Large-area, continuous and high electrical performances of bilayer to few layers MoS2 fabricated by RF sputtering via post-deposition annealing method

Abstract

We report a simple and mass-scalable approach for thin MoS2 films via RF sputtering combined with the post-deposition annealing process. We have prepared as-sputtered film using a MoS2 target in the sputtering system. The as-sputtered film was subjected to post-deposition annealing to improve crystalline quality at 700 °C in a sulfur and argon environment. The analysis confirmed the growth of continuous bilayer to few-layer MoS2 film. The mobility value of ~29 cm2/Vs and current on/off ratio on the order of ~104 were obtained for bilayer MoS2. The mobility increased up to ~173–181 cm2/Vs, respectively, for few-layer MoS2. The mobility of our bilayer MoS2 FETs is larger than any previously reported values of single to bilayer MoS2 grown on SiO2/Si substrate with a SiO2 gate oxide. Moreover, our few-layer MoS2 FETs exhibited the highest mobility value ever reported for any MoS2 FETs with a SiO2 gate oxide. It is presumed that the high mobility behavior of our film could be attributed to low charged impurities of our film and dielectric screening effect by an interfacial MoOxSiy layer. The combined preparation route of RF sputtering and post-deposition annealing process opens up the novel possibility of mass and batch production of MoS2 film.

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“…5. There are two distinct peaks of E 1 2g , and A 1g located at 380 cm −1 and 406 cm −1 , corresponding to the characteristic feature www.nature.com/scientificreports www.nature.com/scientificreports/ of MoS 2 film [38][39][40][41][42][43] . When the films were annealed at 600 °C and 700 °C in argon environment, we observe very interesting behavior and instead of shrinking, the film surprisingly start expanding from its original thickness and intensities of both vibrational modes increased as shown by the blue and the green curves.…”

“…There is a clear redshift of E 1 2g and A 1g vibrational modes, relative to the as grown red curve when the films were annealed at 700 °C. Annealing improves significantly the MoS 2 crystal quality structure and causes the removal of surface contaminants and/or strain relief [40][41][42] . Similarly, we also observe that the increase in film thickness, due to annealing, also affects the characteristic of the Raman peaks and the intensity of the two peaks prominently increases after annealing at 700 °C.…”

“…8b,c, respectively. Two distinct peaks at 229.4 eV and 232.7 eV are attributed to doublet; Mo 3d 5/2 , and Mo 3d 3/2 , respectively [41][42][43] . However, a small peak is observed at 236 eV is corresponding to Mo 6+ obtained from the formation of small amount MoO 3 in the MoS 2 film surface due to exposure to outside environment for longer period of time 38 .…”

“…8c, the two peaks located at 162.5 eV and 163.3 eV correspond to S 2p 3/2 and S 2p 1/2 , respectively. They represent orbital divalent sulfides ions (S 2− ) [42][43][44][45][46] . The observed peak positions of spin-orbit coupled Mo 3d and S 2p states are in agreement with the literature and confirms the synthesis of MoS 2 thin film 38,43 .…”

Highly Enhanced H2 Sensing Performance of Few-Layer MoS2/SiO2/Si Heterojunctions by Surface Decoration of Pd Nanoparticles

“…Recently, physical vapor deposition, mainly including magnetron sputtering technique and pulsed layer deposition [17–22], is proved to be another effective approach to realize the growth of wafer-scale MoS 2 mono/few-layer films at much lower growth temperature of around 300 °C. The results demonstrate that the sputtered few-layer MoS 2 films exhibit remarkable transporting characteristics, such as a high mobility of ~ 181 cm 2 /Vs and a large current on/off ratio of ~ 10 4 [20]. …”