Nanoscale Probing of Surface Charges in Functional Copper‐Metal Organic Clusters by Kelvin Probe Force Microscopy for Field‐Effect Transistors

Abstract

Metal–organic frameworks (MOFs) have recently attracted a great deal of attention especially as conceivable advanced gate dielectrics for next‐generation field‐effect transistors (FETs) and memory device applications. Dielectric surface charge retention mapping is essential for gauging the leakage current and threshold voltage stability. Due to a dearth of systematic real‐time surface charge probing of MOFs dielectrics, in this work, the nanoscale Kelvin probe force microscopy (KPFM) technique is employed for the contact potential difference (CPD) analysis of developed hybrid copper–metal–organic clusters (Cu‐MOCs)/Si systems. Films are synthesized through the sol‐gel process consisting of copper metal core linked with organic ligands. With 3V positive and negative DC bias, charge injection offset between positive and negative bias is observed to be ≈190 mV, indicating the intrinsic Fermi level alignment between KPFM tip and sample surface charges. The high‐resolution surface CPD mappings bring forth the white (≈98 mV) and black (≈−91 mV) contrast profiles with hole (5.09 × 1012 cm−2) and electron (4.74 × 1012 cm−2) charge densities. Also, the 17 h time‐lapse enables the holes and electrons CPD mapping diameter shrinkage by ≈32% and 46%, respectively. In furtherance, a conductive filament model for host‐guest proton‐assisted conduction with charge hopping through fixed/mobile ions is proposed.

Charge-Localized Retention and Long-Term Memory Enabled by Cooperating Sterically Confined Molecular Crystallization with Spiro[fluorene-9,9′-xanthene]-Based Csp3-Hindrance

“…Then, the surface potential distributions of trapped charges can be visualized by KPFM. KPFM has been employed for detecting the localized electrical properties (such as surface potential, work function, charge trapping, and charge recombination) of materials and devices at nanometer scale by scanning the electrostatic force between the AFM tip and the sample surface. − Recently, there also are many reports on the application of KPFM to the study of two-dimensional nanostructures. ,− In our experiments, KPFM is conducted by a dual pass process with amplitude modulation as shown in Figure a . At the first scan, the topography is scanned in the tapping mode.…”