Dr. Yong Zhang

Y_Zhang_JNN Dr. Yong Zhang's research interests include (1) Electronic, optical and related properties of “semiconducting” materials (including III-V, II-VI, artificially or spontaneously ordered quantum structures, nano-materials, inorganic-organic hybrid crystalline materials, transition metal oxides, rare-earth chalcogenides, and these materials with dopants and/or defects), (2) Correlation between the material architecture and the material properties, (3) Optoelectronic applications of the materials of interest (e.g., solar cell, solid state lighting, thermoelectrics), and (4) Interdisciplinary areas (e.g., negative refraction or bending of light and ballistic electron beam, zero-thermal expansion, multi-metallic catalysts). He believes that various experimental and theoretical approaches should be applied as needed for any given problem. He is an expert in both optical spectroscopy (e.g., CW and time-resolved photoluminescence, pump-probe measurement, Raman) and electronic structure computation (e.g., density-functional theory, empirical pseudopotential, k.p perturbation theory), and applies a number of other techniques through collaboration in his research projects (e.g., synchrotron, high-magnetic field, high resolution TEM). He joined the ECE Dept of UNCC in April, 2009 as a Bissell Distinguished Professor of Engineering. He is also a member of the Center for Optoelectronics and Optical Communications at UNCC. Prior to that, he was a Senior Scientist with the Materials and Computational Science Center at NREL.

Education

1994 Ph.D., Solid State Physics, Dept. of Phys., Dartmouth College (with Prof. M. D. Sturge)

1985 M.S., Semiconductor Physics, Dept. of Physics, Xiamen University, China

1982 B.S., Physics, Dept. of Physics, Xiamen University, China

Professional Experience

4/2009 – Bissell Distinguished Professor of Engineering, Department of Electrical and Computer Engineering, The University of North Carolina at Charlotte (UNCC)

1997–2009 Senior Scientist (I, II), Basic Sciences Center/Materials and Computational Science Center, National Renewable Energy Laboratory (NREL)

1994–1997 Postdoctoral Researcher, Basic Sciences Center, NREL

1989–1990 Visiting Researcher, Physics Dept., Dartmouth College

1987–1989 Research Assistant, Physics Dept. Xiamen University, China

1985–1987 Engineer, Xiamen United Development Co., Ltd (XUDC), Xiamen, China

Selected Recent Publications (see more)

1. Y. Zhang, C.-S. Jiang, D. J. Friedman, J. F. Geisz, and A. Mascarenhas, Tailoring the electronic properties of Ga_xIn_1-xP beyond simply varying alloy composition, Appl. Phys. Lett. 94, 091113 (2009).

2. Y. Zhang, S.-H. Lee, A. Mascarenhas, and S. K. Deb, UV photochromic memory effect in proton-based WO₃ electrochromic devices, Appl. Phys. Lett. 93, 203508 (2008).

3. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Interplay of alloying and ordering on the electronic structure of Ga_xIn_1-xP alloys, Phys. Reb. B 78, 235202 (2008).

4. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Non-Bloch nature of alloy states in a conventional semiconductor alloy: Ga_xIn_1-xP as an example, Phys. Rev. Lett. 101, 036403 (2008).

5. K. Wang, J.-J. Chen, W.-L. Zhou, Y. Zhang, Y.-F. Yan, J. Pern, and A. Mascarenhas, Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications, Adv. Mat. 20, 3248 (2008).

6. A. Franceschetti and Y. Zhang, Multiexciton absorption and multiple exciton generation in CdSe quantum Dots, Phys. Rev. Lett. 100, 136805 (2008).

7. Y. Zhang, Z. Islam, Y. Ren, P. Parilla, S. P. Ahrenkiel, P. L. Lee, A. Mascarenhas,M. J. McNevin, I. Naumov, H.-X. Fu, X.-Y. Huang, and J. Li, Zero thermal expansion in a nanostructured inorganic-organic hybrid crystal, Phys. Rev. Lett. 99, 215901 (2007).

8. Y. Zhang, L.-W. Wang, and A. Mascarenhas, “Quantum coaxial cables” for solar energy harvesting, Nano. Lett. 7, 1264 (2007).

9. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Systematic approach to distinguishing a perturbed host state from an impurity state in a supercell calculation for a doped semiconductor: using GaP:N as an example, Phys. Rev. B (Rapid Commun.) 74, 41201(R) (2006).

10. C.-Y. Moon, G. M. Dalpian, Y. Zhang, S.-H. Wei, X.-Y. Huang, and J. Li, Study of phase selectivity of organic-inorganic hybrid semiconductors, Chem. Mater. 18, 2805 (2006).

11. Y. Zhang, G. M. Dalpian, B. Fluegel, S.-H Wei, A. Mascarenhas, X.-Y. Huang, J. Li, and L.-W. Wang, Novel approach to tuning physical properties of organic-inorganic hybrid semiconductors, Phys. Rev. Lett. 96, 026405(2006).

12. Fluegel, Y. Zhang, J. F. Geisz, and A. Mascarenhas, Confirmation of the impurity-band model for GaP_1-xN_x, Phys. Rev. B 72, 073203 (2005).

13. Y. Zhang, A. Mascarenhas, and L.W. Wang, III-V-Bi versus III-V-N: similar and dissimilar aspects, Phys. Rev. B 71, 155201 (2005).

14. S. Smith, Y. Zhang, A. Mascarenhas, and M. Hanna, Effect of localization on excitonic linewidth in partially-ordered GaInP₂, Phys. Rev. B 70, 235301 (2004).

15. Fluegel, Y. Zhang, A. Mascarenhas, X. Huang, and J. Li, Electronic properties of hybrid organic-inorganic semiconductors, Phys. Rev. B 70, 205308 (2004).

16. Y. Zhang, B. Fluegel, and A. Mascarenhas, Total and negative refraction in real crystals for ballistic electrons and light, Phys. Rev. Lett. 91, 157404 (2003).

17. J. H. Li, S. C. Moss, Y. Zhang, A. Mascarenhas, L. N. Pfeiffer, K. W. West, W. K. Ge, and J. Bai, Layer ordering and faulting in (GaAs)_n/(AlAs)_n ultra-short-period superlattices, Phys. Rev. Lett. 91, 106103 (2003).

18. Y. Zhang, B. Fluegel, M. C. Hanna, A. Mascarenhas, L.-W. Wang, Y. J. Wang, and X. Wei, Impurity perturbation to the host band structure and recoil of the impurity state, Phys. Rev. B 68, 75210 (2003).

19. X.-Y. Huang, J. Li, Y. Zhang, and A. Mascarenhas, From 1D Chain to 3D Network: Syntheses, Structures, and Optical Properties of Novel Hybrid II-VI Nanocomposites, J. Am. Chem. Soc. 125, 7049 (2003).

20. Zh. Karazhanov, Y. Zhang, L.-W. Wang, A. Mascarenhas, and S. Deb, Resonant defect states and strong lattice relaxation of oxygen vacancies in WO₃, Phys. Rev. B 68, 233204 (2003).

21. Y.J. Wang, X. Wei, Y. Zhang, A. Mascarenhas, H. P. Xin, Y. G. Hong, and C. W. Tu, Evolution of the electron localization in a non-conventional alloy system GaAs_1-xN_x probed by high magnetic field photoluminescence, Appl. Phys. Lett. 82, 4453 (2003).

22. B. Fluegel, S. Smith, Y. Zhang, A. Mascarenhas, J. F. Geisz, and J. M. Olson, Resonant excitation study of ultrasharp emission lines in ordered Ga_xIn_1-xP, Phys. Rev. B 115320 (2002).

23. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Band alignment between GaAs and partially ordered GaInP, Appl. Phys. Lett. 80, 3111 (2002).

24. A. Mascarenhas, Y. Zhang, J. Verley, and M. J. Seong, Overcoming limitations in semiconductor alloy design, Superlattices and microstructures 29, 395 (2001).

25. Y. Zhang and A. Mascarenhas, Effects of the orientational superlattice on the electronic and vibrational properties of CuPt ordered GaInP alloys, J. Raman Spectrosc. 32, 831 (2001).

26. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Statistical aspects of electronic and structural properties in partially ordered semiconductor alloys, Phys. Rev. B 64, 125207 (2001).

27. Y. Zhang, A. Mascarenhas, and L.-W. Wang, Dependence of the band structure on the order parameter for partially ordered Ga_xIn_1-xP alloy, Phys. Rev. B (Rapid Commun.) 63, R201312 (2001).

28. Y. Zhang, A. Mascarenhas, H. P. Xin, and C. W. Tu, Scaling Of Band Gap Reduction In Heavily Nitrogen Doped GaAs, Phys. Rev. B (Rapid Commun.) 63, 161303 (R) (2001).

29. Y. Zhang, A. Mascarenhas, J. F. Geisz, H. P. Xin, and C. W. Tu, Discrete and continuous spectrum of nitrogen induced bound states in heavily doped GaAs:N, Phys. Rev. B 63, 85205 (2001).

30. S. Francoeur, Y. Zhang, A. G. Norman, F. Alsina, A. Mascarenhas, J. L. Reno, E. D. Jones, S. R. Lee, and D. M. Follstaedt, Optical properties of spontaneous lateral composition modulation in AlAs/InAs short-period superlattices, Appl. Phys. Lett. 77, 1765 (2000).

31. Y. Zhang, B. Fluegel, A. Mascarenhas, H. P. Xin, and C. W. Tu, Optical transitions in isoelectronically doped semiconductor GaP:N: an evolution from isolated centers, pairs, clusters to an impurity band, Phys. Rev. B 62, 4493 (2000).

32. Y. Zhang and A. Mascarenhas, Isoelectronic impurity states in GaAs:N, Phys. Rev. B 61, 15562 (2000).

33. H. M. Cheong, Y. Zhang, A. Mascarenhas, and J. F. Geisz, Observation of nitrogen-induced levels in GaAs_1-xN_x using resonant Raman studies, Phys. Rev. B 61, 13687 (2000).

34. M. Kozhevnikov, V. Narayanamurti, C. V. Reddy, H. P. Xin, C. W. Tu, A. Mascarenhas, and Y. Zhang, Evolution of GaAs_1-xN_x conduction states and giant Au/GaAs_1-xN_x Schottky barrier reduction studied by ballistic electron emission microscopy, Phys. Rev. B (Rapid Commun.) 61, R7861 (2000).

35. H. P. Xin, C. W. Tu, Y. Zhang, and A. Mascarenhas, Effects of nitrogen on the band structure of GaN_xP_1-x alloys, Appl. Phys. Lett. 76, 1267 (2000).

36. Y. Zhang, A. Mascarenhas, S. Smith, J. F. Geisz, J.M. Olson, and M. Hanna, Effects of spontaneous ordering and alloy statistical fluctuations on exciton linewidth in Ga_xIn_1-xP alloys, Phys. Rev. B 61, 9910 (2000).

37. Y. Zhang, A. Mascarenhas, H. P. Xin, and C. W. Tu, Formation of an impurity band and its quantum confinement in heavily doped GaAs:N, Phys. Rev. B 61, 7479 (2000).

38. Y. Zhang, A. Mascarenhas, H. P. Xin, and C. W. Tu, Valence-band splitting and shear deformation potential of dilute GaAs_1-xN_x alloys, Phys. Rev. B 61, 4433 (2000).

39. M. Kozhevnikov and V. Narayanamurti, A. Mascarenhas, Y. Zhang, and J. M. Olson, Ordering-induced band structure effects in GaInP₂ studied by ballistic electron emission microscopy, Appl. Phys. Lett. 75, 1128 (1999).

40. H.M. Cheong, Y. Zhang, A. Norman, J. D. Perkins, A. Mascarenhas, K.Y. Cheng, and K.C. Hsieh, Resonant Raman scattering studies of composition-modulated GaP/InP short-period superlattices, Phys. Rev. B 60, 4883 (1999).

41. B. Fluegel, Y. Zhang, A. Mascarenhas, J. F. Geisz, J. M. Olson, and A. Duda, Crystal anisotropy and spin-polarized photoluminescence of ordered Ga_xIn_1-xP, Phys. Rev. B 60, R11261 (1999).

42. J. D. Perkins, A. Mascarenhas, Y. Zhang, J. F. Geisz, D. J. Friedman, J. M. Olson, and S. R. Kurtz, Nitrogen-activated transitions, level repulsion, and band gap reduction in GaAs_1-xN_x with x < 0.03, Phys. Rev. Lett. 82, 3312 (1999).

43. Y. Zhang and A. Mascarenhas, Scaling of Exciton binding energy and Virial theorem in semiconductor quantum wells and wires, Phys. Rev. B 59, 2040 (1999).

Invited review papers and book chapters:

L. C. Lew Yan Voon, Y. Zhang, B. Lassen, M. Willatzen, Q. Xiong, and P. C. Eklund, Electronic Properties of Semiconductor Nanowires, J. Nanoscience and Nanotechnology 8, 1 (2007).
Y. Zhang and A. Mascarenhas, Negative Refraction of Electromagnetic and Electronic Waves in Uniform Media, in Physics of Negative Refractive and Negative Index Materials, ed. By C. M. Krowne and Y. Zhang (Springer, 2007), p.1.
Y. Zhang and A. Mascarenhas, Total and negative refraction of electromagnetic waves, Modern Physics Letters B 19, 21 (2005).
A. Mascarenhas and Y. Zhang, The physics of tunable disorder in semiconductor alloys, in Spontaneous Ordering in Semiconductor Alloys, ed. by A. Mascarenhas (Kluwer Academic/Plenum Publishers, New York, 2002), p. 283.
A. Mascarenhas and Y. Zhang, Dilute nitride based III-V alloys for laser and solar cell applications, Current Opinions Solid State Mater. Sci. 5, 253 (2001).
Y. Zhang and W.-K. Ge, Behavior of Nitrogen Impurities in III-V Semiconductors, J. Lumin. 85, 247 (2000).