Nano-Scale Structure Control of Organic/Metal Interface and photocurrent Multiplication Device

我们已经观察到一个大的光电流倍增达到105倍，在各种有机薄膜。研究目的在于阐明其倍增机制，并应用于倍增型光感测元件。主要研究结果如下：1.光电流倍增现象的瞬态响应被揭示为具有两个分量，其被确定为初级光电流和后续倍增光电流。这清楚地支持所提出的机制的基础上隧穿电子注入从金属电极的有机层触发的光积累的空间电荷附近的有机/金属界面的陷阱空穴。在此基础上，成功制作了高速响应的乘法器.原子力显微镜（AFM）研究表明，沉积在有机物表面的金属薄膜是纳米尺度的粒子聚集体，且随着纳米粒子尺寸的增大，金属薄膜的增殖速率增大。该结果证实存在空间分离的部分，即，在有机/金属界面上，“死胡同"作为结构陷阱，导致了”倍增“.利用AEM探针对捕获空穴的有机薄膜表面电位进行了显微观察。阐明了结构陷阱位置与表面分子堆积的关系.成功地制作了硅基乘法器。上述结果清楚地表明，倍增现象应用于高灵敏度光电传感器是可能的。

We have observed a large photocurrent multiplication reaching 105-fold in various organic films. Aim of research is the clarification of the multiplication mechanism and the application to the multiplication-type photo-sensing device. Following results were obtained.1. The transient response of the photocurrent multiplication phenomenon was revealed to have two components, which were identified as the primary and the subsequent multiplied photocurrents. This clearly supports the proposed mechanism based on tunneling electron injection from a metal electrode to the organic layer triggered by the photo-accumulated space charges of trapped holes near the organic/metal interface. Based on this result, high speed response of multiplication device was successfully fabricated.2. Metal film deposited on organic surface was revealed to be a gathering of particles of nanometer scale by atomic force microscopy (AFM), and moreover, the multiplication rate increased with the size of nano-particles. This result confirms that there are the spatially separated parts, I.e., the blind alleys acting as the structural traps at organic/metal interface, which causes the multiplication.3. By using AEM probe, microscopic observation of surface potential of organic film capturing holes was accomplished. Relation between the structural trap sites and the surface molecular stacking was suggested.4. Multiplication devices on silicon chip were successfully fabricated. Above results clearly show that the application of multiplication phenomenon to high sensitive photosensor is possible.