Molecular beam epitaxy of large-area SnSe ₂ with monolayer thickness fluctuation

Abstract

The interest in layered materials is largely based on the expectation that they will be beneficial for a variety of applications, from low-power-consuming, wearable electronics to energy harvesting. However, the properties of layered materials are highly dependent on thickness, and the difficulty of controlling thickness over a large area has been a bottleneck for commercial applications. Here, we report layer-by-layer growth of SnSe 2 , a layered semiconducting material, via van der Waals epitaxy. The films were fabricated on insulating mica substrates with substrate temperatures in the range of 210 °C-370 °C. The surface consists of a mixture of N and (N±1) layers, showing that the thickness of the film can be defined with monolayer accuracy (±0.6 nm). High-resolution transmission electron microscopy reveals a polycrystalline film with a grain size of ∼100 nm and clear Moiré patterns from overlapped grains with similar thickness. We also report field effect mobility values of 3.7 cm 2 V −1 s −1 and 6.7 cm 2 V −1 s −1 for 11 and 22 nm thick SnSe 2 , respectively. SnSe 2 films with customizable thickness can provide valuable platforms for industry and academic researchers to fully exploit the potential of layered materials.

Bandgap engineering of two-dimensional semiconductor materials

“…Moreover, the lower growth temperature capability of MBE minimizes issues associated with vertical heterostructure growth, including vacancy formation, layer intermixing, and interface chemical reactions. MBE, therefore, enables a variety of novel materials, including 2D-layered oxides, nitrides, arsenides, and the wide variety of 2D chalcogenides [122][123][124][125][126][127][128] 135 , have all been grown by MBE. In addition, TMDC alloys with mixed metals or mixed chalcogens have been advanced lately, further expanding the library of potential TMDC and heterostructures [136][137][138][139][140][141] .…”

Synthesis and Surface-Enhanced Raman Scattering of Ultrathin SnSe2 Nanoflakes by Chemical Vapor Deposition

“…However, the exfoliated 2D material has limited applications due to poor control in size and low yield. Some other synthetic methods, such as hydrothermal synthesis [ 28 , 29 ], molecular beam epitaxy [ 30 ], and chemical vapor deposition (CVD) [ 25 , 31 , 32 ] have also been used for the synthesis of layered material. Among them, the CVD method has been proposed as an important and successful method to synthesize various single-crystalline ultrathin layered 2D materials, such as MoSe 2 , WSe 2 , and their heterostructures, due to the advantages of high yield and high crystal quality [ 33 ].…”

Half-metals and half-semiconductors in a transition metal doped SnSe2 monolayer: a first-principles study

“…13,14 Few HMMs and HSCs have been predicted in some MoS 2 -like 2D materials doped by transition metal (TM) atoms. [15][16][17] Very recently, a new 2D semiconductor of SnSe 2 monolayer has been grown by molecular beam epitaxy, 18 and few-layer SnSe 2 eld effect transistor with a high current on/off ratio of 10 4 was also fabricated successfully. 19 The studies on 2D SnSe 2 mainly focused on the electronic and optoelectronic properties.…”