(Cd, Mn) Se semimagnetic semiconductor thin films: growth from solution, structural analysis and optical properties

The preparation details and a few aspects pertaining to the crystallographic and spectral characteristics of the Cd1−xMnxSe (0≤x≤0.5) semimagnetic semiconductor thin films are presented in this letter. A series of samples were obtained from an alkaline medium (pH≅10±0.2) composed of Cd2+, Mn2+ and Se2− ions and were co-deposited from their salt solutions to produce thin solid films. The technique offers a free access for growth of these films first by an ion-by-ion condensation and later by adsorption of colloidal particles and is simple, non-expensive and permits for large area depositions. The deposition conditions and process parameters were so manipulated that good quality deposits were obtained. Few of the key parameters are the following: deposition temperature (50 °C), deposition time (120 min), pH (10±0.2) and speed of mechanical churning (70±2 rpm). The CdMnSe deposits were crystalline with preferred orientation along (100) direction and showed homogeneous phase formation up to a value of x equal to 0.1. Beyond this value, both CdSe and MnSe tend to separate out and formed an admixture. The lattice parameters and the intensities of reflections changed continuously with Mn content in CdSe. The optical spectra revealed high absorption coefficient with a band to band direct type of transitions. The estimated energy gap showed decrease, typically from 1.8 to 1.34 eV, on addition of Mn in CdSe and follows non-linear variation. Scanning electron microscopy also suggests the crystalline nature of the deposits.