Controllable Growth And Optoelectronics Properties Of Single-layer Mo_1-xW_xSe₂ Gradient Alloy

Two-dimensional transition metal dichalcogenide?TMDC?,such as MoS₂,MoSe₂,WS₂,etc,open up a new way for the next generation optoelectronics due to unique properties such as optical transparency,high carrier mobility and widely adjustable band gap.Two-dimensional TMDC alloying can continuously adjust the band gap in a wide energy range,thereby making up for the deficiencies of the single TMDC due to the thickness-limited light absorption and the band gap-limited spectral range,promoting the development of photodetectors with broad spectral bands and high photodetection.In this paper,the preparation process and field-effect transistor of single-layer Mo_1-x-x W_xSe₂composition gradient alloy film will be studied.The specific research contents are as follows:?1?A single-layer Mo_1-x-x W_xSe₂ composition gradient alloy film was prepared by chemical vapor deposition?CVD?.The effects of growth parameters such as base-source distance,H₂ gas flow rate,and substrate position on the morphology and size of the single-layer Mo_1-xW_xSe₂ composition gradient alloy film were studied.By adjusting the growth parameters,a single-layer Mo_1-xW_xSe₂ composition gradient alloy film with a lateral dimension of 150?m can be prepared.Atomic force microscopy characterization results show that the thickness of the Mo_1-x-x W_xSe₂ composition gradient film is about1 nm.?2?The photoluminescence spectrum shows that the single-layer Mo_1-xW_xSe₂composition gradient alloy always shows a single peak behavior,and the luminous intensity gradually increases from the center to the edge,and the band gap continuously transitions from 1.53eV to 1.6eV.Raman spectroscopy shows that the single-layer Mo_1-xW_xSe₂ composition gradient alloy always exhibits single-peak behavior during the composition of W change from 0 to 1.During this process,the lattice structure of MoSe₂changed,and the interlayer vibration mode(A_1g)gradually shifted from 240cm^-11 to a high wavenumber,with a maximum offset of 9 wavenumbers.?3?The performance of single-layer Mo_1-xW_xSe₂ alloy field effect transistors with different composition gradients and photoelectric detection were investigated.The results show that single-layer Mo_1-xW_xSe₂ alloy field effect transistors with different composition gradients exhibit different conductive characteristics.The single-layer Mo_1-xW_xSe₂ alloy phototransistor with a composition gradient ranging from 0 to 0.6 showed better gate voltage regulation performance.When the gate voltage is 40V and the source-drain voltage is 5V,the responsivity of the device can reach a maximum of 10000A/W under laser irradiation with a wavelength of 532nm.