Modelling the deposition process on the CdTe/CdS interface

CdTe is an excellent material for low-cost, high efficiency thin film solar cells and holds the record for Watts/$ performance [1, 2]. Defects such as grain boundaries and dislocations lower the efficiency of CdTe solar cells [3], thus it is important to do research on how these defects are formed during the growth process, especially on the interfaces of different materials. In this work we use computer simulation to predict the growth of a sputter deposited CdTe thin film on the CdS surfaces. Single deposition tests have been performed, to study the behaviour of deposited clusters under different conditions. We deposit a CdxTey (x; y = 0; 1) cluster onto the wurtzite (111) Cd and S terminated CdS surfaces with energies ranging from 1 to 40 eV. More than 1,200 simulations have been performed for each of these cases so as to sample the possible deposition positions and to collect sufficient statistics. The results show that Cd atoms are more readily sputtered from the surface than Te atoms and the sticking probability is higher on S terminated surfaces than Cd terminated surfaces. They also show that increasing the deposition energy typically leads to an increase in the number of deposited atoms replacing surface atoms and tends to decrease the number of atoms that sit on the surface layer, whilst increasing the number of interstitials observed.