Anisotropic crystallization in solution processed chalcogenide thin film by linearly polarized laser

Abstract

Abstract:The low activation energy associated with amorphous chalcogenide structures offers broad tunability of material properties with laser-based or thermal processing. In this paper, we study near-bandgap laser induced anisotropic crystallization in solution processed arsenic sulfide.The modified electronic bandtail states associated with laser irritation lead to a distinctive photoluminescence spectrum, compared to thermally annealed amorphous glass. Laser crystalized materials exhibit a periodic subwavelength ripples structure in transmission electron microscopy experiments and show polarization dependent photoluminescence. Analysis of the local atomic 2 structure of these materials using laboratory-based X-ray pair distribution function analysis indicates that laser irradiation causes a slight rearrangement at the atomic length scale, with a small percentage of S-S homopolar bonds converting to As-S heteropolar bonds. These results highlight fundamental differences between laser and thermal processing in this important class of materials.Introduction:

Light Emission from Self‐Assembled and Laser‐Crystallized Chalcogenide Metasurface

“…The top view of the hot spot distribution on the interface between the metasurface and bulk substrate is shown in the Figure 2e. The local temperature can be up to 285 °C, which is beyond the glass transition temperature of 191.7 °C 14. The local photothermal heating removes the amine content and reconstructs the atomic structure from As 2 S 3 to As 4 S 4 .…”

“…The supporting silicon oxide buffer layer is removed via buffered oxide wet etching. As 2 S 3 solution is prepared by uniformly dissolving the powder into n ‐propylamine solvent according to recipes in the prior literature 14,18. The solution is then drop‐casted onto the suspended silicon membrane, forming a thick As 2 S 3 film on top of the Si layer.…”

“…As 2 S 3 dissolved in alkyl amines can be described as a nanocolloidal solution consisting of flat clusters that internally retain the structure of the layer‐like starting material but capped by ionic pairs of sulfide dangling bonds and alkyl ammonium molecules 31. Without annealing, those solvent‐related atomic defect states suppress light emission from As 2 S 3 14…”

“…Upon evaporating the excess solvent, the dried bulk chalcogenide cleanly delaminates from the smooth, flat silicon surface (Figure S2, Supporting Information). Our previous work shows that the room‐temperature dried chalcogenide nanorods still contain solvent‐related residue (CH/NH bond),32 which can be removed by hot plate annealing (170 °C) or laser annealing 14. Energy‐dispersive X‐ray spectroscopy (EDX) mapping is used to verify the chalcogenide arrays in the silicon structure (Figure S3, Supporting Information), and little residual on silicon top surface.…”

“…In this work, we demonstrate the first active chalcogenide metasurface fabricated by self‐assembling with tunable dimensions. The nanophotonic structure is tailored to enhance the light emission efficiency through resonance‐enhanced absorption of excitation, suppressing guided mode at emission wavelength and Purcell enhancement 14–17. The 2D hexagonal chalcogenide nanorod arrays are self‐assembled13 on a silicon template through solution processing 18–24.…”