Nanostructured surfaces

Effect of oxidant [H2O2, (NH4)2Cr2O7] on the chemical-mechanical polishing of PbTe crystals by the “oxidant + HBr + CH2(OH)CH2(OH)” etchants
G.P. Malanych
V. Ye. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 41 Nauky Ave., Kyiv, 03028,Ukraine. 
E-mail: galya.malanich@gmail.com

The chemical-mechanical polishing (CMP) of the surface of PbTe crystals by bromine emerging etching compositions has been investigated. The dependences of the dissolution rate of PbTe in the solutions H2O2 + HBr + CH2(OH)CH2(OH)/ glycerol and (NH4)2Cr2O7 + HBr + CH2(OH)CH2(OH)/ glycerol have been studied. The concentration regions of the polishing solutions were determined.
The single-crystalline ingots of PbTe, grown by the Bridgman method, were cut into 5 × 7 × 1.5 mm size wafers using the string cutting. The cutting-induced surface deformation layer was partially removed by mechanical grinding with aqueous slurries of M10 to M5 and ASM 1/0 abrasive powders. The disturbed during cutting and grinding layer with the thickness of 100-150 μm was removed by CMP using etchant at a polishing rate of 185 μm/min. CMP was carried out on a glass polisher covered with lawn cloth at a continuous supply of etchant (2-3 ml/min) for 2 min and a pressure on the plates in 2-3 kPa. The dissolution rate of crystals was defined using the electronic indicator TESA DIGICO 400.
Some quantity of the viscous component was added to the basic solution B to diminish the polishing rate and to improve the surface properties. It is clear from Fig 1 that the increase of the added glycerol (GL) quantity to etchant B leads to a decrease of the CMP rate of the PbTe single crystal plate.

	Fig. 1 Dependences of the CMP rate of PbTe versus volume ratio of basic etchant B H2O2+HBr+CH2(OH)CH2(OH) (1), (NH4)2Cr2O7+HBr+
CH2(OH)CH2(OH) (2) with glycerol.