Structural characterizations and optical properties of InSe and InSe:Ag semiconductors grown by Bridgman/Stockbarger technique

Undoped InSe and Ag doped InSe (InSe:Ag) single crystals have been grown by using the Bridgman/Stockbarger method. The freshly cleaved crystals have mirror-like surfaces even without using mechanical treatment. The structure and lattice parameters of the undoped InSe and InSe:Ag semiconductors have been analyzed using a X-ray diffractometer (XRD), Scanning electron microscopy (SEM) and energy dispersive X-rays (EDX) techniques. It is found that the InSe and InSe:Ag crystals had hexagonal structure, and calculated lattice constants were found to be a=4.002 Å and c=17.160 Å for InSe and a=4.619 Å and c=17.003 Å for InSe:Ag. The crystallite sizes have been calculated to be 40-150 nm for InSe and 75-120 nm for InSe:Ag from the SEM results. Ag doping causes a significant increase in the XRD peak intensity. It has been observed from EDX results that InSe contains In=57.12%, Se=38.08% and O=4.81%, respectively. Absorption measurements have been carried out in InSe and InSe:Ag samples in the temperature range 10-320 K with a step of 10 K. The first exciton energies for n=1 were calculated as 1.328, 1.260 eV in InSe and were 1.340, 1.282 eV in InSe:Ag at 10 K and 320 K, respectively.