Controllable Growth And Optical Properties Of WSe₂/VOCl Vertical Heterostructures

Tow-dimensional（2D）materials,such as graphene,transition metal dichalcogenides（TMDs）,have attracted great attention on optoelectronics based on their unique features for example the atomic layer thickness,enhanced quantum confinement and strong light–material interaction.However,because of the low optical absorption efficiency,2D materials-based photodetectors therefore unable to be used to attain the high-performance optoelectronic properties.Based on this,the active area of 2D materials is confined and the migration of electrons is very limited.2D magnetic insulators are of great important in both fundamental research and technological application.Even so,most 2D magnetic systems are unstable on the atmospheric environment or under the photo-excitation.Stable 2D vd W magnetic insulators are desire to demonstrate for the potential applications.Recently,an emerging type of 2D layered materials with the molecular formula of MOX have been theoretically predicted to possess the unique electronic and magnetic properties.Nevertheless,these2D MOX are still rarely to be investigated up to now.Herein,for the first time,we successfully demonstrated the synthesis of the ultrathin WSe₂/VOCl heterostructures,which contains TMDs and MOX components,via a simple two-step chemical vapor deposition（CVD）method.Raman spectra were collected to investigate the vibration modes of the lattice between the single materials and the heterostructure,indicating the high quality of the latter.XPS experiments were conducted to illustrate the component structure of the heterostructure.In addition,optical imag es were provided to show the specific morphology for the single monolayer and heterostructure,whereas the scanning electron microscopy images presents more exquisite morphology.Steady-state photoluminescence（PL）were used to investigate the emission performance of the exciton.Moreover,temperature-dependent experiments from 77-300 K were performed to investigate the behaviors of exciton and corresponding PL.Meanwhile,we also studied the power-dependent PL experiments.Intriguingly,we observed that the PL intensity are obviously enhanced at the bottom WSe₂ layer in the WSe₂/VOCl heterostructure compared to the single WSe₂ monolayer.With increasing the excitation power,the enhancement factor is correspondingly increased and eventually reach to more than 2 under the high excitation power.It also indicates that the PL enhancement can be modulated by the excitation power.After further investigating the dynamics of the PL enhancement through the time-resolved and polarization-resolved PL experiments,a energy transfer process involving phonon-assistant was proposed for describing such PL enhancement behavior.In this work,t he successful growth of large area WSe₂/VOCl heterostructures may provide a promising future to engineer the opto-electronic properties of 2D materials.