Nanostructured surfaces

Peculiarities of nanosized relief formation on the CdxHg1-xTe single crystals surface using К2Cr2O7 – HBr – solvent etchants
Chayka M.V.1, Tomashyk Z.F.2, Malanych G.P.2, Tomashyk V.M.2
1 Department of Chemistry, Zhytomyr Ivan Franko State University, 
Velyka Berdychivska Str., 40, Zhytomyr, 10008, Ukraine.
E-mail: laridae92@gmail.com
2 Semiconductor Chemistry Department, V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, Prospect Nauki, 41, Kyiv-03028, Ukraine.

The purpose of this work is to develop procedure for formation of nanosized relief on the CdxHg1-xTe surface. Single crystals of Cd0.2Hg0.8Te which have been grown by Bridgman method were used for experiments. Preliminary surface treatment of plates consisted of the grinding of the samples by abrasive powders, mechanical polishing with diamond paste and chemical etching to remove the damaged layer. A comparative analysis of changes in the parameters of the surface roughness (Rz) of Cd0,2Hg0,8Te after different stages of mechanical treatment was performed (see Table).
Treatment stage of CdxHg1-xTe	Rz, nm	
Cutting string	4580	
Cutting string + grinding by abrasive ASM 10/7	3103	
Cutting string + grinding by abrasive ASM 10/7 + ASM 5/3	1353	
Cutting string + grinding by abrasive ASM10/7 + ASM5/3 + АСМ1/0	430	
The etching mixtures were prepared from 40 % HBr, 10.9 % K2Cr2O7 and ethylene glycol (EG). The chemical-dynamic polishing (CDP) was performed using the method of disc rotating at T = 284 K and disk rotation speed  = 82 min–1. The rates of CDP of Cd0,2Hg0,8Te by developed polishing solutions is within the range of 0.9-7.3 μm/min. Finishing step of chemical-mechanical polishing (CMP) was carried out on a glass polisher covered with a batiste cloth. Etchant were dropped by a drip method from a dropping funnel with a built-in dispenser at a rate of 2-3 ml/min at T = 293 K. Vpol can be partly regulated from 18.7 to 0.8 μm/min due to the simultaneous mechanical and chemical effects on the surface and changes in the composition of the solutions during CMP.
The results of atomic force microscopy of the CdxHg1-xTe surface confirm that polishing the plates using developed solutions promotes the formation of a super smooth surface (Rа ≤ 10 нм). It was found that surface roughness of Cd0,2Hg0,8Te after СDP with K2Cr2O7 – HBr – EG is Ra = 2.5 nm and after СMP – Ra = 1.9 nm.