We have studied the carrier densities n of multilayer and monolayer epitaxial graphene devices over a wide range of temperatures T. It is found that, in the high temperature regime (typically T ≥ 200 ...K), ln(n) shows a linear dependence of 1/T, showing activated behavior. Such results yield activation energies ΔE for charge trapping in epitaxial graphene ranging from 196 meV to 34 meV. We find that ΔE decreases with increasing mobility. Vacuum annealing experiments suggest that both adsorbates on EG and the SiC/graphene interface play a role in charge trapping in EG devices.
We have performed magnetotransport measurements on a multi-layer graphene flake. At the crossing magnetic field
B
c
, an approximately temperature-independent point in the measured longitudinal ...resistivity
ρ
xx
, which is ascribed to the direct insulator-quantum Hall (I-QH) transition, is observed. By analyzing the amplitudes of the magnetoresistivity oscillations, we are able to measure the quantum mobility
μ
q
of our device. It is found that at the direct I-QH transition,
μ
q
B
c
≈ 0.37 which is considerably smaller than 1. In contrast, at
B
c
,
ρ
xx
is close to the Hall resistivity
ρ
xy
, i.e., the classical mobility
μB
c
is
≈
1. Therefore, our results suggest that different mobilities need to be introduced for the direct I-QH transition observed in multi-layered graphene. Combined with existing experimental results obtained in various material systems, our data obtained on graphene suggest that the direct I-QH transition is a universal effect in 2D.
Investigating the charge transport behavior in one-dimensional quantum confined system such as the localized states and interference effects due to the nanoscale grain boundaries and merged domains ...in wide chemical vapor deposition graphene constriction is highly desirable since it would help to realize industrial graphene-based electronic device applications. Our data suggests a crossover from interference coherent transport to carriers flushing into grain boundaries and merged domains when increasing the current. Moreover, many-body fermionic carriers with disordered system in our case can be statistically described by mean-field Gross-Pitaevskii equation via a single wave function by means of the quantum hydrodynamic approximation. The novel numerical simulation method supports the experimental results and suggests that the extreme high barrier potential regions on graphene from the grain boundaries and merged domains can be strongly affected by additional hot charges. Such interesting results could pave the way for quantum transport device by supplying additional hot current to flood into the grain boundaries and merged domains in one-dimensional quantum confined CVD graphene, a great advantage for developing graphene-based coherent electronic devices.
We evaluated carbon dioxide (CO2) adsorption on the
internal surface of the cylinder and the fractionation of CO2 and air
during the preparation of standard mixtures with atmospheric CO2 level
...through multistep dilution. The CO2 molar fractions in the standard
mixtures deviated from the gravimetric values by -0.207±0.060 µmol mol−1 on average, which is larger than the compatibility goal (0.1 µmol mol−1) recommended by the World Meteorological Organization. The deviation was consistent with those calculated using two fractionation factors: one was estimated by the mother–daughter transfer experiment in which CO2–air mixtures were transferred from a mother cylinder to an evacuated daughter cylinder, and another was computed by applying the Rayleigh model to the change in CO2 molar fractions in a source gas as its pressure was depleted from 11.5 to 1.1 MPa. The mother–daughter transfer experiments showed that the deviation was caused by the fractionation of CO2 and air during the transfer of the source gas (CO2–air mixture with a higher CO2 molar fraction than that in the prepared gas
mixture). The CO2 fractionation was less significant when the transfer
speed decreased to less than 3 L min−1, indicating that thermal
diffusion mainly caused the fractionation. The CO2 adsorption on the
internal cylinder surface was experimentally evaluated by emitting a
CO2–air mixture from a cylinder. When the cylinder pressure was reduced
from 11.0 to 0.1 MPa, the CO2 molar fractions in the mixture exiting
the cylinder increased by 0.16±0.04 µmol mol−1. By
applying the Langmuir adsorption–desorption model to the measured data, the amount of CO2 adsorbed on the internal surfaces of a 10 L aluminum cylinder when preparing a standard mixture with atmospheric CO2 level was estimated to be 0.027±0.004 µmol mol−1 at 11.0 MPa.
We evaluated carbon dioxide (CO.sub.2) adsorption on the internal surface of the cylinder and the fractionation of CO.sub.2 and air during the preparation of standard mixtures with atmospheric ...CO.sub.2 level through multistep dilution. The CO.sub.2 molar fractions in the standard mixtures deviated from the gravimetric values by -0.207±0.060 µmol mol.sup.-1 on average, which is larger than the compatibility goal (0.1 µmol mol.sup.-1) recommended by the World Meteorological Organization. The deviation was consistent with those calculated using two fractionation factors: one was estimated by the mother-daughter transfer experiment in which CO.sub.2 -air mixtures were transferred from a mother cylinder to an evacuated daughter cylinder, and another was computed by applying the Rayleigh model to the change in CO.sub.2 molar fractions in a source gas as its pressure was depleted from 11.5 to 1.1 MPa. The mother-daughter transfer experiments showed that the deviation was caused by the fractionation of CO.sub.2 and air during the transfer of the source gas (CO.sub.2 -air mixture with a higher CO.sub.2 molar fraction than that in the prepared gas mixture). The CO.sub.2 fractionation was less significant when the transfer speed decreased to less than 3 L min.sup.-1, indicating that thermal diffusion mainly caused the fractionation. The CO.sub.2 adsorption on the internal cylinder surface was experimentally evaluated by emitting a CO.sub.2 -air mixture from a cylinder. When the cylinder pressure was reduced from 11.0 to 0.1 MPa, the CO.sub.2 molar fractions in the mixture exiting the cylinder increased by 0.16±0.04 µmol mol.sup.-1 . By applying the Langmuir adsorption-desorption model to the measured data, the amount of CO.sub.2 adsorbed on the internal surfaces of a 10 L aluminum cylinder when preparing a standard mixture with atmospheric CO.sub.2 level was estimated to be 0.027±0.004 µmol mol.sup.-1 at 11.0 MPa.
Two-dimensional electron gases (2DEGs) can show exceptional carrier mobility, making them promising candidates for future quantum technologies. However, impurities and defects can significantly ...degrade their performance, impacting transport, conductivity, and coherence times. We leverage scanning gate microscopy (SGM) and machine learning approaches to extract the potential landscape of 2DEGs from SGM data. We compare three techniques: image-to-image translation with generative adversarial networks (GANs), cellular neural networks (CNNs), and an evolutionary search algorithm. Notably, the evolutionary approach outperforms both alternatives in defect identification and analysis. This work clarifies the interaction between defects and 2DEG properties, demonstrating the potential of machine learning for understanding and manipulating quantum materials, facilitating advancements in quantum computing and nanoelectronics.
•SGM is used to estimate the background potential of a 2D electron gas.•Three machine learning techniques are used to estimate the background potential.•Evolutionary search estimates align closer with the anticipated behavior of 2DEGs.
Quantum point contacts (QPCs) are nanoscale constrictions that are realized in a high-mobility two-dimensional electron gas by applying negative bias to split Schottky gates on top of a ...semiconductor. Here, we explore the suitability of these nanodevices to THz detection, by making use of their ability to rectify THz signals via the strong nonlinearities that exist in their conductance. In addition to demonstrating the configuration of these devices that provides optimal THz sensitivity, we also determine their noise equivalent power and responsivity. Our studies suggest that, with further optimization, QPCs can provide a viable approach to broadband THz sensing in the range above 1 THz.
The mass spectrometry (MS)-based analysis of free polysaccharides and glycans released from proteins, lipids and proteoglycans increasingly relies on databases and software. Here, we review progress ...in the bioinformatics analysis of protein-released N- and O-linked glycans (N- and O-glycomics) and propose an e-infrastructure to overcome current deficits in data and experimental transparency. This workflow enables the standardized submission of MS-based glycomics information into the public repository UniCarb-DR. It implements the MIRAGE (Minimum Requirement for A Glycomics Experiment) reporting guidelines, storage of unprocessed MS data in the GlycoPOST repository and glycan structure registration using the GlyTouCan registry, thereby supporting the development and extension of a glycan structure knowledgebase.
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