Exfoliated Graphite Electrodes for Organic Single-Crystal Field-Effect Transistor Devices,ACS Applied Electronic Materials

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Exfoliated Graphite Electrodes for Organic Single-Crystal Field-Effect Transistor Devices
ACS Applied Electronic Materials ( IF 4.3 ) Pub Date : 2019-09-24 , DOI: 10.1021/acsaelm.9b00538
Jinho Lee ₁ , Hyeyeon Cho ₁ , Hee Cheul Choi ₁

Affiliation

In this work, exfoliated graphite was used as an electrode for organic single-crystal field-effect transistor (FET) devices, and the electrode performance was demonstrated. The reduced rigidity of exfoliated graphite allows good physical contact with organic single crystals in various morphologies. Because the work function of graphite matches well the HOMO energy level of most p-type organic molecules or the LUMO level of some n-type molecules, efficient charge injection from graphite electrodes to organic crystals is expected to result in high device performance. Indeed, the rubrene single-crystal FET devices fabricated using graphite electrodes exhibit high mobility (average of 2.38 cm²/V·s) with low threshold voltage and a high on/off current ratio. This is comparable to the FET devices that we fabricated using gold electrodes. Moreover, the graphite electrode devices of phenothiazine, C₆₀, and PTCDA crystals also exhibited similar or improved device performance compared to devices with conventional metal electrodes. Another advantage of using graphite is the availability of chemical and physical treatments by which the work function of graphite can be tuned to a certain degree. We demonstrated improved performance of picene single-crystal FET devices employing oxygen-plasma-treated graphite electrodes. The work function change of graphite upon oxygen-plasma treatment was confirmed using Kelvin probe measurements. We thus confirmed that the improved device performance was achieved by a reduced charge injection barrier when the oxygen-plasma-treated graphite electrode was used. These results indicate that exfoliated graphite should be considered a potential candidate electrode material for organic crystal devices.

中文翻译：

用于有机单晶场效应晶体管器件的片状石墨电极

在这项工作中，使用剥离石墨作为有机单晶场效应晶体管（FET）器件的电极，并论证了电极性能。剥落石墨的刚性降低，可以与各种形态的有机单晶形成良好的物理接触。由于石墨的功函数与大多数p型有机分子的HOMO能级或某些n型分子的LUMO能级很好地匹配，因此，从石墨电极到有机晶体的有效电荷注入有望实现较高的器件性能。实际上，使用石墨电极制造的红荧烯单晶FET器件具有高迁移率（平均2.38 cm ²/ V·s），具有较低的阈值电压和较高的开/关电流比。这可与我们使用金电极制造的FET器件相媲美。此外，吩噻嗪，C ₆₀的石墨电极装置与具有常规金属电极的器件相比，PTCDA晶体和PTCDA晶体还表现出相似或改进的器件性能。使用石墨的另一个优点是可以进行化学和物理处理，通过这种方法可以将石墨的功函数调整到一定程度。我们证明了采用氧等离子体处理的石墨电极改善了野餐单晶FET器件的性能。使用开尔文探针测量证实了氧等离子体处理后石墨的功函数变化。因此，我们证实了当使用经氧等离子体处理的石墨电极时，通过减小的电荷注入势垒实现了改善的器件性能。这些结果表明，应将剥落的石墨视为有机晶体器件的潜在候选电极材料。

更新日期：2019-09-25

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