Silicene, Siloxene, or Silicane? Revealing the Structure and Optical Properties of Silicon Nanosheets Derived from Calcium Disilicide

Journal Article · Tue Nov 12 00:00:00 EST 2019 · Chemistry of Materials

DOI:https://doi.org/10.1021/acs.chemmater.9b04180· OSTI ID:1580708

Ryan, Bradley J.  ^[1]; Hanrahan, Michael P. ^[2]; Wang, Yujie ^[1]; Ramesh, Utkarsh ^[1]; Nyamekye, Charles K. A. ^[2]; Nelson, Rainie D.  ^[1]; Liu, Zhaoyu ^[3]; Huang, Chuankun ^[3]; Whitehead, Bevan ^[4]; Wang, Jigang ^[3]; Roling, Luke T.  ^[1]; Smith, Emily A.  ^[2]; Rossini, Aaron J.  ^[2]; Panthani, Matthew G.  ^[1]

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1. Iowa State Univ., Ames, IA (United States)
2. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)
3. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
4. Ames Lab., Ames, IA (United States)

Si-nanosheets (Si-NSs) have recently attracted considerable attention due to their potential as next-generation materials for electronic, optoelectronic, spintronic, and catalytic applications. Even though monolayer Si-NSs were first synthesized over 150 years ago via topotactic deintercalation of CaSi₂, there is a lack of consensus within the literature regarding the structure and optical properties of this material. Herein, we provide conclusive evidence of the structural and chemical properties of Si-NSs produced by the deintercalation of CaSi₂ with cold (~–30 °C) aqueous HCl and characterize their optical properties. We use a wide range of techniques, including XRD, FTIR, Raman, solid-state NMR, SEM, TEM, EDS, XPS, diffuse reflectance absorbance, steady-state photoluminescence, time-resolved photoluminescence, and thermal decomposition; when they are combined together, these techniques enable unique insight into the structural and optical properties of the Si-NSs. Additionally, we support the experimental findings with density functional theory (DFT) calculations to simulate FTIR, Raman, solid-state NMR, interband electronic transitions, and band structures. We determined that the Si-NSs consist of buckled Si monolayers that are primarily monohydride terminated. We characterize the nanosheet optical properties, finding they have a band gap of ~2.5 eV with direct-like behavior and an estimated quantum yield of ~9%. Given the technological importance of Si, these results are encouraging for a variety of optoelectronic technologies, such as phosphors, light-emitting diodes, and CMOS-compatible photonics. Furthermore, our results provide critical structural and optical properties to help guide the research community in integrating Si-NSs into optoelectronic and quantum devices.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
• Grant/Contract Number: DGE 1744592; FA9550-17-1-0170; 1847370; AC02-07CH11358; CNS 1726447
• OSTI ID: 1580708
• Report Number(s): IS-J-10,121
• Journal Information: Chemistry of Materials, Vol. 32, Issue 2; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE