The synthesis of morphologically good thin chalcogenide films via the two-stage
route is a chemical challenge. The reactivity towards the chalcogen-bearing reactants of the different metals within the precursor film is a trade-off between
thermodynamic driving force and kinetics of binary sulfide formation.
In this work, CuSbS2 and Cu3BiS3 thin films were produced by conversion of
stacked and co-electroplated metal precursor layers in the presence of elemental
sulfur vapour. Ex-situ XRD and SEM/EDS analyses of RTP treated samples were
employed to study the reaction sequence and create ‘‘Time-Temperature-Reaction’’ diagrams for the description of the reaction kinetics. Modified Pilling–Bedworth coefficients were introduced for the interpretation of the experimental results.
The chalcogenizing conditions have a strong influence on the following aspects:
(1) Extent of intermediate phase segregation and/or crystallite size
(2) Thermodynamic (de)stabilization at low temperature
(3) Thermodynamic (de)stabilization at high temperature
The design of a successful synthetic route needs consideration of all these points, so that tailored choices of precursor film configuration and profiles of temperature and reactant partial pressure are made.
The synthesis of single crystals of the system Cu-Zn-Sn-S via the Chemical
Vapour Transport (CVT) with iodine was investigated. Current knowledge of CVT
in multinary systems is limited. A computation of the thermochemistry of the system was performed with the intent to estimate the risk for compositionally incongruent mass transport.
Experimental studies reveal no meaningful effect of the iodine pressure employed
on the composition of the CZTS products. However, samples obtained under
different I2 pressure showed different morphology and had slightly different unit cell sizes.
Longitudinally isothermal treatments were carried out with the intent to form large
size crystals. Under the investigated conditions, the experiments resulted in the
formation of crystals with 2D predominance. A possible explanation for this
phenomenon is proposed, based on considerations of the vessel’s thermal
conductivity and decomposition/crystallization rate at the steady-state equilibrium.
|Date of Award||31 Jul 2012|
|Supervisor||Laurie Peter (Supervisor) & Frank Marken (Supervisor)|