Conductivity and tunneling density of states in granular Cr films

Yu Chen Sun*, Sheng-Shiuan Yeh, Juhn-Jong Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We have measured the tunneling differential conductances, G (V), of four Al/ AlOx /Cr planar tunnel junctions as well as the conductivities, σ (T), of the Cr electrodes at liquid-helium temperatures. The Cr electrodes were made to be granular with dimensionless intergrain tunneling conductance spanning from g≃1 to g≫1, and the dimensionality of the granular array d=3. For the samples with g≫1, we found that the measured G (V) curves display large zero-bias singularities which obey a lnV law at low bias voltages (≲ a few millielectron volt) while crossing over to a √V law at high bias voltages. Simultaneously, the conductivities of the Cr electrodes reveal lnT dependence below a characteristic temperature. These results are explained in terms of the recent theory of granular metals. In a sample with g≃1, in addition to the conductivity dependence σ∞lnT, we observed a universal scaling behavior of the normalized differential conductance [G (V,T) -G (0,T)] /√T with the combined parameter √ e |V| / kB T in a wide temperature interval of 2.5-32 K. This result is not yet understood.

Original languageEnglish
Article number054203
Number of pages7
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number5
StatePublished - 12 Aug 2010


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