Polarization resolved photoluminescence study of pulse laser deposition assisted grown monolayer MoSe$_{\mathrm{2}}$-WSe$_{\mathrm{2}}$ lateral hetero-junction.*

The development of lateral hetero-junctions between 2D semiconductors of different band gaps could pave the way for the fabrication of new 2D electronic devices, such as high-speed transistors, diodes, and light emitting diodes. Here we demonstrate the growth lateral hetero-junction between MoSe$_{\mathrm{2}}$ and WSe$_{\mathrm{2}}$ by pulse laser deposition assisted chemical vapor deposition method. The lateral hetero-junction can be clearly observed in morphological charactarizations. The room temperature photoluminescence spectra at the interface show two strong peaks at 1.52 eV and 1.63 eV, corresponding to the $A$ excitons arising from $K$ point the first Brillion zone of monolayer MoSe$_{\mathrm{2}}$ and WSe$_{\mathrm{2}}$ respectively. The polarization resolved photoluminescence spectra's at 50 K reveals 55.2 {\%} and 29.4 {\%} valley polarization of WSe$_{\mathrm{2}}$ and MoSe$_{\mathrm{2}}$, respectively. However, the inter-band transition around (\textasciitilde 1.32 eV), previously observed in vertical hetero-structure could not be observed in lateral case due to spatial separation of energy bands of MoSe$_{\mathrm{2}}$ and WSe$_{\mathrm{2}}$.