Electrical resistivity and stoichiometry of BaxC60 films

✍ Scribed by R.C. Haddon; G.P. Kochanski; A.F. Hebard; A.T. Fiory; R.C. Morris; A.S. Perel

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 389 KB
• Volume: 203
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)85594-e

✦ Synopsis

Electrical resistance measurements show that uniform intercalation of Ba into Cm films is much more difficult to achieve than in the case of the other alkaline earths (AE), Ca and Sr. Ba,C,, films studied after annealing at 220°C show a resistivity minimum between 1 <x<2, and another weak minimum at X= 5. The activation energies for the conduction process show a minimum at Ba&,,. The resistivities arep,,,,.(xz 1.5)=0.2 R cm andp,,,,(x=5) = 3x lO-JQ cm. This latter value is the lowest yet reported in a doped granular C& thin ( zz 200 A) film and Ba,C, exhibits a metallic (positive) temperature coefficient of resistivity. There is a maximum in the resistivity at x= 3. The results suggest that the conductivities observed in (AE)xC60 films (AE= Ca, Sr, Ba) between 0 <x< 3 are associated with the population of bands derived from the tl, LLJMO levels of C,,, whereas the most conducting phases have the composition X= 5 and involve energy bands derived from the t II LUMO + 1 levels of Cm.