Manganese diluted TlInS2 layered semiconductor: optical, electronic and magnetic properties

Abstract

Manganese–doped TlInS₂ (TlInS₂+Mn) layered semiconductors with different doping concentrations of about 0.1 and 0.3 atomic percent were investigated. Photo–induced current transient spectroscopy (PICTS) measurements in the temperature range of 80 and 300 K have been made for identifying energy levels related to Mn dopant within the electronic bandgap of TlInS₂+Mn crystal. Optical absorption spectra in the photon energy range of ~ 1.8–3.1 eV have been extracted by fitting the transmittance spectra of TlInS₂+Mn recorded at the temperatures varied from ~ 40 to 300 K. A redshift trend of the absorption edge with increasing of temperature was observed. On the other hand, a blue shift in the absorption edge with Mn doping was observed in the absorption spectra. The Mn dopant induced photoluminescence (PL) was also investigated in the visible region ranging from 320 to 960 nm. Seven peaks were observed in the PL spectra of Mn doped TlInS₂ crystal in the regions both ~ 960–620 nm ( ~ 1.3–2 eV) and ~ 620–320 nm ( ~ 2–3.8 eV) due to the electronic states of Mn ions. Laser–induced breakdown spectroscopy (LIBS) technique was applied to establish of the elemental chemical composition and to confirm presence of each constituent element in TlInS₂:Mn. The dc magnetization measurements of TlInS₂+Mn performed in a wide temperature range of ~ 5 and ~ 300 K revealed different (diamagnetic and paramagnetic states) magnetic phases inside the studied temperature range. The X–band electron paramagnetic resonance (ESR) experiments were carried out in the low–temperature phase of TlInS₂+Mn to probe the structure of Mn centers in TlInS₂. The measurements revealed that the ESR spectrum changes drastically in the low–temperature phase of TlInS₂+Mn bulk sample. Finally, a detailed density functional theory (DFT) based computational investigation of electronic band structures, density of states and optical properties of TlInS₂+Mn compound has been performed. The results of ab–initio calculations are discussed for three possible states when the manganese atom was doped by replacing either the Tl, In or S atoms in the unit cell of TlInS₂. Additionally, the effect of interstitial Mn dopant on the electronic structure and optical properties of TlInS₂ material has been simulated.