Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, 789-784, Korea.
J Phys Chem B. 2010 Nov 25;114(46):14854-9. doi: 10.1021/jp106364v. Epub 2010 Oct 28.
We report how treatment of nickel (Ni) with O(2) plasma affects the polarity of Ni surface, crystallinity of pentacene film on the Ni, and electrical properties of pentacene organic thin-film transistors (OTFTs) that use Ni as source-drain electrodes. The polar component of surface energy in Ni surface increased from 8.1 to 43.3 mJ/m(2) after O(2)-plasma treatment for 10 s. From X-ray photoelectron spectra and secondary electron emission spectra, we found that NiO(x) was formed on the O(2)-plasma-treated Ni surface and the work function of O(2)-plasma-treated Ni was 0.85 eV higher than that of untreated Ni. X-ray diffraction and atomic force microscopy measurements showed that pentacene molecules are well aligned as a thin-film and grains grow much larger on O(2)-plasma-treated Ni than on untreated Ni. This change in the growth mode is attributed to the reduction of interaction energy between pentacene and Ni due to formation of oxide at the Ni/pentacene interface. Thus, O(2)-plasma treatment promoted the growth of well-ordered pentacene film and lowered both the hole injection barrier and the contact resistance between Ni and pentacene by forming NiO(x), enhancing the electrical property of bottom-contact OTFTs.
我们报告了用氧气（O2）等离子体处理镍（Ni）如何影响 Ni 表面的极性、Ni 上五苯薄膜的结晶度以及使用 Ni 作为源漏电极的五苯有机薄膜晶体管（OTFT）的电性能。经过 10 秒的 O2 等离子体处理后，Ni 表面的表面能极性分量从 8.1 增加到 43.3 mJ/m2。从 X 光电子能谱和二次电子发射谱中，我们发现 NiO(x)在 O2 等离子体处理的 Ni 表面形成，并且 O2 等离子体处理的 Ni 的功函数比未处理的 Ni 高 0.85 eV。X 射线衍射和原子力显微镜测量表明，五苯分子在 O2 等离子体处理的 Ni 上作为薄膜很好地排列，并且晶粒比在未处理的 Ni 上长得大得多。这种生长模式的变化归因于 Ni/五苯界面处形成氧化物导致五苯和 Ni 之间的相互作用能降低。因此，O2 等离子体处理通过形成 NiO(x)促进了有序五苯薄膜的生长，并降低了空穴注入势垒和 Ni 与五苯之间的接触电阻，从而增强了底接触 OTFT 的电性能。
