Copper indium diselenide: crystallography and radiation-induced dislocation loops

Abstract

Copper indium diselenide (CIS) is a prime candidate as the absorber layer in solar cells for use in extraterrestrial environments due to its good photovoltaic efficiency and ability to resist radiation damage. While CIS-based devices have been tested extensively in the laboratory using electron and proton irradiation, there is still little understanding of the underlying mechanisms which give rise to its radiation hardness. To gain better insight into the response of CIS to displacing radiation, transmission electron microscope samples have been irradiated in situ with 400 keV Xe ions at the Intermediate Voltage Electron Microscope facility at Argonne National Laboratory, USA. At room temperature, dislocation loops were observed to form and grow with increasing fluence. These loops have been investigated using g  ·  b techniques and inside/outside contrast analysis. They have been found to reside on {112} planes and to be interstitial in nature. The Burgers vector were calculated as b  = 1/6 ⟨221⟩. The compositional content of these interstitial loops was found to be indistinguishable from the surrounding matrix within the sensitivity of the techniques used. To facilitate this work, experimental electron-diffraction zone-axis pattern maps were produced and these are also presented, along with analysis of the [100] zone-axis pattern.

Keywords:

• radiation damage
• defect analysis
• dislocation structures
• crystallography
• semiconductors
• TEM
• electron diffraction
• ion irradiation
• copper indium diselenide
• CuInSe₂
• CIS

Acknowledgements

The authors thank R.C. Birtcher, E. Ryan, P. Baldo and A. Liu at the IVEM at Argonne National Laboratory (USA); M.F. Beafourt of the University of Poitiers (France) for advice on dislocation loop analysis and weak beam dark-field TEM; R. Brydson at the University of Leeds (UK) for help with scanning TEM; and B. Mendis and everybody at SuperSTEM, Daresbury Laboratory (UK).