Contactless millimeter wave method for quality assessment of large area graphene

Abstract

We demonstrate that microwave absorption experiments offer a route for efficient measurements of transport properties for fast and accurate quality control of graphene. This conctactless characterization method can be used to quickly evaluate transport properties over large areas without recourse to complex lithographic methods making it suitable as a probe of quality during wafer scale fabrication. In particular, we demonstrate that absorption measurement of transport properties is sensitive to inhomogeneities in sample transport properties. This is in contrast to traditional methods using electrical contacts which tend to overestimate transport properties due to the formation of preferential conducting channels between the electrodes. Here we compare Shubnikov-de Haas oscillations simultaneously detected by microwave absorption and by conventional contact Hall bar measurements in fields up to 15 T on quasi-free standing, large area (≈25 mm 2 ) monolayer graphene. We find that although the evaluated charge carrier densities from both measurements are similar, the mobility differs considerably due to electronic transport inhomogeneity.

Sample Holders for Sub-THz Electron Spin Resonance Spectroscopy

“…4) Chip Sample Holder (ChSH): allows characterization of electrical/electronic devices under m.w. irradiation or to perform magneto-transport measurements [3]. The functional part contains 20 connectors, 16 of which host a chip expander, while the other four connect the T-sensor and the heater.…”

“…The functional part contains 20 connectors, 16 of which host a chip expander, while the other four connect the T-sensor and the heater. The chip expander is a small printed circuit board (PCB) with 16 gold deposited holes and contacts, prepared for wire-bonding of samples [3]. The maximal sample size which can be wire bonded is 8 mm x 8 mm.…”

“…S INCE the discovery of Electron Spin Resonance (ESR) by Zavoisky in 1944 at Kazan University [1], there has been vast development in the field of magnetic resonance. Nowadays, ESR methodologies cover various science disciplines [2], including solid-state physics [3]- [7], quantum information processing [8], [9], biophysics [10]- [14], and chemistry [15]- [17].…”

Nanostructured graphene for nanoscale electron paramagnetic resonance spectroscopy

“…Since the conductance of graphene can be affected by magnetic field (e.g. due to the formation of Landau levels [37][38][39]), it is important to test the effect of an applied magnetic field on the photoresponse of graphene quantum dot bolometers. Figure 3(a) shows the current-voltage characteristics (source-drain current as a function of sourcedrain voltage) of a graphene quantum dot bolometer with the radiation off (black curve) and irradiated with a continuous wave source at 100 GHz (green), without an applied magnetic field, at a temperature of 15 K. We note that the current-voltage characteristic is nonlinear due to heating effects from the bias current [11].…”

Terahertz electron paramagnetic resonance generalized spectroscopic ellipsometry: The magnetic response of the nitrogen defect in 4H-SiC

“…1,21 Millimeter waveguides suffer from high insertion losses at off resonance frequencies and ham-per frequency-scanning EPR. A waveguide-based normalincidence THz high field (15 T) frequency domain (85-720 GHz) EPR spectrometer with co-and cross-polar detection of differential absorbance was presented by Neugebauer et al 3,23 The magnetic polarization causes dispersion in the real and imaginary parts of the magnetic permeability, µ, which modify the complex index of refraction, n = √ µε, where ε is the dielectric permittivity. It is well known from thin film optics that small modifications in both real and imaginary parts of the complex index of refraction can precisely be monitored by analysis of the state of polarization of reflected or transmitted light.…”