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Edelweiss Applied Science and Technology (ISSN: 2576-8484)

Editorial :

Layer-by-Layer Thinning of 2D Materials

Viet Phuong Pham


Two-dimensional (2D) structured materials are receiving huge interests since the discovery of graphene material first by the mechanical exfoliation method using scotch tape from the graphite in 2004 (1). Among them, graphene [1-15], molybdenum disulfide (MoS2) [10,16], black phosphorous [17], hexagonal-boron nitride (h-BN) [18-20], hafnium dioxide (HfO2) [21], molybdenum diselenide (MoSe2) [22], and 2D carbide nanosheets (MXene) [23] are emerging as many promising potential materials with novel properties in electronics and optoelectronics.

Unlike conductive graphene with gapless characteristics, other materials above present different energy band-gap. The controlled tuning of band-gap of 2D materials by layer-by-layer thinning using various strategies related to chemistry, physic, nanotechnology, and engineering in order to obtain the ultra-thinner material layer and resulting in improvement their electrical characteristics is highly desiring with targeting toward practical applications in the industry to serve human society (Figure 1).

The increasing the controlled band-gap of 2D materials would be raising up the current on-off ratio, photoluminescence, and other unexploited and unexplored exotic properties. The electronic properties of 2D layered materials are strongly dependent on their thicknesses. For instance, the thickness modulating of MoS2 layers will activate the optical energy gap which makes it promising for application in optoelectronic devices, such as photodetectors, photovoltaics, light emitters, phototransistors.

Very recently, the progress in layer-by-layer thinning techniques on 2D materials has significant achieved [15-17,19-23]. By adjusting the etching rates (chemical and physical plasma engineering) [15-17,19-22] or gas molecular ratios and temperatures (chemical vapor deposition system) [23], we can achieve complete removal the layer-by-layer precisely and controllability [15-17,19-23]. Especially, the layer-by-layer etching by plasma (inductively coupled plasma, ion beam) without inducing the physical and chemical damage has successfully demonstrated in recent reports [15,17]. 

Consequently, it could unlock and take a leap forward on developing plasma-based thinning methods for other TMDs and low-dimensional materials in various advanced devices and applications.


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3.        Pham VP, Nguyen MT, Park JW, Kwak SS, Nguyen DHT, et al. Chlorine-trapped CVD bilayer graphene for resistive pressure sensor with high detection limit and high sensitivity (2017) 2D Materials 4: 025049.

4.        Pham VP, Kim KN, Jeon MH, Kim KS, Yeom GY. Cyclic chlorine trap-doping for transparent, conductive, thermally stable and damage-free graphene (2014) Nanoscale 6: 15301-15308.

5.        Pham VP, Kim KH, Jeon MH, Lee S H, Kim KN, et al. Low damage pre-doping on CVD graphene/Cu using a chlorine inductively coupled plasma (2015) Carbon 95: 664-671.

6.        Pham VP, Mishra A, Yeom GY. The enhancement of Hall mobility and conductivity of CVD graphene through radical doping and vacuum annealing (2017) RSC Adv. 7: 16104-16108.

7.        Pham VP, Kim DS, Kim KS, Park JW, Yang KC, et al. Low energy BCl3 plasma doping of few-layer graphene (2016) Sci Adv Mater 8: 884-890.

8.        Pham VP. Chemical vapor deposited graphene synthesis with same-oriented hexagonal domains (2018) Eng Press 1: 39-42.

9.        Kim KN, Pham VP, Yeom GY. Chlorine radical doping of a few layer graphene with low damage (2015) ECS J Solid State Sci Technol 4: N5095-N5097.

10.     Pham VP, Yeom GY. Recent advances in doping of molybdenum disulphide: industrial applications and future prospects (2016) Adv Mater 28: 9024-9059.

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17.     Park JW, Jang SK, Kang DH, Kim DS, Jeon MH, et al. Layer-controlled thinning of black phosphorous by an Ar ion beam (2017) J Mater Chem 5: 10888-10893.

18.     Dean CR, Young AF, Lee C, Wang L, Sorgenfrei S, et al. Boron nitride substrates for high-quality graphene electronics (2010) Nature Nanotech. 5: 722-726.

19.     Elbadawi C, Tran TT, Kolibal M, Sikola T, Scott, et al. Electron beam directed etching of hexagonal boron nitride (2016) Nanoscale 8: 16182-16196.

20.     Liao Y, Tu K, Han X, Hu L, Connell JW, et al. Oxidative etching of hexagonal boron towards nanosheets with defined edges and holes (2015) Sci Rep 5: 14510.

21.     Chen J, Yoo WJ, Tan ZYL, Wang Y, Chan DSH. Investigation of etching properties of HfO based high-k dielectrics using inductively coupled plasma (2004) J Vac Sci Technol  22: 1552-1558.

22.     Sha Y, Xiao S, Zhang X, Qin F, Gu X. Layer-by-layer thinning of MoSe2 by soft and reactive plasma etching (2016) Appl Sur Sci 411: 182-188.

23.     Ding B, Wang J, Wang Y, Chang Z, Pang G, et al. A two-step etching route to ultrathin carbon nanosheets for high performance electrical double layer capacitors (2016) Nanoscale 8: 11136-11142.


Graphene, Photodetectors, Light emitters.


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