期刊
ACS APPLIED MATERIALS & INTERFACES
卷 3, 期 5, 页码 1574-1580出版社
AMER CHEMICAL SOC
DOI: 10.1021/am200143g
关键词
P3HT; contact resistance; field-effect mobility; contact-limited; charge transport; charge injection
资金
- National Science Foundation [DMR-0120967]
- Georgia Tech Center for Organic Photonics and Electronics (COPE)
- Georgia Tech
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 x 10(8) Omega was observed. An effective FET mobility of 1.4 x 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 x 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.
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