Temperature-Dependent Structural and Electrical Properties of Metal-Organic CVD MoS₂ Films

Abstract

Metal-Organic CVD method (MOCVD) allows for deposition of ultrathin 2D transition metal dichalcogenides (TMD) films of electronic quality onto wafer-scale substrates. In this work, the effect of temperature on structure, chemical states, and electronic qualities of the MOCVD MoS2 films were investigated. The results demonstrate that the temperature increase in the range of 650 °C to 950 °C results in non-monotonic average crystallite size variation. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy investigation has established the film crystal structure improvement with temperature increase in this range. At the same time, X-Ray photoelectron spectroscopy (XPS) method allowed to reveal non-stoichiometric phase fraction increase, corresponding to increased sulfur vacancies (VS) concentration from approximately 0.9 at.% to 3.6 at.%. Established dependency between the crystallite domains size and VS concentration suggests that these vacancies are form predominantly at the grain boundaries. The results suggest that an increased Vs concentration and enhanced charge carriers scattering at the grains’ boundaries should be the primary reasons of films’ resistivity increase from 4 kΩ·cm to 39 kΩ·cm.

Keywords

• TMD
• MOCVD
• nanocrystalline film
• AFM
• Raman spectroscopy
• XPS