Contactless Measurement of Sheet Resistance of Nanomaterial Using Waveguide Reflection Method.

Ming Ye,Yong-Ning He,Xiao-Long Zhao,Raja Usman Tariq,Wei-Da Li

doi:10.3390/ma13225240

Abstract

Conductive nanomaterials are widely studied and used. The four-point probe method has been widely used to measure nanomaterials’ sheet resistance, denoted as . However, for materials sensitive to contamination or physical damage, contactless measurement is highly recommended if not required. Feasibility of evaluation using a one-port rectangular waveguide working on the microwave band in a contact-free mode is studied. Compared with existed waveguide methods, the proposed method has three advantages: first, by introducing an air gap between the waveguide flange and the sample surface, it is truly contactless; second, within the specified range of , the substrate’s effect may be neglected; third, it does not require a matched load and/or metallization at the sample backside. Both theoretical derivation and simulation showed that the magnitude of the reflection coefficient decreased monotonously with increasing . Through calibration, a quantitative correlation of and was established. Experimental results with various conductive glasses showed that, for in the range of ~10 to 400 Ohm/sq, the estimation error of sheet resistance was below ~20%. The potential effects of air gap size, sample size/location and measurement uncertainty of are discussed. The proposed method is particularly suitable for characterization of conductive glass or related nanomaterials with in the range of tens or hundreds of Ohm/sq.

Highlights

With the development of functional materials, applications for conductive nanomaterials were found in people’s daily lives, industry and scientific research
From the measurement c mathematic fitting, we found that the power function S11,dB = c01 Rs 02 + c03 was suitable for this point of view, if a quantitative correlation could be established between the sheet resistance and S11, purpose
A noncontact resistance measurement method based based on microwave reflectionreflection was proposed noncontactsheet sheet resistance measurement method on microwave was and verified

Summary

Introduction

With the development of functional materials, applications for conductive nanomaterials were found in people’s daily lives, industry and scientific research. Transparent conductive materials attract much attention due to their wide range of applications such as touch screens [1], displays [2], electromagnetic shielding [3], RF/microwave [4], glass heaters [5], solar cells [6], flexible electronics [7], OLED [8] and so on In both science and engineering, sheet resistance Rs is widely used to characterize a nanofilm’s electrical conductivity, and it is usually measured using the four-point probe method [9,10,11,12]. One major drawback is that good contact should be formed between the probes and the sample under test This requirement may increase measurement cost and time, reduce efficiency and pollute or damage the nanomaterial under evaluation. Other contactless methods such as the eddy current method [13,14] and microwave method [15,16,17,18,19] were proposed as potential alternatives for sheet resistance evaluation

Methods

Findings

Discussion

Conclusion