Ion implantation induced disorder in single‐crystal and sputter‐deposited polycrystalline CdTe characterized by ellipsometry and backscattering spectrometry

Abstract

Bulk single‐crystal CdTe, sputter‐deposited polycrystalline CdTe films of about 2.5 micron thickness, and single‐crystal Si (c‐Si) have been ion implanted using 350 keV Xe at fluences ranging from 1×1013 to 16×1013 cm–2 so as to create disorder in a controlled way from fully single‐crystalline to fully amorphous material. The general purpose of the investigations is to seek a parameterization of the critical point structures and establish a database for fitting the optical properties of CdTe films having different unknown grain sizes whereby the grain size will be described in terms of an effective defect density. The polycrystalline CdTe samples were magnetron sputtered onto c‐Si followed by CdCl2 and Br2‐methanol treatment to improve properties in terms of grain size and surface smoothness, respectively. The fluences for use in the ion implantation of CdTe were estimated using the SRIM (Stopping and Range of Ions in Matter) software, and cross‐checked by simultaneous implantation of bulk c‐Si samples. The optical properties were characterized by second derivative analysis and by a generalized critical point model. Although the damage created by 350 keV Xe in the simultaneously implanted c‐Si samples, as measured by both spectroscopic ellipsometry and Rutherford backscattering/ channeling spectrometry (RBS/C), agrees well with the expectations based on the SRIM simulation, the damage created in CdTe remains at a very low level even for doses several times higher than the amorphization level estimated by simulation. The character of the dechanneling of the RBS/C spectra indicates extended defects (presumably dislocation loops). This effect was similar in both single‐crystal and thin film polycrystalline CdTe, although less pronounced in thin film samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In-Situ Control of Defect Dynamics By Ellipsometry During Ion Implantation – Evolution of Disorder and Cavity Structure in Single-Crystalline Ge During Implantation of Sb Ions

“…Broad damage distributions were realized by multiple-step andenergy implantations, which are useful for the determination of optical references. 23 It was also proven that the implantation of heavy elements results in quick total amorphization up to the surface of the sample 38,39 , but without a honeycomb void formation and with less void than found for Ge in the present study.…”

Dielectric Function and Defect Structure of CdTe Implanted by 350-keV Bi Ions

“…This work is a continuation of previous studies on the ion implantation of singlecrystalline and polycrystalline CdTe [1]. Our aim is to study the optical properties and the defect structure of disordered CdTe prepared in a controlled way.…”

“…EXPERIMENT c-CdTe (Nippon Mining & Metals Co., (111)B) samples have been implanted using 175 kV Bi 2+ ions at fluences ranging from 3.75×10 13 cm -2 to 6×10 14 cm -2 . The high-mass Bi ions were chosen because the damage created in previous studies using Xe implantation was too low [1]. Using double-charged Bi ions at 175 kV, each Bi ion will have an energy of 350 keV.…”

Parameterization of the dielectric function of semiconductor nanocrystals

“…Consequently, Poisson statistics apply, and the relative decrease in amplitude is exp(−F a), where F is the fluence and a is the projected size. The application of the method has been demonstrated for different semiconductors including Si, CdTe [51] and SiC [52].…”