Graphene Conductance Uniformity Mapping

Abstract

We demonstrate a combination of micro four-point probe (M4PP) and non-contact terahertz time-domain spectroscopy (THz-TDS) measurements for centimeter scale quantitative mapping of the sheet conductance of large area chemical vapor deposited graphene films. Dual configuration M4PP measurements, demonstrated on graphene for the first time, provide valuable statistical insight into the influence of microscale defects on the conductance, while THz-TDS has potential as a fast, non-contact metrology method for mapping of the spatially averaged nanoscopic conductance on wafer-scale graphene with scan times of less than a minute for a 4-in. wafer. The combination of M4PP and THz-TDS conductance measurements, supported by micro Raman spectroscopy and optical imaging, reveals that the film is electrically continuous on the nanoscopic scale with microscopic defects likely originating from the transfer process, dominating the microscale conductance of the investigated graphene film.

Spatially Resolved Mapping of Electrical Conductivity across Individual Domain (Grain) Boundaries in Graphene

“…14 The ambiguity in these findings arose from a lack of knowledge of the precise domain/grain morphology for the samples measured. While there are recent studies that produced maps of the electronic properties of graphene GBs using scanning tunneling microscope (STM) 21 and of graphene conductance using micro four-point probe and non-contact terahertz time-domain spectroscopy measurements, 22 a one-to-one correspondence between defect structures and transport properties is still lacking. Indeed, because of the large length-scale difference between the atomic-scale defect structures and transport functions whose variations range from atomicscale to mesoscale, few techniques have the capability of probing the relationship between the two.…”

Efficient Modulation of 1.55 μm Radiation with Gated Graphene on a Silicon Microring Resonator

“…10,32,33 This smaller shift in E f also yields a tiny modulation at negative V g as shown in Figure 3c. Our graphene based micro-ring modulator can potentially operate at tens of GHz.…”

Mesoscopic current transport in two-dimensional materials with grain boundaries: Four-point probe resistance and Hall effect

“…17 In previous work, 18 we developed a finite element (FE) model to investigate how the M4PP signature differs for measurements on 2D and quasi-1D materials; these signatures had already been observed experimentally. 15,16 We successfully validated the FE approach by comparing calculations for a single line defect to the analytical result. 19 The model was limited in its scope since only samples with insulating line defects were studied, which may be a reasonable representation of 2D materials in which current transport is dominated by transfer defects such as rips and tears.…”

“…13 Micro four-point probe (M4PP) metrology has previously been used for non-destructive electrical characterization of graphene films. 14 M4PP metrology can be used to measure the sheet resistance (or sheet conductance), and in addition, the method allows for extraction and evaluation of geometry related parameters such as the resistance ratio 15,16 and the Hall effect signal caused by the Lorentz force. 17 In previous work, 18 we developed a finite element (FE) model to investigate how the M4PP signature differs for measurements on 2D and quasi-1D materials; these signatures had already been observed experimentally.…”