Self-Healing Originated van der Waals Homojunctions with Strong Interlayer Coupling for High-Performance Photodiodes

Abstract

The dangling-bond-free surfaces of van der Waals (vdW) materials make it possible to build ultrathin junctions. Fundamentally, the interfacial phenomena and related optoelectronic properties of vdW junctions are modulated by the interlayer coupling effect. However, the weak interlayer coupling of vdW heterostructures limits the interlayer charge transfer efficiency, resulting in low photoresponsivity. Here, a bilayer MoS2 homogeneous junction is constructed by stacking the as-grown onto the self-healed monolayer MoS2. The homojunction barrier of ∼165 meV is obtained by the electronic structure modulation of defect self-healing. This homojunction reveals the stronger interlayer coupling effect in comparison with vdW heterostructures. This ultrastrong interlayer coupling effect is experimentally verified by Raman spectra and angle-resolved photoemission spectroscopy. The ultrafast interlayer charge transfer takes place within ∼447 fs, which is faster than those of most vdW heterostructures. Furthermore, the homojunction photodiode manifests outstanding rectifying behavior with an ideal factor of ∼1.6, perfect air stability over 12 months, and high responsivity of ∼54.6 mA/W. Moreover, the interlayer exciton peak of ∼1.66 eV is found in vdW homojunctions. This work offers an uncommon vdW junction with strong interlayer coupling and perfects the relevance of interlayer coupling and interlayer charge transfer.

Hidden Vacancy Benefit in Monolayer 2D Semiconductors

“…To quantitatively analyze the SV modulation on the electron concentration N A of monolayer MoS 2 , the following formula is used to calculate the N A : [ 10c ] where C i = 1.15 × 10 −4 F m −2 is the gate capacitance of the 300 nm SiO 2 dielectric layer, V G is the gate voltage, V TH is the threshold voltage, and q is the elementary charge. Combined with the V TH (Figure 2b), the electron concentrations of the 1.7%, 4.7%, and 6.7% SV monolayer MoS 2 can be extracted at V G = 0 V are 1.08 × 10 12 , 3.59 × 10 12 , and 2.66 × 10 12 cm −2 , respectively.…”

“…In STEM images of monolayer MoS 2 , the position of SVs lacks one or two S atoms and thus is significantly darker than the positions without SVs. [ 5a,10c ] To more easily distinguish isolated SVs, the interference signals of Mo atoms are removed to magnify the difference between the defective regions (black points) with SVs and the perfect regions (yellow points) with two S atoms in three filtered images (Figure 1c–e, bottom). The isolated SVs are lucidly presented in the filtered STEM images (Figure 1c–e, bottom), as with obviously different colors highlighted by the purple circles or also distinguished by line scan profiles (Figure S1b, Supporting Information).…”

Elimination of interlayer Schottky barrier in borophene/C4N4 vdW heterojunctions via Li-ion adsorption for tunneling photodiodes

“…For comparison, bilayer borophene and bilayer C 4 N 4 were modeled as vdW homojunctions. [31][32][33] In the Atomistix-toolkit Virtual-nano-lab (ATK-VNL) package, the linear combination of atomic orbitals (LCAO) techniques was utilized to optimize the geometry of the stacking superlattice and to calculate its electronic properties. 34,35 A vacuum layer of about 25 Å was introduced to minimize the spurious interaction between neighboring layers.…”

Nonlayered CdSe Flakes Homojunctions

“…Moreover, inspired by the fascinating thickness‐dependent optical and electrical properties and strong quantum confinement of electrons in 2D materials, 2D homojunctions display more unconventional physical, chemical, optical, and electronic properties. They show a lot of excellent performances for optoelectronic devices, such as ideal ohmic contact, strong interlayer coupling, and more efficient current rectification and photovoltaic response due to their unique interface. However, most of them are layered materials with van der Waals interaction between adjacent layers, hindering the further development of 2D homojunctions.…”