Contamination-induced inhomogeneity of noise sources distribution in Al2O3-passivated quasi-free-standing graphene on 4H-SiC(0001)

In this report, we introduce a novel method based on low-frequency noise analysis for the assessment of quality and pattern of inhomogeneity in intentionally-aged Hall effect sensors featuring hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene mesa on semi-insulating high-purity on -axis 4H-SiC(0001), all passivated with a 100-nm-thick atomic-layer-deposited Al(2)O(3)layer. Inferring from the comparison of the measured noise and one calculated for a homogeneous sensor, we hypothesize about possible unintentional contamination of the sensors' active regions. Following in-depth structural characterization based on Nomarski interference contrast optical imaging, confocal micro-Raman spectroscopy, high-resolution Transmission Electron Microscopy and Secondary Ion Mass Spectrometry, we find out that the graphene's quasi-free-standing character and p-type conductance make the Al2O3/graphene interface exceptionally vulnerable to uncontrolled contamination and its unrestrained lateral migration throughout the entire graphene mesa, eventually leading to the blistering of Al2O3. Thus, we prove the method's suitability for the detection of these contaminants' presence and location, and infer on its applicability to the investigation of any contamination-induced inhomogeneity in two-dimensional systems.

Automated summary

This report introduces a novel method based on low-frequency noise analysis for evaluating the quality and pattern of inhomogeneity in intentionally-aged Hall effect sensors. By comparing the measured noise with the calculated noise for a homogeneous sensor, we speculate about the presence of unintentional contamination in the active regions of the sensors. Through in-depth structural characterization, we discover that the graphene's characteristics and interface make it susceptible to uncontrolled contamination, leading to blistering of the material.