Ion Implantation Damage In Cds Using Tem and RBS/Channeling

Abstract

<p>Lattice disorder produced by heavy ion implantation of cadmium sulphide crystals at 50 K and 300 K has been investigated using Transmission Electron Microscopy (TEM) and Rutherford Backscattering (RBS)/- Channeling techniques.</p> <p>TEM observations of Bi⁺, Ar⁺ and Ne⁺ implanted samples showed that two types of dislocation loops were produced, type I with a Burgers vector b= 1/2 <0001> and type II with a Burgers vector b = 1/3' <1120>. Type II loops were nearly twice as large in size and two to three times greater in number density then type I loops. The large loops of type II were predominantly vacancy loops. Both types of loops lie predominantly in the {1100} and {1120} prism planes. The loop size and number density increased with increasing energy deposited into elastic collisions. For increasing ion dose the loop size increased while the number density decreased.</p> <p>In-situ measurements of the lattice disorder have been made using the RBS/ channeling technique with 0.6 MeV to 2.8 MeV He⁺ channeled along the a- and c-axes of the CdS crystals. The amount of disorder was measured in terms of the areal density of cadmium scattering centers (ND), and the minimum dechanneling yield (xmin) . Measured Nd values were found to be two orders of magnitude lower than theoretical prediction and the Xmin values were about an order of magnitude higher than those calculated assuming randomly displaced scattering centers. The disorder was greater measured along the c-axis than along the a-axis. It was also greater at 300 K than at 50 K. These observations suggest that the lattice distortion is greater in the direction perpendicular to the c-axis. It was also found that Nd increased with increasing E₀, while Xmin values were energy independent over the energy range investigated. These results and the rapid increase in Nd values observed when the crystal is tilted slightly away from the channeling direction ('Off-Axis' measurements) are consistent with the presence of dislocation loops as observed by the TEM.</p>