Formation of Two-Dimensional AgTe Monolayer Atomic Crystal on Ag(111) Substrate

We report on the formation of two-dimensional monolayer AgTe crystal on Ag(111) substrates. The samples are prepared in ultrahigh vacuum by deposition of Te on Ag(111) followed by annealing. Using a scanning tunneling microscope(STM) and low electron energy diffraction(LEED), we investigate the atomic structure of the samples.The STM images and the LEED pattern show that monolayer AgTe crystal is formed on Ag(111). Four kinds of atomic structures of AgTe and Ag(111) are observed:(i) flat honeycomb structure,(ii) bulked honeycomb,(iii)stripe structure,(iv) hexagonal structure. The structural analysis indicates that the formation of the different atomic structures is due to the lattice mismatch and relief of the intrinsic strain in the AgTe layer. Our results provide a simple and convenient method to produce monolayer AgTe atomic crystal on Ag(111) and a template for study of novel physical properties and for future quantum devices.

Construction of monolayer IrTe2 and the structural transition under low temperatures

Bulk iridium ditelluride(IrTe2)is a layered material and is known for its interesting electronic and structural properties,such as large spin-orbit coupling,charge ordering,and superconductivity.However,so far there is no experimental study about the fabrication of monolayer IrTe2.Here we report the formation of IrTe2 monolayer on Ir(111)substrate by direct tellurization method.Scanning tunneling microscope(STM)images show the coexistence of 1/5 phase and 1/6 phase structures of IrTe2 at room temperature.We also obtained STM images showing distorted stripe feature under low temperatures.This stripe feature is possibly induced by the strain between the IrTe2 monolayer and the metal substrate.Density functional theory(DFT)calculations show that the IrTe2 monolayer has strong interaction with the underlying Ir(111)substrate.

InSe/hBN/graphite heterostructure for high-performance 2D electronics and flexible electronics

Two-dimensional(2D)materials as channel materials provide a promising alternative route for future electronics and flexible electronics,but the device performance is affected by the quality of interface between the 2D-material channel and the gate dielectric.Here we demonstrate an indium selenide(lnSe)/hexagonal boron nitride(hBN)/graphite heterostructure as a 2D field-effect transistor(FET),with InSe as channel material,hBN as dielectric,and graphite as gate.The fabricated FETs feature high electron mobility up to 1,146 cm2·V^-1·s^-1 at room temperature and on/off ratio up to 1010 due to the atomically flat gate dielectric.Integrated digital inverters based on InSe/hBN/graphite heterostructures are constructed by local gating modulation and an ultrahigh voltage gain up to 93.4 is obtained.Taking advantages of the mechanical flexibility of these materials,we integrated the heterostructured InSe FET on a flexible substrate,exhibiting little modification of device performance at a high strain level of up to 2%.Such high-performance heterostructured device configuration based on 2D materials provides a new way for future electronics and flexible electronics.

Perception of Potential Health Risk of Climate Change and Utilization of Fans and Air Conditioners in a Representative Population of Hong Kong

Climate change, especially as reflected in heat waves, is a rising threat worldwide. Appropriate use of cooling devices can protect people from health impacts during a heat wave. A population-based telephone survey was conducted in a representative sample of residents in Hong Kong to investigate ownership and use of domestic cooling devices, identify correlates, and examine their associations with risk perception of potential health impact of climate change. More than 90% of the 1002 respondents owned and used cooling devices at home. The majority(57.7%) perceived the potential health risk of climate change at a high level. However, risk perception had no relationship with ownership and utilization of cooling devices. Old people(≥ 65 years), the low-educated, those with low income, and those with chronic diseases were more likely not to use air conditioners when feeling hot.Our findings suggest that there are no signs showing people have taken more protective actions although half of respondents recognized climate change as a threat. Familial economic condition may be a major determinant in ownership and use of air conditioners at home. Old people and those with chronic diseases are at high risk of adverse exposure to climate change and therefore should be equipped with appropriate measures to use cooling devices.