11111111111111111111111111111111111111111111111111111111111111111111111111 (12) United States Patent (lo) Patent No.: US 8,808,658 B2 Kaner et al. (45) Date of Patent: Aug. 19, 2014 (54) RAPID SOLID-STATE METATHESIS ROUTES FOREIGN PATENT DOCUMENTS TO NANOSTRUCTURED SILICON-GERMAINUM WO W02008/034578 3/2008 WO W02008034578 Al * 3/2008 (75) Inventors: Richard B. Kaner, Pacific Palisades, CA (US); Sabah K. Bux, Chino Hills, OTHER PUBLICATIONS CA (US); Jean-Pierre Fleurial, Altadena, CA (US); Marc Rodriguez, Bux et al., "Rapid Solid State Synthesis of Nano structured Silicon," Granada Hills, CA (US) Chem. Mater., 2010, 22, 2534-2540. Published online Mar. 16, (73) Assignees: California Institute of Technology, 2010.* Pasadena, CA (US); The Regents of the Gillan et al., "Synthesis of Refractory Ceramics via Rapid Metathesis University of California, Oakland, CA Reactions between Solid-State Precursors," Chem Mater. 1996, 8, (US) 333-343.* Yang et al., "Synthesis of Alkyl-Terminated Silicon Nanoclusters by Notice: Subject to any disclaimer, the term of this a Solution Route," J. Am. Chem. Soc., 1999, 121, 5191-5195.* patent is extended or adjusted under 35 Liu et al., "A new synthetic routhe for the synthesis of hydrogen U.S.C. 154(b) by 117 days. terminated silicon nanoparticles," Materials Science and Engineer- (21) Appl. No.: 13/155,853 ing B96 (2002) 72-75.* Hick, et al., "Mechanochemical Synthesis ofAlkaline Earth Carbides (22) Filed: Jun. 8, 2011 and Intercalation Compounds," Inorg Chem., vol. 48, pp. 2333-2338 (65) Prior Publication Data (2009). US 2011/0318250 Al Dec. 29, 2011 (Continued) Related U.S. Application Data (60) Provisional application No. 61/352,499, filed on Jun. Primary Examiner Anthony J Zimmer 8, 2010. (74) Attorney, Agent, or Firm One LLP (51) Int. Cl. C01B 33102 (2006.01) (57) ABSTRACT C01B 211068 (2006.01) Methods for producing nanostructured silicon and silicon- C01B 33106 (2006.01) germanium via solid state metathesis (SSM). The method of C22C29100 (2006.01) forming nanostructured silicon comprises the steps of com- C22C35100 (2006.01) bining a stoichiometic mixture of silicon tetraiodide (SiI 4) (52) U.S. Cl. and an alkaline earth metal silicide into a homogeneous pow- USPC ............................ 423/349; 423/344; 420/578 der, and imitating the reaction between the silicon tetraiodide (58) Field of Classification Search (SiI4) with the alkaline earth metal silicide. The method of USPC ........................... 423/344, 349, 350; 420/578 forming nanostructured silicon-germanium comprises the See application file for complete search history. steps of combining a stoichiometric mixture of silicon tet- raiodide (SiI4) and a germanium based precursor into a homo- (56) References Cited geneous powder, and initiating the reaction between the sili- U.S. PATENT DOCUMENTS con tetraiodide (SiI 4) with the germanium based precursors. 2008/0023070 Al * 1/2008 Sinha ............................ 136/261 2012/0138843 Al 6/2012 Fleurial et al. 29 Claims, 10 Drawing Sheets US 8,808,658 B2 Page 2 (56) References Cited Werwa et al., Synthesis and processing of silicon nanocrystallites using a pulsed laser ablation supersonic expansion method, Appl. OTHER PUBLICATIONS Phys. Lett. 1994, 64(14), 1821-1823. Xu et al., Self-organized vertically aligned single-crystal silicon Boukai, et al., Silicon nanowires as efficient thermoelectric materi- nanostructures with controlled shape and aspect ratio by reactive als, Nature 2008, 451(7175), 168-171. plasma etching, Appl. Phys. Lett. 2009, 95(11) 111505-3. Bux et al., Nanostructured Bulk Silicon as an Effective Thermoelec- tric Material, Adv. Funct. Mater., 2009, 19(15), 2445-2452. Zhang et al, Synthesis of Ordered Single Crystal Silicon Nanowire Flochbaum et al., Enhanced thermoelectric performance of rough Arrays, Adv. Mater. 2001, 13(16), 1238-1241. silicon nanowires, Nature 2008, 451(7175) 163-167. U.S. Appl. No. 13/156,033, Ex-Parte Quayle, Office Action, Mar. 6, Neiner, et al., Low-Temperature Solution Route to Macroscopic 2013. Amounts of Hydrogen Terminated Silicon Nanoparticles, J. Am. Chem. Soc. 2006, 128, 11016-11017. * cited by examiner U.S. Patent Aug. 19, 2014 Sheet 1 of 10 US 8,808,658 B2 ISN31NI U.S. Patent Aug. 19, 2014 Sheet 2 of 10 US 8,808,658 B2 U.S. Patent Aug. 19, 2014 Sheet 3 of 10 US 8,808,658 B2 LL U.S. Patent Aug. 19, 2014 Sheet 4 of 10 US 8,808,658 B2 TE PERA M TURE ( K) Cq # E E @ @ k E @ # # F E I k # @ E E E I @ E @ E F m m m m ,.,.. - - k ~ # @ @ k 1 F # @ k E @ E 9 ° # @ @ k z E 1 E E # @ E E p LL 1 E @ z E @ k E U F E E F F @ # k C F F E F LU F k k @ @ F E @ I E E E @ F E @ I E E F 8 k E I @ @ E @ CD 51 %0 cs in i l NO 3ZIS 3111,l mo U.S. Patent Aug. 19, 2014 Sheet 5 of 10 US 8,808,658 B2 FIG. 5'' U.S. Patent Aug. 19, 2014 Sheet 6 of 10 US 8,808,658 B2 FIG. 6 U.S. Patent Aug. 19, 2014 Sheet 7 of 10 US 8,808,658 B2 FIG. 7' U.S. Patent Aug. 19, 2014 Sheet 8 of 10 US 8,808,658 B2 00 0 LL U.S. Patent Aug. 19, 2014 Sheet 9 of 10 US 8,808,658 B2 FIG. 9 U.S. Patent Aug. 19, 2014 Sheet 10 of 10 US 8,808,658 B2 FIG. 10 US 8,808,658 B2 2 RAPID SOLID-STATE METATHESIS ROUTES homogeneous powder, and initiating the reaction between the TO NANOSTRUCTURED silicon tetraiodide (SiI4) with the germanium-based precur- SILICON-GERMAINUM sors. Other systems, methods, features and advantages of the example embodiments will be or will become apparent to one CROSS-REFERENCE TO RELATED 5 with skill in the art upon examination of the following figures APPLICATIONS and detailed description. This application claims priority from provisional patent BRIEF DESCRIPTION OF THE DRAWINGS application U.S. Ser. No. 61/352,499 entitled "RAPID SOLID- STATE METATHESIS ROUTES TO NANDSTRUCTURED SILICON-GERMA- 10 FIG. 1 is powder X-ray diffraction pattern of nanostruc- NIUM," filed Jun. 8, 2010 hereby incorporated by reference. tured Si made from SiI4 using (a) CaSi and (b) MgzSi. This invention was made with Government support under FIGS. 2a, 2c and 2d are images of nanostructured silicon Grant No. 1308818, awarded by the Jet Propulsion Labora- produced from the solid state metathesis of SiI 4 and 2CaSi. tory/NASA, Grant No. NNX09AM26H awarded by NASA, FIG. 2b is an EDS image of the nanostructured silicon shown and Grant No. 0805357 awarded by the National Science 15 in FIGS. 2a, 2c and 2d. Foundation. The Government has certain rights in this inven- FIGS. 3a, 3c and 3d are images of nanostructured silicon tion produced from the solid state metathesis of SiI 4 and MgzSi. FIG. 3b is an EDS image of the nanostructured silicon shown FIELD in FIGS. 3a, 3c and 3d. 20 FIG. 4 illustrates crystallite size and calculated maximum The present disclosure relates generally to nanostructured adiabatic temperature as a function of NaCl addition moles silicon and silicon-germanium, and more particularly to according to the reaction of SiI 4 and 2CaSi. methods of producing nanostructured silicon and silicon- FIG. 5 is time-lapse photography images of the reaction germanium via solid state metathesis (SSM). between MgzSi and SiI4 initiated by a drop of ethanol. 25 FIGS. 6a is an image of nanostructured germanium pro- BACKGROUND duced using a germanium-based precursor. FIG. 6b is an EDS image of the nanostructured germanium shown in FIG. 6a. Nanostructured silicon and silicon-germanium are attrac- FIG. 7 is an SEM image of nanostructured silicon-germa- tive materials for a variety of applications due to their abun- nium using germanium in the solid state metathesis reaction dance, stability and low toxicity. Recently, nanostructured 30 of SiI4 and 2CaSi. silicon and silicon-germanium have been utilized in several FIGS. 8a and 8d are images of nanostructured silicon- applications from then noelectric s, photovoltaics, solar cell germanium using germanium in the solid state metathesis batteries and biological imaging. Several methods exist for reaction of SiI4 and 2CaSi. FIGS. 8b and 8c are EDS images producing silicon, such as the pyrolysis of silane, pulsed laser of the nanostructured silicon-germanium shown in FIGS. 8a ablation, MOCVD, MBE, plasma etching and electrochem- 35 and 8d. istry. However, these aforementioned methods are inherently FIGS. 9a and 9b are images of nanostructured silicon using limited due to the expense, complex equipment, toxic precur- tin in the solid state metathesis of SiI4 and 2CaSi. FIG. 9c is an sors and difficulty of scaling up the reactions to produce on a EDS image of the nanostructured silicon shown in FIGS. 9a commercial scale. An alternative method of producing nano- and 9b. structured silicon involves a solution-based synthetic tech- 40 FIGS. 10a and 10b are images of nanostructured silicon- nique. The drawback of the solution-based synthetic tech- germanium produced using a germanium-based precursor. nique is the use of a long chain hydrocarbon capping ligand necessary to prevent particle agglomeration. The capping DETAILED DESCRIPTION ligand, however, adds additional processing steps prior to use of the nanostructured silicon for applications where electron 45 The term, "EDS," as used herein refers to energy dispersive transfer is critical, such as in thermoelectrics or in solar cells. spectroscopy, which is an analytical technique used for the Thus, there is a need for a new method for producing elemental analysis or chemical characterization of a sample. nanostructured silicon and nanostructured silicon-germa- As used herein, the term "nanoparticle" is a microscopic nium, which is relatively inexpensive, does not require expen- particle with at least one dimension less than 100 mu.