Kai Xiao

Kai Xiao

Staff Scientist and UT/ORNL Joint Faculty


Dr. Kai Xiao is a senior staff scientist in the Functional Hybrid Nanomaterials Group at Center for Nanophase Materials Sciences, ORNL and a joint faculty at Bredesen Center and Department of Computer Science and Electrical Engineering, University of Tennessee at Knoxville. He received his Ph.D. degree in Physic Chemistry in 2004 from Institute of Chemistry, Chinese Academy of Sciences. Then he worked as a postdoc associate at CNMS and became a staff scientist in 2008. He has published about 120 papers, several patents, and 4 book chapters.

Google Site homepage: https://sites.google.com/site/xiaokaiemm0/homapage

His research focuses on understanding and controlling the synthesis and processing of thin films and nanostructured materials for energy-related devices.

1. Two-dimensional (2D) nanomaterials, including transition metal dichalcogenides, metal monochalcogenides, and graphene.

Rational design and controlled synthesis, characterization, processing and applications of novel 2D layered materials and fundamental investigation of new chemical, optical, electronic and magnetic properties: Synthesis of 2D nanomaterials and their van der Waals heterostructures using CVD, PVD, mechanic exfoliation, and dry transfer methods; Optical, structural, and electrical characterization of 2D nanomaterials; Charge transport study of 2D nanomaterials;

2. Solution-processed organic semiconductors and hybrid perovskites for thin film electronic devices, including field-effect transistors (FETs) and photovoltaics (PVs), spin valves, organic memory, sensors.

Understanding the correlations between the controlled processing, structure, and device performance of solution-processed semiconductor materials (small molecules, conducting polymers, and hybrid perovskites) with the multiscale characterizations such as electron microscopy, neutron/x-ray scattering, and various optical spectroscopy; Processing those materials using various methods, including spin-coating, thermal deposition, spray printing, to form gradient or doped single/multilayer thin films for energy-related electronic devices (OFETs, OPVs, memories, sensors).

3. Inorganic/organic nanoscale electronics.

Understanding the charge transport process and optoelectronic functionality in 1D and 2D nanoscale electronic devices (FETs, photodetectors, memories) of inorganic/organic nanostructures.


2007 The National Top 100 Excellent Ph. D. Thesis Award in China, Ministry of Education
2006 The Top 50 Excellent Ph. D. Thesis Award of the Chinese Academy of Sciences
2004 Outstanding Thesis Award of the 24th Annual Meeting, Chinese Chemical Society


1. DOE-BES Scientific User Facilities Division, Center for Nanophase Materials Sciences

2. Co-PI, DOE-BES Materials Science and Engineering Division, “ Growth Mechanisms and Controlled Synthesis of Nanomaterials.”

3. PI, ORNL-LDRD, 2013-2015, "Synthesis and Characterization of Novel Two-Dimensional Mesoscale Organic Nanomembranes".

4. Co-PI, DOE-EERE, "Novel photon management for thin-film photovoltaics".

5. Co-PI, ORNL-LDRD, "Rational design of deuterated conjugated polymers with controlled spin-polarized electron transport".


Publications: Full publication list available:
Kai Xiao: Google Scholar (https://scholar.google.com/citations?hl=en&user=s1J22jMAAAAJ&view_op=lis...)
website (https://sites.google.com/site/xiaokaiemm0/homapage)

1. X. Li, J. Dong, J. C. Idrobo, A. A. Puretzky, C. M. Rouleau, D. B. Geohegan, F. Ding, K. Xiao, “Edge-controlled Growth and Etching of Two-Dimensional GaSe Monolayers”, J. Am. Chem. Soc. DOI: 10.1021/jacs.6b11076 (2016)
2. Z. Lin, A. McCreary, N. Briggs, S. Subramanian, K. Zhang, Y. Sun, X. Li, N. Borys, H. Yuan, S. Fullerton-Shirey, A. Chernikov, H. Zhao, S. McDonnell, A. Lindenberg, K. Xiao, B. LeRoy, M. Drndić, J. Hwang, J. Park, M. Chhowalla, R. Schaak, A. Javey, M. Hersam, J. Robinson, M. Terrones, “2D Materials Advances: From Large Scale Synthesis and Controlled Heterostructures to Improved Characterization Techniques, Defects and Applications”, 2D Materials, 2DM-101002 (2016).
3. B. Yang, O. E Dyck, W. Ming, M.-H. Du, S. Das, C. M Rouleau, G. Duscher, D. B Geohegan, K. Xiao,* "Observation of Nanoscale Morphological and Structural Degradation in Perovskite Solar Cells by In Situ TEM", ACS Applied Materials & Interfaces, DOI: 10.1021/acsami.6b11341 (2016).
4. X. Li, A. A. Puretzky, X. Sang, S. KC, M. Tian, F. Ceballos, M. Mahjouri-Samani, K. Wang, R. R. Unocic, H. Zhao, G. Duscher, V. R. Cooper, C. M. Rouleau, D. B. Geohegan, K. Xiao*, "Suppression of Defects and Deep Levels Using Isoelectronic Tungsten Substitution in Monolayer MoSe2", Advanced Functional Materials, DOI:10.1002/adfm.201603850 (2016)
5. X. Li, M.-W. Lin, L. Basile, S. M. Hus, A. A. Puretzky, J. Lee, Y.-C. Kuo, L.-Y. Chang, K. Wang, J. C. Idrobo, A.-P. Li, C.-H. Chen, C. M. Rouleau, D. B. Geohegan, K. Xiao*, “Isoelectronic tungsten doping in monolayer MoSe2 for carrier type modulation”, Adv Mater, 28, 8240 (2016).
6. X. Li, M.-W. Lin, J. Lin, B. Huang, A. A. Puretzkya, C. Ma, K. Wang, W. Zhou, S. T. Pantelides, C. Miao, I. Kravchenko, J. Fowlkes, C. M. Rouleaua, D. B. Geohegan, K. Xiao*, “Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy”, Science Advances, 2, E1501882 (2016).
7. B. Yang, J. Keum, O. S. Ovchinnikova, A. Belianinov, S. Chen, M.-H. Du, I.N. Ivanov, C.M. Rouleau, D. B. Geohegan, K. Xiao*, “Deciphering Halogen Competition in Organometallic Halide Perovskite Growth”. J. Am. Chem. Soc. 138, 5028 (2016).
8. B. Yang, M. Mahjouri-Samani, C. M. Rouleau, D. B. Geohegan, K. Xiao*, “Pulsed Laser Deposition of Hierarchical TiO2 for High Performance Perovskite Solar Cells”, Physical Chemistry Chemical Physics, 18, 27067 (2016). PCCP themed issue: Physical chemistry of hybrid perovskite solar cells. (Invited)
9. S. Das, G. Gu, P. C. Joshi, B. Yang, T. Aytug, C. M Rouleau, D. Geohegan, K. Xiao*, “Low Thermal Budget, Photonic-Cured Compact TiO2 Layer for High-Efficiency Perovskite Solar Cells”, J. Mater. Chem. A, 4, 8695 (2016).
10. X. Li, M.-W. Lin, A. A. Puretzkya, L. Basilea, K. Wang, J. C. Idroboa, C. M. Rouleaua, D. B. Geohegan, K. Xiao*, “Persistent photoconductivity in two-dimensional Mo1−x Wx Se2–MoSe2 van der Waals heterojunctions”, J. Mater. Res. 31, 923 (2016). (Invited for Focus Issue on “Two-Dimensional Heterostructure Materials”)
11. M-W. Lin, I. Kravchenko, J. Fowlkes, X. Li, A. Puretzky, C. Rouleau, D. Geohegan, K. Xiao*, "Thickness Dependent Charge Transport in Few-Layer MoS2 Field-Effect Transistors", Nanotechnology, 27, 165203 (2016).
12. M. Lin, H. L Zhuang, J. Yan, T. Z. Ward, A. A Puretzky, C. M Rouleau, Z. Gai, L. Liang, V. Meunier, B. G Sumpter, P. Ganesh, P. RC Kent, D. B Geohegan, D. G Mandrus, K. Xiao*, “Ultrathin nanosheets of CrSiTe3: a semiconducting two-dimensional ferromagnetic material”, Journal of Materials Chemistry C, 4, 315 (2016).
13. W . Zheng, J. Lin, W. Feng, K. Xiao, Y. Qiu, X. Chen, G. Liu, W. Cao, S. T. Pantelides, W. Zhou P Hu, “Patterned Growth of P-Type MoS2 Atomic Layers Using Sol–Gel as Precursor”, Advanced Functional Materials, 26, 6371 (2016).
14. X. Sang, Y. Xie, M.-W. Lin, M. Alhabeb, K. L. Van Aken, Y. Gogotsi, P. R.C. Kent, K. Xiao, R. R. Unocic, “Atomic Defects in Monolayer Titanium Carbide (Ti3C2Tx) Mxene”, ACS Nano, 10, 9193 (2016).
15. M. Mahjouri-Samani, L. Liang, A. D. Oyedele, Y.-S. Kim, M. Tian, N. Cross, K. Wang, M.-W. Lin, A. Boulesbaa, C. M. Rouleau, A. A. Puretzky, K. Xiao, M. Yoon, G. Eres, G. Duscher, B. G. Sumpter, D. B. Geohegan, “Tailoring Vacancies Far Beyond Intrinsic Levels Changes the Carrier Type in Monolayer MoSe2-x Crystals”, Nano Lett., 16, 5213 (2016).
16. K. Wang, B. Huang, M. Tian, F. Ceballos, M.-W. Lin, M. Mahjouri-Samani, A. Boulesbaa, A. A Puretzky, C. M Rouleau, M. Yoon, H. Zhao, K. Xiao, G. Duscher, D. B Geohegan, “Interlayer Coupling in Twisted WSe2/WS2 Bilayer Heterostructures Revealed by Optical Spectroscopy”, ACS Nano, 10, 6612 (2016).
17. M. J. Simpson, B. Doughty, B. Yang, K. Xiao, Y.-Z. Ma, “Separation of Distinct Photoexcitation Species in Femtosecond Transient Absorption Microscopy”, ACS Photonics, 3, 434 (2016).
18. M. J. Simpson, B. Doughty, B. Yang, K. Xiao, Y.-Z. Ma, “Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy”, The journal of physical chemistry letters, 7, 1725 (2016).
19. B. Doughty, M. J. Simpson, B. Yang, K. Xiao, Y.-Z. Ma, “Simplification of femtosecond transient absorption microscopy data from CH3NH3PbI3 perovskite thin films into decay associated amplitude maps”, Nanotchnology, 27, 114002 (2016).
20. A. A. Puretzky, L. Liang, X. Li, K. Xiao, B. G. Sumpter, V. Meunier, D. B. Geohegan, “Twisted MoSe2 Bilayers with Variable Local Stacking and Interlayer Coupling Revealed by Low-Frequency Raman Spectroscopy”, ACS Nano, 10, 2736–2744 (2016).
21. N. Herath, S. Das, J. Zhu, R. Kumar, J. Chen, K. Xiao, G. Gu, J. F Browning, B. G Sumpter, I. N Ivanov, V. Lauter, “Unraveling the Fundamental Mechanisms of Solvent Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices”, ACS Applied Materials & Interfaces, 8, 20220 (2016).
22. V. Iberi, L. Liang, A. V Ievlev, M. G Stanford, M.-W. Lin, X. Li, M. Mahjouri-Samani, S. Jesse, B. G Sumpter, S. V Kalinin, D. C Joy, K. Xiao, A. Belianinov, O. S. Ovchinnikova, “Nanoforging Single Layer MoSe2 Through Defect Engineering with Focused Helium Ion Beams”, Scientific Report, 6, 30481 (2016).


“Patterned Two-Dimensional Heterocrystals”, D. B. Geohegan, M-W. Lin, M. Mahjouri-Samani, A. Puretzky, C. M. Rouleau, K. Wang, K. Xiao, 201503565, DOE S-138,201.

Facilities Used

Center for Nanophase Materials Sciences (CNMS) http://cnms.ornl.gov

User Facility