2 2 c titanium disulphide tis 2 s toichiometry i s

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Unformatted text preview: y 2 d ependent on the fraction of titanium residing in the Van der Waals gap. The titanium in the Van der Waals gap increases the interlayer interaction inhibiting the mobility of the intercalated species and possibly preventing the intercalation of some species ( 33, 4 7, 5 3 ) . O ptical experiments ( 5 4 , 5 5 ) i ndicate that T i S 2 is a s emiconductor and calculations by Zunger et. al. (61) P a g e - 15i ndicate an indirect band gap of 0 . 2 - 0 . 3 ev. O n the other hand temperature dependent resistivity measurements by Thompson et. a l . ( 44) w ere interpretted to indicate that T iS2 e xibits s e m i - m e t a l l i c properties. observations c a n be reconciled These conflicting (30) by assuming that T i S 2 i s a " dirty semiconductor" meaning that even in stoichiometric T i S s ome of the titanium atoms may be 2 displaced from their usual locations and reside a t vacant interlayer s i t e s . Moret e t . a l . ( 6 2 ) modelled the effect of intersital titanium atoms to explain various anomalies in X-ray diffraction patterns of Ti S l + x 2' T hompson e t . al. ( 5 7 ) have found that the lattice parameters varied with the S /Ti ratio. They have measured the variation in the lattice parameters and the density as a f u n c t i o n of the S /Ti r atio (for S /Ti i n the range 1 . 8 0 - 2 .00) and plotted the results ( 63), t hus providing a direct method for determining the stoichiometry of T i S 2 s amples from the lattice parameters. 2 - 3 ( a ) Intercalation of T iSZ P owders T h e insertion of guest atoms or molecules between the layers of a host ( l a y e r e d compound), without altering the atomic structure of the host l a t t i c e , is generally referred to a s intercalation if the process is r e v e r s i b l e . T h e guest species that has been successfully intercalated resides within the Van der Waals gap between the layers of the t ransition m etal dichalcogenide c o m p o u n d s . . Recent work (33) P age - 1 6 h as shown that Group I b , l a , I I b , I Ia e lements, aluminum, gallium, indium, thallium, a s well as ammonia (or substituted ammonium compounds) can be intercalated into the transition metal dichalcogenides. The m...
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This note was uploaded on 10/08/2009 for the course CME MAT E 630 taught by Professor Dr. during the Fall '09 term at University of Alberta.

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