. B93, 019901(e) (2016). [Link] [PDF]

26. Z.-Y. Ong, G. Zhang, and Y.-W. Zhang, "Anisotropic charged impurity-limited carrier mobility in monolayer phosphorene," J. Appl. Phys. 116, 214505 (2014). [Link] [PDF]

27. Z.-Y. Ong, Y. Cai, G. Zhang, and Y.-W. Zhang, "Strong thermal transport anisotropy and strain modulation in single-layer phosphorene," J. Phys. Chem. C118, 25272 (2014). [Link] [PDF]

28. Z.-Y. Ong and G. Zhang, "Enhancement and reduction of one-dimensional heat conduction with correlated mass disorder," Phys. Rev. B 90, 155459 (2014). [Link] [PDF] [Press release]

29. Z. Yu, Y. Pan, Y. Shen, Z. Wang, Z.-Y. Ong, T. Xu, R. Xin, L. Pan, B. Wang, L. Sun, J. Wang, G. Zhang, Y.-W. Zhang, Y. Shi, and X. Wang, "Towards intrinsic charge transport in monolayer MoS2 by defect and interface engineering," Nature Communications 5, 5290 (2014). [Link] [PDF] [Supplement]

30. Z.-Y. Ong and G. Zhang, "Ballistic heat conduction and mass disorder in one dimension," J. Phys.: Condens. Matter 26, 335402 (2014). [Link] [PDF] [Press release]

31. A.Y. Serov, Z.-Y. Ong, M.V. Fischetti, and E. Pop, "Theoretical analysis of high-field transport in graphene on a substrate," J. Appl. Phys. 116, 034507 (2014). [Link] [PDF]

32. M. V. Fischetti, J. Kim, S. Narayanan, Z.-Y. Ong, C. Sachs, D. K. Ferry, and S. J. Aboud, "Pseudopotential-based studies of electron transport in graphene and graphene nanoribbons," J. Phys.: Condens. Matter 25, 473202 (2013).  [Link] [PDF]

33. Z.-Y. Ong and M.V. Fischetti, "Mobility enhancement and temperature dependence in top-gated single-layer MoS2," Phys. Rev. B 88, 165316 (2013).  [Link] [PDF]

34. Z.-Y. Ong and M.V. Fischetti, "Theory of remote phonon scattering in top-gated single-layer graphene," Phys. Rev. B 88, 045405 (2013). [Link] [PDF]

35. Z.-Y. Ong and M.V. Fischetti, "Top oxide thickness dependence of remote phonon and charged impurity scattering in top-gated graphene," Appl. Phys. Lett.102, 183506 (2013). [Link] [PDF] [Supplement]

36. Z.-Y. Ong, M.V. Fischetti, A.Y. Serov, and E. Pop, "Signatures of dynamic screening in interfacial thermal transport," Phys. Rev. B 87, 195404 (2013). [Link] [PDF]

37. M.-H. Bae, Z. Li, Z. Aksamija, P.N. Martin, F. Xiong, Z.-Y. Ong, I. Knezevic, and E. Pop, "Ballistic to diffusive crossover of heat flow in graphene ribbons," Nature Communications 4, 1734 (2013). [Link] [PDF] [Supplement]

38. A.Y. Serov, Z.-Y. Ong, and E. Pop, "Effect of grain boundaries on thermal transport in graphene," Appl. Phys. Lett. 102, 033104 (2013). [Link] [PDF] [Press release]

39. J.C. Koepke, J.D. Wood, D. Estrada, Z.-Y. Ong, K.T. He, E. Pop, and J.W. Lyding, "Atomic-scale evidence for potential barriers and strong carrier scattering at graphene grain boundaries: a scanning tunneling microscopy study," ACS Nano 7, 75 (2013). [Link] [PDF] [Press release]

40. Z.-Y. Ong and M.V. Fischetti, "Theory of interfacial plasmon-phonon scattering in supported graphene," Phys. Rev. B 86, 165422 (2012). [Link] [PDF]; Z.-Y. Ong and M.V. Fischetti, "Erratum: Theory of interfacial plasmon-phonon scattering in supported graphene," Phys. Rev. B 86, 199904(e) (2012). [Link] [PDF]

41. Z.-Y. Ong and M.V. Fischetti, "Charged impurity scattering in top-gated graphene nanostructures," Phys. Rev. B 86, 121409 (2012). [Link] [PDF]

42. Z.-Y. Ong, E. Pop, and J. Shiomi, "Reduction of phonon lifetimes and thermal conductivity of a carbon nanotube on amorphous silica," Phys. Rev. B 84, 165418 (2011). [Link] [PDF]

43. Z.-Y. Ong and E. Pop, "Effect of substrate modes on thermal transport in supported graphene," Phys. Rev. B 84, 075471 (2011).  [Link] [PDF]

44. M.-H. Bae, Z.-Y. Ong, D. Estrada, and E. Pop, "Imaging, simulation, and electrostatic control of power dissipation in graphene devices," Nano Lett. 10, 4787, (2010).  [Link] [PDF]

45. Z.-Y. Ong and E. Pop, "Frequency and polarization dependence of thermal coupling between carbon nanotubes and SiO2," J. Appl. Phys. 108, 103502 (2010). [Link] [PDF]

46. A. Liao, R. Alizadegan, Z.-Y. Ong, S. Dutta, F. Xiong, K.J. Hsia, and E. Pop, "Thermal dissipation and variability in electrical breakdown of carbon nanotube devices," Phys. Rev. B 82, 205406 (2010). [Link] [PDF]

47. Z.-Y. Ong and E. Pop, "Molecular dynamics simulation of thermal boundary conductance between carbon Nanotubes and SiO2," Phys. Rev. B 81, 155408 (2010).  [Link] [PDF]

48. Z. Wang, I.-S. Chun, X. Li, Z.-Y. Ong, E. Pop, L. Millet, M. Gillete, G. Popescu, "Topography and refractometry of nanostructures using spatial light interference microscopy (SLIM)," Optics Letters 35, 208 (2010). [Link] [PDF]