Flexible Photonic Synapses Based on Graphene Quantum Dots = 그래핀 양자점 기반 인공 시냅스 유연 소자

다국어 초록 (Multilingual Abstract)

In the upcoming "Big Data" era, where the numerous types of unstructured data need to be processed, artificial neural networks have been developed to overcome the limitation of conventional von Neumann computing system. Especially, artificial photonic synapses, consolidating the sensing and processing in a single device, have received tremendous interests for the emulation of human visual system. Herein, flexible photonic flash memory, selectively detecting and processing various UV light stimulus, is designed. As a charge trapping medium, UV light sensitive graphene quantum dots (GQDs), named HBC-PF6, embedded in poly (4-vinyl phenol) (PVP) are utilized. The hybrid GQDs/PVP film-based synaptic transistor exhibits superior flexibility and stability, preserving synaptic performance during over 200 cycle tests bent to a radius of 5 mm. Furthermore, the flash memory successfully mimics synaptic behaviors, such as excitatory post synaptic current (ESPC), pulse paired facilitation (PPF), short/long-term plasticity (STP/LTP), transition of STP to LTP. The energy consumption (~10 fJ per event) ensures that the device can operate at low power, comparable to human brain. Based on the synaptic behaviors, mimicry of the human visual system which has both sensory and synaptic function by learning-forgetting process has been demonstrated by 3×5 pixelated assembly of GQDs based photonic synapse. To validate capability that GQDs based photonic synapse can be utilized for perceiving the unstructured data, recognition test simulation based on Modified National Institute of Standards and Technology (MNIST) dataset is implemented and achieve the 87 % recognition rate. We believe that our work paves the way for synaptic devices to the fields including electronic skin, artificial vision system, and wearable consumer electronics.

목차 (Table of Contents)

• List of Tables (ⅱ)
• List of Figures (ⅲ)
• Abstract (ⅵ)
• Chapter 1. Introduction (1)
• 1. 1. Significance of this research (1)
• Chapter 2. Results and Discussion (17)
• 2. 1. Operation principle of photonic synapse transistors (17)
• 2. 2. Photo-programming of optoelectronic devices (26)
• 2. 3. Flexible optoelectronic devices (40)
• 2. 4. Synaptic properties of flexible optoelectronic devices (49)
• 2. 5. Artificial neural network (54)
• Chapter 3. Experimental Section (58)
• 3. 1. Functionalized PAHs synthesis (58)
• 3. 2. Materials (58)
• 3. 3. Organic semiconductor solution preparation (58)
• 3. 4. Flash memory device fabrication (59)
• 3. 5. Characterization (60)
• 3. 6. Artificial neural network simulation (61)
• Chapter 4. Conclusion (62)
• Reference (63)
• 국문요지 (72)
• Acknowledgement (74)