Synthesis and photo-response study on GaSe and InSe atomic layers.

摘要

The two dimensional atomically layered materials are drawing intense attention in recent years, because of their special physical properties. Graphene, as a layered material with large charge carrier mobility, has been studied for years. Besides, graphene, large amounts of materials exhibit unique electronic and optical properties. GaSe (Gallium Selenide) and InSe (Indium Selenide) are van der Waals type layered crystal and widely applied in the area of photo-sensing, photo-voltage, non-linear optics, etc. The atomically layered GaSe and InSe may exhibit unique optical and electrical properties. In this study, GaSe single atomically layered crystal was grown by vapor phase transport method, InSe atomically layered flakes were prepared by mechanical exfoliation method. TEM and SEM were applied to characterize the quality of the crystals. Raman studies revealed the changes of vibration modes as the number of layers varied. Photo-conductivity measurements were conducted to reveal the band-structure changes. As the number of atomically layers become less and less, the band gaps of both of GaSe and InSe increase. From our study, it is observed that the layered atomically layered GaSe and InSe shows larger photo-current on/off ratio, indicating less non-photo-generated charge carrier in layered GaSe and InSe. Meanwhile, InSe atomically layers have stronger visible-light response than GaSe, which makes InSe more suitable for atomicallyally layered photo-voltage device, and GaSe more suitable for UV detector. Besides, the home-made opto-electronic measurement probe-station is also discussed in detail.