In-situ quantification of the surface roughness for facile fabrications of atomically smooth thin films
),
Xiaofang Zhai1,2(
)
Download citation
552
Views
34
Downloads
8
Crossref
7
WoS
4
Scopus
0
CSCD
This work presents an in-situ technique to quantify the layer-by-layer roughness of thin films and heterostructures by measuring the spectral profile of the reflection high-energy electron diffraction (RHEED). The characteristic features of the diffraction spot, including the vertical to lateral size ratio c/b and the asymmetrical ratio c1/c2 along the vertical direction, are found to be quantitatively dependent on the surface roughness. The quantitative relationships between them are established and discussed for different incident angles of high-energy electrons. As an example, the surface roughnesses of LaCoO3 films grown at different temperatures are obtained using such an in-situ technique, which are confirmed by the ex-situ atomic force microscopy. Moreover, the in-situ measured layer-by-layer roughness oscillations of two LaCoO3 films are demonstrated, revealing drastically different information from the intensity oscillations. The experiments assisted with the in-situ technique demonstrate an outstanding high resolution down to ~ 0.1 Å. Therefore, the new quantitative RHEED technique with real-time feedbacks significantly escalates the thin film synthesis efficiency, especially for achieving atomically smooth surfaces and interfaces. It opens up new prospects for future generations of thin film growth, such as the artificial intelligence-assisted thin film growth.
menu
In-situ quantification of the surface roughness for facile fabrications of atomically smooth thin films
), Xiaofang Zhai1,2(
)
Abstract
This work presents an in-situ technique to quantify the layer-by-layer roughness of thin films and heterostructures by measuring the spectral profile of the reflection high-energy electron diffraction (RHEED). The characteristic features of the diffraction spot, including the vertical to lateral size ratio c/b and the asymmetrical ratio c1/c2 along the vertical direction, are found to be quantitatively dependent on the surface roughness. The quantitative relationships between them are established and discussed for different incident angles of high-energy electrons. As an example, the surface roughnesses of LaCoO3 films grown at different temperatures are obtained using such an in-situ technique, which are confirmed by the ex-situ atomic force microscopy. Moreover, the in-situ measured layer-by-layer roughness oscillations of two LaCoO3 films are demonstrated, revealing drastically different information from the intensity oscillations. The experiments assisted with the in-situ technique demonstrate an outstanding high resolution down to ~ 0.1 Å. Therefore, the new quantitative RHEED technique with real-time feedbacks significantly escalates the thin film synthesis efficiency, especially for achieving atomically smooth surfaces and interfaces. It opens up new prospects for future generations of thin film growth, such as the artificial intelligence-assisted thin film growth.
References(32)
Xiang, X. D.; Sun, X. D.; Briceño, G.; Lou, Y. L.; Wang, K. A; Chang, H.; Wallace-Freedman, W. G.; Chen, S. W; Schultz, P. G. A combinatorial approach to materials discovery. Science 1995, 268, 1738–1740.
He, G.; Wei, Z. X.; Feng, Z. P.; Yu, X. D.; Zhu, B. Y.; Liu, L.; Jin, K.; Yuan, J.; Huan, Q. Combinatorial laser molecular beam epitaxy system integrated with specialized low-temperature scanning tunneling microscopy. Rev. Sci. Instrum. 2020, 91, 013904.
Meng, Z.; Yang, Q.; Yip, P. C.; Eyink, K. G.; Taferner, W. T.; Igelnik, B. Combined use of computational intelligence and materials data for on-line monitoring and control of MBE experiments. Eng. Appl. Artif. Intell. 1998, 11, 587–595.
Provence, S. R.; Thapa, S.; Paudel, R.; Truttmann, T. K.; Prakash, A.; Jalan, B.; Comes, R. B. Machine learning analysis of perovskite oxides grown by molecular beam epitaxy. Phys. Rev. Mater. 2020, 4, 083807.
Vasudevan, R. K.; Tselev, A.; Baddorf, A. P.; Kalinin, S. V. Big-data reflection high energy electron diffraction analysis for understanding epitaxial film growth processes. ACS Nano 2014, 8, 10899–10908.
Martin, L. W.; Chu, Y. H.; Ramesh, R. Advances in the growth and characterization of magnetic, ferroelectric, and multiferroic oxide thin films. Mater. Sci. Eng. R Rep. 2010, 68, 89–133.
Hwang, H. Y.; Iwasa, Y.; Kawasaki, M.; Keimer, B.; Nagaosa, N.; Tokura, Y. Emergent phenomena at oxide interfaces. Nat. Mater. 2012, 11, 103–113.
Ge, J. F.; Liu, Z. L.; Liu, C. H.; Gao, C. L.; Qian, D.; Xue, Q. K.; Liu, Y.; Jia, J. F. Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3. Nat. Mater. 2015, 14, 285–289.
Lee, H.; Campbell, N.; Lee, J.; Asel, T. J.; Paudel, T. R.; Zhou, H.; Lee, J. W.; Noesges, B.; Seo, J.; Park, B. et al. Direct observation of a two-dimensional hole gas at oxide interfaces. Nat. Mater. 2018, 17, 231–236.
Fert, A. Nobel Lecture: Origin, development, and future of spintronics. Rev. Mod. Phys. 2008, 80, 1517.
Chambers, S. A.; Engelhard, M. H.; Shutthanandan, V.; Zhu, Z.; Droubay, T. C.; Qiao, L.; Sushko, P. V.; Feng, T.; Lee, H. D.; Gustafsson, T. et al. Instability, intermixing and electronic structure at the epitaxial LaAlO3/SrTiO3(001) heterojunction. Surf. Sci. Rep. 2010, 65, 317– 352.
Xie, Y. W.; Hikita, Y.; Bell, C.; Hwang, H. Y. Control of electronic conduction at an oxide heterointerface using surface polar adsorbates. Nat. Commun. 2011, 2, 494.
Dai, W. T.; Adhikari, S.; Garcia-Castro, A. C.; Romero, A. H.; Lee, H.; Lee, J. W.; Ryu, S.; Eom, C. B.; Cen, C. Tailoring LaAlO3/SrTiO3 interface metallicity by oxygen surface adsorbates. Nano Lett. 2016, 16, 2739–2743.
Benia, H. M.; Lin, C. T.; Kern, K.; Ast, C. R. Reactive chemical doping of the Bi2Se3 topological insulator. Phys. Rev. Lett. 2011, 107, 177602.
van den Broek, B.; Houssa, M.; Lu, A.; Pourtois, G.; Afanas'ev, V.; Stesmans, A. Silicene nanoribbons on transition metal dichalcogenide substrates: Effects on electronic structure and ballistic transport. Nano Res. 2016, 9, 3394–3406.
Sun, X. D.; Li, W. Y.; Wang, X.; Sui, Qi.; Zhang, T. Y.; Wang, Z.; Liu, L.; Li, D.; Feng, S.; Zhong, S. Y. et al. Room temperature ferromagnetism in ultra-thin van der Waals crystals of 1T-CrTe2. Nano Res. 2020, 13, 3358–3363.
Sauvage-Simkin, M.; Pinchaux, R.; Massies, J.; Claverie, P.; Bonnet, J.; Jedrecy, N.; Robinson, I. K. Structure of in-situ grown GaAs(001) reconstructed surfaces by grazing incidence X-ray diffraction. Surf. Sci. 1989, 211–212, 39–47.
Slobodskyy, T.; Schroth, P.; Grigoriev, D.; Minkevich, A. A.; Hu, D. Z.; Schaadt, D. M.; Baumbach, T. A portable molecular beam epitaxy system for in situ x-ray investigations at synchrotron beamlines. Rev. Sci. Instrum. 2012, 83, 105112.
McKee, R. A.; Walker, F. J.; Conner, J. R.; Specht, E. D. Molecular beam epitaxy growth of epitaxial barium silicide, barium oxide, and barium titanate on silicon. Appl. Phys. Lett. 1991, 59, 782–784.
Gruenewald, J. H.; Nichols, J.; Seo, S. S. A. Pulsed laser deposition with simultaneous in situ real-time monitoring of optical spectroscopic ellipsometry and reflection high-energy electron diffraction. Rev. Sci. Instrum. 2013, 84, 043902.
Lippmaa, M.; Nakagawa, N.; Kawasaki, M.; Ohashi, S.; Koinuma, H. Growth mode mapping of SrTiO3 epitaxy. Appl. Phys. Lett. 2000, 76, 2439–2441.
Sun, H. Y.; Mao, Z. W.; Zhang, T. W.; Han, L.; Zhang, T. T.; Cai, X. B.; Guo, X.; Li, Y. F.; Zang, Y. P.; Guo, W. et al. Chemically specific termination control of oxide interfaces via layer-by-layer mean inner potential engineering. Nat. Commun. 2018, 9, 2965.
Iakoubovskii, K.; Mitsuishi, K.; Nakayama, Y.; Furuya, K. Mean free path of inelastic electron scattering in elemental solids and oxides using transmission electron microscopy: Atomic number dependent oscillatory behavior. Phys. Rev. B 2008, 77, 104102.
Iakoubovskii, K.; Mitsuishi, K. Elastic scattering of 200 keV electrons in elemental solids: experimental observation of atomic-number- dependent oscillatory behavior. J. Phys. Condens. Matter. 2009, 21, 155402.
Mayol, R.; Salvat, F. Total and transport cross sections for elastic scattering of electrons by atoms. Atom. Data Nucl. Data Tables 1997, 65, 55–154.
Robinson, I. K.; Tweet, D. J. Surface X-ray diffraction. Rep. Prog. Phys. 1992, 55, 599–651.
Lent, C. S.; Cohen, P. I. Diffraction from stepped surfaces: I. Reversible surfaces. Surf. Sci. 1984, 139, 121–154.
Korte, U., Maksym, P. A. Role of the step density in reflection high- energy electron diffraction: questioning the step density model. Phys. Rev. Lett. 1997, 78, 2381–2384.
Sullivan, M. C.; Ward, M. J.; Gutiérrez-Llorente, A.; Adler, E. R.; Joress, H.; Woll, A.; Brock, J. D. Complex oxide growth using simultaneous in situ reflection high-energy electron diffraction and x-ray reflectivity: When is one layer complete? Appl. Phys. Lett. 2015, 106, 031604.
Publication history
Copyright
Acknowledgements
The work was supported by the National Science Foundation of China (No. 52072244), the ShanghaiTech Startup Fund, and the Fundamental Research Funds for the Central Universities (No. WK2340000088).
FEEDBACK 
TOP