Ultra‐Long Van Der Waals CdBr₂ Micro/Nanobelts

Abstract

BN-MoS 2) 1D van der Waals heterostructure with a diameter of only 5 nm, which may be the smallest metal-insulator-semiconductor device proven to date. [6] In addition, all of these prior works demonstrated the potential of 1D materials as high-current density conductors. [7] First-principles calculations expose that ultra-long ballistic phonon transmissions are generated by highly focused longitudinal phonons that propagate along one dimension, [8] and thermal conductivity may diverge under 1D limit conditions. [9] Therefore, synthesizing and studying 1D materials are conducive to our understanding of their unique thermal, optical, and electrical properties, thus further promoting various applications of such materials. At present, the growth of 1D van der Waals materials is mainly conducted by chemical vapor deposition (CVD) with the help of CNTs or BNNTs. CVD is an effective strategy for synthesizing layered materials with excellent electro-optical properties. However, large temperature differences (>10 °C) cause growth kinetics to deviate from equilibrium, and the synthesized layered materials usually have a lot of defects and grain boundaries. [10] According to the classical band theory, a large number of defects in a crystal will generate deep levels or trap states inevitably, which usually limits the carrier mobility. [11] Simultaneously, the halogen element is usually not a stable reactant for the CVD method, which also makes it unsuitable for the growth of binary van der Waals materials containing halogen atoms. Therefore, there are still many challenges for synthesizing high-quality and large-size single-crystal van der Waals materials in this method, especially for those containing halogen elements. [10,12] Alternatively, van der Waals materials with large crystal size and high crystal quality can be obtained by mechanical exfoliation, but it is difficult to get them controlled in one dimension. Therefore, for the growth of large-scale 1D van der Waals materials, a new and efficient synthesis method is urgently needed. Here, we propose a new method that combines organic liquid phase synthesis and post-annealing. With the singlechain structure of CdBr 2 •4H 2 O, we successfully synthesized the high-quality and large-sized CdBr 2 van der Waals micro/nanobelts. Compared with CVD, this synthetic method reported in this article has shown two obvious advantages in growing highquality, large-size 1D van der Waals materials. First, according to the crystal growth thermodynamics and defect formation mechanism, [13] there is almost no temperature difference (<0.1 °C) between the crystal and solution. Liquid phase synthesis can Recently, 1D van der Waals materials with appealing optoelectronic properties different from 2D layered materials have attracted widespread attention. However, the existing methods are incapable of growing the high-quality and large-size 1D van der Waals materials to a certain extent. Here, a new method of organic liquid phase synthesis followed by annealing is proposed, which overcomes th...

Au/CdBr2/SiO2/Au Straddling‐Type Heterojunctions Designed as Microwave Multiband Pass Filters, Negative Capacitance Transistors, and Current Rectifiers

“…Namely, the electrical resistivity decreases by approximately three times from 1.21 at 338 K to 3.96 at 353 K. The resistivity activation energy () values in the high‐ and low‐resistivity levels are 0.20 and 0.16 eV, respectively. As the resistivity activation energy values are much less than half of the energy bandgap ( [ 6 ] ), CdBr 2 thin films are regarded as extrinsic semiconductors [ 16 ] with an average acceptor level centered at 0.18 eV. Thus, the Fermi level is located at () 0.09 eV above the valence band () of CdBr 2 .…”

“…[ 5 ] In addition, high‐quality ultralong (millimeter‐level) Van der Waals CdBr 2 micro‐/nanobelts were produced and used as photodetectors. [ 6 ] Similar to AlN photodetectors, [ 7,8 ] CdBr 2 photodetectors displayed high responsivity, nominating them for use in optoelectronics.…”

Molecular engineering for high-performance fullerene broadband photodetectors

“…S6 †, the crystal has a flat, clean, and smooth surface with a uniform thickness of ~90 nm, and the height difference of the microwire in longitudinal direction is less than 3 nm, which lay the foundation for the high-speed migration of electrons in the microwire. 54 AFM tests on C 60 and NiTPP microwires prepared from 1 mg/ml solution were also performed. Both microwires show smooth, flat surfaces and uniform height of ~90 nm, reflecting the high crystallinity of the microwires (Fig.…”