Fast Detection of Precipitates and Oxides on CdZnTe Surfaces by Spectroscopic Ellipsometry

Abstract

We study the surface chemistry of Cd 0.96 Zn 0.04 Te(211)B by X-ray photoelectron spectroscopy and ellipsometry. We obtain first the dielectric functions of amorphous Te and Cd on Cd 0.96 Zn 0.04 Te(211)B by in situ ellipsometry after growing thin films of each material by molecular beam epitaxy. We then study their oxidation in air and show that Cd oxidizes primarily as a hydroxide whereas Te is present as TeO 2 . In neither case is the oxidation of the films complete, as a substantial amount of either metallic Te or Cd remains even after several days of oxidation. We subsequently exploit an electroless chemical etchant based on Ce 4+ to produce Te-rich Cd 0.96 Zn 0.04 Te(211)B surfaces which oxidize very little in air. Another etchant containing KCN reduces the amount of a-Te substantially. Finally, we construct a tentative optical model for the Cd 0.96 Zn 0.04 Te(211)B surface that yields the abundance of amorphous Te on the surface.

Positron annihilation spectroscopy of vacancy-related defects in CdTe:Cl and CdZnTe:Ge at different stoichiometry deviations

“…3 that the curve exhibits a maximum at energy around 2 keV. This indicates that the sample contains a thin surface layer of native oxides most probably a mixture of , and CdO 48 49 . The curve for the u-CdTe sample was fitted by VEPFIT 25 using a two layer model: (i) native oxide layer on the surface and (ii) CdTe bulk region.…”

Dynamics of native oxide growth on CdTe and CdZnTe X-ray and gamma-ray detectors

“…The growth of the surface oxide layer and correlation between metallic tellurium layer evaluated with ellipsometry and tellurium peak height and width in XPS was proven already by Badano et al [16]. However, a detailed insight into the dynamics and the oxide growth rate after the chemical preparation has not been published yet.…”

“…Another peak doublet related to the oxygen bound to tellurium is also visible in Figure 2, marked as ‘oxide’. Because the doublet shift is about 3.3 eV, the measurement indicates a formation of the TeO 2 layer [16, 22]. Then the sample was chemically etched and we performed the XPS experiment again within an hour after the etching.…”

“…Yao et al [15] investigated mechanically polished samples and used a simple layer of CdTe–oxide and an intermix of CdTe–oxide and void on a CdTe substrate. Badano et al [16] used a more complicated structure consisting of a substrate, intermix layer, metallic tellurium layer, oxide layer and surface roughness. Because the etching process induces a higher roughness of the surface, the simple model by Yao et al [15] seems insufficient for ellipsometry investigation.…”

Properties of Al doped CdZnTe film by aluminium induced crystallisation

“…It was indicated that TeO 2 and CdTeO 3 were formed in the surface of the films. [11][12][13] The composition of undoped CdZnTe film is 51?27 at-% Te, 45?16 at-% Cd and 3?57 at-% Zn Typical I-V characteristics of the undoped and Al doped CdZnTe films were shown in Fig. 4.…”