Charge-tunable quantum dots in monolayer WSe2

Origin of Intrinsic Direct Band Gap of Janus Group‐III Chalcogenide Monolayers

“…Based on the 12 minimization of the total energy, the optimized lattice parameter 13 in intrinsic InSe monolayer is a ¼ 4.07 Å, while the monolayer 14 thickness d is 5. 36 Åand the bond lengths of In─Se bond and In- 15 In bond are 2.68 and 2.79 Å, respectively, which is in consistent 16 with the existing theoretical and experimental data. [31][32][33]…”

“…As a representative of such materials, 9 previous studies have shown that a few 10 layers of InSe can be successfully obtained 11 by exfoliating from its bulk crystal or 12 pulsed laser deposition (PLD). [12,13] The 13 pioneer work of Bandurin et al reported 14 the high carrier mobility of 10 3 cm 2 V À 1 s À 1 15 in atomically thin InSe at room tempera- 16 ture, [12,14] which was attributed to weak 17 electron-phonon scattering and anomalous 18 photoluminescence. The high carrier 19 motilities in this type of materials have 20 some advantages among all 2D materials.…”

“…[1,15] Due to quantum confinement effect, the band 41 gap of InSe monolayer increases to 2.11 eV and becomes 42 indirect. [12,16] The band gap of InSe can be controlled by the 43 number of layers so that it can cover the range of visible to 44 infrared light. Therefore, the photo-response of such material 45 can be tuned by the number of layers to achieve full coverage 46 from visible to infrared range.…”

“…[18] Especially, the importance and 12 recent theoretical and experimental progresses of the Janus 2D 13 material have been reviewed, including their structure and 14 stability, electronic properties, fabrication. [19] For instance, it was 15 found that the strain induced at upper or lower Janus structure of 16 In 2 SSe can render the system into direct band gap. [20] In term of 17 TMDCs, Mo 2 SSe Janus single layer has been experimentally 18 realized both from MoS 2 and MoSe 2 .…”

“…Although the calculated band gap value is smaller the Janus structures suggest that it is easier for electron 10 excitation from VBM to CBM than that of intrinsic layers when 11 irradiated by visible light. Interestingly, although the binary 12 analogs of InSe and InTe are both indirect semiconductors, it is 13 found that the Janus structure of In 2 SeTe is a direct band gap 14 semiconductor with its VBM and CBM residing at the Γ point, as 15 shown in Figure 1c, which is similarly to the chalcogenide 16 substitution of Janus Mo 2 SSe single layer. [21] The direct band gap 17 nature of In 2 SeTe is also similar to other Janus group-III 18 chalcogenide, such as Ga 2 SeTe as reported recently.…”