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Direct Chemical Vapor Deposition Synthesis of Phase-Pure Iron Pyrite (FeS<sub>2</sub>) Thin Films
Samad, Leith,Cabá,n-Acevedo, Miguel,Shearer, Melinda J.,Park, Kwangsuk,Hamers, Robert J.,Jin, Song American Chemical Society 2015 Chemistry of materials Vol.27 No.8
<P>Resurgent interest in iron pyrite (FeS<SUB>2</SUB>) as an earth-abundant, nontoxic semiconductor for solar applications has resulted in many attempts to grow phase-pure thin films via chemical vapor deposition (CVD). However, all thin films grown via CVD or sulfidation to date have contained marcasite phase or other iron sulfide impurities. Here, we report the use of metallic cobalt pyrite (cattierite, CoS<SUB>2</SUB>) thin films as an ideal substrate leading to the first direct growth of phase-pure iron pyrite thin films via atmospheric pressure CVD. This synthesis was achieved by reacting FeCl<SUB>3</SUB> and ditert butyl disulfide (TBDS) at 400–450 °C. The products were confirmed as phase-pure iron pyrite using X-ray diffraction (XRD), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDS). In addition to phase-purity, the synthesis produced crystal domains >1 μm and a conformal coating 3–5 μm thick, which are attributed to the <2% lattice mismatch of the isostructural cattierite substrate. The surface was characterized by ultraviolet and X-ray photoelectron spectroscopy (UPS & XPS) and the electrical properties by electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The direct growth of a phase-pure iron pyrite film on a conductive substrate provides the most convenient configuration so far for potential solar cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-8/acs.chemmater.5b00664/production/images/medium/cm-2015-00664c_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00664'>ACS Electronic Supporting Info</A></P>
Franking, Ryan,Kim, Heesuk,Chambers, Scott A.,Mangham, Andrew N.,Hamers, Robert J. American Chemical Society 2012 Langmuir Vol.28 No.33
<P>The UV-induced photochemical grafting of terminal alkenes has emerged as a versatile way to form molecular layers on semiconductor surfaces. Recent studies have shown that grafting reactions can be initiated by photoelectron emission into the reactant liquid as well as by excitation across the semiconductor band gap, but the relative importance of these two processes is expected to depend on the nature of the semiconductors, the reactant alkene and the excitation wavelength. Here we report a study of the wavelength-dependent photochemical grafting of alkenes onto single-crystal TiO<SUB>2</SUB> samples. Trifluoroacetamide-protected 10-aminododec-1-ene (TFAAD), 10-<I>N</I>-BOC-aminodec-1-ene (t-BOC), and 1-dodecene were used as model alkenes. On rutile (110), photons with energy above the band gap but below the expected work function are not effective at inducing grafting, while photons with energy sufficient to induce electronic transitions from the TiO<SUB>2</SUB> Fermi level to electronic acceptor states of the reactant molecules induce grafting. A comparison of rutile (110), rutile (001), anatase (001), and anatase (101) samples shows slightly enhanced grafting for rutile but no difference between crystal faces for a given crystal phase. Hydroxylation of the surface increases the reaction rate by lowering the work function and thereby facilitating photoelectron ejection into the adjacent alkene. These results demonstrate that photoelectron emission is the dominant mechanism responsible for grafting when using short-wavelength (∼254 nm) light and suggest that photoemission events beginning on mid-gap states may play a crucial role.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2012/langd5.2012.28.issue-33/la302169k/production/images/medium/la-2012-02169k_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la302169k'>ACS Electronic Supporting Info</A></P>
Zhang, Lingzhi,Lyons, Leslie,Newhouse, Jocelyn,Zhang, Zhengcheng,Straughan, Megan,Chen, Zonghai,Amine, Khalil,Hamers, Robert J.,West, Robert Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.38
<P>Alkylsilane ethers, containing one or three carbon spacer groups between the silicon atom and oligo(ethylene oxide) moiety, were designed and synthesized. These compounds are non-hydrolyzable and less flammable than their alkoxysilane counterparts. A full cell test using them as electrolyte solvents showed good cycling performance in lithium-ion batteries.</P> <P>Graphic Abstract</P><P>Alkylsilane ethers with oligo(ethylene oxide) substituents were designed and synthesized as safe electrolyte solvents which showed good cycling performance doped with LiBOB in lithium-ion cells. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm01596b'> </P>