Temperature-Driven α-β Phase Transformation and Enhanced Electronic Property of 2H α-InSe.

In recent years, thin layered indium selenide (InSe) has attracted rapidly increasing attention due to its fascinating properties and promising applications. Here, we report the temperature-driven α-β phase transformation and the enhanced electronic property of 2H -InSe. We find that 2H α-InSe transforms to β-InSe when it is heated to a high temperature, and the transformation temperature increases from 550 to 650 K with the thickness decreasing from 67 to 17 nm. Additionally, annealing the sample below the phase transformation temperature can effectively improve the electronic property of a 2H α-InSe field-effect transistor, including increasing the on-state current, decreasing the off-state current, and improving the subthreshold swing. After annealing, not only the contact resistance decreases significantly but also the mobility at 300 K increases more than 2 times to 45.83 cm V s, which is the highest among the reported values. Our results provide an effective method to improve the electrical property and the stability of the InSe nanodevices.