Nanostructured surfaces

Advantages of developed treatment method of PbTe and Pb1-хSnхTe crystals surface after chemical etching
G.P. Malanych
V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 41 Nauky Ave., Kyiv, 03028,Ukraine. 
E-mail: galya.malanich@gmail.com

The surface crystal quality is characterized by its roughness, the crystalline perfection of the surface layers and the degree of physical and chemical purity. In practice chemical-mechanical (CMP) and chemical-dynamic polishing (CDP) in specially selected etching compositions are generally used for preparation required quality surface. Single crystals of PbTe and Pb0.83Sn0.17Te, Pb0.8Sn0.2Te (ІІ) solid solutions grown by the Bridgman method as well as Pb0.8Sn0.2Te (І) obtained through the vapor phase have been investigated.
Samples were cut from the central part of the ingots across their growth direction on a semiconductor cutting machine using a wire saw (with a layer of ~40-μm abrasive grains). After cutting, the resultant semiconductor wafers were 5 × 7 × 1.5 mm in dimensions. 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 process of the CDP was conducted at the facility using the techniques of rotating disk at T = 294-300 K with the disk rotation speed of γ = 86 min–1 using the solution of the same composition, that was used for CDP with the etching rate of ≈ 8 mkm/min.
The crystal dissolution rates were registered by reducing its thickness before and after etching with an electronic indicator TESA DIGICO 400. Microstructure of the plate’s surfaces after various stages of the mechanical and chemical treatments was studied using table scanning microscope JEOL JCM-5000 NeoScope. The sample surface microprofile characteristics and roughness were obtained using a profilometer HOMMEL-ETAMIC W5, which allows to determine the roughness more than 5 nm.
In the process of chemical-mechanical and chemical-dynamic polishing the single crystal polished surface was formed with Ra < 5 nm. The method of PbTe and Pb1-xSnxTe single crystal surface treatment is characterized by high polishing ability.