篇題：Miniaturized Flexible Piezoresistive Pressure Sensors: Poly(3,4- ethylenedioxythiophene):Poly(styrenesulfonate) Copolymers Blended with Graphene Oxide for Biomedical Applications
文章出處：Advanced Functional Materials, DOI:doi.org/10.1002/adfm.202001598
作者： Chia-Ming Yang, Tsung-Cheng Chen, Dharmendra Verma, Lain-Jong Li, Bo Liu, Wen-Hao Chang, Chao-Sung Lai*
任職單位及部門：長庚大學電子工程學系
Neuromorphic computing has been extensively studied to mimic the brain functions of perception, learning, and memory because it may overcome the von Neumann bottleneck. Here, with the light-induced bidirectional photoresponse of the proposed Bi2O2Se/graphene hybrid structure, its potential use in next-generation neuromorphic hardware is examined with three distinct optoelectronic applications. First, a photodetector based on a Bi2O2Se/graphene hybrid structure presents positive and negative photoresponsibility of 88 and −110 A W−1 achieved by the excitation of visible wavelength and ultraviolet wavelength light at intensities of 1.2 and 0.3 mW cm−2 , respectively. Second, this unique photoresponse contributes to the realization of all optically stimulated long-term potentiation or long-term depression to mimic synaptic short-term plasticity and long-term plasticity, which are attributed to the combined effect of photoconductivity, bolometric, and photoinduced desorption. Third, the devices are applied to perform digital logic functions, such as “AND” and “OR,” using full light modulation. The proposed Bi2O2Se/graphene-based optoelectronic device represents an innovative and efficient building block for the development of future multifunctional artificial neuromorphic systems.
文章摘要：
長庚大學電子系賴朝松教授與光電所楊家銘教授團隊長期耕耘二維材料之感測器與電子元件開發，近來研究成果傳出捷報，在頂級SCI期刊，Advanced Functional Materials刊登全球首創利用不同波長光源進行調變的類神經運算元件，此元件分別結合了兩種二維材料：石墨烯與硒氧化鉍(Bi2O2Se) (如圖(a)TEM照片)，可以在紫外光(365 nm)與紅光(635 nm)發光二極體的特定強度照射下，分別對石墨烯與硒氧化鉍產生負光導電(negative photoconductivity, NPC)與正光導電(positive photoconductivity, PPC)，如圖(b)所示。正光導電度常發生於半導體受能量激發後，產生多餘的電子電洞對，增加額外電流，等效於提昇導電度，這點也可以直接在不同光刺激下直接由開爾文探針力顯微鏡(Kelvin probe force microscopy, KPFM)量測出不同材料堆疊的表面功函數變化得到驗證，如圖(c)所示。根據此二元特性，對元件結構與激發光源進行特定排列組合，已經在此篇論文中，驗證出可以進行三種不同的運用，首先是個別對可見光與紫外光作為單一偵測器。第二種運用則是，藉由串連兩個二維材料的電阻式結構，藉635 nm與365 nm兩種不同波長提供全光刺激訊號，發現可以進行增強(excitatory postsynaptic currents, EPSCs) 與抑制(inhibitory postsynaptic currents, IPSCs)電流作用，得到類似神經突觸運作的長期與短期可塑性記憶，例如：short-term memory (STM), long-term memory (LTM), long-term potentiation (LTP), and long-term depression (LTD)等，如圖如圖(f)與(g)所示，這些現象也可以分別藉由光導電性、輻射熱與光引導吸收等機制進行解釋；最後此元件更可以兩種光源(635與525 nm)作為輸入訊號，並且使用365 nm光源照射進行”AND”與”OR”的邏輯閘模式切換，可以用全光訊號對數位訊號進行運算，如圖(h)所示，完整實現單一元件使用不同波長光源進行邏輯運算與類神經元記憶效果，開拓了多功能人造神經元系統發展的可行性。
圖(a)
圖(b)
圖(c)
圖(d)
圖(e)
圖(f)圖(g)
圖(h)
圖 (a) 硒氧化鉍(Bi2O2Se)之結構示意圖與TEM照片、(b)全光神經元件俯視照片、(c)使用不同功率之365與635 nm波長光源照射之輸出電流響應、(d)KPFM量測不同波長照射下的不同表面功函數、(e) 分別使用635與365 nm波長照射可以得到增強(excitatory postsynaptic currents, EPSCs) 與抑制(inhibitory postsynaptic currents, IPSCs)電流作用、此全光元件展示(f)短期與長期記憶功能、(g)長期增強與長期抑制功能與(h)使用不同光波長作為二元輸入與使用365nm進行OR與AND閘極切換的多功能邏輯數位運算結果。