Molecular Beam Epitaxy of Highly Crystalline Monolayer Molybdenum Disulfide on Hexagonal Boron Nitride

Abstract

Atomically thin molybdenum disulfide (MoS), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics, but the scalable synthesis of highly crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly crystalline monolayer MoS film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS grown on h-BN primarily consists of two types of nucleation grains (0° aligned and 60° antialigned domains). By adopting a high growth temperature and ultralow precursor flux, the formation of 60° antialigned grains is largely suppressed. The resulting perfectly aligned grains merge seamlessly into a highly crystalline film. Large-scale monolayer MoS film can be grown on a 2 in. h-BN/sapphire wafer, for which surface morphology and Raman mapping confirm good spatial uniformity. Our study represents a significant step in the scalable synthesis of highly crystalline MoS films on atomically flat surfaces and paves the way to large-scale applications.

Growth and structure of singly oriented single-layer tungsten disulfide on Au(111)

“…There has been recent progress in the growth of single orientation two-dimensional materials, for example for SL BN on Ir(111) [26], as well as for SL MoS 2 on hexagonal boron nitride [21] and Au(111) [24]. Herein, we investigate the growth and structural features of epitaxially-grown SL WS 2 on Au (111).…”

Narrow photoluminescence and Raman peaks of epitaxial MoS 2 on graphene/Ir(1 1 1)

“…Through molecular beam epitaxy (MBE) using elemental sulphur -supplied e.g. from a valved sulphur cracker cell or from a Knudsen cell releasing elemental sulphur out of a compound like FeS 2 -phase pure and epitaxial transition metal disulfide layers could be grown even on van der Waals substrates to which they are only weakly bonded [12,13].…”

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe2 on Inert Amorphous Dielectrics

“…Compared to CVD and other methods, MBE offers great advantages for large‐area layer‐by‐layer growth of highly uniform TMDs by virtue of the precisely controlled molecular beam flux and growth temperature. Intriguingly, endowed by the high formation energy of the 1Tʹ phases and the small lattice mismatches between the superlattices of (4 × 4) MoS 2 and (5 × 5) hBN (+0.98%), (3 × 3) MoSe 2 and (4 × 4) hBN (−1.57%), (3 × 3) WSe 2 and (2 × 2) Al 2 O 3 (+3.84%), van der Waals MBE epitaxy growths of single‐crystal‐like 2H MoS 2 , MoSe 2 and WSe 2 monolayers were established on hBN and sapphire templates . Nevertheless, MoTe 2 is a strain‐sensitive phase change material .…”

“…The large lattice mismatch of −5.44% between the superlattices of (4 × 4) MoTe 2 and (6 × 6) graphene appears to be detrimental for 2H‐phase formation due to strain‐induced 2H → 1Tʹ phase change . Notably, for practical applications, a tedious transfer process from metal catalysts or epitaxial templates to device compatible substrates (e.g., SiO 2 /Si) is inevitable, which adversely degrading the quality of TMDs . Accordingly, a breakthrough in the 2D lateral growth of scalable monolayer TMDs, in particular MoTe 2 , directly on device compatible substrates is highly desired.…”

“…At sufficiently high T G , the migration, diffusion and alignment of adsorbed atoms becomes considerable, producing isotropic films with smooth surface. MoS 2 , MoSe 2 and WSe 2 are classic examples of thermodynamics‐limited fractal growth . The phase transformation of 2H → 1Tʹ is very challenging because the formation energy of the 1Tʹ phase is obviously higher than that of the 2H phase; therefore, the concept of two mobilities “low‐temperature nucleation + high‐temperature growth” is widely applied to suppress vertical nucleation and promote lateral growth in MoS 2 (750 + 900 °C) .…”