Related Experiment Video
Updated: Jun 2, 2026

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM
Published on: January 23, 2013
Electrical contact properties between the accumulation layer and metal electrodes in ultrathin
Byoungnam Park1, Avishek Aiyar, Jung-Il Hong
1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA. metalpbn@gmail.com
Abstract:
Probing contact properties between an ultrathin conjugated polymer film and metal electrodes in field effect transistors (FETs) is crucial not only to understanding charge transport properties in the accumulation layer but also in building organic sensors with high sensitivity. We investigated the contact properties between gold electrodes and poly(3-hexylthiophene) (P3HT) as a function of film thickness using gated four-point sheet resistance measurements. In an FET with a 2 nm thick P3HT film, a large voltage drop of 1.9 V (V(D) = -3 V) corresponding to a contact resistance of 2.3 × 10(8) Ω was observed. An effective FET mobility of 1.4 × 10(-3) cm(2)/(V s) was calculated when the voltage drop at the contacts was factored out, which is approximately a factor of 3 greater than the two-contact FET mobility of 5.5 × 10(-4) cm(2)/(V s). A sharp decrease in the ratio of the contact resistance to the channel resistance was observed with increasing film thickness up to a thickness of approximately 6 nm, separating a contact limited regime from a charge transport limited regime. The origin of the large contact resistance observed in the device prepared with an ultrathin P3HT film is discussed in light of results from X-ray diffraction (XRD) and atomic force microscopy (AFM) studies.
Related Concept Videos
Metal-Semiconductor Junctions
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
The Electrical Double Layer
Field Effect Transistor
P-N junction
Design Example: Resistive Touchscreen
When a user touches the screen, the two layers make contact at a specific point known as the touchpoint. This contact reduces the resistance between...
