Lassnig R, Striedinger B, Hollerer M, Fian A, Stadlober B, Winkler A
Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
Materials Division, Joanneum Research Materials, Franz-Pichler-Straße 30, A-8160 Weiz, Austria.
J Appl Phys. 2014 Sep 21;116(11):114508. doi: 10.1063/1.4895992.
The fabrication of organic thin film transistors with highly reproducible characteristics presents a very challenging task. We have prepared and analyzed model pentacene thin film transistors under ultra-high vacuum conditions, employing surface analytical tools and methods. Intentionally contaminating the gold contacts and SiO channel area with carbon through repeated adsorption, dissociation, and desorption of pentacene proved to be very advantageous in the creation of devices with stable and reproducible parameters. We mainly focused on the device properties, such as mobility and threshold voltage, as a function of film morphology and preparation temperature. At 300 K, pentacene displays Stranski-Krastanov growth, whereas at 200 K fine-grained, layer-like film growth takes place, which predominantly influences the threshold voltage. Temperature dependent mobility measurements demonstrate good agreement with the established multiple trapping and release model, which in turn indicates a predominant concentration of shallow traps in the crystal grains and at the oxide-semiconductor interface. Mobility and threshold voltage measurements as a function of coverage reveal that up to four full monolayers contribute to the overall charge transport. A significant influence on the effective mobility also stems from the access resistance at the gold contact-semiconductor interface, which is again strongly influenced by the temperature dependent, characteristic film growth mode.
制造具有高度可重复性特征的有机薄膜晶体管是一项极具挑战性的任务。我们在超高真空条件下制备并分析了并五苯薄膜晶体管模型，采用了表面分析工具和方法。通过并五苯的反复吸附、解离和脱附故意用碳污染金触点和SiO沟道区域，结果证明这对于制造具有稳定且可重复参数的器件非常有利。我们主要关注器件特性，如迁移率和阈值电压，作为薄膜形态和制备温度的函数。在300 K时，并五苯呈现斯特兰斯基-克拉斯坦诺夫生长，而在200 K时则发生细颗粒、层状薄膜生长，这主要影响阈值电压。与温度相关的迁移率测量结果与已建立的多陷阱和释放模型高度吻合，这反过来表明在晶粒和氧化物-半导体界面处浅陷阱占主导地位。迁移率和阈值电压随覆盖率的测量结果表明，多达四个完整单分子层对整体电荷传输有贡献。金触点-半导体界面处的接触电阻对有效迁移率也有显著影响，而接触电阻又受到与温度相关的特征薄膜生长模式的强烈影响。
