Study of compositional changes (altered layer) in (Hg,Cd)Te targets sputtered with Hg vapor

Author

• Robert Granville Bourne, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

5-31-1982

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical Engineering

First Advisor

Roy H. Cornely

Second Advisor

Lawrence Suchow

Third Advisor

W. H. Warren Ball

Abstract

Six mercury cadmium telluride targets (5.74 cm diameter) with six polycrystalline (Hg_0.8 Cd_0.2 )Te ingots (1 x 3 x 0.7 cm ± 20%) epoxied on them, were r.f. sputtered in an MRC-8800 triode system for 1, 2, 3, and 5 minutes. The six sputtering runs were made with 3 different Hg pressures of 1.0, 1.25, and 1.6μm while the uniform target power density was kept constant at 7.7W/cm². After sputtering a target, Br₂ +CH₃OH was used to chemically etch the sputtered ingots to different depths. The surface composition of the etched ingots was measured with x-ray Photo Spectroscopy (XPS). The Hg,Cd and Te concentrations were thus obtained at six different depths into the target. From these data, the formation of the altered layer as a function of Hg pressure and sputtering time was studied.

The compositional studies indicated that the first 4000Å of the sputtered ingots was enriched in Te and depleted of both Hg and Cd. The results also revealed that it takes three minutes for the surface composition to reach equilibrium. As the Hg sputtering gas pressure increased, the Hg surface concentration increased while the Te concentration decreased.

A mathematical model was developed for computing the altered layer composition of (Hg,Cd)Te targets under different sputtering conditions and as a function of time. Some experimental data were used to obtain constants for the mathematical model. Computer results using the mathematical model were in good agreement with experimental results.

Below 1.45μm Hg gas pressure, the surface concentration ratio was experimentally found to be 12:1:87 (Hg:Cd:Te). As the Hg gas pressure increased to 1.6pm, the Hg concentration increased, and the Te concentration decreased. The computer analysis showed that above 1.6μm of Hg pressure the concentration ratio remains constant at 31:1:68 (Hg:Cd:Te).

Recommended Citation

Bourne, Robert Granville, "Study of compositional changes (altered layer) in (Hg,Cd)Te targets sputtered with Hg vapor" (1982). Theses. 3592.
https://digitalcommons.njit.edu/theses/3592