Pulsed laser annealing of amorphous two-dimensional transition metal dichalcogenides

Abstract

Large-area, flexible, two-dimensional transition metal dichalcogenide semiconductor materials (MoS2 and WSe2) were synthesized via magnetron sputtering of amorphous stoichiometric precursor materials on polydimethylsiloxane polymer substrates. Purely amorphous precursor materials and amorphous materials with pre-existing nanocrystalline regions observed via transmission electron microscopy were grown for the studies presented here. The MoS2 and WSe2 material precursors were then illuminated with a pulsed 532 nm laser to induce crystallization to their semiconducting hexagonal phases. The laser optics included an axicon lens to shape the Gaussian pulsed laser into a “Bessel beam” characterized by annular ring geometry. The pattern of the beam, with its rings of high-intensity laser light around a higher-intensity core, produced crystalline rings of the material around an ablation zone on the polymer substrate for MoS2 and WSe2 materials. The crystalline structure and density of atomic defects over the crystalline regions decreased as the same sample area was illuminated with additional pulses. The lateral coherence of the crystal lattice increased with the first 4 pulses but decreased with each subsequent pulse. The impact of preexisting nanocrystalline nanoinclusions in an amorphous film on the crystallization rate for WSe2 precursor materials was examined. The presence of nanocrystalline regions in the amorphous materials increased the crystallization rate under the photonic annealing conditions examined here. This approach of direct synthesis and patterning of materials is a route toward the fabrication of inexpensive flexible electronic devices.

Recent Progress in the Synthesis of MoS2 Thin Films for Sensing, Photovoltaic and Plasmonic Applications: A Review

“…(ii) its highest instantaneous deposition rate along with the highly-energetic aspect of the ablated species (~10 times higher than in sputtering) enables the growth of metastable phases and/or crystalline phases even at room temperature; and (iii) its process latitude, which makes it easy to control almost independently each of the deposition parameters (laser intensity, number of laser ablation pulses, background gas pressure, and substrate temperature), and hence the properties of the deposited materials [92][93][94]. While the early studies on the PLD of MoS 2 date back to the 1990s [95][96][97][98][99][100], it is only recently that important advancements have been made in PLD synthesis of 2D-MoS 2 films onto various substrates opening thereby the way to their use for different optoelectronic applications. In 2014, PLD was successfully used to grow one to several layers of MoS 2 onto different metal, semiconducting, and sapphire substrates [101,102].…”

Ultrashort‐Pulsed‐Laser Annealing of Amorphous Atomic‐Layer‐Deposited MoS2 Films

“…[ 23 ] For amorphous MoS 2 , a first‐pulsed‐laser‐induced crystallization was reported, as a crystalline ring was formed during the processing with nanosecond Bessel beam pulses. [ 24 ] In this article, we demonstrated that amorphous MoS 2 , deposited by low‐temperature thermal ALD, can be 2D crystallized upon irradiation with highly overlapped picosecond laser pulses and without any ablation. Moreover, we demonstrate formation of self‐organized nanopatterns in the MoS 2 layer, as the laser fluence increases.…”

Synthesis of Large-Area Crystalline MoS2 by Sputter Deposition and Pulsed Laser Annealing

“…For example, Ahmadi et al 46 used a nanosecond pulsed fiber laser, with a wavelength of 1064 nm, pulse duration in the range of 261 ns, and a repetition rate of 1 MHz, to crystallize pulsed laser deposited MoS 2 on a silica substrate, and characterized the films by UV−vis spectroscopy and Raman. Rai et al 31 worked with a 532 nm Nd:YAG laser source to crystallize MoS 2 and WSe 2 on PDMS substrates and characterized their material modification by TEM, Raman, XPS, and vis−UV spectroscopy. Furthermore, Wuenschell et al 47 used a 473 nm continuous-wave (CW) laser and a 355 nm pulsed NdYVO 3 laser for their work on crystallizing magnetron sputtered MoS 2 on glass and yttrium-stabilized zirconia substrates.…”

“…Many authors initially have focused on MoS 2 flakes, − but the work has recently moved to thin films, , often sputter-deposited . The substrate usually depends on the application, mentioned previously, but the most common are SiO 2 on Si , and glass, , while studies have also been undertaken using polydimethylsiloxane (PDMS), , and boron nitride (BN). , Moreover, MoS 2 and other TMDs have been laser processed on a variety of high- k dielectrics on top of a handle substrate. ,, The choice of substrate will potentially affect the irradiation reflectance or absorbance and hence may require specific tuning of the laser conditions to find the optimum setup. Different laser sources and wavelengths have been used on the laser processing of MoS 2 .…”

“…Many authors initially have focused on MoS 2 flakes, 22−24 but the work has recently moved to thin films, 25,26 often sputter-deposited. 27 The substrate usually depends on the application, mentioned previously, but the most common are SiO 2 on Si 19,28 and glass, 10,29 while studies have also been undertaken using polydimethylsiloxane (PDMS), 30,31 and boron nitride (BN). 32,33 Moreover, MoS 2 and other TMDs have been laser processed on a variety of high-k dielectrics on top of a handle substrate.…”