Atomic-scale characterization of two-dimensional magnets and their heterostructures

The realization of long-range magnetic ordering in two-dimensional(2D)van der Waals systems significantly expands the scope of the 2D family as well as their possible spin-related phenomena and device applications.The atomically thin nature of 2D materials makes their magnetically ordered states sensitive to local environments,and this necessitates advanced characterization at the atomic scale.Here,we briefly review several representative 2D magnetic systems,namely,iron chalcogenides,chromium chalcogenides,chromium trihalides,and their het-erostructures.With powerful scanning-probe microscopy,atomically resolved characterization of their crystalline configurations,electronic structures,and magnetization distributions has been achieved,and novel phenomena such as giant tunneling magnetoresistance and topological superconductivity have been observed.Finally,we discuss the challenges and new perspectives in this flourishing field.

High-sensitive two-dimensional PbI_(2)photodetector with ultrashort channel

Photodetectors based on two-dimensional(2D)semiconductors have attracted many research interests owing to their excellent optoelectronic characteristics and application potential for highly integrated applications.However,the unique morphology of 2D materials also restricts the further improvement of the device performance,as the carrier transport is very susceptible to intrinsic and extrinsic environment of the materials.Here,we report the highest responsivity(172 A/W)achieved so far for a PbI_(2)-based photodetector at room temperature,which is an order of magnitude higher than previously reported.Thermal scanning probe lithography(t-SPL)was used to pattern electrodes to realize the ultrashort channel(~60 nm)in the devices.The shortening of the channel length greatly reduces the probability of the photo-generated carriers being scattered during the transport process,which increases the photocurrent density and thus the responsivity.Our work shows that the combination of emerging processing technologies and 2D materials is an effective route to shrink device size and improve device performance.

Vorticity Measurements Using a 6-Sensor Hot-Wire Probe in a Tangentially Fired Furnace

Vorticity, which represents the rotation of a fluid element, is an important characteristic of turbulence. Various methods have been used to measure vorticity. A hot-wire/hot-film anemometer (HWA) was used here to measure the vorticity in turbulent flows. The velocity components and their partial derivatives were simultaneously measured with a new 6-sensor hot-wire (HW) probe assuming ideal yaw and pitch factors with Jorgensen's expression and Taylor's hypothesis to analyze the data. The accurate 6-sensor hot-wire probe results for the velocity field were used to determine the velocity gradients and, therefore, the vorticity vector field. The data was measured in an isothermal model of a tangentially fired furnace. The experimental results in the tangentially fired furnace agree with numerical results.

Graphene and 2D TMD material optical characterization with scanning probe microscopy

Two-dimensional(2D)materials distinguish themselves by high specific surface areas and wide tunability in nanophotonics research.As the developing of 2D materials optical and opto-electronic investigations,scanning probe microscopy provides high spatial resolution and strong local field confinement,which can realize the single molecular and atomic level of characterization.Here,we review the nanophotonic and opto-electronic features of both pristine and hybrid 2Dmaterials which are measured by scanning probe microscopy.The conclusion and prospective of scanning probe techniques for the future2Dmaterials characterization and practical applications are presented.