Spectro-structural characterisation of CdSe1-xTex alloyed thin films

摘要

This paper presents information pertaining to the chemo-synthesis of Cd(Se, Te) thin films of variable composition which has been brought about with the objectives to study the deposition history, growth kinetics and the structural and optical changes caused due to the addition of Te in CdSe. The effects due to various process parameters such as deposition time, temperature, concentration of the basic species, speed of the substrate rotation, pH, etc. on the growth and quality of the films are studied experimentally. The films are crystalline in nature over whole range of the composition parameter with a homogeneous predominant wurtzite structure for 0 less than or equal to x less than or equal to 0.08 and 0.7 less than or equal to x less than or equal to 1 regions. For the middle range (0.15 less than or equal to x less than or equal to 0.7), the material tends towards a mixture of both the wurtzite and zinc blende phases rather than the homogenous solid solution. The cubic phase also under goes solid solution for 0 less than or equal to x less than or equal to 0.15 range of composition parameter. The lattice parameters have been computed for all the ranges and phases to identify the solid solutions. The crystallite sizes were determined from a well known Schemers relation and found to be varied smoothly with variation in the film composition. The spectral studies showed a high coefficient of absorption (alpha = 10(4) to 10(5) cm(-1)) with an allowed direct type of transitions. The energy gap varied nonlinearly, from 1.76 to 1.44 eV as x was increased from 0 to 1. (C) 2002 Published by Elsevier Science B.V. [References: 17]