Two-dimensional (2D) ferromagnetic (FM) semiconductors with a high Curie temperature and tunable electronic properties are a long-term pursuing target for the development of high-performance spin-dependent optoelectronic devices. Herein, on the basis of density functional theory calculations, we report a new strategy to tune the Curie temperature and electronic structures of a ferromagnetic CrBr 3 monolayer through the formation of CrBr 3 /GaN van der Waals heterostructures. Our calculated results demonstrate that the Curie temperature and band alignment of CrBr 3 /GaN heterostructures strongly depend on the thickness and polarization direction of the GaN layer. The combination of the CrBr 3 monolayer with N-terminated GaN nanosheets leads to enhanced FM coupling via superexchange interactions between the Cr-t 2g and Cr-e g orbitals, consequently resulting in a Curie temperature of CrBr 3 of up to 67 K. Moreover, self-doped p−n junctions can be naturally formed in the heterostructures without additional modulation of external fields. The enhanced FM coupling and self-doping effect in the heterostructures are associated with the intrinsic polarization of the GaN layer that drives interfacial electron transfers from GaN to CrBr 3 . Therefore, this work not only offers an efficient scheme to boost the Curie temperature of the CrBr 3 monolayer but also opens up a new route to realize nonvolatile van der Waals p−n junctions.
The rational control of the nucleation
and growth kinetics to enable
the high-quality growth of two-dimensional (2D) semiconducting metal
chalcogenide heterostructures is a key step for the realization of
their applications in nanoelectronics and optoelectronics. Here, we
report a facile one-step chemical vapor deposition synthesis of 2D
SnS–SnS2 heterostructures with controlled interfacial
structures and stacking configurations via tuning S-precursor concentration
during the growth. We demonstrate that the change of S-precursor concentration
can drive growth transition from vertically stacking SnS2/SnS van der Waals heterostructures to SnS/SnS2 core–shell
structures with both the lateral and vertical interfaces. Such a transition
originates from a delicate competition between the nucleation of SnS
and SnS2. High-resolution spectroscopy measurements and
density functional theory (DFT) calculations reveal these SnS–SnS2 heterostructures with the type-II band alignment, and the
measured valence and conduction band offsets are 1.33 and 0.34 eV
for vertical SnS2/SnS heterostructures and 1.43 and 0.54
eV for SnS/SnS2 core–shell ones, respectively. This
work provides an efficient strategy to control the growth of 2D SnS–SnS2 heterostructures for optoelectronic applications, such as
photodetectors and solar cells.
The development of high-quality GaN-based heterojunctions breaks through the limitation of lattice mismatch, which is of particular importance for promoting their optoelectronic applications. Herein, we report an incommensurate heteroepitaxial growth...
Monolayer transition metal dichalcogenide (TMD) alloys with tunable band gaps exhibit huge potential in nanoelectronics, optoelectronics, and photonics. The scalable production of uniform atomically thin TMD alloys is a key step for the realization of their device applications but remains a large challenge so far. Here, we report oxygen-assisted chemical vapor deposition (CVD) of uniform atomically thin MoS 2(1−x) Se 2x semiconductor alloys via a vertical Mo-precursor supply strategy. The growth scheme leads to the formation of highly crystalline MoS 2(1−x) Se 2x monolayer films within a short growth time of 8 min, which benefits from a stable and homogeneous Mo-precursor feeding environment and the synergic effect of NaBr and oxygen carrier on the growth. The high-resolution spectral characterizations and density functional theory calculations demonstrate that the chemical composition of the as-grown MoS 2(1−x) Se 2x monolayers can be continuously tuned from x = 0 to 1, leading to the corresponding band gap being gradually changed from 1.81 to 1.55 eV. This work provides an efficient strategy to obtain large-area uniform MoS 2(1−x) Se 2x monolayer alloys with tunable compositions and optical properties, which is essential for driving their applications in various functional optoelectronic devices, especially for high-performance flexible photodetectors.
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