Tuning the charge carrier mobility in few-layer PtSe2 films by Se : Pt ratio

Abstract

Recently, few-layer PtSe₂ films have attracted significant attention due to their properties and promising applications in high-speed electronics, spintronics and optoelectronics. Until now, the transport properties of this material have not reached the theoretically predicted values, especially with regard to carrier mobility. In addition, it is not yet known which growth parameters (if any) can experimentally affect the carrier mobility value. This work presents the fabrication of horizontally aligned PtSe₂ films using one-zone selenization of pre-deposited platinum layers. We have identified the Se : Pt ratio as a parameter controlling the charge carrier mobility in the thin films. The mobility increases more than twice as the ratio changes in a narrow interval around a value of 2. A simultaneous reduction of the carrier concentration suggests that ionized impurity scattering is responsible for the observed mobility behaviour. This significant finding may help to better understand the transport properties of few-layer PtSe₂ films.

Fig. 1. (a) Typical XRD pattern of PtSe₂ film prepared by selenization of 1 nm thick Pt layer at 550 °C during 30 min. (b) Typical XRR spectra of PtSe₂ film prepared by selenization of 1 nm thick Pt layer at 550 °C during 30 min. (c) Corresponding φ-scan of 101 diffraction of PtSe₂ and 104 diffraction of sapphire.

Fig. 2. Normalized Raman spectra of PtSe₂ films prepared by selenization of 1 nm thick Pt layer at 550 °C during 30 min with different nitrogen flow rates.

Fig. 3. Typical XPS spectra of PtSe₂ films prepared by selenization of 1 nm thick Pt layer at 550 °C during 30 min.

Fig. 4. Se : Pt ratio vs. charge carrier mobility and carrier concentration of PtSe₂ films prepared by selenization of 1 nm thick Pt layer at 550 °C during 30 min with different N₂ flow rate. The solid lines are a linear fits to the experimental values. Error bars represent uncertainty in XPS peak background removal.