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

Layer-by-Layer Thinning of 2D Materials

Viet Phuong Pham

Avaliable from January, 2018


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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2.        Pham  VP,  Jang  HS,  Whang  D and Choi  JY.  Direct  growth  of graphene  on  rigid  and  flexible  substrates:  progress,  applications and challenges (2017) Chem Soc Rev 46: 6276-6300.

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 and Yeom  GY.  Cyclic chlorine trap-doping for transparent, conductive, thermally stable and damage-free graphene (2014) Nanoscale 6: 15301-15308. DOI: 10.1039/C4NR04387A

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 and Yeom  GY.  The  enhancement  of  Hall mobility  and  conductivity  of  CVD  graphene  through  radical doping and vacuum annealing (2017) RSC Adv. 7: 16104-16108. DOI: 10.1039/C7RA01330B

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. DOI: 10.28964/EngPress-1-107

9.        Kim KN, Pham VP and Yeom GY. Chlorine radical doping of a few layer  graphene  with  low  damage  (2015)  ECS  J  Solid  State  Sci Technol 4: N5095-N5097. doi: 10.1149/2.0141506jss

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

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*Corresponding author:

Viet Phuong Pham, SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do 440-746, Republic of Korea E-mail:


Viet Phuong Pham. Layer-by-Layer Thinning of 2D Materials (2018) Edelweiss Appli Sci Tech 2: 36-37