| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Monday Sessions |
| Session 2D+MI-MoA |
| Session: | Dopants, Defects and Interfaces in 2D Materials |
| Presenter: | Angelica Azcatl, The University of Texas at Dallas |
| Authors: | A. Azcatl, The University of Texas at Dallas R.M. Wallace, The University of Texas at Dallas |
| Correspondent: | Click to Email |
Two-dimensional tungsten diselenide (WSe2) is a layered material that have shown a promising performance when implemented in field effect transistors, exhibiting a hole mobility up to 250 cm2/V·s. [1] Furthermore, WSe2 possess hole and electron effective masses smaller than those of MoS2, another widely studied transition metal dichalcogenide, making WSe2 a promising candidate channel material for tunnel field effect transistor applications (TFETs). For the realization of WSe2 based TFETs, a high quality ultra-thin high-k dielectric film is a key requirement. However, the integration of high-k dielectrics by a conventional atomic layer deposition (ALD) process results challenging due to the dearth of nucleation sites at the WSe2 surfaces. Previous studies have shown that the deposition of high-k dielectrics by water-based ALD on WSe2 leads to non-uniform dielectric films. [2]
In this work, we explore the use of an alternative ALD approach to obtain uniform dielectric films on WSe2 through the use of ozone as oxidant precursor. The surface chemistry of WSe2 upon ozone exposure was studied by in-situ X-ray photoelectron spectroscopy to understand the reactivity between ozone and the WSe2 surface. Then, the ozone-based ALD process was studied for the deposition of Al2O3 and HfO2 on WSe2. It was found that the interfacial chemistry and the nucleation of the dielectric have a dependence on the deposition temperature. Based on these results, a temperature window was identified at which interfacial oxide formation is avoided while a uniform dielectric film is obtained. Furthermore, the differences in reactivity and growth rate between HfO2 and Al2O3 will be discussed. This study helps to elucidate the reaction mechanism of the ozone based ALD process on WSe2 and facilitates the implementation of the ozone based ALD approach to obtain uniform and thin dielectric films on WSe2 for TFETs applications.
This work is supported in part the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, and by the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST.
References
[1] H. Fang, et al., Nano Lett. 2012, 12, 3788−3792
[1] A. Azcatl, et al. 2D Materials, 2015, 2, 1, 014004