# Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers
## 1 Introduction
### Irradiated MoS\({}_{2}\) Materials
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**MoS\({}_{2}\)** & **Irradiation** & **Particle Energy** & **Dose/fluence** & **Irradiation Source** & **Irradiation Conditions** & **Results** & **Ref.** \\ \hline
200 \(\mu\)m thickness & electron & 0.7 MeV & 150-600 K\(\gamma\) & electron accelerator & RT & created S vacancies & [74] \\ \hline
200 \(\mu\)m thickness & electron & 2.0 MeV & 100-250 K\(\gamma\) & electron accelerator & RT & created S vacancies and Mo vacancies, diamagnetic to ferromagnetic phase transition & [74] \\ \hline
20 layer & electron & 5 keV & 50 nA for 15 min & SEM beam & in vacuum & formed crystalline islands & [75] \\ \hline mono-layer & electron & 60 keV & 10\({}^{-10}\) electron / mm\({}^{2}\) & STEM beam & 400-700 °C in vacuum & induced 2H/1T phase transition & [76] \\ \hline \(\sim\)10 layer & electron & 3–15 keV & n/a & FEMA & in vacuum & broke the inversion symmetry & [77] \\ \hline mono-layer & electron & 80 keV & n/a & TEM beam & in vacuum & removed top and bottom S atoms & [78] \\ \hline mono-layer & electron & 200 keV & 3000 electrons/mm\({}^{2}\)/s & TEM beam & in vacuum & created S vacancies, increased electric resistance & [79] \\ \hline mono-layer & electron & 15 keV & 280 \(\mu\)c/ cm\({}^{2}\) & EBL & in vacuum & produced local strain and changed band structure & [80] \\ \hline mono-layer & electron & 80 keV & 40 A/cm\({}^{2}\) & TEM beam & in vacuum & produced holes and MoS\({}_{2}\) nanoribbons & [81] \\ \hline amorphous 5-7 layer & electron & 1 keV & 1–10 min & EBL & in vacuum & crystallized & [82] \\ \hline mono-layer & U\({}^{28}\) & 1.14 GeV & 4000 \(\mu\)cm\({}^{2}\)/s & heavy ion accelerator & in vacuum & total damaged & [83] \\ \hline micron thickness & Ar\({}^{+}\) & 500 eV & \(2.2\times 10^{35}\) ions/cm\({}^{2}\) & plasma & UHV & produced S vacancies & [84] \\ \hline bi-layer & Ar\({}^{+}\) & 500 eV & \(10^{14}\)-\(10^{35}\) ions/cm\({}^{2}\) & plasma & UHV & produced S vacancies and Mo\({}_{6}\) vacancy clusters & [84] \\ \hline mono-layer & Ar\({}^{+}\) & 500 eV & \(2.2\times 10^{35}\) ions/cm\({}^{2}\) & plasma & UHV & damaged & [84] \\ \hline
200 \(\mu\)m thickness & proton & 3.5 MeV & \(5\times 10^{18}\) ions/cm\({}^{2}\) & Singleton facility & RT & preserved lattice structure, produced defects, changed magnetic moments & [85] \\ \hline few-layer & proton & 10 MeV & \(10^{12}\)-\(10^{43}\) ions/cm\({}^{2}\) & MC-50 cyclotron & n/a & decreased electrical conductance & [86] \\ \hline mono-layer & proton & 100 keV & \(10^{12}\)-\(10^{43}\) particles/cm\({}^{2}\) & LEAF & n/a & created defects & [87] \\ \hline bi-layer & proton & 100 keV & \(6\times 10^{44}\) particles/cm\({}^{2}\) & LEAF & n/a & created defects & [87] \\ \hline bulk & He\({}^{2+}\) & 1.66 MeV & 900 McGy & ion accelerator & n/a & changed Raman scattering slightly & [88] \\ \hline nanosheet & He\({}^{2+}\) & 1.66 MeV & 900 McGy & ion accelerator & n/a & invariant & [88] \\ \hline few-layer & He\({}^{2+}\) & 30 keV & \(10^{18}\) ions/cm\({}^{2}\) & FIB beam & in vacuum & milled or damaged & [89] \\ \hline mono-layer & He\({}^{2+}\) & 3.04 MeV & \(8\times 10^{3}\) particles/cm\({}^{2}\) & PTA & n/a & produced defects & [90] \\ \hline mono-layer & He\({}^{+}\) & 30 keV & \(10^{12}\)-\(10^{43}\) ions/cm\({}^{2}\) & HIM & in vacuum & produced S vacancies & [91] \\ \hline mono-layer & He\({}^{+}\) & 30 keV & \(10^{12}\)-\(10^{73}\) ions/cm\({}^{2}\) & NFM & in vacuum & generated disorder & [92] \\ \hline bulk & Ar\({}^{+}\) & 500 eV & \(3\times 10^{-3}\) ions/cm\({}^{2}\) & STM & UHV & removed S atoms & [93] \\ \hline micron thickness & Ar\({}^{+}\) & 500 eV & \(10^{14}\)-\(10^{35}\) ions/cm\({}^{2}\) & n/a & UHV & produced S vacancies at low doses and Mo/Mo\({}_{6}\)s & [84] \\ \hline powder & Ar\({}^{+}\) & 3 keV & 0.1 A/cm\({}^{2}\) & n/a & n/a & removed S atoms & [94] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Radiation Induced Defects in 2H MoS\({}_{2}\).