Anomalous Diffusion Profiles of Ag in CdTe due to Chemical Self-Diffusion

Abstract

Anomalous diffusion profiles of Ag in single crystalline CdTe were observed using the radiotracer 111 Ag. The diffusion anneals were performed at 800 K under Cd or Te vapor and in a vacuum for different Ag concentrations. The measured Ag profiles directly reflect the distribution of the self-interstitials and vacancies of the Cd sublattice and are the result of chemical self-diffusion which describes the variation of the deviation from stoichiometry of the binary crystal as a function of depth and time.

First-principles multiple-barrier diffusion theory: The case study of interstitial diffusion in CdTe

“…For example, at T = 800 K, Cd i has a diffusion coefficient of 9.07 × 10 −7 cm 2 /s and Cd i 2+ has a diffusion coefficient of 3.65 × 10 −6 cm 2 /s. Our theoretical result agrees very well with the experimental measurement for Cd i , which is 1.75 × 10 −6 cm 2 /s [38]. For Cu i and Cu i + , the calculated diffusion coefficients at T = 800 K are 6.22 × 10 −5 and 8.28 × 10 −6 cm 2 /s, respectively.…”

Empirical Correlations Between the Arrhenius’ Parameters of Impurities’ Diffusion Coefficients in CdTe Crystals

“…It seems that the reason of that is not small statistic or low apparatus sensitivity or other typical experimental difficulties but rather ''abnormall'' behavior of them in some cases. According to recent publications [65][66][67][68][69] at temperatures ranged 700-900 K the diffusion of Cu, Ag, Au in CdTe exhibits anomalous concentration profiles (uphill) depending upon the external conditions during diffusion; these anomalies essentially reflect the profile of the deviation from stoichiometry. As evident, there is considerable variation in the pre-exponential factor of copper diffusion, while values of the activation energy are much closer.…”

Pre‐requisites for the formation of unusual diffusion profiles in II–VI semiconductors

“…In contrast, for the group I elements Cu, Ag, Au, and Na unusual diffusion profiles (uphill diffusion) have been observed in CdTe and in case of Ag also in CdZnTe and ZnTe, after implantation (60 keV) into one side and subsequent annealing under Cd pressure at temperatures typically in the range 700-900 K (60 min) [2,3]. In case of CdTe, a metal layer evaporated onto the implanted surface significantly enhances the diffusion of the Ag atoms in CdTe towards the opposite side of the crystal.…”