Differential Thickness Layer Resistance Measurement method for measurements of contact resistance of organic semiconductor thin films

• A new contact resistance measurement method called DTLRM was developed.
• It is based on resistance measurement on two samples of differing thickness.
• A transversal current flow through the high-ohmic ultrathin organic layer is used.
• DTLRM method was tested on zinc phthalocyanine (ZnPc) ultrathin films.
• In this arrangement (transversal current flow) contact resistance cannot be neglected.

The objective, basic theory and application of a new DTLRM (Differential Thickness Layer Resistance Measurement) method of contact resistance Rc (resistance of interface) and contact resistivity measurements are described. The method was developed for ultrathin films of high-ohmic organic semiconductors. The method is based on measurements of total resistance RT,1, RT,2 between two opposite planar contacts on two samples of differing thickness L1, L2 prepared from the same organic semiconductor. The important requirements are that both the opposite contacts are ohmic, that linear dimensions of the contacts are much larger than the film thickness, and that the actual measured data are consistent in the sense of condition 1 < RT,2/RT,1 < L2/L1. The DTLRM method was verified on zinc phthalocyanine samples with Au and Pt contacts. If the basic assumptions are fulfilled, the DTLRM method can be applied to a broad range of high-ohmic thin films.