Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe2 with large domain size and fast growth rate

Orientation-controlled growth of two-dimensional(2D)transition metal dichalcogenides(TMDCs)may enable many new electronic and optical applications.However,previous studies reporting aligned growth of WSe2 usually yielded very small domain sizes.Herein,we introduced gold vapor into the chemical vapor deposition(CVD)process as a catalyst to assist the growth of WSe2 and successfully achieved highly aligned monolayer WSe2 triangular flakes grown on c-plane sapphire with large domain sizes(130μm)and fast growth rate(4.3μm·s^−1).When the aligned WSe2 domains merged together,a continuous monolayer WSe2 was formed with good uniformity.After transferring to Si/SiO2 substrates,field effect transistors were fabricated on the continuous monolayer WSe2,and an average mobility of 12 cm^2·V^−1·s−1 was achieved,demonstrating the good quality of the material.This report paves the way to study the effect of catalytic metal vapor in the CVD process of TMDCs and contributes a novel approach to realize the growth of aligned TMDC flakes.

Alloy-buffer-controlled van der Waals epitaxial growth of aligned tellurene

Group-VI elemental two-dimensional(2D)materials(e.g.,tellurene(Te))have unique crystalline structures and extraordinarily physical properties.However,it still remains a great challenge to controllably grow 2D Te with good repeatability,uniformity,and highly aligned orientation using vapor growth method.Here,we design a Cu foil-assisted alloy-buffer-controlled growth method to epitaxially grow aligned single-crystalline 2D Te on an insulating mica substrate.The in-situ formation of Cu-Te alloy plays a key role on 2D Te growth,alleviating the spatial and temporal non-uniformity of precursor in conventional vapor deposition process.Through transmission electron microscopy(TEM)analysis combined with theoretical calculations,we unveil that the alignment growth of Te in the[110]direction is along the[600]direction of mica,owing to the small lattice mismatch(0.15%)and strong binding strength.This work presents a method to grow aligned high-quality 2D Te in a controllable manner.

Unidirectionally aligned diphenylalanine nanotube/ microtube arrays with excellent supercapacitive performance

High-temperature （150-220 ℃） growth leads to the formation of some peptide nanotube/microtube （NT/MT） arrays but the NTs/MTs exhibit closed ends, irreversible phase modification and eliminations of piezoelectric and hydrophilic properties. Here we demonstrate the fabrication of unidirectionally aligned and stable diphenylalanine NT/MT arrays with centimeter scale area at room temperature by utilizing an external electric field. The interactions between the applied electric field and dipolar electric field on the NTs and surface positive charges are responsible for the formation. The unidirectionally aligned MT array exhibits a supercapacitance of 1,000 μF·cm^-2 at a scanning rate of 50 mV·s^-1; this is much larger than the values reported previously in peptide NT/MT arrays.