Detailed Study of Defects in Silicon Solar Cells by Cathodoluminescence Spectrum Imaging: Preprint

We have recently developed a spectrum imaging system for cathodoluminescence (CLsi) at NREL, which has been successfully applied to different semiconductors. The advanced multi-channel detection required for CLsi consists of an ultrafast spectrum acquisition triggered by the electron beam during scanning. Spectra are acquired either with a Roper Scientific silicon EEV-1340?400 cryogenic CCD or anInGaAs 512?1 cryogenic PDA, depending on the range of spectral emission. Acquisition times by pixel are typically of 10 to 20 ms (180 seconds for a 100?100 pixel image). The output of spectrum imaging measurements is thus represented by a series of emission spectra. CCDIMAG, the software developed for CLsi, processes this spectrum series to reconstruct monochromatic images or extract thespectrum from any area on the image. This system is operated on the JEOL-5800 scanning electron microscope (SEM). CLsi measurements can be performed at temperatures between 15 K and 300 K. A low-vibration ARS Displex DE-202 closed-circuit cryostat provides cryogenic operation. The interface for vibration isolation has been developed to be compatible with SEM observation.