基于双栅有机场效应晶体管存储器的多值存储研究

Organic nonvolatile memory based on organic field effect transistor (OFET) is a core component of flexible organic electronic devices, which possesses advantages of nondestructive programming /reading processes and architectural compatibility with logic circuits. Multi-bit capability is highly desirable due to the increased memory density as well as cost reduction. However, the conventional technology of multi-level cell (MLC) requires accurate charge control/charge placement and highly reliable charge storage, which is a great challenge for the present OFET memories. In this research proposal, a multi-bit double-gate OFET memory is proposed and demonstrated. By selectively charging/discharging the top and bottom charge trapping layers, a 2-bit 4-value memory device could be achieved. The requirements of charge control /charge placement as well as charge storage are the same as simple 1-bit OFET memory device, which ensures a good feasibility without sacrificing device reliability and stability. We will analyze the dependence of charge interference between two separated charge trapping layers on the film thicknesses and dielectric constants of the tunneling layer and semiconductor layer. Based on the experimental data, the device structure will be optimized and an additional gate bias during programming will be applied to eliminate the charge interference. During the process of coating upper functional layers, the orthogonal solvents will be chosen and/or cross-linked polymers will be employed to prevent the dissolution of underlying layers. The investigation will provide useful experimental information for the design of OFET memory with multi-bit capability.

有机场效应晶体管存储器具有无损读写、与逻辑电路兼容等优点，是未来有机柔性电子信息产品的核心部件之一。在单个器件上实现多值存储，可极大提高数据的存储密度、降低单位信息的存储成本。传统的多级多值存储技术要求通过改变编程条件来精确控制阈值电压的多点分布，然而目前有机存储器难以达到这一要求。我们拟采用双栅电极结构，利用两个分立的电荷存储层分别存储1位信息，以此实现单个器件存储2位4值信息。编程时通过施加特定的顶栅、底栅电压，分别控制电荷注入或逃离上、下电荷存储层，实现多值存储并不以牺牲器件的可靠性与稳定性为代价。通过调控半导体薄膜和隧穿绝缘层的厚度以及介电常数优化器件结构，并采取纠正措施消除上、下电荷存储层间的相互干扰。 在多层器件制备中，选择正交溶剂和采用交联聚合物来克服溶剂对相邻功能层的影响。本项目将为具有多值存储能力的有机场效应晶体管存储器的结构设计、材料选择和技术优化提供关键的实验依据。

在单个有机晶体管存储器器件上实现多值存储是提高数据存储密度、降低单位信息存储成本的有效途径。本项目按计划开展了基于双栅有机场效应晶体管存储器的多值存储研究工作：实验方面，利用两个分立的电荷存储层分别存储1位信息，编程时通过施加特定的顶栅、底栅电压，分别控制电荷注入或逃离上、下电荷存储层，在单个有机晶体管器件上实现了2位4值信息的存储。本课题实现多值存储不以牺牲器件的可靠性与稳定性为代价，为具有多值存储能力的有机场效应晶体管存储器的结构设计提供了有效实验方案；存储机理研究方面，阐明了有机晶体管存储器拐点电压的物理含义, 是被俘获的电子刚要从电荷存储层逃逸出来时对应的状态点，对优化有机晶体管存储器的性能具有重要指导意义;项目执行期间发表与本项目相关且受本基金标注科研SCI论文8篇，其中6篇项目承担者作为第一或者通讯作者；申请中国发明专利2项，与另两位老师合作出版《纳米材料专业实验》教材一部；在2017 美国圣地亚哥 SPIE 会议主题为“Hybrid Memory Devices and Printed Circuits”的分会和2016宁波“2nd International Conference on Organic Optoelectronics”会议上作口头报告汇报了相关研究成果；受邀担任SCI杂志“Active and Passive Electronic Components”主题为“Advanced Charge-Trapping Memory Devices”特刊的客座编辑；在项目资助下，培养研究生4人。