Impact of N-plasma and Ga-irradiation on MoS2 layer in molecular beam epitaxy
Ng, Tien Khee
Hedhili, Mohamed N.
Anjum, Dalaver H.
Alias, Mohd Sharizal
Ooi, Boon S.
KAUST DepartmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division
Imaging and Characterization Core Lab
Physical Sciences and Engineering (PSE) Division
KAUST Grant NumberBAS/1/1614-01-01
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AbstractRecent interest in two-dimensional materials has resulted in ultra-thin devices based on the transfer of transition metal dichalcogenides (TMDs) onto other TMDs or III-nitride materials. In this investigation, we realized p-type monolayer (ML) MoS2, and intrinsic GaN/p-type MoS2 heterojunction by the GaN overgrowth on ML-MoS2/c-sapphire using the plasma-assisted molecular beam epitaxy. A systematic nitrogen plasma (N∗2N2*) and gallium (Ga) irradiation studies are employed to understand the individual effect on the doping levels of ML-MoS2, which is evaluated by micro-Raman and high-resolution X-Ray photoelectron spectroscopy (HRXPS) measurements. With both methods, p-type doping was attained and was verified by softening and strengthening of characteristics phonon modes E12gE2g1 and A1gA1g from Raman spectroscopy. With adequate N∗2N2*-irradiation (3 min), respective shift of 1.79 cm−1 for A1gA1g and 1.11 cm−1 for E12gE2g1 are obtained while short term Ga-irradiated (30 s) exhibits the shift of 1.51 cm−1 for A1gA1g and 0.93 cm−1 for E12gE2g1. Moreover, in HRXPS valence band spectra analysis, the position of valence band maximum measured with respect to the Fermi level is determined to evaluate the type of doping levels in ML-MoS2. The observed values of valance band maximum are reduced to 0.5, and 0.2 eV from the intrinsic value of ≈1.0 eV for N∗2N2*- and Ga-irradiated MoS2 layers, which confirms the p-type doping of ML-MoS2. Further p-type doping is verified by Hall effect measurements. Thus, by GaN overgrowth, we attained the building block of intrinsic GaN/p-type MoS2 heterojunction. Through this work, we have provided the platform for the realization of dissimilar heterostructure via monolithic approach.
CitationMishra P, Tangi M, Ng TK, Hedhili MN, Anjum DH, et al. (2017) Impact of N-plasma and Ga-irradiation on MoS2 layer in molecular beam epitaxy. Applied Physics Letters 110: 012101. Available: http://dx.doi.org/10.1063/1.4973371.
SponsorsThis publication is based upon the work supported by the King Abdulaziz City for Science and Technology (KACST), Grant No. KACST TIC R2-FP-008, and the King Abdullah University of Science and Technology (KAUST) baseline funding BAS/1/1614-01-01.
JournalApplied Physics Letters
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