Defect Scaling with Contact Area in EGaIn-Based Junctions: Impact on Quality, Joule Heating, and Apparent Injection Current

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• 作者：Li Jiang ; C. S. Suchand Sangeeth ; Albert Wan ; Ayelet Vilan ; Christian A. Nijhuis
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：January 15, 2015
• 年：2015
• 卷：119
• 期：2
• 页码：960-969
• 全文大小：473K
• ISSN：1932-7455

文摘

Although the tunneling rates decrease exponentially with a decay coefficient 尾 close to 1.0 n_C^鈥? across n-alkanethiolate (SC_n) monolayer based tunneling junctions determined over a multitude of test beds, the origins of the large spread of injection current densities鈥攖he hypothetical current density, J₀ (in A/cm²), that flows across the junction when n = 0鈥攐f up to 12 orders of magnitude are unclear. Every type of junction contains a certain distribution of defects induced by, for example, defects in the electrode materials or impurities. This paper describes that the presence of defects in the junctions is one of the key factors that cause an increase in the observed values of J₀. We controlled the number of defects in Ag^TS-SC_n//GaO_x/EGaIn junctions by varying the geometrical contact area (A_geo) of the junction. The value of J₀ (鈭?0² A/cm²) is independent of the junction size when A_geo is small (<9.6 脳 10² 渭m²) but increased by 3 orders of magnitude (from 10² to 10⁵ A/cm²) when A_geo increased from 9.6 脳 10² to 1.8 脳 10⁴ 渭m². With increasing J₀ values the yields in nonshorting junctions decreased (from 78 to 44%) and 尾 increased (from 1.0 to 1.2 n_C^鈥?). We show that the quality of the junctions can be qualitatively determined by examining the curvature of the dJ/dV curves (defects change the sign of the curvature from positive鈥攁ssociated with tunneling鈥攖o negative鈥攁ssociated with Joule heating) and fitting the J(V) curves to the full Simmons equation to (crudely) estimate the effective separation of the top- and bottom-electrode d_eff. This analysis confirmed that the electrical characteristics of large junctions are dominated by thin-area defects, while small junctions are dominated by the molecular structure.