Abstract
We report a comprehensive study of the time-resolved photoluminescence (PL), carrier recombination, and carrier diffusion under diverse laser pulse excitation in TlInS2. The 2D-layered crystals were grown by the Bridgman method without or with the presence of a small amount of erbium in the melt. The investigation exposes large differences in two crystal types, although, a linear nonradiative lifetime and carrier diffusivity attain close values under high excitation with no contribution of the Auger recombination and the absence of the band gap narrowing effect. Moreover, at high pulse power, we detect imprinted transient grating fringes which are attributed to a new crystal phase formed by 2D electron-hole charge separation on local layers. The versatile model of the spontaneously polarized 2D-crystal has been developed to explain the observed features and ergodicity of charge dynamic processes. The model embraces the planar stacking fault (PSF) which edge provides a distortion and act as sink of strong recombination. The reduced occurrence of the PSFs in the erbium doped TlInS2 is the main attribute which determines the enhancement of PL by a factor of 50 and improves carrier diffusion along 2D-layers. The simulation permits evaluation of the PSF sizes of about 0.7 μm. The presented results allow improving 2D-crystal growth technology for novel sensor devices with separated excess charges.
Highlights
IntroductionAkin to TlInS2, belong to the class of specific 2D multilayered crystals which obey quite unique properties and attract extensive research interest.[1]
Thallium based ternary dichalcogenides, akin to TlInS2, belong to the class of specific 2D multilayered crystals which obey quite unique properties and attract extensive research interest.[1]
We report a comprehensive study of the time-resolved photoluminescence (PL), carrier recombination, and carrier diffusion under diverse laser pulse excitations in TlInS2
Summary
Akin to TlInS2, belong to the class of specific 2D multilayered crystals which obey quite unique properties and attract extensive research interest.[1]. Tl+ ion deviation and grouping occurs in the interlayer [8,9] and the I-phase is accompanied by strong resonance of complex dielectric function.[10] The lattice unit quadrupling within I-phase occurs around 200 K.[5] Weakness of interlayer bonds results from the sp-hybridization of the Tl electrons wave function where a strong coupling among the spins of Tl and In metal ions on neighboring layers is observed These couplings were first discovered by the nuclear magnetic resonance.[11,12,13] The interlayer wave function overlap is the important mechanism in the formation of the valence band maximum (VBM) and the conduction band minimum (CBM) and determines the electronic structure of the compound. There is another set of smaller SPL in about 2 times distribution with a larger Raman background intensity and increase of the FWHM on the main Raman doublet lines centered at 285 cm-1 Such different alternation is implying that two different crystal phases are created with larger periodicity than TG period. More investigations clearly are needed for understanding the stability and mechanism of the light imprint fringes in TlInS2 crystals
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