Modulation of Schottky Barrier Height by Nitrogen Doping and Its Influence on Responsivity of Monolayer MoS₂ Photodetector

Abstract

Monolayer MoS2 flakes are prepared by low‐pressure chemical vapor deposition on p‐type and n‐type silicon substrates and post‐treated under nitrogen (N2)‐rich conditions to incorporate nitrogen atoms in sulfur vacancies. Ultraviolet photoelectron spectroscopy (UPS) shows an increase in work function value by 0.47 eV and 0.53 eV compared to undoped MoS2 when grown on p and n‐type substrates, respectively. Photodetection experiments conducted for doped and undoped MoS2 grown on p‐type substrate reveal a decrease in the value of photo responsivity for N2 doped MoS2 (191 A W−1) compared with undoped MoS2 (572 A W−1). Also, MoS2 crystals grown and doped on an n‐type substrate display an important enhancement of the photoresponsivity from 63 A W−1 for undoped to 606 A W−1 for N2 doped MoS2. The modulation of Schottky barrier height for N2 doped MoS2 on p type substrate decreased whereas for n type substrate the high electric field created due to the difference in the Fermi level allows for greater separation of photogenerated charge carriers. This modulation in the photoresponsivity due to the selection of the type of substrate opens up new avenues of research and engineering of atomically thin optoelectronic devices.

Nitrogen Pretreatment of Growth Substrates for Vacancy-Saturated MoS2

“…The hybridization of these chemically bonded species generates new bands close to the band edge that can neutralize the donor states of sulfur vacancies, leading to doping of MoS 2 toward the intrinsic regime. 11,12,14 These results are corroborated by Raman spectroscopy, which shows a blue-shift brought about by a hole-induced stiffening of the in-plane vibration modes due to reduced electron−phonon interactions (see Figure S6). [10][11][12]30 Analysis of the Raman spectra after transfer demonstrates that nitrogen saturation persists and is independent of the substrate.…”

“…These results agree with previous theoretical reports on the substitutional effects of oxygen and nitrogen in chalcogen vacancies. The hybridization of these chemically bonded species generates new bands close to the band edge that can neutralize the donor states of sulfur vacancies, leading to doping of MoS 2 toward the intrinsic regime. ,, …”

“…Moreover, vacancy saturation by chemical doping leads to charge transfer and Fermi level depinning. Recently, the incorporation of metal , or light elements such as oxygen , or nitrogen , to passivate intrinsic disorder in 2D materials has gained attention. However, these methods have shortcomings due to an increased complexity, increased thermal budget of the growth process, or due to introducing other impurities that limit their suitability for device integration. , …”

Angle-Resolved Polarized Raman Spectra of Linear MoS2 Nanostructures for Optical Anisotropy Detection

“…MoS 2 is a well-known two-dimensional material, which belongs to hexagonal layered structure . MoS 2 with different morphologies can be prepared by adjusting the growth conditions, and the geometric morphology plays a crucial role in regulating its properties. , Therefore, MoS 2 have broad application prospects such as photodetectors, biosensors, and photocatalysis . When one dimension of MoS 2 in the plane reaches or is less than the characteristic length (for example, the width size is less than a few hundred nanometers), it will show a linear nanostructure.…”

Facile synthesis and effect of thermal treatment on MoO3−x@MoS2 (x = 0, 1) bilayer nanostructure: toward photoelectrochemical applications

“…In recent years, molybdenum sulfide (MoS 2 ), a metal dichalcogenide, has emerged as a versatile material for diverse applications, including photodetector [1][2][3], light-emitting diode [4,5], gas sensor [6][7][8], supercapacitor [9,10], field effect transistor [11,12], photoelectrochemical or hydrogen evolution reaction (HER) [13][14][15][16][17][18][19], photocatalysis [20], Li-battery [21,22], and environmental treatment [23,24]. The two-dimensional (2D) MoS 2 nanoflake structure exhibits a pseudo-quantum confinement effect, which gives rise to superior properties such as high carrier mobility, fast photoexcited electron-hole pair separation/transfer, adjustable energy bandgap, and robust thermal stability [1,7,[25][26][27].…”