Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userScanning-gate microscopy of semiconductor nanostructures: an overview
210
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
This paper presents an overview of scanning-gate microscopy applied to the imaging of electron transport through buried semiconductor nanostructures. After a brief description of the technique and of its possible artifacts, we give a summary of some of its most instructive achievements found in the literature and we present an updated review of our own research. It focuses on the imaging of GaInAs-based quantum rings both in the low magnetic field Aharonov-Bohm regime and in the high-field quantum Hall regime. In all of the given examples, we emphasize how a local-probe approach is able to shed new, or complementary, light on transport phenomena which are usually studied by means of macroscopic conductance measurements.
rate research
Read More
Local variations in the Seebeck coefficient in low-dimensional materials-based nanostructures and devices play a major role in their thermoelectric performance. Unfortunately, currently most thermoelectric measurements probe the aggregate characteristics of the device as a whole, failing to observe the effects of the local variations and internal structure. Such variations can be caused by local defects, geometry, electrical contacts or interfaces and often substantially influence thermoelectric properties, most profoundly in two-dimensional (2D) materials. Here, we use Scanning Thermal Gate Microscopy (STGM), a non-invasive method not requiring an electrical contact between the nanoscale tip and the probed sample, to obtain nanoscale resolution 2D maps of the thermovoltage in graphene samples. We investigate a junction formed between single-layer and bilayer graphene and identify the impact of internal strain and Fermi level pinning by the contacts using a deconvolution method to directly map the local Seebeck coefficient. The new approach paves the way for an in-depth understanding of thermoelectric behaviour and phenomena in 2D materials nanostructures and devices.
We have used scanning gate microscopy to explore the local conductivity of a current-annealed graphene flake. A map of the local neutrality point (NP) after annealing at low current density exhibits micron-sized inhomogeneities. Broadening of the local e-h transition is also correlated with the inhomogeneity of the NP. Annealing at higher current density reduces the NP inhomogeneity, but we still observe some asymmetry in the e-h conduction. We attribute this to a hole doped domain close to one of the metal contacts combined with underlying striations in the local NP.
In scanning gate microscopy, where the tip of a scanning force microscope is used as a movable gate to study electronic transport in nanostructures, the shape and magnitude of the tip-induced potential are important for the resolution and interpretation of the measurements. Contaminations picked up during topography scans may significantly alter this potential. We present an in situ high-field treatment of the tip that improves the tip-induced potential. A quantum dot was used to measure the tip-induced potential.
We use Scanning Gate Microscopy to demonstrate the presence of localized states arising from potential inhomogeneities in a 50nm-wide, gate-defined conducting channel in encapsulated bilayer graphene. When imaging the channel conductance under the influence of a local tip-induced potential, we observe ellipses of enhanced conductance as a function of the tip position. These ellipses allow us to infer the location of the localized states and to study their dependence on the displacement field. For large displacement fields, we observe that localized states tend to occur halfway into the channel. All our observations can be well explained within the framework of stochastic Coulomb blockade.
Electronic Mach-Zehnder interferometers in the Quantum Hall (QH) regime are currently discussed for the realization of quantum information schemes. A recently proposed device architecture employs interference between two co-propagating edge channels. Here we demonstrate the precise control of individual edge-channel trajectories in quantum point contact devices in the QH regime. The biased tip of an atomic force microscope is used as a moveable local gate to pilot individual edge channels. Our results are discussed in light of the implementation of multi-edge interferometers.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
