Direct Growth of Two-Dimensional Semiconductor Monolayers on Si Substrates by Chemical Vapor Deposition
Han Yeh1*, Wen-Hao Chang1
1Department of Electrophysics, National Chiao Tung UniversityHsinchu, Taiwan, Hsinchu, Taiwan
* Presenter:Han Yeh,
Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) monolayers with direct energy band gap, atomically thin thickness and electrostatically tunable carrier concentration are suitable for developing novel electronic and optoelectronic devices. Integrating 2D semiconductors on conventional three-dimensional (3D) bulk semiconductors (such as Si and GaN) emerged as new hybrid 2D/3D heterojunctions for developing new device architectures that are compatible with the conventional semiconductor device technology. Such 2D/3D heterojunctions can be formed by either mechanical exfoliation from TMD bulk crystals or transferring chemical vapor deposition (CVD) grown TMD monolayers from sapphire substrates to a 3D semiconductor substrate. However, it could easily lead to interface contaminations, structural damages or unintentional doping during the transfer process. For those reasons, directly growth of 2D TMDs on conventional 3D semiconductor substrates is an important technique to be developed. So that, we try to directly grow TMDC on Si heavy doped substrate. Here we demonstrate using organic molecules, perylene-tetracarboxylicacid-dianhydride (PTCDA), as seeding promoters to grow monolayer WSe2 and MoS2 on Si substrates. Heterogeneous nucleation provided by organic molecules effectively reduce the formation energy of WSe2 and MoS2 nuclei in comparison with homogeneous nucleation . We found that with the seeding promoters the grain size of monolayers WSe2 can be up to 10 μm on <111> Si substrate. Experimentally, we observed that both WSe2 and MoS2 monolayers on Si substrate exhibit very uniform surface potential. The surface potential between Si substrate and WSe2 is around 140 meV and for MoS2 is around 110 meV.

Keywords: transition metal dichalcogenides , Si substrates, surface potential