A laser-assisted chlorination process for reversible writing of doping patterns in graphene

Abstract

Chemical doping has been extensively studied for control of charge carrier polarity and concentration in two-dimensional (2D) van der Waals materials. However, conventional routes by substitutional doping or absorbed molecules suffer from degradation of the electrical mobility due to structural disorder, while the maximum doping density is set by the solubility limit of dopants. Here, we show that laser assisted chlorination can achieve high doping concentration (> 3×10 13 cm − 2 ) in graphene monolayer with minimal mobility drop, while holding reversibility and spatial selectivity. Such superior doping scheme is enabled by two lasers with selected photon energies and geometric con gurations, resulting to high Cl coverage ratio (C 2 Cl) and subsequent local Cl-removal without damaging graphene. Based on this method, we demonstrate rewritable graphene photodetector, manifesting high quality reversible doping patterns in graphene. We believe that the presented results offer a new route for chemical doping of 2D materials that may enable exotic optoelectronic applications.

Tailorable Electronic and Electric Properties of Graphene with Selective Decoration of Silver Nanoparticles by Laser-Assisted Photoreduction

“…The significant enhancement of the overall spectral intensity including 2D and G peaks may be due to the surface-enhanced Raman scattering (SERS) effects, which are well-known to be induced by localized surface plasmon resonances in metal nanoparticles [ 21 , 26 , 29 , 33 , 34 ]. The shift of the peak positions and the changes in the ratios of the peak intensities in Raman spectra represent the variations in microscopic aspects and internal stress states of the graphene as well as the doping effects of the AgNPs into the graphene [ 13 , 21 , 33 , 44 , 45 , 46 ]. Herein, the peak intensities of the D, G, and 2D bands were set as , , and respectively.…”

“…Herein, the peak intensities of the D, G, and 2D bands were set as , , and respectively. The increase in the intensity ratio by ~81.2% through the PR process indicated the creation of defects in the GF during the AgNP growth [ 13 , 21 , 33 , 44 , 45 ]. In addition, while the 2D and G peaks were blue-shifted by 17.6 cm −1 and 1.7 cm −1 , respectively, the intensity ratio dropped by ~40.6% representing simultaneous doping effects and structural disorder evolution [ 13 , 21 , 33 , 44 , 45 ].…”

“…Graphene, a monatomic sheet of a honeycomb crystal structure composed of sp 2 -hybridized carbon atoms, has been studied extensively for a couple of decades since it does not only show fundamentally unique phenomena including unordinary valley structures and quantum Hall effects [ 1 ] but it also has many beneficial physical properties such as ultrahigh charge carrier mobility [ 2 ], superb mechanical strength and elastic modulus [ 3 , 4 ], high transparency [ 5 ], etc., leading to a variety of potential applications such as electronic and optoelectronic devices [ 6 , 7 , 8 , 9 ], electrical energy storage [ 10 ], flexible electronics [ 11 ], metastructures [ 12 ], and so forth. Particularly for electronic and optoelectronic graphene-based devices, to broaden the scope of their applications further, it is highly required to tune the carrier concentration and majority carrier type of graphene, as the doping level of conventional semiconductors should be tailored in a wide range to meet the differing needs of contemporary electronics and optoelectronics [ 13 ].…”

“…From this perspective, although it is quite challenging to control the electronic properties in two-dimensional (2D) structures, various approaches have been developed for doping 2D materials such as substitutional doping [ 14 , 15 ], electrostatic gating [ 8 ], surface functionalization [ 16 , 17 ], gas adsorption [ 13 ], ion irradiation [ 18 ], intercalation [ 19 , 20 ], and so on. The growth of metal nanoparticles on the graphene surface is also one of the effective doping methods to modulate the electronic state of graphene properly via charge carrier transfer across metal/graphene interfaces [ 21 ].…”

“…Since graphene is a gapless semi-metal, AgNP growth can be activated by direct photoexcitation more easily on graphene than on a 2D semiconductor. Further, by adopting a focused-laser beam as an irradiation source for the PR process, AgNPs can be selectively formed on a desired area of graphene [ 13 , 36 ]. This one-step process may even allow microscale complicated patterns of AgNPs to be written on graphene without any additional lithography and subsequent high-temperature annealing processes required for the conventional area-selective fabrication of AgNPs based on physical deposition techniques [ 13 , 26 , 35 , 36 , 37 , 38 ].…”