Chukhnenko P. Interaction of undoped and doped CdTe with (NH4)2Cr2O7 - HHal - organic acid etching solutions

Thesis is devoted to the investigation of a chemical interaction of undoped and doped CdTe crystals with the (NH4)2Cr2O7 - HHal - organic acid solutions. According to the results of mathematical simulation using the simplex method 20 diagrams "etchant composition - etching rate" with determining the regions of polishing and unpolishing solutions have been constructed. The kinetic behaviours and the limits stages of dissolution process of undoped and doped CdTe crystals were investigated, the influence of doping on the etching rate and the regions of polishing solutions was determined. It is shown that at the replacement НBr to HCl in (NH4)2Cr2O7 - HHal - organic acid etching compositions etching rates of mentioned above crystals rise up to 9 ?m/min and a transition take place from selective and unpolishing nature of etching to polishing. Dependence between composition of etchant solutions, pH of solution and the state of crystal's surfaces was found out. A great advantage of developed etchants on the basis of aqueous solutions (NH4)2Cr2O7 - HBr - C4H6O6 is possibility to choose solutions with the different value of pH and polishing rates depending on technological tasks. The compositions of polishing solutions suitable for the chemical-mechanical polishing of undoped and doped CdTe surfaces using as viscosity modifiers glycol and lactic acid are given. It was shown that the crystals surfaces after their polishing by the solutions (NH4)2Cr2O7 - HHal - organic acid have the stoichiometric composition and the nanoscale roughness. There were optimized the polishing compositions in the investigated systems and developed the methods and technological procedures of the polishing surfaces obtaining of the CdTe, CdTe(Ge), CdTe(Sn) and CdTe(Pb).